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Ex) Article Title, Author, Keywords

Original Article
Impact of Smaller Gantry Arc Increments on Volumetric Modulated Arc Radiation Therapy in the Monaco Treatment Planning System
Progress in Medical Physics 2024; 35(3): 65-72
Original Article
Development of a Flexible Eye Shield Phantom for Artifact-Free Computed Tomography Images
Progress in Medical Physics 2024; 35(3): 59-64
Original Article
Analysis of the Multi-Leaf Collimator Quality Assurance for the HalcyonTM Linear Accelerator
Progress in Medical Physics 2024; 35(2): 45-51
Original Article
Dosimetric Evaluations of HyperArc and RapidArc in Stereotactic Radiosurgery for a Single Brain Metastasis
Progress in Medical Physics 2024; 35(2): 36-44
Review Article
Motion Management and Image-Guided Technique in Photon Radiation Therapy: A Review of an Advanced Technology
Progress in Medical Physics 2024; 35(2): 21-35

  • Review Article 2024-12-31

    Principle, Development, and Application of Electrical Conductivity Mapping Using Magnetic Resonance Imaging

    Geon-Ho Jahng1 , Mun Bae Lee2 , Oh In Kwon2

    Progress in Medical Physics 2024; 35(4): 73-88

    https://doi.org/10.14316/pmp.2024.35.4.73
    Abstract
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    Magnetic resonance imaging (MRI)-related techniques can provide information related to the electrical properties of the body. Understanding the electrical properties of human tissues is crucial for developing diagnostic tools and therapeutic approaches for various medical conditions. This study reviewed the principles, development, and application of electrical conductivity mapping using MRI. To review the magnetic resonance electrical properties tomography (MREPT)-based conductivity mapping technique and its application to brain imaging, first, we explain the definition and fundamental principles of electrical conductivity, some factors that influence changes in ionic conductivity, and the background of mapping cellular conductivities. Second, we explain the concepts and applications of magnetic resonance electrical impedance tomography (MREIT) and MREPT. Third, we describe our recent technical developments and their clinical applications. Finally, we explain the benefits, impacts, and challenges of MRI-based conductivity in clinical practice. MRI techniques, such as MREIT and MREPT, enabled the measurement of conductivity-related properties within the body. MREIT assessed low-frequency conductivity by applying a low-frequency external current, whereas MREPT captured high-frequency conductivity (at the Larmor frequency) without applying an external current. In MREIT, the subject’s safety should be ensured because electrical current is applied, particularly around sensitive areas, such as the brain, or in subjects with implanted electronic devices. Our previous studies have highlighted the potential of conductivity indices as biomarkers for Alzheimer’s disease. MREPT is usually applied to humans rather than MREIT. MREPT holds promise as a noninvasive tool for characterizing tissue properties and understanding pathological conditions.

  • Original Article 2024-12-31

    Evaluation of the Dosimeter Volume Effect on Small-Field Dosimetry Using the Elekta Harmony Pro Linear Accelerator

    Hyojun Park1,2 , Jin Jegal1,2 , Yoonsuk Huh1,2 , Inbum Lee1,2 , Sung Hyun Lee1,2,3 , Chang Heon Choi1,2,3 , Jung-In Kim1,2,3 , Seonghee Kang1,2,3

    Progress in Medical Physics 2024; 35(4): 89-97

    https://doi.org/10.14316/pmp.2024.35.4.89
    Abstract
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    Purpose: This study investigated the dose perturbation according to the size of the sensitive volume in the dosimeter in small-field dosimetry.
    Methods: The dose profiles with different field sizes were measured using three different dosimeters: the CC13, Razor ion chamber, and Edge solid-state detector. Both the open and wedged beams with different field sizes were employed in the measurement. The profiles were measured in a water phantom at maximum dose depths of 5, 10, and 20 cm. The penumbra and width of the open-beam profiles were compared according to the types of the dosimeters and beam. The dose fall-off between the peak and 20% dose was evaluated for the wedged beam profiles.
    Results: In the open-beam measurement, the fall-off of the profile was steeper with the Edge detector, which has the smallest sensitive volume. Meanwhile, the dose in the out-of-field region was the smallest with the Edge detector. The widths of the penumbra were 6.10, 4.47, and 4.03 mm for the profile of the 3×3 cm2 field measured by the CC13 chamber, Razor chamber, and Edge detector, respectively. The width of the profile was not changed even if different dosimeters were used in the measurement. The wedged beam profiles showed more clear peaks at the field edge when a smaller dosimeter was used.
    Conclusions: The results demonstrate the necessity of dosimeters with a small sensitive volume for measuring a small-field beam or a steep dose gradient.

  • Original Article 2024-12-31

    Evaluation of Methods for Characterizing Kilovoltage Beam Quality from the Varian TrueBeam STx

    Inbum Lee1,2 , Yoonsuk Huh1,2 , Jin Jegal1,2 , Hyojun Park1,2 , Chang Heon Choi1,2,3 , Jung-in Kim1,2,3 , Seonghee Kang1,2,3

    Progress in Medical Physics 2024; 35(4): 98-105

    https://doi.org/10.14316/pmp.2024.35.4.98
    Abstract
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    Purpose: This study evaluated various methods for determining the half-value layer (HVL) of kilovoltage (kV) beams produced by the Varian TrueBeam STx on-board imager. By comparing these methods with the standard ionization chamber approach, the study aimed to identify practical solutions for HVL determination and dosimetric characterization of kV beams, particularly in resource-limited settings.
    Methods: HVLs for kV beams (40–140 kVp) were measured using an Exradin A12 ionization chamber and a Piranha MULTI meter. The ionization chamber measurements adhered to American Association of Physicists in Medicine Task Group 61 guidelines and served as the reference standard. Additionally, HVL values were calculated using two model-based approaches: SpekPy (a Python-based tool) and Monte Carlo (MC) simulations using Geant4 and GATE. The results from these methods were compared to assess consistency and reliability.
    Results: Deviations across all methods were generally below 4%. At 40 kV, the most significant discrepancies were attributed to lower signal levels from the ionization chamber. The consistency between the model-based methods and experimental measurements demonstrates the reliability of these alternative approaches for HVL determination.
    Conclusions: Although the ionization chamber remains the gold standard, the Piranha MULTI meter and model-based methods, i.e., SpekPy and MC simulations, have shown promise as viable alternatives, especially in resource-constrained settings. These in silico approaches also offer advantages in convenience and accuracy, supporting their potential for broader future applications.

  • Original Article 2024-12-31

    Optimizing DICOM File Processing: A Comprehensive Workflow for AI and 3D Printing in Medicine

    Dong Hyeok Choi1,2,3 , Jin Sung Kim1,2,3 , So Hyun Ahn4,5,6

    Progress in Medical Physics 2024; 35(4): 106-115

    https://doi.org/10.14316/pmp.2024.35.4.106
    Abstract
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    Purpose: This study aims to develop a comprehensive preprocessing workflow for Digital Imaging and Communications in Medicine (DICOM) files to facilitate their effective use in AI-driven medical applications. With the increasing utilization of DICOM data for AI learning, analysis, Metaverse platform integration, and 3D printing of anatomical structures, the need for streamlined preprocessing is essential. The workflow is designed to optimize DICOM files for diverse applications, improving their usability and accessibility for advanced medical technologies.
    Methods: The proposed workflow employs a systematic approach to preprocess DICOM files for AI applications, focusing on noise reduction, normalization, segmentation, and conversion to 3D-renderable formats. These steps are integrated into a unified process to address challenges such as data variability, format incompatibilities, and high computational demands. The study incorporates real-world medical imaging datasets to evaluate the workflow’s effectiveness and adaptability for AI analysis and 3D visualization. Additionally, the workflow’s compatibility with virtual environments, such as Metaverse platforms, is assessed to ensure seamless integration.
    Results: The implementation of the workflow demonstrated significant improvements in the preprocessing of DICOM files. The processed files were optimized for AI analysis, yielding enhanced model performance and accuracy in learning tasks. Furthermore, the workflow enabled the successful conversion of DICOM data into 3D-printable formats and virtual environments, supporting applications like anatomical visualization and simulation. The study highlights the workflow's ability to reduce preprocessing time and errors, making advanced medical imaging technologies more accessible.
    Conclusions: This study emphasizes the critical role of effective preprocessing in maximizing the potential of DICOM data for AI-driven applications and innovative medical solutions. The proposed workflow simplifies the preprocessing of DICOM files, facilitating their integration into AI models, Metaverse platforms, and 3D printing processes. By enhancing usability and accessibility, the workflow fosters broader adoption of advanced imaging technologies in the medical field.

  • Original Article 2024-12-31

    A Commissioning Report on the Magnetic Resonance-Compatible Geneva Brachytherapy Applicator

    Yoonsuk Huh1,2 , Hyojun Park1,2 , Jin Jegal1,2 , Inbum Lee1,2 , Jaeman Son1,2,3,4 , Seonghee Kang1,2,3 , Chang Heon Choi1,2,3 , Jung-in Kim1,2,3 , Hyeongmin Jin1,2,3,4

    Progress in Medical Physics 2024; 35(4): 116-124

    https://doi.org/10.14316/pmp.2024.35.4.116
    Abstract
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    Purpose: Brachytherapy is essential for treating gynecological cancers as it offers precise radiation delivery to tumors while minimizing radiation exposure to surrounding healthy tissues. The Geneva applicator, introduced in 2020 as a replacement for older models like the Utrecht applicator, enhances MRI-based brachytherapy with improved imaging capabilities and more accurate applicator placement. In 2021, updates to non-reimbursement policies in Korea for MRI-based 3D brachytherapy planning further promoted the adoption of advanced techniques such as the Geneva applicator. This study aims to commission the Geneva applicator, focusing on wall thickness, dummy marker positions, and source dwell positions to ensure accurate dose delivery and safety.
    Methods: The commissioning process involved measuring wall thickness in both the longitudinal and transverse directions for the tandem and lunar-shaped ovoid tubes and comparing these measurements with the manufacturer’s specifications. Dummy marker positions were verified using CT imaging, with a focus on alignment tolerances of ±1 mm. Source dwell positions were planned using the Oncentra treatment planning system, with measurements taken using EBT4 film and analyzed with RIT software.
    Results: Wall thickness measurements and dummy marker positions were within the specified tolerance ranges, confirming their accuracy. The source dwell positions, measured and analyzed through multiple tests, were all within the ±1 mm tolerance, ensuring the applicator’s reliability.
    Conclusions: The Geneva applicator met all standards for safe and effective use in brachytherapy. The use of a 3D-printed holder was crucial for precise alignment and measurement. With updated reimbursement policies in Korea for MRI-based brachytherapy, the Geneva applicator is expected to significantly impact the future of advanced brachytherapy treatments and research.

  • Original Article 2024-12-31

    Development of a 3D-Printed Lithophane Breast Anthropomorphic Phantom for Dose Optimization in an Automatic Exposure Control System

    Hye-Jin Kim , Youl-Hun Seoung

    Progress in Medical Physics 2024; 35(4): 125-134

    https://doi.org/10.14316/pmp.2024.35.4.125
    Abstract
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    Purpose: This study aimed to develop a 3D-printed lithophane breast anthropomorphic phantom for optimizing the automatic exposure control (AEC) in a digital mammography system, thereby reducing radiation dose while maintaining high image quality.
    Methods: Craniocaudal breast radiograhic images from 72 patients, categorized as high-density and low-density by radiologists, were used to design the phantom. A digital lithophane technology was employed to create an anatomic breast plate, fabricated using a digital light processing 3D printer with resin. Polymenthylmethacrylate (PMMA) support thickness was adjusted incrementally until the exposure index and deviation index values approximated those of the American College of Radiology phantom. Phantom images were acquired across five AEC density levels (−6, −3, 0, 3, 6), and the optimal dose was determined as the lowest autoexposure mAs value with superior image quality. Two radiologists scored image quality on a 7-point Likert scale to identify the best configurations.
    Results: The optimal PMMA support thicknesses were determined as 3 cm for high-density and 4 cm for low-density breasts. The optimized AEC condition corresponded to the lowest density level (−6) with the least mAs value, maintaining excellent image quality. The use of the phantom resulted in a reduction of automatic exposure tube current by 39.4%–43.4% while producing images comparable to human breast radiographic images.
    Conclusions: The developed 3D-printed lithophane breast anthropomorphic phantom effectively optimized AEC settings, reducing radiation dose and maintaining high-quality breast radiographic images. This study has the potential to enhance safety and diagnostic efficacy in digital mammography.

  • Original Article 2024-12-31

    Evaluating the Influence of Scan Timing on Dosimetric Accuracy in EBT3 and EBT4 Radiochromic Films

    Jin Dong Cho , Su Chul Han , Jason Joon Bock Lee , Hyebin Lee , Heerim Nam

    Progress in Medical Physics 2024; 35(4): 135-144

    https://doi.org/10.14316/pmp.2024.35.4.135
    Abstract
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    Purpose: This study compares the dosimetric properties of EBT3 and EBT4 GAFchromic films in transmission and reflection scanning modes, focusing on dose response, sensitivity, and postirradiation stability.
    Methods: The EBT3 and EBT4 films were irradiated at doses of 0–10 Gy using a Varian TrueBeam linear accelerator at 6 MV. The films were scanned at intervals between 1 and 336 hours after irradiation in both transmission and reflection modes. Net optical density (NetOD) values from each scan were used to evaluate dose response and sensitivity, with calibration curves created for each film and scan mode. Dose differences between calculated and delivered doses were assessed over time.
    Results: The EBT3 and EBT4 films exhibited similar dose–response curves and stable NetOD values across both scanning modes. However, EBT4 exhibited reduced sensitivity variability in response to dose changes. After irradiation, NetOD values increased up to 24 hours before stabilizing, suggesting that a 24-hour scan time is sufficient for consistent measurements. Dose differences between films and modes remained within ±4%.
    Conclusions: EBT4 offers comparable dosimetric performance to EBT3, with additional benefits, such as improved dose–response linearity and reduced sensitivity fluctuations. The findings indicate that EBT4 can serve as a reliable successor to EBT3.

  • Original Article 2024-12-31

    Intra-Fractional Dose Evaluation for Patients with Breast Cancer Using Synthetic Computed Tomography

    Sohyun Ahn1,2 , So Eun Choi3 , Jeong-Heon Kim4,5,6 , Kwangwoo Park7 , Hai-Jeon Yoon8

    Progress in Medical Physics 2024; 35(4): 145-154

    https://doi.org/10.14316/pmp.2024.35.4.145
    Abstract
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    Purpose: This study investigated the use of synthetic computed tomography (CT) images derived from cone beam CT (CBCT) scans to analyze dose changes in breast cancer patients undergoing treatment and to evaluate the optimal timing for implementing adaptive radiotherapy.
    Methods: A retrospective analysis was conducted on five breast cancer patients treated with tomotherapy-based volumetric-modulated arc therapy at Yongin Severance Hospital. Each patient received 15 fractions, with doses of 320 centigray (cGy) to the high-dose planning target volume (PTV) and 267 cGy to the low-dose PTV. Planning CT images were acquired using the Aquilion scanner, and CBCT images were captured with the VersaHD linear accelerator’s on-board imager. These images were registered in RayStation using a hybrid deformable image registration method to generate synthetic CT images. Dose distributions were reanalyzed using the synthetic CT images, and dosevolume histogram parameters, including the dose to 95% of the volume (D95) and mean dose (Dmean) for the PTV, as well as D95, Dmean, the percentage of the volume receiving at least 5 Gy (V5) and 10 Gy (V10) for organs-at-risk (OARs), were extracted using MATLAB to assess dose changes during treatment.
    Results: For the original plans, the mean D95 for PTV high across all patients was 287.13±31.32 cGy, while for PTV low, it was 245.53±6.21 cGy. In contrast, the adaptive plans yielded a mean D95 of 298.17±12.37 cGy for PTV High and 247.25±4.23 cGy for PTV low. The ART Plan may lead to increased dose exposure in certain structures, such as the spinal cord, while providing targeted improvements in reducing radiation exposure in specific OARs (e.g., contralateral breast and esophagus).
    Conclusions: Synthetic CT images generated from CBCT scans provide a fast and efficient means of quantifying dose changes, supporting precise patient care through interfractional evaluation. Future studies will aim to apply this method to other organs and larger patient cohorts.

  • Original Article 2024-12-31

    Dosimetric Comparison of Stereotactic Radiosurgery for Brain Metastases: Volumetric Modulated Arc Therapy vs. Dynamic Conformal Arc

    Youngkuk Kim1,2 , Sangwook Lim1,3 , Ji Hoon Choi1,3 , Kyung Ran Park1,3

    Progress in Medical Physics 2024; 35(4): 155-162

    https://doi.org/10.14316/pmp.2024.35.4.155
    Abstract
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    Purpose: This study aimed to compare the dose characteristics of the volumetric modulated arc therapy (VMAT) and dynamic conformal arc (DCA) techniques for metastatic brain tumor treatment using various indices to evaluate the quality of the plan and provide insights into the clinical implications of each approach.
    Methods: Twelve patients with single metastatic brain tumors treated with VMAT were retrospectively analyzed. For comparison with DCA, identical geometric parameters (excluding multileaf collimators) were applied. Dose coverage, normal tissue sparing, and treatment efficiency were evaluated using indices such as CILIM98, CIICRU, CIRTOG, QCRTOG, CISALT, HTCISALT, and CIPADDIC. These indices were statistically assessed to evaluate the differences between VMAT and DCA.
    Results: VMAT was superior to DCA in most indices for both small and large planning target volumes (PTVs). DCA plans for large PTVs showed a higher V12Gy, exceeding 10 mL and failing to meet the recommended criteria (<10 mL). However, DCA required nearly half the monitor units (MUs) of VMAT, resulting in shorter treatment times. All indices, except for QCRTOG, demonstrated significant differences between VMAT and DCA.
    Conclusions: Careful consideration is necessary for larger PTVs when deciding a plan because DCA can occasionally result in V12Gy of a brain minus PTV >10 mL. Conversely, DCA provides the advantage of shorter treatment times because of its lower MU. This study highlights the importance of using a combination of indices to comprehensively assess treatment plan quality.

  • Original Article 2024-12-31

    Evaluation of Radioactivity in Therapeutic Radiopharmaceutical Waste

    Jung Ju Jo1,2 , Su Hyoung Lee3 , Beom Hoon Ki3 , Ho Jin Ryu3 , Tae Hwan Kim4 , Gi Sub Kim3 , Sang Kyu Lee5 , Dong Wook Kim6 , Kum Bae Kim1,2 , Sangrok Kim3 , Sang Hyoun Choi1,2

    Progress in Medical Physics 2024; 35(4): 163-171

    https://doi.org/10.14316/pmp.2024.35.4.163
    Abstract
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    Purpose: This study aims to systematically analyze the radioactive waste generated from treatments using radioactive Iodine-131 (I-131), Lutetium-177 (Lu-177), and Actinium-225 (Ac-225) to facilitate safe waste management practices.
    Methods: I-131 is primarily used in thyroid cancer treatment, while Lu-177 and Ac-225 are used to treat prostate cancer. Radioactive waste generated after these treatments was collected from patients at the Korea Cancer Center Hospital and categorized into clothing, slippers, syringes, and other items. The radioactivity concentration of each item was measured using a calibrated high-purity germanium detector. Using measurements, the self-disposal date of each waste item was calculated according to the permissible disposal levels defined by the Nuclear Safety and Security Commission (NSSC) under domestic nuclear safety regulations.
    Results: For the I-131 radioactive waste, clothing, towels, and tableware exhibited high radioactivity concentrations, with most items exceeding the permissible self-disposal levels. Conversely, the type and quantity of waste generated from Lu-177 and Ac-225 that were intravenously injected were relatively minimal, with certain items below the self-disposal thresholds, enabling immediate disposal. For Ac-225, no permissible self-disposal concentration is specified by the NSSC, unlike other therapeutic nuclides. Hence, additional studies are required to establish clear guidelines.
    Conclusions: These findings provide valuable data for optimizing radioactive waste management, potentially reducing disposal time and costs, minimizing radiation exposure, and enhancing hospital safety practices.

  • Original Article 2024-12-31

    Clinical Applications of Thermoplastic Sheets as Patient-Specific Gonadal Shields During Computed Tomography Simulation

    Jin Jegal1,2 , Hyojun Park1,2 , Seonghee Kang1,2,3,4 , Chang Heon Choi1,2,3,4 , Jung-in Kim1,2,3,4

    Progress in Medical Physics 2024; 35(4): 172-177

    https://doi.org/10.14316/pmp.2024.35.4.172
    Abstract
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    Purpose: Conventional gonadal shields are manufactured in standardized sizes and shapes and do not conform to individual testicular contours, causing discomfort. We developed a novel patient-specific gonadal shield using thermoplastic sheets and tested its feasibility through dosimetric evaluations.
    Methods: During the computed tomography simulation, custom lead shields were fabricated using thermoplastic sheets that were molded to the testicular shape of the patient. The shielding efficacy was evaluated using optically stimulated luminescent dosimeters (OSLDs) for point dose measurements.
    Results: The thermoplastic sheet was molded to fit closely to the skin with a minimal air gap of approximately 8.4 cm³, providing comfort to the patient during treatment. The patient-specific shield effectively reduced the surface dose from 28 cGy to less than 15 cGy. By combining the OSLDs located in the same row and calculating the mean dose value, a shielding effect was achieved with a maximum dose reduction of 56.1%.
    Conclusions: Customized gonadal shields were successfully created using thermoplastic sheets to minimize patient discomfort during application. However, further improvements in lead shield fabrication are needed to ensure full conformity.

  • Original Article 2024-12-31

    Development of an Instantaneously Interpretable Real-Time Dosimeter System for Quality Assurance of a Medical Linear Accelerator

    Dongyeon Lee1,2 , Sung Jin Kim2 , Wonjoong Cheon3 , Hyosung Cho1 , Youngyih Han2,4

    Progress in Medical Physics 2024; 35(4): 178-204

    https://doi.org/10.14316/pmp.2024.35.4.178
    Abstract
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    Purpose: Modern radiotherapy delivers radiation doses to targets within a few minutes using intricate multiple-beam segments determined with multi-leaf collimators (MLC). Therefore, we propose a scintillator-based dosimetry system capable of assessing the dosimetric and mechanical performance of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) in real time.
    Methods: The dosimeter was equipped with a scintillator plate and two digital cameras. The dose distribution was generated by applying deep learning-based signal processing to correct the intrinsic characteristics of the camera sensor and a tomographic image reconstruction technique to rectify the geometric distortion of the recorded video. Dosimetric evaluations were performed using a gamma analysis against a two-dimensional array and radiochromic film measurements for 20 clinical cases. The average difference in the MLC position measurements and machine log files was tested for the applicability of the mechanical quality assurance (QA) of MLCs.
    Results: The agreement of the dose distribution in the IMRT and VMAT plans was clinically acceptable between the proposed system and conventional dosimeters. The average differences in the MLC positions for the IMRT/VMAT plans were 1.7010/2.8107 mm and 1.4722/2.7713 mm in banks A and B, respectively.
    Conclusions: In this study, we developed an instantaneously interpretable real-time dosimeter for QA in a medical linear accelerator using a scintillator plate and digital cameras. The feasibility of the proposed system was investigated using dosimetric and mechanical evaluations in the IMRT and VMAT plans. The developed system has clinically acceptable accuracy in both the dosimetric and mechanical QAs of the IMRT and VMAT plans.

  • Original Article 2024-12-31

    Institution-Specific Autosegmentation for Personalized Radiotherapy Protocols

    Wonyoung Cho1 , Gyu Sang Yoo2 , Won Dong Kim2 , Yerim Kim1 , Jin Sung Kim1,3 , Byung Jun Min2

    Progress in Medical Physics 2024; 35(4): 205-213

    https://doi.org/10.14316/pmp.2024.35.4.205
    Abstract
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    Purpose: This study explores the potential of artificial intelligence (AI) in optimizing radiotherapy protocols for personalized cancer treatment. Specifically, it investigates the role of AI-based segmentation tools in improving accuracy and efficiency across various anatomical regions.
    Methods: A dataset of 500 anonymized patient computed tomography scans from Chungbuk National University Hospital was used to develop and validate AI models for segmenting organs-atrisk. The models were tailored for five anatomical regions: head and neck, chest, abdomen, breast, and pelvis. Performance was evaluated using Dice Similarity Coefficient (DSC), Mean Surface Distance, and the 95th Percentile Hausdorff Distance (HD95).
    Results: The AI models achieved high segmentation accuracy for large, well-defined structures such as the brain, lungs, and liver, with DSC values exceeding 0.95 in many cases. However, challenges were observed for smaller or complex structures, including the optic chiasm and rectum, with instances of segmentation failure and infinity values for HD95. These findings highlight the variability in performance depending on anatomical complexity and structure size.
    Conclusions: AI-based segmentation tools demonstrate significant potential to streamline radiotherapy workflows, reduce inter-observer variability, and enhance treatment accuracy. Despite challenges with smaller structures, the integration of AI enables dynamic, patient-specific adaptations to anatomical changes, contributing to more precise and effective cancer treatments. Future work should focus on refining models for anatomically complex structures and validating these methods in diverse clinical settings.
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  • Original Article 2023-09-30

    Influence of Two-Dimensional and Three-Dimensional Acquisitions of Radiomic Features for Prediction Accuracy

    Ryohei Fukui , Ryutarou Matsuura , Katsuhiro Kida , Sachiko Goto

    Progress in Medical Physics 2023; 34(3): 23-32

    https://doi.org/10.14316/pmp.2023.34.3.23
    Abstract
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    Purpose: In radiomics analysis, to evaluate features, and predict genetic characteristics and survival time, the pixel values of lesions depicted in computed tomography (CT) and magnetic resonance imaging (MRI) images are used. CT and MRI offer three-dimensional images, thus producing three-dimensional features (Features_3d) as output. However, in reports, the superiority between Features_3d and two-dimensional features (Features_2d) is distinct. In this study, we aimed to investigate whether a difference exists in the prediction accuracy of radiomics analysis of lung cancer using Features_2d and Features_3d.
    Methods: A total of 38 cases of large cell carcinoma (LCC) and 40 cases of squamous cell carcinoma (SCC) were selected for this study. Two- and three-dimensional lesion segmentations were performed. A total of 774 features were obtained. Using least absolute shrinkage and selection operator regression, seven Features_2d and six Features_3d were obtained.
    Results: Linear discriminant analysis revealed that the sensitivities of Features_2d and Features_3d to LCC were 86.8% and 89.5%, respectively. The coefficients of determination through multiple regression analysis and the areas under the receiver operating characteristic curve (AUC) were 0.68 and 0.70 and 0.93 and 0.94, respectively. The P-value of the estimated AUC was 0.87.
    Conclusions: No difference was found in the prediction accuracy for LCC and SCC between Features_2d and Features_3d.

  • Original Article 2023-09-30

    Initial Dosimetry of a Prototype Ultra-High Dose Rate Electron-Beam Irradiator for FLASH RT Preclinical Studies

    Hyun Kim , Heuijin Lim , Sang Koo Kang , Sang Jin Lee , Tae Woo Kang , Seung Wook Kim , Wung-Hoa Park , Manwoo Lee , Kyoung Won Jang , Dong Hyeok Jeong

    Progress in Medical Physics 2023; 34(3): 33-39

    https://doi.org/10.14316/pmp.2023.34.3.33
    Abstract
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    Purpose: FLASH radiotherapy (RT) using ultra-high dose rate (>40 Gy/s) radiation is being studied worldwide. However, experimental studies such as preclinical studies using small animals are difficult to perform due to the limited availability of irradiation devices and methods for generating a FLASH beam. In this paper, we report the initial dosimetry results of a prototype electron linear accelerator (LINAC)-based irradiation system to perform ultra-high dose rate (UHDR) preclinical experiments.
    Methods: The present study used the prototype electron LINAC developed by the Research Center of Dongnam Institute of Radiological and Medical Sciences (DIRAMS) in Korea. We investigated the beam current dependence of the depth dose to determine the optimal beam current for preclinical experiments. The dose rate in the UHDR region was measured by film dosimetry.
    Results: Depth dose measurements showed that the optimal beam current for preclinical experiments was approximately 33 mA, corresponding to a mean energy of 4.4 MeV. Additionally, the average dose rates of 80.4 Gy/s and 162.0 Gy/s at a source-to-phantom surface distance of 30 cm were obtained at pulse repetition frequencies of 100 Hz and 200 Hz, respectively. The dose per pulse and instantaneous dose rate were estimated to be approximately 0.80 Gy and 3.8×105 Gy/s, respectively.
    Conclusions: Film dosimetry verified the appropriate dose rates to perform FLASH RT preclinical studies using the developed electron-beam irradiator. However, further research on the development of innovative beam monitoring systems and stabilization of the accelerator beam is required.

  • Technical Note 2023-03-31

    Clinical Impact of Patient’s Head Position in Supraclavicular Irradiation of the Whole Breast Radiotherapy

    Surega Anbumani , Lohith G. Reddy , Priyadarshini V , Sasikala P , Ramesh S. Bilimagga

    Progress in Medical Physics 2023; 34(1): 10-13

    https://doi.org/10.14316/pmp.2023.34.1.10
    Abstract
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    Patients with breast cancer can be positioned with their head turned to the contra lateral side or with their head straight during the radiation therapy treatment set-up. In our hospital, patients with locally advanced breast cancer who were receiving radiation therapy have experienced swallowing difficulty after 2 weeks of irradiation. In this pilot study, the impact of head position on reducing dysphagia occurrence was dosimetrically evaluated. Patients were divided into two groups viz., HT (head turned to the contra lateral side of the breast) and HS (head straight) with 10 members in each. Treatment planning was performed, and the dosimetric parameters such as Dmin, Dmax, Dmean, V5, V10, V20, V30, V40, and V50 of both groups were extracted from the dose volume histogram (DVH) of esophagus. The target coverage in the supraclavicular fossa (SCF) region was analyzed using D95 and D98; moreover, the dose heterogeneity was assessed with D2 from the DVHs. The average values of the dose volume parameters were 27.6%, 58.6%, 35.4%, 19%, 13.8%, 14.1%, 11.8%, 8.4%, and 8.1% higher in the HT group compared with those in the HS group. Furthermore, for the SCF, the mean values of D98, D95, and D2 were 42.4, 47.5, and 54 Gy, respectively, in the HS group and 38.9, 45.35, and 55.5 Gy, respectively, in the HT group. This pilot study attempts to give a solution for the poor quality of life of patients after breast radiotherapy due to dysphagia. The findings confirm that the head position could play a significant role in alleviating esophageal toxicity without compromising tumor control.

  • Technical Note 2023-06-30

    Comparison between Old and New Versions of Electron Monte Carlo (eMC) Dose Calculation

    Seongmoon Jung1,2,3,4 , Jaeman Son1,2,3 , Hyeongmin Jin1,2,3 , Seonghee Kang1,2,3 , Jong Min Park1,2,3,5 , Jung-in Kim1,3,5 , Chang Heon Choi1,3,5

    Progress in Medical Physics 2023; 34(2): 15-22

    https://doi.org/10.14316/pmp.2023.34.2.15
    Abstract
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    This study compared the dose calculated using the electron Monte Carlo (eMC) dose calculation algorithm employing the old version (eMC V13.7) of the Varian Eclipse treatment-planning system (TPS) and its newer version (eMC V16.1). The eMC V16.1 was configured using the same beam data as the eMC V13.7. Beam data measured using the VitalBeam linear accelerator were implemented. A box-shaped water phantom (30×30×30 cm3) was generated in the TPS. Consequently, the TPS with eMC V13.7 and eMC V16.1 calculated the dose to the water phantom delivered by electron beams of various energies with a field size of 10×10 cm2. The calculations were repeated while changing the dose-smoothing levels and normalization method. Subsequently, the percentage depth dose and lateral profile of the dose distributions acquired by eMC V13.7 and eMC V16.1 were analyzed. In addition, the dose-volume histogram (DVH) differences between the two versions for the heterogeneous phantom with bone and lung inserted were compared. The doses calculated using eMC V16.1 were similar to those calculated using eMC V13.7 for the homogenous phantoms. However, a DVH difference was observed in the heterogeneous phantom, particularly in the bone material. The dose distribution calculated using eMC V16.1 was comparable to that of eMC V13.7 in the case of homogenous phantoms. The version changes resulted in a different DVH for the heterogeneous phantoms. However, further investigations to assess the DVH differences in patients and experimental validations for eMC V16.1, particularly for heterogeneous geometry, are required.

  • Original Article 2023-03-31

    Feasibility of a Linear Diode Array Detector for Commissioning of a Radiotherapy Planning System

    Seung Mo Hong , Uiseob Lee , Sung-woo Kim , Youngmoon Goh , Min-Jae Park , Chiyoung Jeong , Jungwon Kwak , Byungchul Cho

    Progress in Medical Physics 2023; 34(1): 1-9

    https://doi.org/10.14316/pmp.2023.34.1.1
    Abstract
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    Purpose: Although ionization chambers are widely used to measure beam commissioning data, point-by-point measurements of all the profiles with various field size and depths are timeconsuming tasks. As an alternative, we investigated the feasibility of a linear diode array for commissioning a treatment planning system.
    Methods: The beam data of a Varian TrueBeam® radiotherapy system at 6 and 10 MV with/without a flattening filter were measured for commissioning of an Eclipse Analytical Anisotropic Algorithm (AAA) ver.15.6. All of the necessary beam data were measured using an IBA CC13 ionization chamber and validated against Varian “Golden Beam” data. After validation, the measured CC13 profiles were used for commissioning the Eclipse AAA (AAACC13). In addition, an IBA LDA-99SC linear diode array detector was used to measure all of the beam profiles and for commissioning a separate model (AAALDA99). Finally, the AAACC13 and AAALDA99 dose calculations for each of the 10 clinical plans were compared.
    Results: The agreement of the CC13 profiles with the Varian Golden Beam data was confirmed within 1% except in the penumbral region, where ≤2% of a discrepancy related to machinespecific jaw calibration was observed. Since the volume was larger for the CC13 chamber than for the LDA-99SC chamber, the penumbra widths were larger in the CC13 profiles, resulting in ≤5% differences. However, after beam modeling, the penumbral widths agreed within 0.1 mm. Finally the AAALDA99 and AAACC13 dose distributions agreed within 1% for all voxels inside the body for the 10 clinical plans.
    Conclusions: In conclusion, the LDA-99SC diode array detector was found to be accurate and efficient for measuring photon beam profiles to commission treatment planning systems.

  • Review Article 2024-03-31

    Impact of Planning Target Volume Margins in Stereotactic Radiosurgery for Brain Metastasis: A Review

    Emmanuel Fiagbedzi1,2 , Francis Hasford1 , Samuel Nii Tagoe1

    Progress in Medical Physics 2024; 35(1): 1-9

    https://doi.org/10.14316/pmp.2024.35.1.1
    Abstract
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    Margin inclusion or exclusion remains the most critical and controversial aspect of stereotactic radiosurgery (SRS) for metastatic brain tumors. This review aimed to examine the available literature on the impact of margins in SRS of brain metastasis and to assess the response of some medical physicists on the use of these margins. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses method was used to review articles published in PubMed, Embase, and Science Direct databases from January 2012 to December 2022 using the following keywords: planning target volume, brain metastasis, margin, and stereotactic radiosurgery. A simple survey consisting of five questions was completed by ten medical physicists with experience in SRS treatment planning. The results were analyzed using IBM SPSS Statistics version 26.0. Of the 1,445 articles identified, only 38 articles were chosen. Of these, eight papers were deemed relevant to the focus of this review. These papers showed an increase in the risk of radionecrosis, whereas differences in local control were variable as the margin increased. In the survey, the response rate to whether or not to use margins in SRS, a critical question, was 50%. Margin addition increases the risk of radio necrosis. The local control rate varies among treatment modalities and cannot be generalized. From the survey, no consensus was reached regarding the use of these margins. This calls for further deliberations among professionals directly involved in SRS.

  • Original Article 2023-12-31

    Dosimetric Comparison of Three-Dimensional Conformal, Intensity-Modulated Radiotherapy, Volumetric Modulated Arc Therapy, and Dynamic Conformal Arc Therapy Techniques in Prophylactic Cranial Irradiation

    Ismail Faruk Durmuş1 , Dursun Esitmez2 , Guner Ipek Arslan1 , Ayse Okumus1

    Progress in Medical Physics 2023; 34(4): 41-47

    https://doi.org/10.14316/pmp.2023.34.4.41
    Abstract
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    Purpose: This study aimed to dosimetrically compare the technique of three-dimensional conformal radiotherapy (3D CRT), which is a traditional prophylactic cranial irradiation method, and the intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques used in the last few decades with the dynamic conformal arc therapy (DCAT) technique.
    Methods: The 3D CRT, VMAT, IMRT, and DCAT plans were prepared with 25 Gy in 10 fractions in a Monaco planning system. The target volume and the critical organ doses were compared. A comparison of the body V2, V5, and V10 doses, monitor unit (MU), and beam on-time values was also performed.
    Results: In planned target volume of the brain (PTVBrain), the highest D99 dose value (P<0.001) and the most homogeneous (P =0.049) dose distribution according to the heterogeneity index were obtained using the VMAT technique. In contrast, the lowest values were obtained using the 3D CRT technique in the body V2, V5, and V10 doses. The MU values were the lowest when DCAT (P =0.001) was used. These values were 0.34% (P =0.256) lower with the 3D CRT technique, 66% (P =0.001) lower with IMRT, and 72% (P =0.001) lower with VMAT. The beam on-time values were the lowest with the 3D CRT planning (P<0.001), 3.8% (P =0.008) lower than DCAT, 65% (P =0.001) lower than VMAT planning, and 76% (P =0.001) lower than IMRT planning.
    Conclusions: Without sacrificing the homogeneous dose distribution and the critical organ doses in IMRTs, three to four times less treatment time, less low-dose volume, less leakage radiation, and less radiation scattering could be achieved when the DCAT technique is used similar to conventional methods. In short, DCAT, which is applicable in small target volumes, can also be successfully planned in large target volumes, such as the whole-brain.

  • Original Article 2024-03-31

    Evaluations of a Commercial CLEANBOLUS-WHITE for Clinical Application

    Geum Bong Yu1,2 , Jung-in Kim1,2 , Jaeman Son1,2

    Progress in Medical Physics 2024; 35(1): 10-15

    https://doi.org/10.14316/pmp.2024.35.1.10
    Abstract
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    Purpose: This study aimed to comprehensively investigate the diverse characteristics of a novel commercial bolus, CLEANBOLUS-WHITE (CBW), to ascertain its suitability for clinical application.
    Methods: The evaluation of CBW encompassed both physical and biological assessments. Physical parameters such as mass density and shore hardness were measured alongside analyses of element composition. Biological evaluations included assessments for skin irritation and cytotoxicity. Dosimetric properties were examined by calculating surface dose and beam quality using a treatment planning system (TPS). Additionally, doses were measured at maximum and reference depths, and the results were compared with those obtained using a solid water phantom. The effect of air gap on dose measurement was also investigated by comparing measured doses on the RANDO phantom, under the bolus, with doses calculated from the TPS.
    Results: Biological evaluation confirmed that CBW is non-cytotoxic, nonirritant, and non-sensitizing. The bolus exhibited a mass density of 1.02 g/cm3 and 14 shore 00. Dosimetric evaluations revealed that using the 0.5 cm CBW resulted in less than a 1% difference compared to using the solid water phantom. Furthermore, beam quality calculations in the TPS indicated increased surface dose with the bolus. The air gap effect on dose measurement was deemed negligible, with a difference of approximately 1% between calculated and measured doses, aligning with measurement uncertainty.
    Conclusions: CBW demonstrates outstanding properties for clinical utilization. The dosimetric evaluation underscores a strong agreement between calculated and measured doses, validating its reliability in both planning and clinical settings.

  • Review Article 2024-06-30

    Motion Management and Image-Guided Technique in Photon Radiation Therapy: A Review of an Advanced Technology

    Jin Jegal1,2 , Hyojun Park1,2 , Seonghee Kang1,2,3,4 , Chang Heon Choi1,2,3,4 , Jung-in Kim1,2,3,4

    Progress in Medical Physics 2024; 35(2): 21-35

    https://doi.org/10.14316/pmp.2024.35.2.21
    Abstract
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    Herein, we provide a concise review of the critical role of motion management in radiation therapy, with a focus on photon radiation therapy, real-time control of respiratory motion, and image-guided radiation therapy (IGRT) in lung stereotactic body radiation therapy (SBRT). The dynamic nature of human anatomy, particularly in regions prone to movement such as the thoracic and abdominal areas, poses significant challenges in accurately targeting tumors during radiation therapy. This review explores the implications of organ and tumor motion, emphasizing the necessity for precise treatment delivery. We assess the advancements in four-dimensional (4D) imaging techniques such as 4D computed tomography, which provide time-resolved images for enhanced treatment planning. The review highlights various motion management strategies, including motionencompassing methods, respiratory-gating, breath-hold techniques, and real-time tumor tracking, discussing their implementation and impact on treatment efficacy. The role of IGRT in lung SBRT is particularly emphasized, showcasing how real-time imaging and advanced targeting techniques enhance the precision of high-dose radiation delivery while minimizing exposure to surrounding healthy tissues. This comprehensive review aims to underscore the significance of integrating motion management in radiation therapy, highlighting its pivotal role in improving treatment accuracy, reducing toxicity, and ultimately enhancing patient outcomes in cancer care.

  • Original Article 2023-12-31

    Dosimetric Analysis of Lung Stereotactic Body Radiotherapy Using Halcyon Linear Accelerator

    Shinhaeng Cho1 , Ick Joon Cho1 , Yong Hyub Kim1 , Jea-Uk Jeong2 , Mee Sun Yoon2 , Taek-Keun Nam2 , Sung-Ja Ahn2 , Ju-Young Song2

    Progress in Medical Physics 2023; 34(4): 48-54

    https://doi.org/10.14316/pmp.2023.34.4.48
    Abstract
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    Purpose: In this study, the dosimetric characteristics of lung stereotactic body radiotherapy (SBRT) plans using the new Halcyon system were analyzed to assess its suitability.
    Methods: We compared the key dosimetric parameters calculated for the Halcyon SBRT plans with those of a conventional C-arm linear accelerator (LINAC) equipped with a high-definition multileaf collimator (HD-MLC)—Trilogy Tx. A total of 10 patients with non-small-cell lung cancer were selected, and all SBRT plans were generated using the RapidArc technique.
    Results: Trilogy Tx exhibited significant superiority over Halcyon in terms of target dose coverage (conformity index, homogeneity index, D0.1 cc, and D95%) and dose spillage (gradient). Trilogy Tx was more efficient than Halcyon in the lung SBRT beam delivery process in terms of the total number of monitor units, modulation factor, and beam-on time. However, it was feasible to achieve a dose distribution that met SBRT plan requirements using Halcyon, with no significant differences in satisfying organs at risk dose constraints between both plans.
    Conclusions: Results confirm that Halcyon is a viable alternative for performing lung SBRT in the absence of a LINAC equipped with HD-MLC. However, extra consideration should be taken in determining whether to use Halcyon when the planning target volume setting is enormous, as in the case of significant tumor motions.

  • Corrigendum 2023-03-31

    Corrigendum: Image Guided Radiation Therapy

    Ui-Jung Hwang1 , Byung Jun Min2 , Meyoung Kim3 , Ki-Hwan Kim1

    Progress in Medical Physics 2023; 34(1): 14-14

    https://doi.org/10.14316/pmp.2023.34.1.14
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  • Letter to the Editor 2024-03-31

    Formulation of a New En Score in the Proficiency Test

    Chul-Young Yi , In Jung Kim , Jong In Park , Yun Ho Kim , Young Min Seong

    Progress in Medical Physics 2024; 35(1): 16-19

    https://doi.org/10.14316/pmp.2024.35.1.16
    Abstract
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    A new En score of the proficiency test (PT) is formulated; it is applicable when a correlation exists between the reference and participant’s values. Based on the uncertainty propagation rule given in ISO/IEC Guide 98-3 (GUM:1995), the En score covering the correlation case is newly developed for the PT. The new En score will be applied in a future PT organized by the Korea Research Institute of Standards and Science (KRISS) dosimetry team. The new En score will enhance measurement traceability and contribute to improving the quality management system of participants in the KRISS PT by avoiding performance underestimation.

  • Original Article 2024-06-30

    Analysis of the Multi-Leaf Collimator Quality Assurance for the HalcyonTM Linear Accelerator

    Jin Jegal1,2 , Hyojun Park1,2 , Seonghee Kang1,2,3 , Jung-in Kim1,2,3,4 , Chang Heon Choi1,2,3,4

    Progress in Medical Physics 2024; 35(2): 45-51

    https://doi.org/10.14316/pmp.2024.35.2.45
    Abstract
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    Purpose: Accurate operation of the multi-leaf collimator (MLC), a key technology in intensity modulated radiation therapy (IMRT), is essential for safe and optimal radiation treatment. The HalcyonTM linear accelerator has a collimator with low leakage and radiation transmission, making it suitable for IMRT. The limitations of the existing HalcyonTM MLC quality assurance (QA) method were supplemented with a mathematical method, and the results were analyzed.
    Methods: Electric portal imaging device (EPID) images obtained by performing the MLC QA plan on the HalcyonTM was analyzed using Python. The picket fence tests were performed and compared using the maximum pixel value and mathematical methods. Dose rate, gantry speed, and leaf speed variation plan were performed for dose transmission comparison.
    Results: For the maximum pixel value, the minimum distance between leaf junctions was 13.86 mm, and the maximum was 16.06 mm. However, for the mathematical method, the minimum and maximum were 14.54 mm and 15.68 mm, respectively. This suggests that setting the peak value to the highest value may cause an error in interpretation due to the limitations of the pixels of the EPID image. Performing QA on the remaining items confirmed that the measured values were within 3% of tolerance.
    Conclusions: The presented analysis method applied to the MLC QA can derive more reasonable and valid values than existing methods, which will help with MLC monitoring by reducing errors in excessive interpretation.

  • Original Article 2024-06-30

    Dosimetric Evaluations of HyperArc and RapidArc in Stereotactic Radiosurgery for a Single Brain Metastasis

    So-Yeon Park , Noorie Choi , Na Young Jang

    Progress in Medical Physics 2024; 35(2): 36-44

    https://doi.org/10.14316/pmp.2024.35.2.36
    Abstract
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    Purpose: This study assessed and compared the dosimetric performance of HyperArc and RapidArc in stereotactic radiosurgery (SRS) for a single brain metastasis.
    Methods: Twenty patients with intracranial brain metastases, each presenting a distinct target volume, were retrospectively selected. Subsequently, volumetric modulated arc therapy (VMAT) plans were designed using RapidArc (VMATRA) and HyperArc (VMATHA) for each patient. For planning comparisons, dose-volumetric histogram (DVH) parameters for planning target volumes (PTVs) and normal brain regions were computed across all VMAT plans. Subsequently, their total monitor units (MUs), total beam-on times, and modulation complexity scores for the VMAT (MCSv) were compared. A statistical test was used to evaluate the dosimetric disparities in the DVH parameters, total MUs, total beam-on times, and MCSv between the VMATHA and VMATRA plans.
    Results: For the PT Vs, VMATHA presented a higher homogeneity index (HI) than VMATRA. Moreover, VMATHA p resented s ignificantly s maller g radient i ndex ( GI) v alues (P<0.001) than VMATRA. Thus, VMATHA demonstrated better performance in the DVH parameters for the PTV than VMATRA. For normal brain tissues, VMATHA p resented l ower v olume r eceiving 5 0% o f t he prescription dose and V2Gy to the normal brain tissues than VMATRA (P<0.0001). While the total MUs required for VMATHA was significantly higher than those for VMATRA, the total beam-on time for VMATHA was superior to that for VMATRA.
    Conclusions: Thus, VMATHA exhibited superior performance in achieving rapid dose fall-offs (as indicated by the GI) and a higher HI at the PTV compared to VMATRA in brain SRS. This advancement positions HyperArc as a significant development in the field of radiation therapy, offering optimized treatment outcomes for brain SRS.

  • Original Article 2024-09-30

    Impact of Smaller Gantry Arc Increments on Volumetric Modulated Arc Radiation Therapy in the Monaco Treatment Planning System

    Seonghee Kang1,2,3 , Hyejo Ryu4 , Do Hoon Oh4 , Lee Yoo4 , Minsoo Chun2,4,5

    Progress in Medical Physics 2024; 35(3): 65-72

    https://doi.org/10.14316/pmp.2024.35.3.65
    Abstract
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    Purpose: This study aims to evaluate the impact of smaller gantry arc increment (GAI) values on the plan quality and deliverability of volumetric modulated arc therapy (VMAT) for head and neck (HN) and prostate cancer cases using the Monaco treatment planning system. The study investigates whether a smaller GAI can enhance organ at risk (OAR) sparing without compromising target coverage or significantly increasing plan complexity.
    Methods: VMAT plans were created for 20 patients (10 HN and 10 prostate cancer) using GAI values of 15° and 30°. Dose-volumetric parameters, such as conformity number, homogeneity and gradient indices, were assessed alongside plan complexity metrics like the modulation complexity score for VMAT (MCSv) and monitor unit (MU). Statistical significance was determined using the Wilcoxon signed-rank test.
    Results: For HN cases, a 15° increment significantly reduced the D0.03cc for the spinal cord and the Dmean for both parotid glands compared to a 30° increment, improving OAR sparing. However, no significant differences were observed in the OAR doses for prostate cases. The 15° increment resulted in higher plan complexity, reflected by a lower MCSv, but the MU difference was not significant.
    Conclusions: Smaller GAI values, such as 15°, can significantly reduce OAR doses in HN VMAT plans, offering potential clinical benefits despite increased plan complexity. However, no substantial advantages were observed in prostate cases. These findings suggest that smaller GAI values may be particularly beneficial for cases requiring high modulation.

  • Original Article 2024-09-30

    Development of a Flexible Eye Shield Phantom for Artifact-Free Computed Tomography Images

    Seonghee Kang1,2,3 , Chang Heon Choi1,2,3 , Jung-in Kim1,2,3 , Geum Bong Yu2,4 , Jin Dong Cho5

    Progress in Medical Physics 2024; 35(3): 59-64

    https://doi.org/10.14316/pmp.2024.35.3.59
    Abstract
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    Purpose: This study aimed to develop a flexible eye shield phantom to acquire artifact-free computed tomography (CT) images for electron beam radiotherapy.
    Methods: A flexible eye shield phantom for a newly designed eye shield was fabricated. Because of metal artifacts caused by an eye shield composed of high-density materials such as tungsten or lead, CT image acquisition is not appropriate for treatment planning because of inaccurate dose calculation and organ-at-risk delineation. To acquire artifact-free CT images, a mold of the same size as the outer dimension of the metallic eye shield was manufactured using 3D printing. The flexible eye shield phantom was imaged using a Philips Brilliance CT Big Bore under the same condition as the measurement. The phantom image with an average of 200 Hounsfield unit (HU) was imported into the treatment planning systems (TPS) and assigned a value of 26,750 HU to consider the material density of tungsten. The dosimetric comparison using a 6-MeV electron beam was performed. Measurement was performed using a metal oxide semiconductor field effect transistor detector for point doses at 3 and 10 mm.
    Results: The artifact-free CT images using a flexible eye shield phantom without air bubbles were transferred into the TPS. The dose at 10 mm calculated using the TPS agreed with the ionchamber measurements within 2 cGy. Conversely, a larger dose discrepancy between the measured and calculated doses was found at 3 mm depth.
    Conclusions: The flexible eye shield phantom was successfully fabricated to apply electron treatment planning by acquiring artifact-free CT images. The dose calculated using the artifact-free image was comparable to the measured dose at lens depth when applying an eye shield.

  • Original Article 2024-06-30

    Simulating the Effect of Junction Setup Error in Dual-Isocentric Volumetric Modulated Arc Therapy for Pelvic Radiotherapy with a Large Target

    Hojeong Lee1 , Dong Woon Kim1 , Ji Hyeon Joo1,2 , Yongkan Ki1,2 , Wontaek Kim2,3 , Dahl Park3 , Jiho Nam3 , Dong Hyeon Kim2,3 , Hosang Jeon1

    Progress in Medical Physics 2024; 35(2): 52-57

    https://doi.org/10.14316/pmp.2024.35.2.52
    Abstract
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    Purpose: The use of two adjacent radiation beams to treat a lesion that is larger than the maximum field of a machine may lead to higher or lower dose distribution at the junction than expected. Therefore, evaluation of the junction dose is crucial for radiotherapy. Volumetric modulated arc therapy (VMAT) can effectively protect surrounding normal tissues by implementing a complex dose distribution; therefore, two adjacent VMAT fields can effectively treat large lesions. However, VMAT can lead to significant errors in the junction dose between fields if setup errors occur due to its highly complex dose distributions.
    Methods: In this study, setup errors of ±1, ±3, and ±5 mm were assumed during radiotherapy for treating large lesions in the lower abdomen, and their effects on the treatment dose distribution and target coverage were analyzed using gamma pass rate (GP) and homogeneity index (HI). All studies were performed using a computational simulation method based on our radiation treatment planning software.
    Results: Consequently, when the setup error was more than ±3 mm, most GP values using a 3%/3-mm criterion decreased by <90%. GP was independent of the direction of the field gap (FG), whereas HI values were relatively more affected by negative values for FG.
    Conclusions: Therefore, the size and direction of setup errors should be carefully managed when performing dual-isocentric VMATs for large targets.

  • Original Article 2024-12-31

    Evaluation of Radioactivity in Therapeutic Radiopharmaceutical Waste

    Jung Ju Jo1,2 , Su Hyoung Lee3 , Beom Hoon Ki3 , Ho Jin Ryu3 , Tae Hwan Kim4 , Gi Sub Kim3 , Sang Kyu Lee5 , Dong Wook Kim6 , Kum Bae Kim1,2 , Sangrok Kim3 , Sang Hyoun Choi1,2

    Progress in Medical Physics 2024; 35(4): 163-171

    https://doi.org/10.14316/pmp.2024.35.4.163
    Abstract
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    Purpose: This study aims to systematically analyze the radioactive waste generated from treatments using radioactive Iodine-131 (I-131), Lutetium-177 (Lu-177), and Actinium-225 (Ac-225) to facilitate safe waste management practices.
    Methods: I-131 is primarily used in thyroid cancer treatment, while Lu-177 and Ac-225 are used to treat prostate cancer. Radioactive waste generated after these treatments was collected from patients at the Korea Cancer Center Hospital and categorized into clothing, slippers, syringes, and other items. The radioactivity concentration of each item was measured using a calibrated high-purity germanium detector. Using measurements, the self-disposal date of each waste item was calculated according to the permissible disposal levels defined by the Nuclear Safety and Security Commission (NSSC) under domestic nuclear safety regulations.
    Results: For the I-131 radioactive waste, clothing, towels, and tableware exhibited high radioactivity concentrations, with most items exceeding the permissible self-disposal levels. Conversely, the type and quantity of waste generated from Lu-177 and Ac-225 that were intravenously injected were relatively minimal, with certain items below the self-disposal thresholds, enabling immediate disposal. For Ac-225, no permissible self-disposal concentration is specified by the NSSC, unlike other therapeutic nuclides. Hence, additional studies are required to establish clear guidelines.
    Conclusions: These findings provide valuable data for optimizing radioactive waste management, potentially reducing disposal time and costs, minimizing radiation exposure, and enhancing hospital safety practices.

  • Original Article 2024-12-31

    Optimizing DICOM File Processing: A Comprehensive Workflow for AI and 3D Printing in Medicine

    Dong Hyeok Choi1,2,3 , Jin Sung Kim1,2,3 , So Hyun Ahn4,5,6

    Progress in Medical Physics 2024; 35(4): 106-115

    https://doi.org/10.14316/pmp.2024.35.4.106
    Abstract
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    Purpose: This study aims to develop a comprehensive preprocessing workflow for Digital Imaging and Communications in Medicine (DICOM) files to facilitate their effective use in AI-driven medical applications. With the increasing utilization of DICOM data for AI learning, analysis, Metaverse platform integration, and 3D printing of anatomical structures, the need for streamlined preprocessing is essential. The workflow is designed to optimize DICOM files for diverse applications, improving their usability and accessibility for advanced medical technologies.
    Methods: The proposed workflow employs a systematic approach to preprocess DICOM files for AI applications, focusing on noise reduction, normalization, segmentation, and conversion to 3D-renderable formats. These steps are integrated into a unified process to address challenges such as data variability, format incompatibilities, and high computational demands. The study incorporates real-world medical imaging datasets to evaluate the workflow’s effectiveness and adaptability for AI analysis and 3D visualization. Additionally, the workflow’s compatibility with virtual environments, such as Metaverse platforms, is assessed to ensure seamless integration.
    Results: The implementation of the workflow demonstrated significant improvements in the preprocessing of DICOM files. The processed files were optimized for AI analysis, yielding enhanced model performance and accuracy in learning tasks. Furthermore, the workflow enabled the successful conversion of DICOM data into 3D-printable formats and virtual environments, supporting applications like anatomical visualization and simulation. The study highlights the workflow's ability to reduce preprocessing time and errors, making advanced medical imaging technologies more accessible.
    Conclusions: This study emphasizes the critical role of effective preprocessing in maximizing the potential of DICOM data for AI-driven applications and innovative medical solutions. The proposed workflow simplifies the preprocessing of DICOM files, facilitating their integration into AI models, Metaverse platforms, and 3D printing processes. By enhancing usability and accessibility, the workflow fosters broader adoption of advanced imaging technologies in the medical field.

  • Original Article 2024-12-31

    Institution-Specific Autosegmentation for Personalized Radiotherapy Protocols

    Wonyoung Cho1 , Gyu Sang Yoo2 , Won Dong Kim2 , Yerim Kim1 , Jin Sung Kim1,3 , Byung Jun Min2

    Progress in Medical Physics 2024; 35(4): 205-213

    https://doi.org/10.14316/pmp.2024.35.4.205
    Abstract
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    Purpose: This study explores the potential of artificial intelligence (AI) in optimizing radiotherapy protocols for personalized cancer treatment. Specifically, it investigates the role of AI-based segmentation tools in improving accuracy and efficiency across various anatomical regions.
    Methods: A dataset of 500 anonymized patient computed tomography scans from Chungbuk National University Hospital was used to develop and validate AI models for segmenting organs-atrisk. The models were tailored for five anatomical regions: head and neck, chest, abdomen, breast, and pelvis. Performance was evaluated using Dice Similarity Coefficient (DSC), Mean Surface Distance, and the 95th Percentile Hausdorff Distance (HD95).
    Results: The AI models achieved high segmentation accuracy for large, well-defined structures such as the brain, lungs, and liver, with DSC values exceeding 0.95 in many cases. However, challenges were observed for smaller or complex structures, including the optic chiasm and rectum, with instances of segmentation failure and infinity values for HD95. These findings highlight the variability in performance depending on anatomical complexity and structure size.
    Conclusions: AI-based segmentation tools demonstrate significant potential to streamline radiotherapy workflows, reduce inter-observer variability, and enhance treatment accuracy. Despite challenges with smaller structures, the integration of AI enables dynamic, patient-specific adaptations to anatomical changes, contributing to more precise and effective cancer treatments. Future work should focus on refining models for anatomically complex structures and validating these methods in diverse clinical settings.

  • Review Article 2024-12-31

    Principle, Development, and Application of Electrical Conductivity Mapping Using Magnetic Resonance Imaging

    Geon-Ho Jahng1 , Mun Bae Lee2 , Oh In Kwon2

    Progress in Medical Physics 2024; 35(4): 73-88

    https://doi.org/10.14316/pmp.2024.35.4.73
    Abstract
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    Magnetic resonance imaging (MRI)-related techniques can provide information related to the electrical properties of the body. Understanding the electrical properties of human tissues is crucial for developing diagnostic tools and therapeutic approaches for various medical conditions. This study reviewed the principles, development, and application of electrical conductivity mapping using MRI. To review the magnetic resonance electrical properties tomography (MREPT)-based conductivity mapping technique and its application to brain imaging, first, we explain the definition and fundamental principles of electrical conductivity, some factors that influence changes in ionic conductivity, and the background of mapping cellular conductivities. Second, we explain the concepts and applications of magnetic resonance electrical impedance tomography (MREIT) and MREPT. Third, we describe our recent technical developments and their clinical applications. Finally, we explain the benefits, impacts, and challenges of MRI-based conductivity in clinical practice. MRI techniques, such as MREIT and MREPT, enabled the measurement of conductivity-related properties within the body. MREIT assessed low-frequency conductivity by applying a low-frequency external current, whereas MREPT captured high-frequency conductivity (at the Larmor frequency) without applying an external current. In MREIT, the subject’s safety should be ensured because electrical current is applied, particularly around sensitive areas, such as the brain, or in subjects with implanted electronic devices. Our previous studies have highlighted the potential of conductivity indices as biomarkers for Alzheimer’s disease. MREPT is usually applied to humans rather than MREIT. MREPT holds promise as a noninvasive tool for characterizing tissue properties and understanding pathological conditions.

  • Original Article 2024-12-31

    Evaluation of the Dosimeter Volume Effect on Small-Field Dosimetry Using the Elekta Harmony Pro Linear Accelerator

    Hyojun Park1,2 , Jin Jegal1,2 , Yoonsuk Huh1,2 , Inbum Lee1,2 , Sung Hyun Lee1,2,3 , Chang Heon Choi1,2,3 , Jung-In Kim1,2,3 , Seonghee Kang1,2,3

    Progress in Medical Physics 2024; 35(4): 89-97

    https://doi.org/10.14316/pmp.2024.35.4.89
    Abstract
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    Purpose: This study investigated the dose perturbation according to the size of the sensitive volume in the dosimeter in small-field dosimetry.
    Methods: The dose profiles with different field sizes were measured using three different dosimeters: the CC13, Razor ion chamber, and Edge solid-state detector. Both the open and wedged beams with different field sizes were employed in the measurement. The profiles were measured in a water phantom at maximum dose depths of 5, 10, and 20 cm. The penumbra and width of the open-beam profiles were compared according to the types of the dosimeters and beam. The dose fall-off between the peak and 20% dose was evaluated for the wedged beam profiles.
    Results: In the open-beam measurement, the fall-off of the profile was steeper with the Edge detector, which has the smallest sensitive volume. Meanwhile, the dose in the out-of-field region was the smallest with the Edge detector. The widths of the penumbra were 6.10, 4.47, and 4.03 mm for the profile of the 3×3 cm2 field measured by the CC13 chamber, Razor chamber, and Edge detector, respectively. The width of the profile was not changed even if different dosimeters were used in the measurement. The wedged beam profiles showed more clear peaks at the field edge when a smaller dosimeter was used.
    Conclusions: The results demonstrate the necessity of dosimeters with a small sensitive volume for measuring a small-field beam or a steep dose gradient.

  • Original Article 2024-12-31

    Development of an Instantaneously Interpretable Real-Time Dosimeter System for Quality Assurance of a Medical Linear Accelerator

    Dongyeon Lee1,2 , Sung Jin Kim2 , Wonjoong Cheon3 , Hyosung Cho1 , Youngyih Han2,4

    Progress in Medical Physics 2024; 35(4): 178-204

    https://doi.org/10.14316/pmp.2024.35.4.178
    Abstract
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    Purpose: Modern radiotherapy delivers radiation doses to targets within a few minutes using intricate multiple-beam segments determined with multi-leaf collimators (MLC). Therefore, we propose a scintillator-based dosimetry system capable of assessing the dosimetric and mechanical performance of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) in real time.
    Methods: The dosimeter was equipped with a scintillator plate and two digital cameras. The dose distribution was generated by applying deep learning-based signal processing to correct the intrinsic characteristics of the camera sensor and a tomographic image reconstruction technique to rectify the geometric distortion of the recorded video. Dosimetric evaluations were performed using a gamma analysis against a two-dimensional array and radiochromic film measurements for 20 clinical cases. The average difference in the MLC position measurements and machine log files was tested for the applicability of the mechanical quality assurance (QA) of MLCs.
    Results: The agreement of the dose distribution in the IMRT and VMAT plans was clinically acceptable between the proposed system and conventional dosimeters. The average differences in the MLC positions for the IMRT/VMAT plans were 1.7010/2.8107 mm and 1.4722/2.7713 mm in banks A and B, respectively.
    Conclusions: In this study, we developed an instantaneously interpretable real-time dosimeter for QA in a medical linear accelerator using a scintillator plate and digital cameras. The feasibility of the proposed system was investigated using dosimetric and mechanical evaluations in the IMRT and VMAT plans. The developed system has clinically acceptable accuracy in both the dosimetric and mechanical QAs of the IMRT and VMAT plans.

  • Original Article 2024-12-31

    A Commissioning Report on the Magnetic Resonance-Compatible Geneva Brachytherapy Applicator

    Yoonsuk Huh1,2 , Hyojun Park1,2 , Jin Jegal1,2 , Inbum Lee1,2 , Jaeman Son1,2,3,4 , Seonghee Kang1,2,3 , Chang Heon Choi1,2,3 , Jung-in Kim1,2,3 , Hyeongmin Jin1,2,3,4

    Progress in Medical Physics 2024; 35(4): 116-124

    https://doi.org/10.14316/pmp.2024.35.4.116
    Abstract
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    Purpose: Brachytherapy is essential for treating gynecological cancers as it offers precise radiation delivery to tumors while minimizing radiation exposure to surrounding healthy tissues. The Geneva applicator, introduced in 2020 as a replacement for older models like the Utrecht applicator, enhances MRI-based brachytherapy with improved imaging capabilities and more accurate applicator placement. In 2021, updates to non-reimbursement policies in Korea for MRI-based 3D brachytherapy planning further promoted the adoption of advanced techniques such as the Geneva applicator. This study aims to commission the Geneva applicator, focusing on wall thickness, dummy marker positions, and source dwell positions to ensure accurate dose delivery and safety.
    Methods: The commissioning process involved measuring wall thickness in both the longitudinal and transverse directions for the tandem and lunar-shaped ovoid tubes and comparing these measurements with the manufacturer’s specifications. Dummy marker positions were verified using CT imaging, with a focus on alignment tolerances of ±1 mm. Source dwell positions were planned using the Oncentra treatment planning system, with measurements taken using EBT4 film and analyzed with RIT software.
    Results: Wall thickness measurements and dummy marker positions were within the specified tolerance ranges, confirming their accuracy. The source dwell positions, measured and analyzed through multiple tests, were all within the ±1 mm tolerance, ensuring the applicator’s reliability.
    Conclusions: The Geneva applicator met all standards for safe and effective use in brachytherapy. The use of a 3D-printed holder was crucial for precise alignment and measurement. With updated reimbursement policies in Korea for MRI-based brachytherapy, the Geneva applicator is expected to significantly impact the future of advanced brachytherapy treatments and research.

  • Original Article 2024-12-31

    Intra-Fractional Dose Evaluation for Patients with Breast Cancer Using Synthetic Computed Tomography

    Sohyun Ahn1,2 , So Eun Choi3 , Jeong-Heon Kim4,5,6 , Kwangwoo Park7 , Hai-Jeon Yoon8

    Progress in Medical Physics 2024; 35(4): 145-154

    https://doi.org/10.14316/pmp.2024.35.4.145
    Abstract
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    Purpose: This study investigated the use of synthetic computed tomography (CT) images derived from cone beam CT (CBCT) scans to analyze dose changes in breast cancer patients undergoing treatment and to evaluate the optimal timing for implementing adaptive radiotherapy.
    Methods: A retrospective analysis was conducted on five breast cancer patients treated with tomotherapy-based volumetric-modulated arc therapy at Yongin Severance Hospital. Each patient received 15 fractions, with doses of 320 centigray (cGy) to the high-dose planning target volume (PTV) and 267 cGy to the low-dose PTV. Planning CT images were acquired using the Aquilion scanner, and CBCT images were captured with the VersaHD linear accelerator’s on-board imager. These images were registered in RayStation using a hybrid deformable image registration method to generate synthetic CT images. Dose distributions were reanalyzed using the synthetic CT images, and dosevolume histogram parameters, including the dose to 95% of the volume (D95) and mean dose (Dmean) for the PTV, as well as D95, Dmean, the percentage of the volume receiving at least 5 Gy (V5) and 10 Gy (V10) for organs-at-risk (OARs), were extracted using MATLAB to assess dose changes during treatment.
    Results: For the original plans, the mean D95 for PTV high across all patients was 287.13±31.32 cGy, while for PTV low, it was 245.53±6.21 cGy. In contrast, the adaptive plans yielded a mean D95 of 298.17±12.37 cGy for PTV High and 247.25±4.23 cGy for PTV low. The ART Plan may lead to increased dose exposure in certain structures, such as the spinal cord, while providing targeted improvements in reducing radiation exposure in specific OARs (e.g., contralateral breast and esophagus).
    Conclusions: Synthetic CT images generated from CBCT scans provide a fast and efficient means of quantifying dose changes, supporting precise patient care through interfractional evaluation. Future studies will aim to apply this method to other organs and larger patient cohorts.

  • Original Article 2024-12-31

    Evaluation of Methods for Characterizing Kilovoltage Beam Quality from the Varian TrueBeam STx

    Inbum Lee1,2 , Yoonsuk Huh1,2 , Jin Jegal1,2 , Hyojun Park1,2 , Chang Heon Choi1,2,3 , Jung-in Kim1,2,3 , Seonghee Kang1,2,3

    Progress in Medical Physics 2024; 35(4): 98-105

    https://doi.org/10.14316/pmp.2024.35.4.98
    Abstract
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    Purpose: This study evaluated various methods for determining the half-value layer (HVL) of kilovoltage (kV) beams produced by the Varian TrueBeam STx on-board imager. By comparing these methods with the standard ionization chamber approach, the study aimed to identify practical solutions for HVL determination and dosimetric characterization of kV beams, particularly in resource-limited settings.
    Methods: HVLs for kV beams (40–140 kVp) were measured using an Exradin A12 ionization chamber and a Piranha MULTI meter. The ionization chamber measurements adhered to American Association of Physicists in Medicine Task Group 61 guidelines and served as the reference standard. Additionally, HVL values were calculated using two model-based approaches: SpekPy (a Python-based tool) and Monte Carlo (MC) simulations using Geant4 and GATE. The results from these methods were compared to assess consistency and reliability.
    Results: Deviations across all methods were generally below 4%. At 40 kV, the most significant discrepancies were attributed to lower signal levels from the ionization chamber. The consistency between the model-based methods and experimental measurements demonstrates the reliability of these alternative approaches for HVL determination.
    Conclusions: Although the ionization chamber remains the gold standard, the Piranha MULTI meter and model-based methods, i.e., SpekPy and MC simulations, have shown promise as viable alternatives, especially in resource-constrained settings. These in silico approaches also offer advantages in convenience and accuracy, supporting their potential for broader future applications.

  • Original Article 2024-12-31

    Dosimetric Comparison of Stereotactic Radiosurgery for Brain Metastases: Volumetric Modulated Arc Therapy vs. Dynamic Conformal Arc

    Youngkuk Kim1,2 , Sangwook Lim1,3 , Ji Hoon Choi1,3 , Kyung Ran Park1,3

    Progress in Medical Physics 2024; 35(4): 155-162

    https://doi.org/10.14316/pmp.2024.35.4.155
    Abstract
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    Purpose: This study aimed to compare the dose characteristics of the volumetric modulated arc therapy (VMAT) and dynamic conformal arc (DCA) techniques for metastatic brain tumor treatment using various indices to evaluate the quality of the plan and provide insights into the clinical implications of each approach.
    Methods: Twelve patients with single metastatic brain tumors treated with VMAT were retrospectively analyzed. For comparison with DCA, identical geometric parameters (excluding multileaf collimators) were applied. Dose coverage, normal tissue sparing, and treatment efficiency were evaluated using indices such as CILIM98, CIICRU, CIRTOG, QCRTOG, CISALT, HTCISALT, and CIPADDIC. These indices were statistically assessed to evaluate the differences between VMAT and DCA.
    Results: VMAT was superior to DCA in most indices for both small and large planning target volumes (PTVs). DCA plans for large PTVs showed a higher V12Gy, exceeding 10 mL and failing to meet the recommended criteria (<10 mL). However, DCA required nearly half the monitor units (MUs) of VMAT, resulting in shorter treatment times. All indices, except for QCRTOG, demonstrated significant differences between VMAT and DCA.
    Conclusions: Careful consideration is necessary for larger PTVs when deciding a plan because DCA can occasionally result in V12Gy of a brain minus PTV >10 mL. Conversely, DCA provides the advantage of shorter treatment times because of its lower MU. This study highlights the importance of using a combination of indices to comprehensively assess treatment plan quality.

  • Original Article 2024-12-31

    Development of a 3D-Printed Lithophane Breast Anthropomorphic Phantom for Dose Optimization in an Automatic Exposure Control System

    Hye-Jin Kim , Youl-Hun Seoung

    Progress in Medical Physics 2024; 35(4): 125-134

    https://doi.org/10.14316/pmp.2024.35.4.125
    Abstract
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    Purpose: This study aimed to develop a 3D-printed lithophane breast anthropomorphic phantom for optimizing the automatic exposure control (AEC) in a digital mammography system, thereby reducing radiation dose while maintaining high image quality.
    Methods: Craniocaudal breast radiograhic images from 72 patients, categorized as high-density and low-density by radiologists, were used to design the phantom. A digital lithophane technology was employed to create an anatomic breast plate, fabricated using a digital light processing 3D printer with resin. Polymenthylmethacrylate (PMMA) support thickness was adjusted incrementally until the exposure index and deviation index values approximated those of the American College of Radiology phantom. Phantom images were acquired across five AEC density levels (−6, −3, 0, 3, 6), and the optimal dose was determined as the lowest autoexposure mAs value with superior image quality. Two radiologists scored image quality on a 7-point Likert scale to identify the best configurations.
    Results: The optimal PMMA support thicknesses were determined as 3 cm for high-density and 4 cm for low-density breasts. The optimized AEC condition corresponded to the lowest density level (−6) with the least mAs value, maintaining excellent image quality. The use of the phantom resulted in a reduction of automatic exposure tube current by 39.4%–43.4% while producing images comparable to human breast radiographic images.
    Conclusions: The developed 3D-printed lithophane breast anthropomorphic phantom effectively optimized AEC settings, reducing radiation dose and maintaining high-quality breast radiographic images. This study has the potential to enhance safety and diagnostic efficacy in digital mammography.

  • Original Article 2024-12-31

    Clinical Applications of Thermoplastic Sheets as Patient-Specific Gonadal Shields During Computed Tomography Simulation

    Jin Jegal1,2 , Hyojun Park1,2 , Seonghee Kang1,2,3,4 , Chang Heon Choi1,2,3,4 , Jung-in Kim1,2,3,4

    Progress in Medical Physics 2024; 35(4): 172-177

    https://doi.org/10.14316/pmp.2024.35.4.172
    Abstract
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    Purpose: Conventional gonadal shields are manufactured in standardized sizes and shapes and do not conform to individual testicular contours, causing discomfort. We developed a novel patient-specific gonadal shield using thermoplastic sheets and tested its feasibility through dosimetric evaluations.
    Methods: During the computed tomography simulation, custom lead shields were fabricated using thermoplastic sheets that were molded to the testicular shape of the patient. The shielding efficacy was evaluated using optically stimulated luminescent dosimeters (OSLDs) for point dose measurements.
    Results: The thermoplastic sheet was molded to fit closely to the skin with a minimal air gap of approximately 8.4 cm³, providing comfort to the patient during treatment. The patient-specific shield effectively reduced the surface dose from 28 cGy to less than 15 cGy. By combining the OSLDs located in the same row and calculating the mean dose value, a shielding effect was achieved with a maximum dose reduction of 56.1%.
    Conclusions: Customized gonadal shields were successfully created using thermoplastic sheets to minimize patient discomfort during application. However, further improvements in lead shield fabrication are needed to ensure full conformity.

  • Original Article 2024-12-31

    Evaluating the Influence of Scan Timing on Dosimetric Accuracy in EBT3 and EBT4 Radiochromic Films

    Jin Dong Cho , Su Chul Han , Jason Joon Bock Lee , Hyebin Lee , Heerim Nam

    Progress in Medical Physics 2024; 35(4): 135-144

    https://doi.org/10.14316/pmp.2024.35.4.135
    Abstract
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    Purpose: This study compares the dosimetric properties of EBT3 and EBT4 GAFchromic films in transmission and reflection scanning modes, focusing on dose response, sensitivity, and postirradiation stability.
    Methods: The EBT3 and EBT4 films were irradiated at doses of 0–10 Gy using a Varian TrueBeam linear accelerator at 6 MV. The films were scanned at intervals between 1 and 336 hours after irradiation in both transmission and reflection modes. Net optical density (NetOD) values from each scan were used to evaluate dose response and sensitivity, with calibration curves created for each film and scan mode. Dose differences between calculated and delivered doses were assessed over time.
    Results: The EBT3 and EBT4 films exhibited similar dose–response curves and stable NetOD values across both scanning modes. However, EBT4 exhibited reduced sensitivity variability in response to dose changes. After irradiation, NetOD values increased up to 24 hours before stabilizing, suggesting that a 24-hour scan time is sufficient for consistent measurements. Dose differences between films and modes remained within ±4%.
    Conclusions: EBT4 offers comparable dosimetric performance to EBT3, with additional benefits, such as improved dose–response linearity and reduced sensitivity fluctuations. The findings indicate that EBT4 can serve as a reliable successor to EBT3.
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Korean Society of Medical Physics

Vol.35 No.4
December 2024

pISSN 2508-4445
eISSN 2508-4453
Formerly ISSN 1226-5829

Frequency: Quarterly

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Aims and Scope

Progress in Medical Physics (PMP) is an international publication dedicated to clinical medical physics. PMP covers all aspects of the application of radiation physics to biological sciences, radiotherapy, radiodiagnosis, nuclear medicine, dosimetry, radiation standards and radiation protection. PMP is a quarterly publication Korean Society of Medical Physicis (KSMP). PMP published the first issue in 20 October, 1990. PMP is published quarterly at the end of March, June, September and December, one volume per year.

The official title of the journal is “Progress in Medical Physics” and abbreviated title is “Prog. Med. Phys.”. Some, or all, of the articles in this journal are indexed in KCI, KoreaMed, Synapse, KoMCI, CrossRef, Google Scholar. The URL adress of the Journal is www.progmedphys.org where full text is available. For subscription of printed journals, please contact the office of the Korean Society of Medical Physics.

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