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Ex) Article Title, Author, Keywords

  • Review Article 2022-12-31

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

    Progress in Medical Physics 2022; 33(4): 37-52

    https://doi.org/10.14316/pmp.2022.33.4.37
    Abstract
    Over the past decades, radiation therapy combined with imaging modalities that ensure optimal image guidance has revolutionized cancer treatment. The two major purposes of using imaging modalities in radiotherapy are to clearly delineate the target prior to treatment and set up the patient during radiation delivery. Image guidance secures target position prior to and during the treatment. High quality images provide an accurate definition of the treatment target and the possibility to reduce the treatment margin of the target volume, further lowering radiation toxicity and improving the quality of life of cancer patients. In this review, the various types of image guidance modalities used in radiation therapy are distinguished into ionized (kilovoltage and megavoltage image) and nonionized imaging (magnetic resonance image, ultrasound, surface imaging, and radiofrequency). The functional aspects, advantages, and limitation of imaging using these modalities are described as a subsection of each category. This review only focuses on the technological viewpoint of these modalities and any clinical aspects are omitted. Image guidance is essential, and its importance is rapidly increasing in modern radiotherapy. The most important aspect of using image guidance in clinical settings is to monitor the performance of image quality, which must be checked during the periodic quality assurance process.
  • Review Article 2022-12-31

    Na Hye Kwon1,2 , Hye Sung Park3 , Taehwan Kim4,5 , Sang Rok Kim5 , Kum Bae Kim6,7 , Jin Sung Kim1,2,8 , Sang Hyoun Choi6,7 , Dong Wook Kim1,2

    Progress in Medical Physics 2022; 33(4): 53-62

    https://doi.org/10.14316/pmp.2022.33.4.53
    Abstract
    In this study, we have investigated the shielding evaluation methodology for facilities using kV energy generators. We have collected and analysis of safety evaluation criteria and methodology for overseas facilities using radiation generators. And we investigated the current status of shielding evaluation of domestic industrial radiation generators. According to the statistical data from the Radiation Safety Information System, as of 2022, a total of 7,679 organizations are using radiation generating devices. Among them, 6,299 facilities use these devices for industrial purposes, which accounts for a considerable portion of radiation. The organizations that use these devices evaluate whether the exposure dose for workers and frequent visitors is suitable as per the limit regulated by the Nuclear Safety Act. Moreover, during this process, the safety shields are evaluated at the facilities that use the radiation generating devices. However, the facilities that use radiating devices having energy less than or equal to 6 MV for industrial purposes are still mostly evaluated and analyzed according to the National Council on Radiation Protection and Measurements 49 (NCRP 49) report published in 1976. We have investigated the technical standards of safety management, including the maximum permissible dose and parameters assessment criteria for facilities using radiation generating devices, based on the NCRP 49 and the American National Standards Institute/Health Physics Society N.43.3 reports, which are the representative reports related to radiation shielding management cases overseas.
  • Original Article 2022-12-31

    Ryohei Fukui1 , Miho Numata2 , Saki Nishioka2 , Ryutarou Matsuura1 , Katsuhiro Kida1 , Sachiko Goto1

    Progress in Medical Physics 2022; 33(4): 63-71

    https://doi.org/10.14316/pmp.2022.33.4.63
    Abstract
    Purpose: To clarify the relationship between the diameter of the simulated bead and the Z-resolution of the tomosynthesis image.
    Methods: A simulated bead was placed on a 1,024×1,024×1,024-pixel base image. The diameters were set to 0.025, 0.05, 0.1, 0.2, 0.3, 0.7, 1.0, and 1.3 mm. A bead was placed at the center of the base image and projected at a simulated X-ray angle range of ±45° to obtain a projected image. A region of interest was placed at the center of the bead image and the slice sensitivity profile (SSP) was obtained by acquiring pixel values in the z-direction. The full width at half maximum of the SSP was defined as the Z-resolution and the frequency response was obtained by the 1-D Fourier transform of the SSP.
    Results: Z-resolution increased with increasing bead diameter. However, there was no change in Z-resolution between 0.025 and 0.1 mm. The frequency response was similar to that of the Z-resolution, with a significant difference between 0.1 and 0.2 mm diameter.
    Conclusions: Z-resolution is dependent on the diameter of the bead, which should be selected considering the pixel size of the tomosynthesis image.
  • Original Article 2022-12-31

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

    Progress in Medical Physics 2022; 33(4): 72-79

    https://doi.org/10.14316/pmp.2022.33.4.72
    Abstract
    Purpose: The proficiency test was conducted to assess the performance of the dosimetry audit service provider in the readout practice of the dose delivered to patients in medical institutions.
    Methods: A certain amount of the absorbed dose to water for the high-energy X-ray from the medical linear accelerator (LINAC) installed in the Korea Research Institute of Standards and Science (KRISS) was delivered to the postal dose audit package given by the dosimetry audit service provider, in which the radio-photoluminescence (RPL) glass dosimeters were mounted. The dosimetry audit service provider read the RPL glass dosimeters and sent the readout dose value with its uncertainty to KRISS. The performance of the dosimetry audit service provider was evaluated based on the En number given in ISO/IEC 17043:2010.
    Results: The evaluated En number was −0.954. Based on the ISO/IEC 17043, the performance of the dosimetry service provider is “satisfactory.”
    Conclusions: As part of the conformity assessment, the KRISS performed the proficiency test over the postal dose audit practice run by the dosimetry audit service provider. The proficiency test is in line with confirming the traceability of the medical institutions to the primary standard of absorbed dose to the water of the KRISS and ensuring the confidence of the dosimetry audit service provider.
  • Original Article 2022-12-31

    Seohyeon An1,2 , Sang-il Pak1 , Seonghoon Jeong1 , Soonki Min3 , Tae Jeong Kim2 , Dongho Shin1 , Youngkyung Lim1 , Jong Hwi Jeong1 , Haksoo Kim1 , Se Byeong Lee1

    Progress in Medical Physics 2022; 33(4): 80-87

    https://doi.org/10.14316/pmp.2022.33.4.80
    Abstract
    Purpose: Proton therapy has different relative biological effectiveness (RBE) compared with X-ray treatment, which is the standard in radiation therapy, and the fixed RBE value of 1.1 is widely used. However, RBE depends on a charged particle’s linear energy transfer (LET); therefore, measuring LET is important. We have developed a LET measurement method using the inefficiency characteristic of an EBT3 film on a proton beam’s Bragg peak (BP) region.
    Methods: A Gafchromic EBT3 film was used to measure the proton beam LET. It measured the dose at a 10-cm pristine BP proton beam in water to determine the quenching factor of the EBT3 film as a reference beam condition. Monte Carlo (MC) calculations of dose-averaged LET (LETd) were used to determine the quenching factor and validation. The dose-averaged LETs at the 12-, 16-, and 20-cm pristine BP proton beam in water were calculated with the quenching factor.
    Results: Using the passive scattering proton beam nozzle of the National Cancer Center in Korea, the LETd was measured for each beam range. The quenching factor was determined to be 26.15 with 0.3% uncertainty under the reference beam condition. The dose-averaged LETs were measured for each test beam condition.
    Conclusions: We developed a method for measuring the proton beam LET using an EBT3 film. This study showed that the magnitude of the quenching effect can be estimated using only one beam range, and the quenching factor determined under the reference condition can be applied to any therapeutic proton beam range.
  • Original Article 2022-12-31

    Chang Hyun Yoo1 , Junghwan Goh1 , Geon-Ho Jahng2

    Progress in Medical Physics 2022; 33(4): 88-100

    https://doi.org/10.14316/pmp.2022.33.4.88
    Abstract
    Purpose: Cerebral microbleeds are more susceptible than surrounding tissues and have been associated with a variety of neurological and neurodegenerative disorders that are indicative of an underlying vascular pathology. We investigated relaxivity changes and microvascular indices in the presence of microbleeds in an imaging voxel by evaluating those before and after contrast agent injection.
    Methods: Monte Carlo simulations were run with a variety of conditions, including different magnetic field strengths (B0), different echo times, and different contrast agents. ΔR2* and ΔR2 and microvascular indices were calculated with varying microvascular vessel sizes and microbleed loads.
    Results: As B0 and the concentration of microbleeds increased, ΔR2* and ΔR2 increased. ΔR2* increased, but ΔR2 decreased slightly as the vessel radius increased. When the vessel radius was increased, the vessel size index (VSI) and mean vessel diameter (mVD) increased, and all other microvascular indices except mean vessel density (Q) increased when the concentration of microbleeds was increased.
    Conclusions: Because patients with neurodegenerative diseases often have microbleeds in their brains and VSI and mVD increase with increasing microbleeds, microbleeds can be altered microvascular signals in a voxel in the brain of a neurodegenerative disease at 3T magnetic resonance imaging.
  • Original Article 2022-12-31

    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 2022; 33(4): 101-107

    https://doi.org/10.14316/pmp.2022.33.4.101
    Abstract
    Purpose: Radiotherapy after bladder filling protocol (BFP) is known to enhance treatment quality and reduce side effects in prostate cancer, a common male solid cancer globally. However, due to the need to hold back urine during treatment, patients frequently complain of discomfort, and treatment is frequently suspended when patients urinate during treatment and urine penetrates the treatment device, causing malfunction. Therefore, the effect of minimizing treatment time when partial-arc volumetric modulated arc therapy (VMAT) was used instead of full-arc was assessed in this study.
    Methods: A total of 70 plans were created in 10 patients using 7 different arc sizes, and the treatment time for each plan was calculated.
    Results: Reduced arc size by half resulted in a 54.4% decrease in mean treatment duration, with a proportional tendency observed. Furthermore, the effect of VMAT arc size reduction on target dose homogeneity was significantly limited, and the effect on surrounding organs at risk (OAR) was negligible. It should be noted, however, that when the arc size decreases by >40%, the dose increases in the area without OAR around the target.
    Conclusions: The results of this study demonstrated that partial-arc VMAT for enhancing treatment convenience and efficacy of prostate cancer patients undergoing BFP can achieve a considerable reduction in treatment time while preserving treatment quality, and it is expected to be useful for partial-arc VMAT plan design and implementation in practice.
  • Original Article 2022-12-31

    Sang-il Pak1 , Sungkoo Cho2 , Seohyeon An1,3 , Seonghoon Jeong1 , Dongho Shin1 , Youngkyung Lim1 , Jong Hwi Jeong1 , Haksoo Kim1 , Se Byeong Lee1

    Progress in Medical Physics 2022; 33(4): 108-113

    https://doi.org/10.14316/pmp.2022.33.4.108
    Abstract
    Purpose: Proton therapy has been used for optimal cancer treatment by adapting its Bragg-peak characteristics. Recently, a tissue-sparing effect was introduced in ultrahigh-dose-rate (FLASH) radiation; the high-energy transmission proton beam is considered in proton FLASH therapy. In measuring high-energy/ultrahigh-dose-rate proton beam, Faraday Cup is considered as a dose-rate- independent measurement device, which has been widely studied. In this paper, the feasibility of the simply designed Faraday Cup (Poor Man’s Faraday Cup, PMFC) for transmission proton FLASH therapy is investigated.
    Methods: In general, Faraday cups were used in the measurement of charged particles. The simply designed Faraday Cup and Advanced Markus ion chamber were used for high-energy proton beam measurement in this study.
    Results: The PMFC shows an acceptable performance, including accuracy in general dosimetric tests. The PMFC has a linear response to the dose and dose rate. The proton fluence was decreased with the increase of depth until the depth was near the proton beam range. Regarding secondary particles backscatter from PMFC, the effect was negligible.
    Conclusions: In this study, we performed an experiment to investigate the feasibility of PMFC for measuring high-energy proton beams. The PMFC can be used as a beam stopper and secondary monitoring system for transmission proton beam FLASH therapy.
  • Original Article 2022-12-31

    Abstract
    Purpose: Particle beam therapy is advantageous over photon therapy. However, adequately delivering therapeutic doses to tumors near critical organs is difficult. Nanoparticle-aided radiation therapy can be used to alleviate this problem, wherein nanoparticles can passively accumulate at higher concentrations in the tumor tissue compared to the surrounding normal tissue. In this study, we investigate the dose enhancement effect due to gold nanoparticle (GNP) when Carbon-12, He-4, and proton beams are irradiated on GNP.
    Methods: First, monoenergetic Carbon-12 and He-4 ion beams of energy of 283.33 MeV/u and 150 MeV/u, respectively, and a proton beam of energy of 150 MeV were irradiated on a water phantom of dimensions 30 cm×30 cm×30 cm. Subsequently, the secondary-particle information generated near the Bragg peak was recorded in a phase-space (phsp) file. Second, the obtained phsp file was scaled down to a nanometer scale to irradiate GNP of diameter 50 nm located at the center of a 4 µm×4 µm×4 µm water phantom. The dose enhancement ratio (DER) was calculated in intervals of 1 nm from the GNP surface.
    Results: The DER of GNP computed at 1 nm from the GNP surface was 4.70, 4.86, and 4.89 for Carbon-12, He-4, and proton beams, respectively; the DER decreased rapidly with increasing distance from the GNP surface.
    Conclusions: The results indicated that GNP can be used as radiosensitizers in particle beam therapy. Furthermore, the dose enhancement effect of the GNP absorbed by tumor cells can aid in delivering higher therapeutic doses.
  • Original Article 2022-12-31

    Chang Heon Choi1,2,3 , Jin Ho Kim1,3 , Jaeman Son1,2,3 , Jong Min Park1,2,3,4 , Jung-in Kim1,2,3

    Progress in Medical Physics 2022; 33(4): 121-128

    https://doi.org/10.14316/pmp.2022.33.4.121
    Abstract
    Purpose: T his s tudy e valuated t he q uality of plans based on magnetic resonance-guided radiotherapy (MRgRT) tri-Co-60, linac, and conventional linac-based volumetric modulated arc therapy (linac-VMAT) for prostate cancer.
    Methods: Twenty patients suffering from prostate cancer with intermediate risk who were treated by MAT were selected. Additional treatment plans (primary and boost plans) were generated based on MRgRT-tri-Co-60 and MRgRT-linac. The planning target volume (PTV) of MRgRT-based plans was created by adding a 3 mm margin from the clinical target volume (CTV) due to high soft-tissue contrast and real-time motion imaging. On the other hand, the PTV of conventional linac was generated based on a 1 cm margin from CTV. The targets of primary and boost plans were prostate plus seminal vesicle and prostate only, respectively. All plans were normalized to cover 95% of the target volume by 100% of the prescribed dose. Dosimetric characteristics were evaluated for each of the primary, boost, and sum plans.
    Results: For target coverage and conformity, the three plans showed similar results. In the sum plans, the average value of V65Gy of the rectum of MRgRT-linac (2.62%±2.21%) was smaller than those of MRgRT tri-Co-60 (9.04%±3.01%) and linac-VMAT (9.73%±7.14%) (P<0.001). In the case of bladder, the average value of V65Gy of MRgRT-linac was also smaller.
    Conclusions: In terms of organs at risk sparing, MRgRT-linac shows the best value while maintaining comparable target coverage among the three plans.
  • Original Article 2022-12-31

    Suah Yu1,2 , Na Hye Kwon3 , Young Jae Jang1 , Byungchae Lee4 , Jihyun Yu4 , Dong-Wook Kim3 , Gyu-Seok Cho1 , Kum-Bae Kim1 , Geun Beom Kim1 , Cheol Ha Baek2 , Sang Hyoun Choi1

    Progress in Medical Physics 2022; 33(4): 129-135

    https://doi.org/10.14316/pmp.2022.33.4.129
    Abstract
    Purpose: A full-energy-peak (FEP) efficiency correction is required through a Monte Carlo simulation for accurate radioactivity measurement, considering the geometrical characteristics of the detector and the sample. However, a relative deviation (RD) occurs between the measurement and calculation efficiencies when modeling using the data provided by the manufacturers due to the randomly generated dead layer. This study aims to optimize the structure of the detector by determining the dead layer thickness based on Monte Carlo simulation.
    Methods: The high-purity germanium (HPGe) detector used in this study was a coaxial p-type GC2518 model, and a certified reference material (CRM) was used to measure the FEP efficiency. Using the MC N-Particle Transport Code (MCNP) code, the FEP efficiency was calculated by increasing the thickness of the outer and inner dead layer in proportion to the thickness of the electrode.
    Results: As the thickness of the outer and inner dead layer increased by 0.1 mm and 0.1 µm, the efficiency difference decreased by 2.43% on average up to 1.0 mm and 1.0 µm and increased by 1.86% thereafter. Therefore, the structure of the detector was optimized by determining 1.0 mm and 1.0 µm as thickness of the dead layer.
    Conclusions: The effect of the dead layer on the FEP efficiency was evaluated, and an excellent agreement between the measured and calculated efficiencies was confirmed with RDs of less than 4%. It suggests that the optimized HPGe detector can be used to measure the accurate radioactivity using in dismantling and disposing medical linear accelerators.
  • Original Article 2022-12-31

    Hyung Jin Choun1 , Jung-in Kim2,3,4 , Jong Min Park2,3,4 , Jaeman Son2,3,4

    Progress in Medical Physics 2022; 33(4): 136-141

    https://doi.org/10.14316/pmp.2022.33.4.136
    Abstract
    Purpose: This study aimed to develop a breath control training system for breath-hold technique and respiratory-gated radiation therapy wherein the patients can learn breath-hold techniques in their convenient environment.
    Methods: The breath control training system comprises a sensor device and software. The sensor device uses a loadcell sensor and an adjustable strap around the chest to acquire respiratory signals. The device connects via Bluetooth to a computer where the software is installed. The software visualizes the respiratory signal in near real-time with a graph. The developed system can signal patients through visual (software), auditory (buzzer), and tactile (vibrator) stimulation when breath-holding starts. A motion phantom was used to test the basic functions of the developed breath control training system. The relative standard deviation of the maxima of the emulated free breathing data was calculated. Moreover, a relative standard deviation of a breath-holding region was calculated for the simulated breath-holding data.
    Results: The average force of the maxima was 487.71 N, and the relative standard deviation was 4.8%, while the average force of the breath hold region was 398.5 N, and the relative standard deviation was 1.8%. The data acquired through the sensor was consistent with the motion created by the motion phantom.
    Conclusions: We have developed a breath control training system comprising a sensor device and software that allow patients to learn breath-hold techniques in their convenient environment.
  • Original Article 2022-12-31

    Hyeongmin Jin1,2 , Hyun Joon An1 , Eui Kyu Chie1,2,3 , Jong Min Park1,2,3 , Jung-in Kim1,2

    Progress in Medical Physics 2022; 33(4): 142-149

    https://doi.org/10.14316/pmp.2022.33.4.142
    Abstract
    Purpose: This study seeks to compare the dosimetric parameters of the bulk electron density (ED) approach and synthetic computed tomography (CT) image in terms of position variation of the air cavity in magnetic resonance-guided radiotherapy (MRgRT) for patients with pancreatic cancer.
    Methods: This study included nine patients that previously received MRgRT and their simulation CT and magnetic resonance (MR) images were collected. Air cavities were manually delineated on simulation CT and MR images in the treatment planning system for each patient. The synthetic CT images were generated using the deep learning model trained in a prior study. Two more plans with identical beam parameters were recalculated with ED maps that were either manually overridden by the cavities or derived from the synthetic CT. Dose calculation accuracy was explored in terms of dose-volume histogram parameters and gamma analysis.
    Results: The D95% averages were 48.80 Gy, 48.50 Gy, and 48.23 Gy for the original, manually assigned, and synthetic CT-based dose distributions, respectively. The greatest deviation was observed for one patient, whose D95% to synthetic CT was 1.84 Gy higher than the original plan.
    Conclusions: The variation of the air cavity position in the gastrointestinal area affects the treatment dose calculation. Synthetic CT-based ED modification would be a significant option for shortening the time-consuming process and improving MRgRT treatment accuracy.
  • Original Article 2022-12-31

    Geum Bong Yu1 , Chang Heon Choi1,2,3 , Jung-in Kim1,2,3 , Jin Dong Cho1,2 , Euntaek Yoon4 , Hyung Jin Choun2,4 , Jihye Choi5,6 , Soyeon Kim5,6 , Yongsik Kim6 , Do Hoon Oh7 , Hwajung Lee7 , Lee Yoo7 , Minsoo Chun3,7

    Progress in Medical Physics 2022; 33(4): 150-157

    https://doi.org/10.14316/pmp.2022.33.4.150
    Abstract
    Purpose: Elekta synergy® was commissioned in the Seoul National University Veterinary Medical Teaching Hospital. Recently, Chung-Ang University Gwang Myeong Hospital commissioned Elekta Versa HDTM. The beam characteristics of both machines are similar because of the same AgilityTM MLC Model. We compared measured beam data calculated using the Elekta treatment planning system, Monaco®, for each institute.
    Methods: Beam of the commissioning Elekta linear accelerator were measured in two independent institutes. After installing the beam model based on the measured beam data into the Monaco®, Monte Carlo (MC) simulation data were generated, mimicking the beam data in a virtual water phantom. Measured beam data were compared with the calculated data, and their similarity was quantitatively evaluated by the gamma analysis.
    Results: We compared the percent depth dose (PDD) and off-axis profiles of 6 MV photon and 6 MeV electron beams with MC calculation. With a 3%/3 mm gamma criterion, the photon PDD and profiles showed 100% gamma passing rates except for one inplane profile at 10 cm depth from VMTH. Gamma analysis of the measured photon beam off-axis profiles between the two institutes showed 100% agreement. The electron beams also indicated 100% agreement in PDD distributions. However, the gamma passing rates of the off-axis profiles were 91%–100% with a 3%/3 mm gamma criterion.
    Conclusions: The beam and their comparison with MC calculation for each institute showed good performance. Although the measuring tools were orthogonal, no significant difference was found.
  • Original Article 2022-12-31

    Abstract
    Purpose: We subjected scanning electron microscopic (SEM) images of the active layer of EBT3 film to texture analysis to determine the dose-response curve.
    Methods: Uncoated Gafchromic EBT3 films were prepared for direct surface SEM scanning. Absorbed doses of 0–20 Gy were delivered to the film’s surface using a 6 MV TrueBeam STx photon beam. The film’s surface was scanned using a SEM under 100× and 3,000× magnification. Four textural features (Homogeneity, Correlation, Contrast, and Energy) were calculated based on the gray level co-occurrence matrix (GLCM) using the SEM images corresponding to each dose. We used R-square to evaluate the linear relationship between delivered doses and textural features of the film’s surface.
    Results: C orrelation r esulted i n h igher l inearity a nd d ose-response c urve s ensitivity t han Homogeneity, Contrast, or Energy. The R-square value was 0.964 for correlation using 3,000× magnified SEM images with 9-pixel offsets. Dose verification was used to determine the difference between the prescribed and measured doses for 0, 5, 10, 15, and 20 Gy as 0.09, 1.96, −2.29, 0.17, and 0.08 Gy, respectively.
    Conclusions: Texture analysis can be used to accurately convert microscopic structural changes to the EBT3 film’s surface into absorbed doses. Our proposed method is feasible and may improve the accuracy of film dosimetry used to protect patients from excess radiation exposure.
  • Technical Note 2022-12-31

    Tae Hwan Kim2,5 , Kum Bae Kim3 , Geun Beom Kim1 , Dong Wook Kim3 , Sang Rok Kim2 , Sang Hyoun Choi1

    Progress in Medical Physics 2022; 33(4): 164-171

    https://doi.org/10.14316/pmp.2022.33.4.164
    Abstract
    The number of facilities using radiation generators increases and related regulations are strengthened, the establishment of a shielding management and evaluation technology has become important. The characteristics of the radiation generator used in previous report differ from those of currently available high-frequency radiation generators. This study aimed to manufacture lead, iron, and concrete shielding materials for the re-verification of half-value layers, tenth-value layers, and attenuation curve. For a comparison of attenuation ratio, iron, lead, and concrete shields were manufactured in this study. The initial dose was measured without shielding materials, and doses measured under different types and thicknesses of shielding material were compared with the initial dose to calculate the transmission rate on 50–300 kVp X-ray. All the three shielding materials showed a tendency to require greater shielding thickness for higher energy. The attenuation graph showed an exponential shape as the thickness decreased and a straight line as the thickness increased. The difference between the measurement results and the previous study, except in extrapolated parts, may be due to the differences in the radiation generation characteristics between the generators used in the two studies. The attenuated graph measured in this study better reflects the characteristics of current radiation generators, which would be more effective for shield designing.
  • Technical Note 2022-12-31

    Se Hyung Lee1,2 , Bo-Wi Cheon3 , Chul Hee Min3 , Haegin Han1 , Chan Hyeong Kim1 , Min Cheol Han4 , Seonghoon Kim5

    Progress in Medical Physics 2022; 33(4): 172-179

    https://doi.org/10.14316/pmp.2022.33.4.172
    Abstract
    Recently, tetrahedral phantoms have been newly adopted as international standard mesh-type reference computational phantoms (MRCPs) by the International Commission on Radiological Protection, and a program has been developed to convert them to computational tomography images and DICOM-RT structure files for application of radiotherapy. Through this program, the use of the tetrahedral standard phantom has become available in clinical practice, but utilization has been difficult due to various library dependencies requiring a lot of time and effort for installation. To overcome this limitation, in this study a newly developed TET2DICOM-GUI, a TET2DICOM program based on a graphical user interface (GUI), was programmed using only the MATLAB language so that it can be used without additional library installation and configuration. The program runs in the same order as TET2DICOM and has been optimized to run on a personal computer in a GUI environment. A tetrahedron-based male international standard human phantom, MRCP-AM, was used to evaluate TET2DICOM-GUI. Conversion into a DICOM-RT dataset applicable in clinical practice in about one hour with a personal computer as a basis was confirmed. Also, the generated DICOM-RT dataset was confirmed to be effectively implemented in the radiotherapy planning system. The program developed in this study is expected to replace actual patient data in future studies.
  • Corrigendum 2022-12-31

    Jaeman Son1,2 , Seongmoon Jung1,2 , Jong Min Park1,2,3,4 , Chang Heon Choi1,2,3 , Jung-in Kim1,2,3

    Progress in Medical Physics 2022; 33(4): 180-180

    https://doi.org/10.14316/pmp.2022.33.4.180
  • Review Article 2021-03-31

    Abstract
    The evolution of X-ray computed tomography (CT) has been based on the discovery of X-rays, the inception of the Radon transform, and the development of X-ray digital data acquisition systems and computer technology. Unlike conventional X-ray imaging (general radiography), CT reconstructs cross-sectional anatomical images of the internal structures according to X-ray attenuation coefficients (approximate tissue density) for almost every region in the body. This article reviews the essential physical principles and technical aspects of the CT scanner, including several notable evolutions in CT technology that resulted in the emergence of helical, multidetector, cone beam, portable, dual-energy, and phase-contrast CT, in integrated imaging modalities, such as positron-emission-tomography一CT and single-photon-emission-computed-tomography一CT, and in clinical applications, including image acquisition parameters, CT angiography, image adjustment, versatile image visualizations, volumetric/surface rendering on a computer workstation, radiation treatment planning, and target localization in radiotherapy. The understanding of CT characteristics will provide more effective and accurate patient care in the fields of diagnostics and radiotherapy, and can lead to the improvement of image quality and the optimization of exposure doses.
  • Review Article 2021-06-30

    Young Kyung Lim , Dohyeon Kim

    Progress in Medical Physics 2021; 32(2): 25-39

    https://doi.org/10.14316/pmp.2021.32.2.25
    Abstract
    Brachytherapy, along with external beam radiation therapy (EBRT), is an essential and effective radiation treatment process. In brachytherapy, in contrast to EBRT, the radiation source is radioisotopes. Because these isotopes can be positioned inside or near the tumor, it is possible to protect other organs around the tumor while delivering an extremely high-dose of treatment to the tumor. Brachytherapy has a long history of more than 100 years. In the early 1900s, the radioisotopes used for brachytherapy were only radium or radon isotopes extracted from nature. Over time, however, various radioisotopes have been artificially produced. As radioisotopes have high radioactivity and miniature size, the application of brachytherapy has expanded to high-dose-rate brachytherapy. Recently, advanced treatment techniques used in EBRT, such as image guidance and intensity modulation techniques, have been applied to brachytherapy. Three-dimensional images, such as ultrasound, computed tomography, magnetic resonance imaging, and positron emission tomography are used for accurate delineation of treatment targets and normal organs. Intensity-modulated brachytherapy is anticipated to be performed in the near future, and it is anticipated that the treatment outcomes of applicable cancers will be greatly improved by this treatment’s excellent dose delivery characteristics.
  • Original Article 2021-12-31

    Sung Yeop Kim1 , Jaehyeon Park2,3 , Jae Won Park2,3 , Ji Woon Yea2,3 , Se An Oh2,3

    Progress in Medical Physics 2021; 32(4): 107-115

    https://doi.org/10.14316/pmp.2021.32.4.107
    Abstract
    Purpose: The purpose of this study was to compare the clinical quality assurance results of portal dosimetry using an electronic portal imaging device, a method that is extensively used for patientspecific quality assurance, and the newly released Mobius3D for intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT).
    Methods: This retrospective study includes data from 122 patients who underwent IMRT and VMAT on the Novalis Tx and VitalBeam linear accelerators between April and June 2020. We used a paired t-test to compare portal dosimetry using an electronic portal imaging device and the average gamma passing rates of MobiusFX using log files regenerated after patient treatment.
    Results: The average gamma passing rates of portal dosimetry (3%/3 mm) and MobiusFX (5%/3 mm) were 99.43%±1.02% and 99.32%±1.87% in V it alBeam and 97.53%±3.34% and 96.45%±13.94% in Novalis Tx, respectively. Comparison of the gamma passing rate results of portal dosimetry (3%/3 mm) and MobiusFX (5%/3 mm as per the manufacturer’s manual) does not show any statistically significant difference.
    Conclusions: Log file-based patient-specific quality assurance, including independent dose calculation, can be appropriately used in clinical practice as a second-check dosimetry, and it is considered comparable with primary quality assurance such as portal dosimetry.
  • Original Article 2021-09-30

    Gourav Kumar1 , Manindra Bhushan1 , Lalit Kumar1 , Vimal Kishore2 , Kothanda Raman1 , Pawan Kumar1 , Soumitra Barik1 , Sandeep Purohit1

    Progress in Medical Physics 2021; 32(3): 70-81

    https://doi.org/10.14316/pmp.2021.32.3.70
    Abstract
    Purpose: This study was designed to investigate the dosimetric difference between intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) in head and neck cancer (HNC). The study primarily focuses on low-dose spillage evaluation between these two techniques.
    Methods: This retrospective study involved 45 patients with HNC. The treatment plans were generated using the IMRT and VMAT techniques for all patients. Dosimetric comparisons were performed in terms of target coverage, organ-at-risk (OAR) sparing, and various parameters, including conformity index, uniformity index, homogeneity index, conformation number, low-dose volumes, and normal tissue integral dose (NTID).
    Results: No significant (P>0.05) difference in planning target volume coverage (D95%) was observed between IMRT and VMAT plans for supraglottic larynx, hard palate, and tongue cancers. A decrease in dose volumes ranging from 1 Gy to 30 Gy was observed for VMAT plans compared with those for IMRT plans, except for V1Gy and V30Gy for supraglottic larynx cancer and V1Gy for tongue cancer. Moreover, decreases (P<0.05) in NTID were observed for VMAT plans compared with that for IMRT plans in supraglottic larynx (4.50%), hard palate (12.80%), and tongue (7.76%) cancers. In contrast, a slight increase in monitor units for VMAT compared with those for IMRT in supraglottic larynx (0.46%), hard palate (2.54%), and tongue (7.56%) cancers.
    Conclusions: For advanced-stage HNC, both IMRT and VMAT offer satisfactory clinical plans. VMAT offers a conformal and homogeneous dose distribution with comparable OAR sparing and higher dose falloff outside the target volume than IMRT, which provides an edge to reduce the risk of secondary malignancies for HNC over IMRT.
  • Original Article 2021-12-31

    Abstract
    Purpose: The Halcyon radiotherapy platform at Groote Schuur Hospital was delivered with a factory-configured analytical anisotropic algorithm (AAA) beam model for dose calculation. In a recent system upgrade, the Acuros XB (AXB) algorithm was installed. Both algorithms adopt fundamentally different approaches to dose calculation. This study aimed to compare the dose distributions of cervical carcinoma RapidArc plans calculated using both algorithms.
    Methods: A total of 15 plans previously calculated using the AAA were retrieved and recalculated using the AXB algorithm. Comparisons were performed using the planning target volume (PTV) maximum (max) and minimum (min) doses, D95%, D98%, D50%, D2%, homogeneity index (HI), and conformity index (CI). The mean and max doses and D2% were compared for the bladder, bowel, and femoral heads.
    Results: The AAA calculated slightly higher targets, D98%, D95%, D50%, and CI, than the AXB algorithm (44.49 Gy vs. 44.32 Gy, P=0.129; 44.87 Gy vs. 44.70 Gy, P=0.089; 46.00 Gy vs. 45.98 Gy, P=0.154; and 0.51 vs. 0.50, P=0.200, respectively). For target min dose, D2%, max dose, and HI, the AAA scored lower than the AXB algorithm (41.24 Gy vs. 41.30 Gy, P=0.902; 47.34 Gy vs. 47.75 Gy, P<0.001; 48.62 Gy vs. 50.14 Gy, P<0.001; and 0.06 vs. 0.07, P=0.002, respectively). For bladder, bowel, and left and right femurs, the AAA calculated higher mean and max doses.
    Conclusions: Statistically significant differences were observed for PTV D2%, max dose, HI, and bowel max dose (P>0.05).
  • Original Article 2021-06-30

    Abstract
    Purpose: This study aimed to develop a surface-guided radiosurgery system customized for a neurosurgery clinic that could be used as an auxiliary system for improving the accuracy, monitoring the movements of patients while performing hypofractionated radiosurgery, and minimizing the geometric misses.
    Methods: RGB-D cameras were installed in the treatment room and a monitoring system was constructed to perform a three-dimensional (3D) scan of the body surface of the patient and to express it as a point cloud. This could be used to confirm the exact position of the body of the patient and monitor their movements during radiosurgery. The image from the system was matched with the computed tomography (CT) image, and the positional accuracy was compared and analyzed in relation to the existing system to evaluate the accuracy of the setup.
    Results: The user interface was configured to register the patient and display the setup image to position the setup location by matching the 3D points on the body of the patient with the CT image. The error rate for the position difference was within 1-mm distance (min, 一0.21 mm; max, 0.63 mm). Compared with the existing system, the differences were found to be as follows: x=0.08 mm, y=0.13 mm, and z=0.26 mm.
    Conclusions: We developed a surface-guided repositioning and monitoring system that can be customized and applied in a radiation surgery environment with an existing linear accelerator. It was confirmed that this system could be easily applied for accurate patient repositioning and inter-treatment motion monitoring.
  • Original Article 2021-03-31

    Hosang Jeon1 , Dong Woon Kim1 , Ji Hyeon Joo1 , Yongkan Ki2 , Wontaek Kim2 , Dahl Park3 , Jiho Nam3 , Dong Hyeon Kim3

    Progress in Medical Physics 2021; 32(1): 18-24

    https://doi.org/10.14316/pmp.2021.32.1.18
    Abstract
    Purpose: Kilovoltage computed tomography (kV-CT) is essential for radiation treatment planning. However, kV-CT images are significantly distorted by artifacts when a metallic prosthesis is present in the patient's body. Thus, the accuracies of target delineation and treatment dose calculation are inevitably lowered. We evaluated the accuracy of the calculated doses using an image restoration method with hybrid CT, which was introduced in our previous study.
    Methods: A cylindrical phantom containing four metals, namely, silver, copper, tin, and tungsten, was scanned using kV-CT and megavoltage CT to produce hybrid CT images. We created six verification plans for three head and neck patients on kV-CT and hybrid CT images of the phantom and calculated their doses. The actual doses were measured with film patches during beam delivery using tomotherapy. We used the gamma evaluation method to compare dose distribution between kV-CT and hybrid CT with three gamma criteria, namely, 3%/3 mm, 2%/2 mm, and 1%/1 mm.
    Results: The gamma pass rates decreased as the gamma criteria were strengthened, and the pass rate of hybrid CT was higher than that of kV-CT in all cases. When the 1%/1 mm criterion was used, the difference in gamma pass rates between them was up to 13%p.
    Conclusions: According to our findings, we expect that the use of hybrid CT can be a suitable approach to avoid the effect of severe metal artifacts on the accuracy of dose calculation and contouring.
  • Review Article 2022-06-30

    Nam Joong Jeon1 , Jung Min Cho2 , Jung-Keun Lee3

    Progress in Medical Physics 2022; 33(2): 11-24

    https://doi.org/10.14316/pmp.2022.33.2.11
    Abstract
    X-ray detection has widely been applied in medical diagnostics, security screening, nondestructive testing in the industry, etc. Medical X-ray imaging procedures require digital flat detectors operating with low doses to reduce radiation health risks. Recently, metal halide perovskites (MHPs) have shown great potential in high-performance X-ray detection because of their attractive properties, such as strong X-ray absorption, high mobility–lifetime product, tunable bandgap, lowtemperature fabrication, near-unity photoluminescence quantum yields, and fast photoresponse. In this paper, we review and introduce the development status of new perovskite X-ray detectors and imaging, which have emerged as a new promising high-sensitivity X-ray detection technology. We discuss the latest progress and future perspective of MHP-based X-ray detection in medical imaging. Finally, we compare the conventional detection methods with quantum-enhanced detection, pointing out the challenges and perspectives for future research directions toward perovskite-based X-ray applications.
  • Original Article 2021-12-31

    Kwon Hee Kim1,2 , Tae Seong Back2 , Eun Ji Chung2 , Tae Suk Suh1 , Wonmo Sung1

    Progress in Medical Physics 2021; 32(4): 116-121

    https://doi.org/10.14316/pmp.2021.32.4.116
    Abstract
    Purpose: To investigate the effects of dose rate on intensity-modulated radiation therapy (IMRT) quality assurance (QA).
    Methods: We performed gamma tests using portal dose image prediction and log files of a multileaf collimator. Thirty treatment plans were randomly selected for the IMRT QA plan, and three verification plans for each treatment plan were generated with different dose rates (200, 400, and 600 monitor units [MU]/min). These verification plans were delivered to an electronic portal imager attached to a Varian medical linear accelerator, which recorded and compared with the planned dose. Root-mean-square (RMS) error values of the log files were also compared.
    Results: With an increase in dose rate, the 2%/2-mm gamma passing rate decreased from 90.9% to 85.5%, indicating that a higher dose rate was associated with lower radiation delivery accuracy. Accordingly, the average RMS error value increased from 0.0170 to 0.0381 cm as dose rate increased. In contrast, the radiation delivery time reduced from 3.83 to 1.49 minutes as the dose rate increased from 200 to 600 MU/min.
    Conclusions: Our results indicated that radiation delivery accuracy was lower at higher dose rates; however, the accuracy was still clinically acceptable at dose rates of up to 600 MU/min.
  • Review Article 2021-12-31

    Sang Hyoun Choi1 , Dong Oh Shin2 , Jae-ik Shin3 , Na Hye Kwon3 , So Hyun Ahn3 , Dong Wook Kim3

    Progress in Medical Physics 2021; 32(4): 83-91

    https://doi.org/10.14316/pmp.2021.32.4.83
    Abstract
    Various types of high-precision radiotherapy, such as intensity-modulated radiation therapy (IMRT), tomotherapy (Tomo), and stereotactic body radiation therapy have been available since 1997. After being covered by insurance in 2015, the number of IMRT cases rapidly increased 18-fold from 2011 to 2018 in Korea. IMRT, which uses a high-beam irradiation monitor unit, requires higher shielding conditions than conventional radiation treatments. However, to date, research on the shielding of facilities using IMRT and the current understanding of its status are insufficient, and detailed safety regulation procedures have not been established. This study investigated the recommended criteria for the shielding evaluation of facilities using medical linear accelerators (LINACs), including 1) the current status of safety management regulations and systems in domestic and international facilities using medical LINACs and 2) the current status of the recommended standards for safety management in domestic and international facilities using medical LINACs. It is necessary to develop and introduce a safety management system for facilities using LINACs for clinical applications that is suitable for the domestic medical environment and corresponds to the safety management systems for LINACs used overseas.
  • Original Article 2021-12-31

    Abstract
    Purpose: T his s tudy a imed t o i nvestigate t he a ccuracy o f h ead s catter f actor ( Sc) by applying a developed multi-leaf collimator (MLC) scatter source model for an unflattened photon beam.
    Methods: Sets of Sc values were measured for various jaw-defined square and rectangular fields and MLC-defined square fields for developing dual-source model (DSM) and MLC scatter model. A 6 MV unflattened photon beam has been used. Measurements were performed using a 0.125 cm3 cylindrical ionization chamber and a mini phantom. Then, the parameters of both models have been optimized, and Sc has been calculated. The DSM and MLC scatter models have been verified by comparing the calculated values to the three Sc set measurement values of the jaw-defined field and the two Sc set measurement values of MLC-defined fields used in the existing modeling, respectively.
    Results: For jaw-defined fields, the calculated Sc using the DSM was consistent with the measured Sc value. This demonstrates that the DSM was properly optimized and modeled for the measured values. For the MLC-defined fields, the accuracy between the calculated and measured Sc values with the addition of the MLC scatter source appeared to be high, but the only use of the DSM resulted in a significantly bigger differences.
    Conclusions: Both the DSM and MLC models could also be applied to an unflattened beam. When considering scattered radiation from the MLC by adding an MLC scatter source model, it showed a higher degree of agreement with the actual measured Sc value than when using only DSM in the same way as in previous studies.
  • Original Article 2022-09-30

    Sougoumarane Dashnamoorthy1 , Karthick Rajamanickam1 , Ebenezar Jeyasingh2 , Vindhyavasini Prasad Pandey3 , Kathiresan Nachimuthu1 , Imtiaz Ahmed4 , Pitchaikannu Venkatraman5

    Progress in Medical Physics 2022; 33(3): 25-35

    https://doi.org/10.14316/pmp.2022.33.3.25
    Abstract
    Purpose: Planning for radiotherapy relies on implicit estimation of the probability of tumor control and the probability of complications in adjacent normal tissues for a given dose distribution.
    Methods: The aim of this pilot study was to reconstruct dose-volume histograms (DVHs) from text files generated by the Eclipse treatment planning system developed by Varian Medical Systems and to verify the integrity and accuracy of the dose statistics.
    Results: We further compared dose statistics for intensity-modulated radiotherapy of the head and neck between the Eclipse software and software developed in-house. The dose statistics data obtained from the Python software were consistent, with deviations from the Eclipse treatment planning system found to be within acceptable limits.
    Conclusions: The in-house software was able to provide indices of hotness and coldness for treatment planning and store statistical data generated by the software in Oracle databases. We believe the findings of this pilot study may lead to more accurate evaluations in planning for radiotherapy.
  • Original Article 2021-12-31

    Seonghee Kang1,2,3 , Chang Heon Choi1,2,3 , Jong Min Park1,2,3 , Jin-Beom Chung4 , Keun-Yong Eom4 , Jung-in Kim1,2,3

    Progress in Medical Physics 2021; 32(4): 153-158

    https://doi.org/10.14316/pmp.2021.32.4.153
    Abstract
    Purpose: This study evaluated the features of a pressure mapping system for patient motion monitoring in radiation therapy.
    Methods: The pressure mapping system includes an MS 9802 force sensing resistor (FSR) sensor with 2,304 force sensing nodes using 48 columns and 48 rows, controller, and control PC (personal computer). Radiation beam attenuation caused by pressure mapping sensor and signal perturbation by 6 and 10 mega voltage (MV) photon beam was evaluated. The maximum relative pressure value (mRPV), average relative pressure value (aRPV), the center of pressure (COP), and area of pressure distribution were obtained with/without radiation using the upper body of an anthropomorphic phantom for 30 minutes with 15 MV.
    Results: It was confirmed that the differences in attenuation induced by the FSR sensor for 6 and 10 MV photon beams were small. The differences in mRPV, aRPV, area of pressure distribution with/without radiation are about 0.6%, 1.2%, and 0.5%, respectively. The COP values with/without radiation were also similar.
    Conclusions: The characteristics of a pressure mapping system during radiation treatment were evaluated on the basis of attenuation and signal perturbation using radiation. The pressure distribution measured using the FSR sensor with little attenuation and signal perturbation by the MV photon beam would be helpful for patient motion monitoring.
  • Original Article 2021-12-31

    Seongmoon Jung1,2,3 , Bitbyeol Kim1 , Euntaek Yoon4 , Jung-in Kim1,2,3 , Jong Min Park1,2,3,4,5,6 , Chang Heon Choi1,2,3

    Progress in Medical Physics 2021; 32(4): 165-171

    https://doi.org/10.14316/pmp.2021.32.4.165
    Abstract
    Purpose: This study aimed to evaluate the effect of collimator width on effective atomic number (EAN), relative electron density (RED), and stopping power ratio (SPR) measured by dual-layer dual-energy computed tomography (DL-DECT).
    Methods: CIRS electron density calibration phantoms with two different arrangements of material plugs were scanned by DL-DECT with two different collimator widths. The first phantom included two dense bone plugs, while the second excluded dense bone plugs. The collimator widths selected were 64 mm×0.625 mm for wider collimators and 16 mm×0.625 mm for narrow collimators. The scanning parameters were 120 kVp, 0.33 second gantry rotation, 3 mm slice thickness, B reconstruction filter, and spectral level 4. An image analysis portal system provided by a computed tomography (CT) manufacturer was used to derive the EAN and RED of the phantoms from the combination of low energy and high energy CT images. The EAN and RED were compared between the images scanned using the two different collimation widths.
    Results: The CT images with the wider collimation width generated more severe artifacts, particularly with high-density material (i.e., dense bone). RED and EAN for tissues (excluding lung and bones) with the wider collimation width showed significant relative differences compared to the theoretical value (4.5% for RED and 20.6% for EAN), while those with the narrow collimation width were closer to the theoretical value of each material (2.2% for EAN and 2.3% for RED). Scanning with narrow collimation width increased the accuracy of SPR estimation even with highdensity bone plugs in the phantom.
    Conclusions: The effect of CT collimation width on EAN, RED, and SPR measured by DL-DECT was evaluated. In order to improve the accuracy of the measured EAN, RED, and SPR by DL-DECT, CT scanning should be performed using narrow collimation widths.
  • Original Article 2021-12-31

    Na Hye Kwon1 , Young Jae Jang2,4 , Jinsung Kim1 , Kum Bae Kim4 , Jaeryong Yoo3 , So Hyun Ahn1 , Dong Wook Kim1 , Sang Hyoun Choi4

    Progress in Medical Physics 2021; 32(4): 145-152

    https://doi.org/10.14316/pmp.2021.32.4.145
    Abstract
    Purpose: During the treatments of cancer patients with a linear accelerator (LINAC) using photon beams with energies ≥8 MV, the components inside the LINAC head get activated through the interaction of photonuclear reaction (γ, n) and neutron capture (n, γ). We used spectroscopy and measured the dose rate for the LINAC in operation after the treatment ended.
    Methods: We performed spectroscopy and dose rate measurements for three units of LINACs with a portable high-purity Germanium (HPGe) detector and a survey meter. The spectra were obtained after the beams were turned off. Spectroscopy was conducted for 3,600 seconds, and the dose rate was measured three times. We identified the radionuclides for each LINAC.
    Results: According to gamma spectroscopy results, most of the nuclides were short-lived radionuclides with half-lives of 100 days, except for 60Co, 65Zn, and 181W nuclides. The dose rate for three LINACs obtained immediately in front of the crosshair was in the range of 0.113 to 0.129 μSv/h. The maximum and minimum dose rates measured on weekends were 0.097 μSv/h and 0.092 μSv/h, respectively. Compared with the differences in weekday data, there was no significant difference between the data measured on Saturday and Sunday.
    Conclusions: Most of the detected radionuclides had half-lives <100 days, and the dose rate decreased rapidly. For equipment that primarily used energies ≤10 MV, when the equipment was transferred after at least 10 minutes after shutting it down, it is expected that there will be little effect on the workers’ exposure.
  • Original Article 2022-03-31

    Abstract
    Purpose: To evaluate the effective volume of the Korea Research Institute of Standards and Science free air chamber (KRISS FAC) L1 used for the primary standard device of the low-energy X-ray air kerma.
    Methods: The mechanical dimensions were measured using a 3-dimensional coordinate measuring machine (3-d CMM, Model UMM 500, Carl Zeiss). The diameter of the diaphragm was measured by a ring gauge calibrator (Model KRISS-DM1, KRISS). The elongation of the collector length due to electric field distortion was determined from the capacitance measurement of the KRISS FAC considering the result of the finite element method (FEM) analysis using the code QuickField v6.4.
    Results: The measured length of the collector was 15.8003±0.0014 mm with a 68% confidence level (k =1). The aperture diameter of the diaphragm was 10.0021±0.0002 mm (k =1). The mechanical measurement volume of the KRISS FAC L1 was 1.2415±0.0006 cm3 (k =1). The elongated length of the collector due to the electric field distortion was 0.170±0.021 mm. Considering the elongated length, the effective measurement volume of the KRISS FAC L1 was 1.2548±0.0019 cm3 (k =1).
    Conclusions: The effective volume of the KRISS FAC L1 was determined from the mechanically measured value by adding the elongated volume due to the electric field distortion in the FAC. The effective volume will replace the existing mechanically determined volume in establishing and maintaining the primary standard of the low-energy X-ray.
  • Original Article 2021-09-30

    Shu-Chin Yang1,2 , Su-Hua Lo3 , Li-Tsuen Shie1 , Sung-Wei Lee1 , Sheng-Yow Ho1,4,5

    Progress in Medical Physics 2021; 32(3): 59-69

    https://doi.org/10.14316/pmp.2021.32.3.59
    Abstract
    Purpose: The relationship between computed tomography (CT) number and electron density (ED) has been investigated in previous studies. However, the role of these measures for guiding cancer treatment remains unclear.
    Methods: The CT number was plotted against ED for different imaging protocols. The CT number was imported into ED tables for the Pinnacle treatment planning system (TPS) and was used to determine the effect on dose calculations. Conversion tables for radiation dose calculations were generated and subsequently monitored using a dosimeter to determine the effect of different CT scanning protocols and treatment sites. These tables were used to retrospectively recalculate the radiation therapy plans for 41 patients after an incorrect scanning protocol was inadvertently used. The gamma index was further used to assess the dose distribution, percentage dose difference (DD), and distance-to-agreement (DTA).
    Results: For densities <1.1 g/cm3, the standard deviation of the CT number was ±0.6% and the greatest variation was noted for brain protocol conditions. For densities >1.1 g/cm3, the standard deviation of the CT number was ±21.2% and the greatest variation occurred for the tube voltage and head and neck (H&N) protocol conditions. These findings suggest that the factors most affecting the CT number are the tube voltage and treatment site (brain and H&N). Gamma index analyses for the 41 retrospective clinical cases, as well as brain metastases and H&N tumors, showed gamma passing rates >90% and <90% for the passing criterion of 2%/2 and 1%/1 mm, respectively.
    Conclusions: The CT protocol should be carefully decided for TPS. The correct protocol should be used for the corresponding TPS based on the treatment site because this especially affects the dose distribution for brain metastases and H&N tumor recognition. Such steps could help reduce systematic errors.
  • Original Article 2021-12-31

    Sihwan Kim1 , Chulkyun Ahn2 , Woo Kyoung Jeong3 , Jong Hyo Kim1,4,5,6,7 , Minsoo Chun7,8

    Progress in Medical Physics 2021; 32(4): 92-98

    https://doi.org/10.14316/pmp.2021.32.4.92
    Abstract
    Purpose: This study automatically discriminates homogeneous and structure edge regions on computed tomography (CT) images, and it evaluates the noise level and edge preservation ratio (EPR) according to the different types of iterative reconstruction (IR).
    Methods: The dataset consisted of CT scans of 10 patients reconstructed with filtered back projection (FBP), statistical IR (iDose4), and iterative model-based reconstruction (IMR). Using the 10th and 85th percentiles of the structure coherence feature, homogeneous and structure edge regions were localized. The noise level was estimated using the averages of the standard deviations for five regions of interests (ROIs), and the EPR was calculated as the ratio of standard deviations between homogeneous and structural edge regions on subtraction CT between the FBP and IR.
    Results: The noise levels were 20.86±1.77 Hounsfield unit (HU), 13.50±1.14 HU, and 7.70±0.46 HU for FBP, iDose4, and IMR, respectively, which indicates that iDose4 and IMR could achieve noise reductions of approximately 35.17% and 62.97%, respectively. The EPR had values of 1.14±0.48 and 1.22±0.51 for iDose4 and IMR, respectively.
    Conclusions: The iDose4 and IMR algorithms can effectively reduce noise levels while maintaining the anatomical structure. This study suggested automated evaluation measurements of noise levels and EPRs, which are important aspects in CT image quality with patients’ cases of FBP, iDose4, and IMR. We expect that the inclusion of other important image quality indices with a greater number of patients’ cases will enable the establishment of integrated platforms for monitoring both CT image quality and radiation dose.
  • Original Article 2021-06-30

    Ryohei Fukui , Ryutaro Matsuura , Katsuhiro Kida , Sachiko Goto

    Progress in Medical Physics 2021; 32(2): 50-58

    https://doi.org/10.14316/pmp.2021.32.2.50
    Abstract
    Purpose: In this study, we investigated the relationship between the noise characteristics and the number of projected images in tomosynthesis using a digital phantom.
    Methods: The digital phantom consisted of a columnar phantom in the center of the image and a spherical phantom with a diameter of 80 pixels. A virtual scan was performed, and 128 projected images (Tomo_w/o) of the phantoms were obtained. The image noise according to the Poisson distribution was added to the projected images (Tomo_×1). Furthermore, another projected image with additional noise was prepared (Tomo_×1/2). For each dataset, we created datasets with 64 (half) and 32 (quarter) projections by removing the even-numbered images twice from the 128 (fully) projected images. Tomosynthesis images were reconstructed by filtered back projection (FBP). The modulation transfer function (MTF) was estimated using the sphere method, and the noise power spectrum (NPS) was estimated using the two-dimensional Fourier transform method.
    Results: The MTFs did not change between datasets, and the NPSs improved as the number of projected images increased. The noise characteristics of the Tomo_×1_half images were the same as those of the Tomo_×1/2_full.
    Conclusions: To achieve a reduction in the patient dose in tomosynthesis acquisition, we recommend reducing the number of projected images rather than reducing the dose per projection.
  • Original Article 2021-12-31

    Yona Choi1,2 , Kook Jin Chun2 , Eun San Kim2 , Young Jae Jang1,2 , Ji-Ae Park3 , Kum Bae Kim1 , Geun Hee Kim4 , Sang Hyoun Choi1

    Progress in Medical Physics 2021; 32(4): 99-106

    https://doi.org/10.14316/pmp.2021.32.4.99
    Abstract
    Purpose: In this study, we aimed to manufacture a patient-specific gel phantom combining threedimensional (3D) printing and polymer gel and evaluate the radiation dose and dose profile using gel dosimetry.
    Methods: The patient-specific head phantom was manufactured based on the patient’s computed tomography (CT) scan data to create an anatomically replicated phantom; this was then produced using a ColorJet 3D printer. A 3D polymer gel dosimeter called RTgel-100 is contained inside the 3D printing head phantom, and irradiation was performed using a 6 MV LINAC (Varian Clinac) X-ray beam, a linear accelerator for treatment. The irradiated phantom was scanned using magnetic resonance imaging (Siemens) with a magnetic field of 3 Tesla (3T) of the Korea Institute of Nuclear Medicine, and then compared the irradiated head phantom with the dose calculated by the patient's treatment planning system (TPS).
    Results: The comparison between the Hounsfield unit (HU) values of the CT image of the patient and those of the phantom revealed that they were almost similar. The electron density value of the patient’s bone and brain was 996±167 HU and 58±15 HU, respectively, and that of the head phantom bone and brain material was 986±25 HU and 45±17 HU, respectively. The comparison of the data of TPS and 3D gel revealed that the difference in gamma index was 2%/2 mm and the passing rate was within 95%.
    Conclusions: 3D printing allows us to manufacture variable density phantoms for patient-specific dosimetric quality assurance (DQA), develop a customized body phantom of the patient in the future, and perform a patient-specific dosimetry with film, ion chamber, gel, and so on.
  • Original Article 2021-12-31

    Hyeongmin Jin1 , Seonghee Kang1 , Hyun-Cheol Kang1 , Chang Heon Choi1,2

    Progress in Medical Physics 2021; 32(4): 172-178

    https://doi.org/10.14316/pmp.2021.32.4.172
    Abstract
    Purpose: This study aimed to develop a deep learning architecture combining two task models to generate synthetic computed tomography (sCT) images from low-tesla magnetic resonance (MR) images to improve metallic marker visibility.
    Methods: Twenty-three patients with cervical cancer treated with intracavitary radiotherapy (ICR) were retrospectively enrolled, and images were acquired using both a computed tomography (CT) scanner and a low-tesla MR machine. The CT images were aligned to the corresponding MR images using a deformable registration, and the metallic dummy source markers were delineated using threshold-based segmentation followed by manual modification. The deformed CT (dCT), MR, and segmentation mask pairs were used for training and testing. The sCT generation model has a cascaded three-dimensional (3D) U-Net-based architecture that converts MR images to CT images and segments the metallic marker. The performance of the model was evaluated with intensity-based comparison metrics.
    Results: The proposed model with segmentation loss outperformed the 3D U-Net in terms of errors between the sCT and dCT. The structural similarity score difference was not significant.
    Conclusions: Our study shows the two-task-based deep learning models for generating the sCT images using low-tesla MR images for 3D ICR. This approach will be useful to the MR-only workflow in high-dose-rate brachytherapy.
  • Original Article 2021-12-31

    Jaeman Son1,2 , Seongmoon Jung1,2 , Jong Min Park1,2,3,4 , Chang Heon Choi1,2,3 , Jung-in Kim1,2,3

    Progress in Medical Physics 2021; 32(4): 159-164

    https://doi.org/10.14316/pmp.2021.32.4.159
    Abstract
    Purpose: We investigated the properties of CLEANBOLUS based on silicone with suitable characteristics for clinical use.
    Methods: We evaluated the characteristics of CLEANBOLUS and compared the results with the commercial product (Super-Flex bolus). Also, we conducted physical evaluations, including shore hardness, element composition, and elongation break. Transparency was investigated through the measured absorbance within the visible region (400–700 nm). Also, dosimetric characteristics were investigated with surface dose and beam quality. Finally, the volume of unwanted air gap was investigated based on computed tomography images for breast, chin, and nose using Super-Flex bolus and CELANBOLUS.
    Results: CLEANBOLUS showed excellent physical properties for a low shore hardness (000–35) and elongation break (>1,000%). Additionally, it was shown that CLEANBOLUS is more transparent than Super-Flex bolus. Dosimetric results obtained through measurement and calculation have an electron density similar to water in CLEANBOLUS. Finally, CLEANBOLUS showed that the volume of unwanted air gap between the phantom and each bolus is smaller than Super-Flex bolus for breast, chin, and nose.
    Conclusions: The physical properties of CLEANBOLUS, including excellent adhesive strength and lower shore hardness, reduce unwanted air gaps and ensure accurate dose distribution. Therefore, it would be an alternative to other boluses, thus improving clinical use efficiency.
  • Technical Note 2021-12-31

    Seongmoon Jung1,3,4 , Jin Dong Cho2,3,4 , Jung-in Kim1,3,4 , Jong Min Park1,3,4,5,6 , Chang Heon Choi1,3,4

    Progress in Medical Physics 2021; 32(4): 179-184

    https://doi.org/10.14316/pmp.2021.32.4.179
    Abstract
    This study aimed to determine the optimal thickness of the active layer and scan mode for a flexible radiochromic film (F-RCF) based on the active lithium salt of pentacosa-10,12-diynoic acid (LiPCDA). F-RCFs of 90, 120, 140, and 170-μm thickness were fabricated using LiPCDA. Several pieces of the F-RCFs were exposed to doses ranging from 0 to 3 Gy. Transmission and reflection modes were used to scan the irradiated F-RCFs. Their dose-response curves were obtained using a second-order polynomial equation. Their sensitivity was evaluated for both scanning modes, and the uniformity of the batch was also examined. For both the transmission and reflection modes, the sensitivity increased as the film thickness increased. For the reflection mode, the dose response increased dramatically under 1 Gy. The value of the net optical density varied rapidly as the thickness of the film increased. However, the dose-response curves showed a supralinear-curve relationship at doses greater than 2 Gy. The sensitivity of the reflection scan at doses greater than 2 Gy was higher than that of the reflection scan within 0–2 Gy. The sensitivity steadily decreased with increasing doses, and the sensitivity of the two modes was within 0.1 to 0.2 at 2 Gy and was saturated beyond that. For the transmission scan, the sensitivity was approximately 0.2 at 3 Gy. For the intra-batch test result, the maximum net optical density difference of the intra-batch was 5.5% at 2 Gy and 7.4% at 0.2 Gy in the transmission and reflection scans, respectively. In the low-dose range, film thickness of more than 120-μm was proper in the transmission mode. In contrast, the transmission mode showed a better result compared to the reflection mode. Therefore, the proper scan mode should be selected according to the dose range.
  • Original Article 2021-12-31

    Abstract
    Purpose: This study aimed to design a multipurpose dose verification phantom for external audits to secure safe and optimal radiation therapy.
    Methods: In this s tudy, we u sed I nternational Atomic Energy Agency (IAEA) LiF p owder thermoluminescence dosimeter (TLD), which is generally used in the therapeutic radiation dose assurance project. The newly designed multipurpose phantom (MPP) consists of a container filled with water, a TLD holder, and two water-pressing covers. The size of the phantom was designed to be sufficient (30×30×30 cm3). The water container was filled with water and pressed with the cover for normal incidence to be fixed. The surface of the MPP was devised to maintain the same distance from the source at all times, even in the case of oblique incidence regardless of the water level. The MPP was irradiated with 6, 10, and 15 MV photon beams from Varian Linear Accelerator and measured by a 1.25 cm3 ionization chamber to get the correction factors. Monte Carlo (MC) simulation was also used to compare the measurements.
    Results: The result obtained by MC had a relatively high uncertainty of 1% at the dosimetry point, but it showed a correction factor value of 1.3% at the 5 cm point. The energy dependence was large at 6 MV and small at 15 MV. Various dosimetric parameters for external audits can be performed within an hour.
    Conclusions: The results allow an objective comparison of the quality assurance (QA) of individual hospitals. Therefore, this can be employed for external audits or QA systems in radiation therapy institutions.
  • Erratum 2021-09-30

  • Technical Note 2022-12-31

    Se Hyung Lee1,2 , Bo-Wi Cheon3 , Chul Hee Min3 , Haegin Han1 , Chan Hyeong Kim1 , Min Cheol Han4 , Seonghoon Kim5

    Progress in Medical Physics 2022; 33(4): 172-179

    https://doi.org/10.14316/pmp.2022.33.4.172
    Abstract
    Recently, tetrahedral phantoms have been newly adopted as international standard mesh-type reference computational phantoms (MRCPs) by the International Commission on Radiological Protection, and a program has been developed to convert them to computational tomography images and DICOM-RT structure files for application of radiotherapy. Through this program, the use of the tetrahedral standard phantom has become available in clinical practice, but utilization has been difficult due to various library dependencies requiring a lot of time and effort for installation. To overcome this limitation, in this study a newly developed TET2DICOM-GUI, a TET2DICOM program based on a graphical user interface (GUI), was programmed using only the MATLAB language so that it can be used without additional library installation and configuration. The program runs in the same order as TET2DICOM and has been optimized to run on a personal computer in a GUI environment. A tetrahedron-based male international standard human phantom, MRCP-AM, was used to evaluate TET2DICOM-GUI. Conversion into a DICOM-RT dataset applicable in clinical practice in about one hour with a personal computer as a basis was confirmed. Also, the generated DICOM-RT dataset was confirmed to be effectively implemented in the radiotherapy planning system. The program developed in this study is expected to replace actual patient data in future studies.
  • Review Article 2022-12-31

    Na Hye Kwon1,2 , Hye Sung Park3 , Taehwan Kim4,5 , Sang Rok Kim5 , Kum Bae Kim6,7 , Jin Sung Kim1,2,8 , Sang Hyoun Choi6,7 , Dong Wook Kim1,2

    Progress in Medical Physics 2022; 33(4): 53-62

    https://doi.org/10.14316/pmp.2022.33.4.53
    Abstract
    In this study, we have investigated the shielding evaluation methodology for facilities using kV energy generators. We have collected and analysis of safety evaluation criteria and methodology for overseas facilities using radiation generators. And we investigated the current status of shielding evaluation of domestic industrial radiation generators. According to the statistical data from the Radiation Safety Information System, as of 2022, a total of 7,679 organizations are using radiation generating devices. Among them, 6,299 facilities use these devices for industrial purposes, which accounts for a considerable portion of radiation. The organizations that use these devices evaluate whether the exposure dose for workers and frequent visitors is suitable as per the limit regulated by the Nuclear Safety Act. Moreover, during this process, the safety shields are evaluated at the facilities that use the radiation generating devices. However, the facilities that use radiating devices having energy less than or equal to 6 MV for industrial purposes are still mostly evaluated and analyzed according to the National Council on Radiation Protection and Measurements 49 (NCRP 49) report published in 1976. We have investigated the technical standards of safety management, including the maximum permissible dose and parameters assessment criteria for facilities using radiation generating devices, based on the NCRP 49 and the American National Standards Institute/Health Physics Society N.43.3 reports, which are the representative reports related to radiation shielding management cases overseas.
  • Review Article 2022-12-31

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

    Progress in Medical Physics 2022; 33(4): 37-52

    https://doi.org/10.14316/pmp.2022.33.4.37
    Abstract
    Over the past decades, radiation therapy combined with imaging modalities that ensure optimal image guidance has revolutionized cancer treatment. The two major purposes of using imaging modalities in radiotherapy are to clearly delineate the target prior to treatment and set up the patient during radiation delivery. Image guidance secures target position prior to and during the treatment. High quality images provide an accurate definition of the treatment target and the possibility to reduce the treatment margin of the target volume, further lowering radiation toxicity and improving the quality of life of cancer patients. In this review, the various types of image guidance modalities used in radiation therapy are distinguished into ionized (kilovoltage and megavoltage image) and nonionized imaging (magnetic resonance image, ultrasound, surface imaging, and radiofrequency). The functional aspects, advantages, and limitation of imaging using these modalities are described as a subsection of each category. This review only focuses on the technological viewpoint of these modalities and any clinical aspects are omitted. Image guidance is essential, and its importance is rapidly increasing in modern radiotherapy. The most important aspect of using image guidance in clinical settings is to monitor the performance of image quality, which must be checked during the periodic quality assurance process.
  • Original Article 2022-12-31

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

    Progress in Medical Physics 2022; 33(4): 72-79

    https://doi.org/10.14316/pmp.2022.33.4.72
    Abstract
    Purpose: The proficiency test was conducted to assess the performance of the dosimetry audit service provider in the readout practice of the dose delivered to patients in medical institutions.
    Methods: A certain amount of the absorbed dose to water for the high-energy X-ray from the medical linear accelerator (LINAC) installed in the Korea Research Institute of Standards and Science (KRISS) was delivered to the postal dose audit package given by the dosimetry audit service provider, in which the radio-photoluminescence (RPL) glass dosimeters were mounted. The dosimetry audit service provider read the RPL glass dosimeters and sent the readout dose value with its uncertainty to KRISS. The performance of the dosimetry audit service provider was evaluated based on the En number given in ISO/IEC 17043:2010.
    Results: The evaluated En number was −0.954. Based on the ISO/IEC 17043, the performance of the dosimetry service provider is “satisfactory.”
    Conclusions: As part of the conformity assessment, the KRISS performed the proficiency test over the postal dose audit practice run by the dosimetry audit service provider. The proficiency test is in line with confirming the traceability of the medical institutions to the primary standard of absorbed dose to the water of the KRISS and ensuring the confidence of the dosimetry audit service provider.
  • Original Article 2022-12-31

    Seohyeon An1,2 , Sang-il Pak1 , Seonghoon Jeong1 , Soonki Min3 , Tae Jeong Kim2 , Dongho Shin1 , Youngkyung Lim1 , Jong Hwi Jeong1 , Haksoo Kim1 , Se Byeong Lee1

    Progress in Medical Physics 2022; 33(4): 80-87

    https://doi.org/10.14316/pmp.2022.33.4.80
    Abstract
    Purpose: Proton therapy has different relative biological effectiveness (RBE) compared with X-ray treatment, which is the standard in radiation therapy, and the fixed RBE value of 1.1 is widely used. However, RBE depends on a charged particle’s linear energy transfer (LET); therefore, measuring LET is important. We have developed a LET measurement method using the inefficiency characteristic of an EBT3 film on a proton beam’s Bragg peak (BP) region.
    Methods: A Gafchromic EBT3 film was used to measure the proton beam LET. It measured the dose at a 10-cm pristine BP proton beam in water to determine the quenching factor of the EBT3 film as a reference beam condition. Monte Carlo (MC) calculations of dose-averaged LET (LETd) were used to determine the quenching factor and validation. The dose-averaged LETs at the 12-, 16-, and 20-cm pristine BP proton beam in water were calculated with the quenching factor.
    Results: Using the passive scattering proton beam nozzle of the National Cancer Center in Korea, the LETd was measured for each beam range. The quenching factor was determined to be 26.15 with 0.3% uncertainty under the reference beam condition. The dose-averaged LETs were measured for each test beam condition.
    Conclusions: We developed a method for measuring the proton beam LET using an EBT3 film. This study showed that the magnitude of the quenching effect can be estimated using only one beam range, and the quenching factor determined under the reference condition can be applied to any therapeutic proton beam range.
Korean Society of Medical Physics

Vol.33 No.4
December, 2022

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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