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  • Review Article 2022-12-31 2022-12-31 \ 0 \ 2018 \ 469

    Image Guided Radiation Therapy

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

    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 2022-12-31 \ 1 \ 1455 \ 397

    Review of Shielding Evaluation Methodology for Facilities Using kV Energy Radiation Generating Devices Based on the NCRP-49 Report

    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

    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 2022-12-31 \ 0 \ 813 \ 278

    Effect of Bead Device Diameter on Z-Resolution Measurement in Tomosynthesis Images: A Simulation Study

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

    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 2022-12-31 \ 1 \ 1107 \ 368

    Proficiency Test for the Dosimetry Audit Service Provider

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

    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 2022-12-31 \ 1 \ 1245 \ 468

    Measurement of Proton Beam Dose-Averaged Linear Energy Transfer Using a Radiochromic Film

    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

    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 2022-12-31 \ 0 \ 940 \ 294

    Contribution of Microbleeds on Microvascular Magnetic Resonance Imaging Signal

    Chang Hyun Yoo1 , Junghwan Goh1 , Geon-Ho Jahng2

    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 2022-12-31 \ 1 \ 891 \ 248

    Minimization of Treatment Time Using Partial-Arc Volumetric Modulated Arc Therapy with Bladder Filling Protocol for Prostate Cancer

    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

    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 2022-12-31 \ 0 \ 946 \ 277

    Feasibility Test of Flat-Type Faraday Cup for Ultrahigh-Dose-Rate Transmission Proton Beam Therapy

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

    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 2022-12-31 \ 1 \ 892 \ 284

    Monte Carlo Investigation of Dose Enhancement due to Gold Nanoparticle in Carbon-12, Helium-4, and Proton Beam Therapy

    Sang Hee Ahn

    https://doi.org/10.14316/pmp.2022.33.4.114

    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 2022-12-31 \ 0 \ 1014 \ 299

    Evaluation of Treatment Plan Quality between Magnetic Resonance-Guided Radiotherapy and Volumetric Modulated Arc Therapy for Prostate Cancer

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

    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.
Korean Society of Medical Physics

Vol.35 No.1
2022-12-31

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

Frequency: Quarterly

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