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  • Original Article 2017-06-30 2017-06-30 \ 3 \ 531 \ 171

    Evaluation of Dosimetric Effect and Treatment Time by Plan Parameters for Endobronchial Brachytherapy

    Chang Heon Choi, Jong Min Park, So-Yeon Park, SungHee Kang, Jin Dong Cho, Jung-in Kim

    https://doi.org/10.14316/pmp.2017.28.2.39

    Abstract

    This study aims to analyze dose distribution and treatment time of endobronchial brachytherapy (EBBT) by changing the position step size of the dwell position. A solid water phantom and an intraluminal catheter were used in the treatment plan. The treatment plans were generated for 3, 5, 7, and 10 cm treatment lengths, respectively. For each treatment length, the source position step sizes were set as 2.5, 5, and 10 mm. Three reference points were set 1 cm away from the central axis of the catheter, along the axis, for uniform dose distribution. Volumetric dose distribution was calculated to evaluate the dosimetric effect. The total radiation delivery time and total dwell time were estimated for treatment efficiency, which were increased with position step sizes. At half-life time, the differences between the position step sizes in the total radiation delivery time were 18.1, 15.4, 18.0, and 24.0 s for 3, 5, 7, and 10 cm treatment lengths, respectively. The dose distributions were more homogenous by increasing the position step sizes. The dose difference of the reference point was less than 10%. In brachytherapy, this difference can be negligible. For EBBT, the treatment time is the key factor while considering the patient status. To reduce the total treatment time, EBBT can be performed with 2.5 mm position step size.

  • Original Article 2017-06-30 2017-06-30 \ 0 \ 503 \ 100

    Assessment of Radiation Dose from Radioactive Wedge Filters during High-Energy X-Ray Therapy

    Geum-mun Back, Sung Ho Park, Tae-Hyung Kim

    https://doi.org/10.14316/pmp.2017.28.2.45

    Abstract

    This paper evaluated the amount of radiation generated by wedge filters during radiation therapy using a high-energy linear accelerator, and the dose to the worker during wedge replacement. After 10-MV photon beam was irradiated with wedge filter, the wedge was removed from the linear accelerator, and the dose rate and energy spectrum were measured. The initial measurement was approximately 1 uSv/h, and the radiation level was reduced to 0.3 uSv/h after 6 min. The effective half-life derived from the dose rate measurement was approximately 3.5 min, and the influence of AI-28 was about 53%. From the energy spectrum measurements, a peak of 1,799 keV was measured for AI-28, while the peak for Co-58 was not measured in the control room. The peaks for Au-106 and Cd-105 were found only measurement was done without wedge removement from the linear accelerator. The additional doses received by the radiation worker during wedge replacement were estimated to be 0.08–0.4 mSv per year.

  • Original Article 2017-06-30 2017-06-30 \ 1 \ 561 \ 226

    Electron Energy Distribution for a Research Electron LINAC

    Heuijin Lim, Manwoo Lee, Jungyu Yi, Sang Koo Kang, Me Young Kim, Dong Hyeok Jeong

    https://doi.org/10.14316/pmp.2017.28.2.49

    Abstract

    The energy distribution was calculated for an electron beam from an electron linear accelerator developed for medical applications using computational methods. The depth dose data for monoenergetic electrons from 0.1 MeV to 8.0 MeV were calculated by the DOSXYZ/nrc code. The calculated data were used to generate the energy distribution from the measured depth dose data by numerical iterations. The measured data in a previous work and an in-house computer program were used for the generation of energy distribution. As results, the mean energy and most probable energy of the energy distribution were 5.7 MeV and 6.2 MeV, respectively. These two values agreed with those determined by the IAEA dosimetry protocol using the measured depth dose.

  • Original Article 2017-06-30 2017-06-30 \ 3 \ 484 \ 147

    Feasibility Study of Patient Specific Quality Assurance Using Transit Dosimetry Based on Measurement with an Electronic Portal Imaging Device

    Tae Seong Baek, Eun Ji Chung, Jaeman Son, Myonggeun Yoon

    https://doi.org/10.14316/pmp.2017.28.2.54

    Abstract

    This study was designed to measure transit dose with an electronic portal imaging device (EPID) in eight patients treated with intensity modulated radiotherapy (IMRT), and to verify the accuracy of dose delivery to patients. The calculated dose map of the treatment planning system (TPS) was compared with the EPID based dose measured on the same plane with a gamma index method. The plan for each patient was verified prior to treatment with a diode array (MapCHECK) and portal dose image prediction (PDIP). To simulate possible patient positioning errors during treatment, outcomes were evaluated after an anthropomorphic phantom was displaced 5 and 10 mm in various directions. Based on 3%/3 mm criteria, the mean±SD passing rates of MapCHECK, PDIP (pre-treatment QA) for 47 IMRT were 99.8±0.1%, 99.0±0.7%, and, respectively. Besides, passing rates using transit dosimetry was 90.0±1.5% for the same condition. Setup errors of 5 and 10 mm reduced the mean passing rates by 1.3% and 3.0% (inferior to superior), 2.2% and 4.3% (superior to inferior), 5.9% and 10.9% (left to right), and 8.9% and 16.3% (right to left), respectively. These findings suggest that the transit dose-based IMRT verification method using EPID, in which the transit dose from patients is compared with the dose map calculated from the TPS, may be useful in verifying various errors including setup and/or patient positioning error, inhomogeneity and target motions.

  • Original Article 2017-06-30 2017-06-30 \ 7 \ 749 \ 274

    Gamma Evaluation with Portal Dosimetry for Volumetric Modulated Arc Therapy and Intensity-Modulated Radiation Therapy

    Jung-in Kim, Chang Heon Choi, So-Yeon Park, HyunJoon An, Hong-Gyun Wu, Jong Min Park

    https://doi.org/10.14316/pmp.2017.28.2.61

    Abstract

    The aim of this study is to investigate the characteristics of portal dosimetry in comparison with the MapCHECK2 measurments. In this study, a total of 65 treatment plans including both volumetric modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) were retrospectively selected and analyzed (45 VMAT plans and 20 IMRT plans). A total of 4 types of linac models (VitalBeam, Trilogy, Clinac 21EXS, and Clianc iX) were used for the comparison between portal dosimetry and the MapCHECK2 measurements. The VMAT plans were delivered with two VitalBeam linacs (VitalBeam1 and VitalBeam2) and one Trilogy while the IMRT plans were delivered with one Clinac 21EXS and one Clinacl iX. The global gamma passing rates of portal dosimetry and the MapCHECK2 measurements were analyzed with a gamma criterion of 3%/3 mm for IMRT while those were analyzed with a gamma criterion of 2%/2 mm for VMAT. Spearman’s correlation coefficients (r) were calculated between the gamma passing rates of portal dosimetry and those of the MapCHECK2 measurements. For VMAT, the gamma passing rates of portal dosimetry with the VitalBeam1, VitalBeam2, and Trilogy were 97.3%±3.5%, 97.1%±3.4%, and 97.5%±1.9%, respectively. Those of the MapCHECK2 measurements were 96.8%±2.5%, 96.3%±2.7%, and 97.4%±1.3%, respectively. For IMRT, the gamma passing rates of portal dosimetry with Clinac 21EXS and Clinac iX were 99.7%±0.3% and 99.8%±0.2%, respectively. Those of the MapCHECK2 measurements were 96.5%±3.3% and 97.7%±3.2%, respectively. Except for the result with the Trilogy, no correlations were observed between the gamma passing rates of portal dosimetry and those of the MapCHECK2 measurements. Therefore, both the MapCHECK2 measurements and portal dosimetry can be used as an alternative to each other for patient-specific QA for both IMRT and VMAT.

  • Technical Report 2017-06-30 2017-06-30 \ 0 \ 546 \ 161

    Proposal for Comprehensive Quality Control of Heavy-Ion Medical Accelerator

    Dong-wook Kim, Dong-oh Shin, Young-hoon Ji, Hyun-do Heo

    https://doi.org/10.14316/pmp.2017.28.2.67

    Abstract

    Prior to the introduction of a medical apparatus based on heavy-ion medical accelerator in Korea, a study is needed on quality control in clinical operation for the safe and appropriate usage of the instrument. Data relevant for the study were obtained via information sharing sessions and visits by the Particle Therapy Co-Operative Group (PTCOG) and other related academic associations. Furthermore, investigative analysis of the European and Japanese performance evaluation guidelines for heavy ion, as well as research on relevant literature, were conducted. In addition, instrumental standards were analyzed through an investigation of the current usage status of the heavy-ion medical accelerator, and further analysis was conducted on the evaluation methods for the performance, safety, and significance of the instrument. Based on these analyses, regular quality control procedures for heavy-ion medical accelerators in hospitals and other institutes were extrapolated. It is hoped that the results of this study will facilitate hospitals that have introduced heavy-ion medical accelerators, or are considering the implementation of the instrument, in their understanding of the fundamental standards and capabilities of the treatment system, as well as in establishing and carrying out quality control procedures for clinical operations such that it will contribute to the safety of patients and the efficiency of medical practitioners.

Korean Society of Medical Physics

Vol.35 No.1
2017-06-30

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

Frequency: Quarterly

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