Sang Hyoun Choi

HDRK-MAN: A WHOLE BODY VOXEL MODEL BASED ON HIGH-RESOLUTION COLOR SLICE IMAGES OF A KOREAN ADULT MALE CADAVER

In a previous study, we constructed a male reference Korean phantom; HDRK-Man (High-Definition Reference Korean-Man), to represent Korean adult males for radiation protection purposes. In the present study, a female phantom; HDRK-Woman (High-Definition Reference Korean-Woman), was constructed to represent Korean adult females. High-resolution color photographic images obtained by serial sectioning of a 26 year-old Korean adult female cadaver were utilized. The body height and weight, the skeletal mass, and the dimensions of the individual organs and tissues were adjusted to the reference Korean data. The phantom was then compared with the International Commission on Radiological Protection (ICRP) female reference phantom in terms of calculated organ doses and organ-depth distributions. Additionally, the effective doses were calculated using both the HDRK-Man and HDRK-Woman phantoms, and the values were compared with those of the ICRP reference phantoms.

Dosimetric comparison of volumetric modulated arc therapy with robotic stereotactic radiation therapy in hepatocellular carcinoma.

Purpose To compare volumetric modulated arc therapy of RapidArc with robotic stereotactic body radiation therapy (SBRT) of CyberKnife in the planning and delivery of SBRT for hepatocellular carcinoma (HCC) treatment by analyzing dosimetric parameters. Materials and Methods Two radiation treatment plans were generated for 29 HCC patients, one using Eclipse for the RapidArc plan and the other using Multiplan for the CyberKnife plan. The prescription dose was 60 Gy in 3 fractions. The dosimetric parameters of planning target volume (PTV) coverage and normal tissue sparing in the RapidArc and the CyberKnife plans were analyzed. Results The conformity index was 1.05 ± 0.02 for the CyberKnife plan, and 1.13 ± 0.10 for the RapidArc plan. The homogeneity index was 1.23 ± 0.01 for the CyberKnife plan, and 1.10 ± 0.03 for the RapidArc plan. For the normal liver, there were significant differences between the two plans in the low-dose regions of V1 and V3. The normalized volumes of V60 for the normal liver in the RapidArc plan were drastically increased when the mean dose of the PTVs in RapidArc plan is equivalent to the mean dose of the PTVs in the CyberKnife plan. Conclusion CyberKnife plans show greater dose conformity, especially in small-sized tumors, while RapidArc plans show good dosimetric distribution of low dose sparing in the normal liver and body.

Construction of a high-definition ‘Reference Korean’ voxel phantom for organ and tissue radiation dose calculation

The voxel phantoms, which are used to calculate the radiation dose distribution in a human body, are usually constructed using the CT or MR images. The CT and MR images are, however, gray images and the organs and tissue are not very clearly identified in the images, making it very difficult to construct an accurate model of a human body. In this study, we developed a very accurately defined voxel phantom (HDRK-Man) to represents the male radiation workers in Korea by adjusting the voxel phantom to the ‘Reference Korean’ data. HDRK-Man is 171 cm and 67.8 kg and has the organs and tissue of the Korean reference size. The current version of the voxel phantom is made of 29,602,950 voxels and the size of each voxel is 1.981 mm×1.981 mm×2.085 mm. The developed voxel phantom was implemented in a Monte Carlo radiation transport code, MCNPX, and the radiation dose to various organs and tissue in a human body was calculated for several irradiation geometries (AP, LLAT, PA) and photon energies (0.015 to 10 MeV).

Construction of a High-quality Voxel Model VKH-Man Using Serially Sectioned Images from Visible Korean Human Project in Korea

In this study, a high-quality voxel model of a Korean adult male was constructed using the Visible Korean Human (VKH) project’s serially sectioned anatomical images. The VKH images are transverse color photographs obtained from the serial sectioning of an adult Korean male cadaver (164 cm, 55 kg) at 0.2 mm intervals. A total of 28 organs and tissues were segmented with the color photographic images. The height and weight of the constructed voxel model, VKH-Man, is 164 cm and 59.6 kg, respectively. The voxel resolution of the model is 1.875 mm × 1.875 mm × 2 mm. The developed model was implemented into a Monte Carlo particle transport simulation code, MCNPX, to calculate the organ and tissue doses and, thereby, the effective doses, and the calculated values were compared with the values obtained from other computational models (KTMAN-2, VIP-Man, and ICRP-74).

Development of a Reference Korean Voxel Model by Adjusting the Size of the Organs and Tissues

The objective of this study was to adjust the height, weight, and organ and tissue sizes of a Korean voxel model in order to construct a Reference Korean voxel model. The adjustment of the height and skeletal mass was achieved by scaling the voxel dimensions. The sizes of the organs and tissues were adjusted to the Reference Korean data by adding or removing voxels on the surface. The adjusted voxel model is 171 cm in height, 68 kg in weight, which exactly matches the Reference Korean data. The size of the voxels (= voxel resolution) is 1.981 mm × 1.981 mm × 2.0854 mm. The organ and tissue masses of the adjusted model also are in a good agreement with the Reference Korean data; the differences are less than 7% for most of the organs and tissues. The unadjusted and adjusted voxel models were ported to the MCNPX Monte Carlo particle transport simulation code to calculate the equivalent doses to the organs and tissues and the effective doses. The calculated values were then compared in order to quantify the effect of the adjustment.

Status and Perception of Risk Management in Radiation Therapy: Survey Among Korean Medical Physicists

Abstract This study was conducted as part of an endeavor to improve the risk management system of radiation therapy departments in the Republic of Korea. An online survey on the status and perception of Korea’s medical physicists on risk management in radiation therapy was carried out. A total of 40 domestic radiation oncology departments participated. This survey is divided into three categories: (1) work environment; (2) risk management status; and (3) opinions on how to improve risk management. Based on the results of the survey, the conclusions that can be derived are (1) the majority of respondents have a high interest in the risk management of radiation therapy; (2) the lack of staffing is one cause of risk management difficulties; (3) a risk-related terminology and classification system at the national or professional association level are required; (4) each hospital should create a voluntary reporting system for the handling of incidents; (5) medical physicists should establish incident reporting, analysis and countermeasures; and (6) government should develop education and training programs. It was confirmed that the current risk management system should be changed by education in the hospital and at the national level in order to improve risk management related to radiation therapy. In addition, it was recognized that a dedicated staff and a risk management certification system and organization for patient safety in radiotherapy are needed.

SU‐E‐T‐36: Determination of the Beam Quality Correction Factor for the Liquid Ioinization Chamber in a Clinical Photon Beam

Purpose: The beam quality correction factor Koo0 of microLion chamber is still unknown and should be determined for the application of the chamber to the reference dosimetry. The objective of this study is to calculate the beam quality correction factor of microLion chamber for the high energy 6MV photon beam from Clinac iX (Varian, USA) using two alternative ways; Monte Carlo simulation, in particular EGSnrc system and experimental decision. Methods: For the present work the Cobalt60 gamma beam (Theratron780) is employed as beam source in the calibration beam quality and the high energy 6MV photon beam from the Linac (Clinac iX) is selected as quality of user beam. We have employed the egs cavity code, the EGSnrc user code, to model microLion chamber. Results: The correction factor of the PTW30013 chamber is given 0.995 for the photon beam quality TPR20,10 of 0.663. We get the Result of 1.024(±0.58%) for the TPR20,10 factor of the microLion chamber for the 6MV photon beam with its beam quality TPR20,10 of 0.663 using Monte Carlo simulation. The correction factor is calculated for the microLion chamber and for the 6MV photon beam with its beam quality of 0.665 is and shows good agreements within 0.56% with the one measured (1.024). Conclusion: The beam quality correction factor of the microLion chamber was determined with its correction factor unknown for the 6MV photon. The results from two methods were in good agreements within acceptable uncertainties. There remains a problem that uncertainties associated with microLion chamber should be studied further, but we think the averaged factor 1.0212 could be used for the microLion chamber and for the same photon beam quality as in this study in the reference dosimetry.

Monte Carlo Calculations of Neutron Dose Conversion Coefficients for Reference Korean Male

Abstract Neutron fluence-to-organ dose conversion coefficients (DCCs) were calculated for a Reference Korean-adjusted male voxel model, HDRK-Man, for some standard irradiation geometries of external neutron beams using the Monte Carlo radiation transport code MCNPX. The calculated values were compared with those for other models. The results show that HDRK-Man provides consistent results for the DCC values considering the differences in the voxel models.

The Feasibility of Goggle Monitor for Respiratory Biofeedback of Patient to Reduce Correlation Error Using Real-Time Tumor Tracking System

The aim of this study was to reduce correlation error using goggle monitor during treatment radisurgery using CyberKnife system. We analyzed the correlation error during treatment radiosurgery without goggle monitor and with using goggle monitor. The correlation error for free breathing was form 0.215 mm to 9. Oil mm. However, using goggle monitor is from 0.239 mm to 8.376 mm. We commended to use goggle monitor which can biofeedback her respiratory cycle and shape to reduced correlation error during treatment radiosurgery

Energy Correction Factors for Silicon Semiconductor Dosimeter in Adult-male Phantom for Accurate Measurement of Organ Doses

Metal oxide semiconductor field effect transistor (MOSFET) dosimeters are used to measure radiation dose in various medical applications and radiation safety. The advantage of the MOSFET dosimeter is that it is very small and provides practically real-time reading. However, given the fact that it is made mainly of silicon and epoxy, which are not ideally tissue equivalent, the MOSFET dosimeter shows some energy dependence for low-energy photons and will overestimate the energy deposition or absorbed dose in tissue when it is used in a phantom, due to the existence of scattered low-energy photons in the phantom. The present study determined, by Monte Carlo simulations with MCNPX, the relative response of the MOSFET dosimeter to the tissue dose, and thereby the energy correction factors, at various dosimeter locations in the ATOM adult-male phantom, in order to be able to accurately measure organ and tissue doses. The calculated values of relative response were 1.0-1.2 and 1.0-1.1 for 0.662 MeV and 1.25 MeV photons, respectively, which shows that if we do not use appropriate correction factors, the measurement of an organ dose could be overestimated by 10-20%, depending on the measurement condition. The result in study also shows that the energy correction factors are not very sensitive to the detailed energy spectrum of the photon field, and that the energy correction factors determined from the 0.662 MeV and 1.25 MeV photons can be used in the radiation fields in nuclear power plants without significant errors.