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The activity of gamma-ray emitting nuclides is calculated assuming that each gamma-ray is detected individually; thus, the magnitude of the coincidence summing signal must be considered during activity calculations. Here, the correction factor for the coincidence summing effect was calculated, and the detection efficiencies of two HPGe detectors were compared. The CANBERRA Inc. GC4018 high-purity Ge detector provided an estimate for the peak-to-total ratio using a point source to determine the coincidence summing correction factor. The ORTEC Inc. GEM60 high-purity Ge detector uses EFFTRAN in LVis to obtain the parameters of the detector and source model and the gamma-gamma and gamma-X match estimates, in order to determine the coincidence summing correction factor. Nuclide analyses, radioactivity comparisons, and analyses of reference material samples were performed utilizing certified reference materials to accurately determine the detection efficiencies. For both Co-60 and Y-88, the detection efficiency for a point source increased by an average of at least 12–13%, whereas the detection efficiency determined using LVis increased by an average of at least 13–15%. The calculated radioactivity values of the certified reference material and reference material samples were accurate to within 3% and 6% of the measured values, respectively.

In this study, we evaluated the effect of radiation dose on gonads during paediatric kidney nuclear medicine tests. Using Monte Carlo simulations, the distribution and effects of radiation were physically evaluated by displaying the distribution path of the source in the human body over time. In particular, the evaluation of doses in children, who are sensitive to radiation during nuclear medicine tests that use internal exposure among several types of medical exposures, was conducted to obtain data for the management of medical exposures. Our results indicated that under normal kidney function, the dose received by the target kidney was 0.430 mGy/mCi, which is ~6% higher than the dose suggested by the International Commission on Radiation Protection (ICRP). Furthermore, when kidney function was compromised, the dose estimated was 0.726 mGy/mCi, which is ~2% lower than the dose suggested by the ICRP. In the male and female gonads, namely the testicles and ovaries, the doses received were 0.359 mGy/mCi and 0.394 mGy/mCi, respectively, under normal kidney function. Similarly, under abnormal kidney function, the doses ranged from 0.187 to 0.353 mGy/mCi and 0.238 to 0.388 mGy/mCi in the male and female gonads, respectively.

During image-guided radiation therapy, the patient is exposed to unwanted radiation from imaging devices built into the medical LINAC. In the present study, the effective dose delivered to a patient from a cone beam computed tomography (CBCT) machine was measured. Absorbed doses in specific organs listed in ICRP Publication 103 were measured with glass dosimeters calibrated with kilovolt (kV) X-rays using a whole body physical phantom for typical radiotherapy sites, including the head and neck, chest, and pelvis. The effective dose per scan for the head and neck, chest, and pelvis were 3.37±0.29, 7.36±0.33, and 4.09±0.29 mSv, respectively. The results highlight the importance of the compensation of treatment dose by managing imaging dose.

This study was intended toward the evaluation of the correlation between the quenching coefficients and the counting efficiency for the physical quenching phenomenon and the effects of the properties of the standard sources for quenching on the tritium radioactivity concentration in the process of analyzing the tritium radioactivity concentration. Accordingly, a series of standard sources for quenching was prepared using three types of vials with different properties used for correction by the quenching phenomenon; the calculated values of the counting efficiency of a series of standard sources for quenching, relative errors in the counting values, uncertainty, and properties of the quenching correction curve were evaluated. On the basis of the results, nine samples (three glass-vial-type samples, three plastic-vial-type samples, and three Teflon-vial-type samples) were obtained and evaluated by applying Parameter Groups 1, 2, and 3, for which the efficiency was calibrated using the WinQ program in accordance with the properties of a series of standard sources for quenching. The results of this study are expected to serve as an aid in accurately understanding the standard sources for quenching, counting, and analyzing environmental samples that are subject to counting and analysis.

The intensity-modulated radiation therapy (IMRT) planning strategies for nasopharyngeal cancer among Korean radiation oncology facilities were investigated. Five institutions with IMRT planning capacity using the same planning system were invited to participate in this study. The institutions were requested to produce the best plan possible for 2 cases that would deliver 70 Gy to the planning target volume of gross tumor (PTV1), 59.4 Gy to the PTV2, and 51.5 Gy to the PTV3 in which elective irradiation was required. The advised fractionation number was 33. The planning parameters, resultant dose distributions, and biological indices were compared. We found 2-3-fold variations in the volume of treatment targets. Similar degree of variation was found in the delineation of normal tissue. The physician-related factors in IMRT planning had more influence on the plan quality. The inhomogeneity index of PTV dose ranged from 4 to 49% in Case 1, and from 5 to 46% in Case 2. Variation in tumor control probabilities for the primary lesion and involved LNs was less marked. Normal tissue complication probabilities for parotid glands and skin showed marked variation. Results from this study suggest that greater efforts in providing training and continuing education in terms of IMRT planning parameters usually set by physician are necessary for the successful implementation of IMRT.

Purpose: To investigate the feasibility of intensity-modulated radiotherapy (IMRT) as a method of boost radiotherapy after the initial irradiation by the conventional anterior/posterior opposed beams for centrally located non–small-cell lung cancer through the evaluation of dose distributions according to the various boost methods. Methods and Materials: Seven patients with T3 or T4 lung cancer and mediastinal node enlargement who previously received radiotherapy were studied. All patients underwent virtual simulation retrospectively with the previous treatment planning computed tomograms. Initial radiotherapy plans were designed to deliver 40 Gy to the primary tumor and involved nodal regions with the conventional anterior/posterior opposed beams. Two radiation dose levels, 24 and 30 Gy, were used for the boost radiotherapy plans, and four different boost methods (a three-dimensional conformal radiotherapy [3DCRT], five-, seven-, and nine-beam IMRT) were applied to each dose level. The goals of the boost plans were to deliver the prescribed radiation dose to 95% of the planning target volume (PTV) and minimize the volumes of the normal lungs and spinal cord irradiated above their tolerance doses. Dose distributions in the PTVs and lungs, according to the four types of boost plans, were compared in the boost and sum plans, respectively. Results: The percentage of lung volumes irradiated >20 Gy (V20) was reduced significantly in the IMRT boost plans compared with the 3DCRT boost plans at the 24- and 30-Gy dose levels ( p = 0.007 and 0.0315 respectively). Mean lung doses according to the boost methods were not different in the 24- and 30-Gy boost plans. The conformity indexes (CI) of the IMRT boost plans were lower than those of the 3DCRT plans in the 24- and 30-Gy plans ( p = 0.001 in both). For the sum plans, there was no difference of the dose distributions in the PTVs and lungs according to the boost methods. Conclusions: In the boost plans the V20s and CIs were reduced significantly by the IMRT plans, but in the sum plans the effects of IMRT on the dose distributions in the tumor and lungs, like CI and V20, were offset. Therefore, to keep the beneficial effect of IMRT in radiotherapy for lung cancer, it would be better to use IMRT as a whole treatment plan rather than as a boost treatment.

We investigated the characteristics of the multi-channel dosimeter (MCD) system for dose distribution by the moving wedge in clinical photon beams. Also we developed an electrometer for the multi-channel dosimeter system for radiation therapy. In dynamic field irradiation, the virtual wedge technique and its fraction methods are available through the computer-controlled asymmetric independent collimator. The modified MCD system consists of an electrometer, a solid detector and an array phantom. The MCD is used for the point dose measurement and the field size scanning. Thus, we evaluated the dosimetric characteristics of the virtual wedge and the conventional fixed wedge by the radiation field analyzer (RFA). In our analysis for the 6 and 10 MV photon beams, the maximum dose in the virtual-wedge and the fixed-wedge factors varied from 1.2 % to 1.6 % for square collimator setting ranging from 10 to 20 cm, respectively. We constructed the modified MCD system with the developed electrometer for radiation the...

A computer code to calculate the trajectory of charged particles in a medium under external electric and magnetic fields was designed. Using this code, the trajectories considered the energy loss and the direction change of the primary particles determined by stopping power and Lorentz force respectively could be calculated. The results show the variation of trajectories as a function of kinetic energy and external fields. The code can be useful for finding the information about the enhancement of energy deposition in a medium irradiated by charged particle beam. Since only the energy loss and the direction change for primary particles are considered, there are errors in this calculation. However, the results can be applied to the study of dose enhancement in radiation therapy. More accurate calculations can be achieved by considering multiple scattering of primary particles and the effect of secondary particles.

We have designed the stack ionization chamber for quality assurance of clinical photon beam. The stack chamber was composed of solid phantom inserted several chambers. The chamber as a mini plane parallel chamber was made of carbon coated microfilms. Estimated transmission rate of stack type ionization chambers for radiation beam by using Monte Carlo. The stack type ionization chambers In here the electrical characteristics of the six chambers in the solid phantom were evaluated using 6 MV photon beam. The leakage currents were 0.5 pA, reproducibility was less than 0.5%, linearity was less than 0.5%, and dose rate effect was less than 0.7%. In addition the effect of dose variation due to other chambers was estimated to maximum 0.8% approximately. The designed dosimeter can be used for quality determination in output dosimetry or measurement of percentage depth dose approximately for clinical photon beam..

Energy spectra for clinical electron beams were calculated from the mono energetic depth dose data obtained by electro-gamma shower calculations. The depth dose calculations for 1∼18 MeV mono energetic electrons were performed by simulation code and measurements for clinical electron beams of 6, 9, 12, and 15 MeV from a medical linear accelerator. The numerical calculations based on least square method were performed to obtained the energy spectra by reapeated fitting for measured depth dose curves. The calculated spectra were estimated by comparision of measured and calculated Ep, E0, and depth dose curves. As a result of the comparison, the differences were −1∼−2.5% for Ep, −3.1∼−6.1% for E0, and less than ±3% at the depth range from phantom surface to R50 depth.

To evaluate the effect of an intravenous contrast agent (CA) on dose calculations and its clinical significance in intensity modulated radiation therapy (IMRT) plans for head and neck cancer.Fifteen patients with head and neck cancer and involved neck nodes were enrolled. Each patient took two sets of computerized tomography (CT) in the same position before and after intravenous CA injections. Target volumes and organs at risk (OAR) were contoured on the enhanced CT, and then an IMRT plan of nine equiangular beams with a 6 MV X-ray was created. After the fusion of non-enhanced and enhanced CTs, the contours and the IMRT plan created from the enhanced CT were copied and placed to the non-enhanced CT. Doses were calculated again from the non-enhanced CT by the same IMRT plan. The radiation doses calculated from the two sets of CTs were compared with regard to planning target volumes (PTV) and the three OARs, both parotid glands and the spinal cord, by Wilcoxon's signed rank test.The doses (maximum, mean, and the dose of 95% of PTV received (D95%)) of PTV70 and PTV59.4 calculated from the enhanced CTs were lower than those from the non-enhanced CTs (p0.05), but the dose differences were less than 1% compared to the doses calculated from the enhanced CTs. The doses of PTV50.4, parotid glands, and spinal cord were not significantly different between the non-enhanced and enhanced CTs.The difference between the doses calculated from the CTs with and without CA enhancement was tolerably small, therefore using intravenous CA could be recommended for the planning CT of head and neck IMRT.

123 This research was supported by National R&D Program through the Dongnam Inst. of Radiological&Medical Sciences funded by the Ministry of Science, ICT & Future Planning (50497-2014). Received 29 May 2014, Revised 29 July 2014, Accepted 13 August 2014 Correspondence: Dong Hyeok Jeong (physics@dirams.re.kr) Tel: 82-51-720-5813, Fax: 82-51-720-5826 cc This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Determination of TRS-398 Quality Factors for Cs-137 Gamma Rays in Reference Dosimetry

Applicator of various kind of number ten kinds is used to raise from efficiency of brachytherapy to maximum. The compatibility of radiation source and applicator is very important subject for safety brachytherapy. Developed high dose rate brachytherapy source through Hanaro nuclear reactor in Korea Atomic Energy Research Institute and improve compatibility with using equipment in present. In this research, we wished to evaluate stability mechanical safety of radiation source and we developed phantom for evaluate several quality about Ir-192 sealed source that improve newly in Korea Atomic Energy Research Institute and is improved. The result for suitability of Ir-192 HDR source with brachytherapy tools that did normal operation in 2.2∼2.7 cm extent about change of equal curvature and consider change of sudden curvature that did normal operation in radius 1.5∼1.8 cm extent. 󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏󰠏

†‡ † Purpose: For the first time, a nationwide survey of the Patterns of Care Study (PCS) for the various radiotherapy treatments of esophageal cancer was carried out in Sout h Korea. In order to observe the different parameters, as well as offer a solid cooperative system, we compared the Korean results with those observed in the United States (US) and Japan. Materials and Methods: Two hundreds forty-six esophageal cancer patients from 21 institutions were enrolled in the South Korean study. The patients received radiation ther aphy (RT) from 1998 to 1999. In order to compare these results with those from the United States, a published study by Suntharalingam, which included 414 patients [treated by Radiotherapy (RT)] from 59 institutions between 1996 and 1999 was chosen. In order to compare the South Korean with the Japanese data, we choose two different studies. The results published by Gomi were selected as the surgery group, in which 220 esophageal cancer patients were analyzed from 76 facilities. The patients underwent surgery and received RT with or without chemotherapy between 1998 and 2001. The non-surgery group originated from a study by Murakami, in which 385 patients were treated either by RT alone or RT with chemotherapy, but no surgery, between 1999 and 2001. Results : The median age of enrolled patients was highest in the Japanese non-surgery group (71 years old). The gender ratio was approximately 9：1 (male：female) in both the Korean and Japanese studies, whereas females made up 23.1% of the study population in the US study. Adenocarcinoma outnumbered squamous cell carcinoma in the US study, whereas squamous cell carcinoma was more prevalent both the Korean and Japanese studies (Korea 96.3%, Japan 98%). An esophagogram, endoscopy, and chest CT scan were the main modalities of diagnostic evaluation used in all three countries. The US and Japan used the abdominal CT scan more frequently than the abdominal ultrasonography. Radiotherapy alone treatment was most rarely used in the US study (9.5%), compared to the Korean (23.2%) and Japanese (39%) studies. The combination of the three modalities (Surgery+RT+Chemotherapy) was performed least often in Korea (11.8%) compared to the Japanese (49.5%) and US (32.8%) studies. Chemotherapy (89%) and chemotherapy with concurrent chemoradiotherapy (97%) was most frequently used in the US study. Fluorouracil (5-FU) and Cisplatin were the most preferred drug treatments used in all three countries. The median radiation dose was 50.4 Gy in the US study, as compared to 55.8 Gy in the Korean study regardless of whether an operation was performed. However, in Japan, different median doses were delivered for the surgery (48 Gy) and non-surgery groups (60 Gy). Conclusion : Although some aspects of the evaluation of esophageal cancer and its various treatment modalities were heterogeneous among the three countries surveyed, we found no remarkable differences in the RT dose or technique, which includes the number of portals and energy beams.