• Radiation Oncology Journal
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• 제28권3호
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• pp.166-176
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• 2010

Purpose: To determine the appropriate prostate planning target volume (PTV) margins for 3-dimensitional (3D) conformal radiotherapy (CRT) and intensity-modulated radiation therapy (IMRT) patients treated with an endorectal balloon (ERB) under our institutional treatment condition. Materials and Methods: Patients were treated in the supine position. An ERB was inserted into the rectum with 70 cc air prior to planning a CT scan and then each treatment fraction. Electronic portal images (EPIs) and digital reconstructed radiographs (DRR) of planning CT images were used to evaluate inter-fractional patient's setup and ERB errors. To register both image sets, we developed an in-house program written in visual $C^{++}$. A new method to determine prostate PTV margins with an ERB was developed by using the common method. Results: The mean value of patient setup errors was within 1 mm in all directions. The ERB inter-fractional errors in the superior-inferior (SI) and anterior-posterior (AP) directions were larger than in the left-right (LR) direction. The calculated 1D symmetric PTV margins were 3.0 mm, 8.2 mm, and 8.5 mm for 3D CRT and 4.1 mm, 7.9 mm, and 10.3 mm for IMRT in LR, SI, and AP, respectively according to the new method including ERB random errors. Conclusion: The ERB random error contributes to the deformation of the prostate, which affects the original treatment planning. Thus, a new PTV margin method includes dose blurring effects of ERB. The correction of ERB systematic error is a prerequisite since the new method only accounts for ERB random error.

• Progress in Medical Physics
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• 제21권4호
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• pp.340-347
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• 2010

DQA, a patient specific quality assurance in tomotherapy, is usually performed using an ion chamber and a film. The result of DQA is analysed with the treatment planning system called Tomo Planning Station (TomoPS). The two-dimensional dose distribution of film measurement is compared with the dose distribution calculated by TomoPS using the ${\gamma}$-index analysis. In ${\gamma}$-index analysis, the criteria such as 3%/3 mm is used and we verify that whether the rate of number of points which pass the criteria (pass rate) is within tolerance. TomoPS does not provide any quantitative information regarding the pass rate. In this work, a method to get the pass rate of the ${\gamma}$-index analysis was suggested and a software PassRT which calculates the pass rate was developed. The results of patient specific QA of the intensity modulated radiation therapy measured with I'mRT MatriXX (IBA Dosimetry, Germany) and DQA of tomotherapy measured with film were used to verify the proposed method. The pass rate was calculated using PassRT and compared with the pass rate calculated by OmniPro I'mRT (IBA Dosimetry, Germany). The average difference between the two pass rates was 0.00% for the MatriXX measurement. The standard deviation and the maximum difference were 0.02% and 0.02%, respectively. For the film measurement, average difference, standard deviation and maximum difference were 0.00%, 0.02% and 0.02%, respectively. For regions of interest smaller than $24.3{\times}16.6cm^2$ the proposed method can be used to calculate the pass rate of the gamma index analysis to one decimal place and will be helpful for the more accurate DQA in tomotherapy.

• Journal of Energy Engineering
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• 제29권1호
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• pp.63-74
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• 2020

The Kori-Unit 1 nuclear power plant, which is scheduled for decommissioning after permanent shutdown, is expected to generate a large amount of various types of radioactive waste during decommissioning process. For concrete radioactive waste, which is expected to occupy the most amount, it is important to analyze the current waste disposal status and legal limitations and to prepare an appropriate and efficient disposal method. Concrete radioactive waste is waste of various levels, of which the clearance level is bioshield concrete. In this paper, clearance radioactive waste safety evaluation was performed using the RESRAD code, which is a safety evaluation code, based on the activation evaluation results for the wastes with the clearance level. The clearance scenario of the target radioactive waste was selected and the individual's exposure dose was calculated at the time of clearance to determine whether the clearance criteria limit prescribed by the Nuclear Safety Act was satisfied. As a result of the evaluation, the results showed significantly lower results and satisfied the criteria value. Based on the results of this clearance safety assessment, the appropriate disposal method for bioshield concrete, which are the clearance wastes of subject of deregulation, was suggested.

• Radiation Oncology Journal
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• 제20권1호
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• pp.81-90
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• 2002

Purpose : To establish and verify the proper and the practical IMRT (Intensity--modulated radiation therapy) patient QA (Quality Assurance). Materials and Methods : An IMRT QA which consists of 3 steps and 16 items were designed and examined the validity of the program by applying to 9 patients, 12 IMRT cases of various sites. The three step OA program consists of RTP related QA, treatment information flow QA, and a treatment delivery QA procedure. The evaluation of organ constraints, the validity of the point dose, and the dose distribution are major issues in the RTP related QA procedure. The leaf sequence file generation, the evaluation of the MLC control file, the comparison of the dry run film, and the IMRT field simulate image were included in the treatment information flow procedure QA. The patient setup QA, the verification of the IMRT treatment fields to the patients, and the examination of the data in the Record & Verify system make up the treatment delivery QA procedure. Results : The point dose measurement results of 10 cases showed good agreement with the RTP calculation within $3\%$. One case showed more than a $3\%$ difference and the other case showed more than $5\%$, which was out side the tolerance level. We could not find any differences of more than 2 mm between the RTP leaf sequence and the dry run film. Film dosimetry and the dose distribution from the phantom plan showed the same tendency, but quantitative analysis was not possible because of the film dosimetry nature. No error had been found from the MLC control file and one mis-registration case was found before treatment. Conclusion : This study shows the usefulness and the necessity of the IMRT patient QA program. The whole procedure of this program should be peformed, especially by institutions that have just started to accumulate experience. But, the program is too complex and time consuming. Therefore, we propose practical and essential QA items for institutions in which the IMRT is performed as a routine procedure.

• Journal of the Korean Society of Radiology
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• 제18권6호
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• pp.621-627
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• 2024

With the increasing utilization of cyclotrons in medical, research, and industrial applications, effective shielding in cyclotron rooms has become crucial to ensure worker safety. This study focuses on optimizing the shielding wall thickness by using a water-based composite shielding wall in cyclotron rooms. The Moyer model was employed to calculate the external dose rates from neutron reactions at various energy levels (8.4, 13, 18, 30, and 50 MeV) on an Nb target. The neutron energy spectra required for the calculations were derived using the Talys program. The shielding efficiency of the water-based composite wall was compared with that of a conventional concrete wall. The results showed that the optimal thicknesses of the composite shielding wall were 1.38m at 8.4 MeV, 1.58m at 13 MeV, 15.8m at 18 MeV, 15.8m at 30 MeV, and 1.58m at 50 MeV. The composite wall demonstrated its potential for more efficient neutron shielding by reducing the required thickness across various energy levels. This study provides foundational data for neutron shielding design in cyclotron facilities and is expected to contribute to the optimization of practical shielding materials and thicknesses.

• The Korean Journal of Nuclear Medicine
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• 제35권3호
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• pp.131-141
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• 2001

Purpose: We evaluated the sensitivity of the F-18 FDG PET by visual assessment and statistical parametric mapping (SPM) analysis for the localization of the epileptogenic zones in frontal lobe epilepsy. Materials and Methods: Twenty-four patients with frontal lobe epilepsy were examined. All patients exhibited improvements after surgical resection (Engel class I or II). Upon pathological examination, 18 patients revealed cortical dysplasia, 4 patients revealed tumor, and 2 patients revealed cortical scar. The hypometabolic lesions were found in F-18 FDG PET by visual assessment and SPM analysis. On SPM analysis, cutoff threshold was changed. Results: MRI showed structural lesions in 12 patients and normal results in the remaining 12. F-18 FDG PET correctly localized epileptogenic zones in 13 patients (54%) by visual assessment. Sensitivity of F-18 FDG PET in MR-negative patients (50%) was similar to that in MR-positive patients (67%). On SPM analysis, sensitivity decreased according to the decrease of p value. Using uncorrected p value of 0.05 as threshold, sensitivity of SPM analysis was 53%, which was not statistically different from that of visual assessment. Conclusion: F-18 FDG PET was sensitive in finding epileptogenic zones by revealing hypometabolic areas even in MR-negative patients with frontal lobe epilepsy as well as in MR-positive patients. SPM analysis showed comparable sensitivity to visual assessment and could be used as an aid in the diagnosis of epileptogenic zones in frontal lobe epilepsy.