Finite Element Analysis of the Effects of Pixel Geometry on Electrical Properties in Semiconductor Pixel Detectors

박하령,윤한빈,한종철,감수화,김호경 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.5

The development of photon-counting pixel detectors for spectral x-ray imaging is in its prime. The optimization of pixel geometry is crucial for obtaining a reliable spectral response in each pixel element with the least distortion due to fundamental x-ray interactions and electrical properties. We investigated the fundamental electrical properties in semiconductor pixel detectors with respect to normalized pixel geometries: the aspect ratio (the length ratio between pixel pitch and detector thickness) and the fill factor (the area ratio between the pixel electrode and pixel extent). For various geometries, we performed three-dimensional field simulations using a commercial finite element analysis code, and obtained the potential and field distributions. Based on weighting potential distributions, we calculated the net charge buildup for various interaction positions within the boundary of pixel, where a single electron-hole pair starts to drift, assuming no charge trapping and diffusion. For upper limit performance, a small aspect-ratio and fill-factor design would be preferable for fast and reliable signal measurements. The results and methodology from this study can offer insight into the optimal design of pixel geometries in photon-counting pixel detectors.

토모테라피에서 MVCT 영상을 이용한 환자 테이블의 처짐 정도의 분석

박하령,김용호,박달,김원택,기용간,김동현,배진숙,Park, Ha Ryung,Kim, Yong Ho,Park, Dahl,Kim, Wontaek,Ki, Yongkan,Kim, Donghyun,Bae, Jin Suk 한국의학물리학회 2015 의학물리 Vol.26 No.2

토모테라피(Tomotherapy)는 치료 시 환자의 무게에 의한 환자 테이블의 처짐(sag)이 발생한다. 본 연구에서는 이 테이블의 처짐 정도를 토모테라피의 MVCT 영상 처리를 통해 객관적으로 분석하는 방법을 제시하였다. 이 방법을 사용하여 22명의 두경부 환자와 한명의 두개척수조사(CSI) 환자에 대하여 테이블 처짐을 측정하였다. 두경부 환자의 경우 0.4~1.54 mm의 환자 테이블 처짐과 평균 $0.7^{\circ}$의 처짐 각도를 보였다. 치료범위가 길수록 처짐의 정도는 커졌고 처짐 각도는 큰 상관이 없었다. 두개척수조사(CSI) 환자의 경우 4.97 mm의 환자 테이블 처짐을 보였다. 이 방법을 사용하면 객관적이고 간편한 방법으로 환자 테이블 처짐을 측정할 수 있고 이런 측정을 통하여 테이블 처짐에 의한 오차를 고려한 치료범위 설정에 도움이 될 것이다. In Tomotherapy the couch sags during the treatment due to the weight of the patient. In this study, we developed a simple method to obtain the amount of the sag and the pitch angle of the couch using the image processing technique of MVCT images in Tomotherapy. Using the method we evaluated the sag and pitch of couch for 22 head and neck patients and one craniospinal irradiation (CSI) patient. The sag and the average pitch angle of couch were 0.40~1.54 mm and $0.7^{\circ}$ for head and neck patients, respectively. For head and neck patients, the sag increased as the longitudinal length of the irradiation volume increased and the pitch angle showed no relationship with the longitudinal length. For the CSI patient the sag was 4.97 mm. Using the method the amount of the couch sag could be measured easily and the measured data could be useful in determination of margins considering the table sag error.

간헐외사시 수술력이 있는 환아에서 저농도 아트로핀의 근시진행 억제 효과

박하령,정승아 대한안과학회 2024 대한안과학회지 Vol.65 No.3

목적: 간헐외사시 수술력이 있는 근시 환아에서 저농도 아트로핀의 근시진행 억제 효과에 대해 알아보고자 하였다. 대상과 방법: 아트로핀 0.05%를 1년 이상 점안한 근시 환아 중 간헐외사시 수술력이 있는 45명과 없는 57명의 의무기록을 후향적으로조사하였다. 점안 전후 6개월, 1년에 측정한 구면렌즈대응치와 안구 길이의 연간 변화량을 간헐외사시 수술군의 우세안과 근시대조군의 우안, 비우세안과 좌안을 짝지어 비교하였다. 간헐외사시 수술군에서는 점안 시작 무렵 10프리즘디옵터(prism diopters, PD) 이내로 교정된 군과 안된 군의 차이도 분석하였다. 결과: 평균 -3.81 ± 1.53디옵터(diopters, D)인 102명은 평균 8.2세부터 16.8개월 동안 저농도 아트로핀을 점안하였다. 간헐외사시수술군은 평균 7.8세에 28.1 PD의 외편위로 수술받았다. 간헐외사시 수술군은 점안 1년 후 -0.52 ± 0.89 D/year, 0.27 ± 0.40 mm/year, 근시대조군은 -0.47 ± 0.83 D/year, 0.31 ± 0.24 mm/year의 근시진행률을 보여 의미 있는 차이는 없었다. 다만, 점안6개월 후 간헐외사시 수술군의 우세안은 -0.84 ± 1.61 D/year, 0.27 ± 0.33 mm/year, 근시대조군의 우안은 -0.56 ± 0.80 D/year, 0.22 ± 0.21 mm/year의 근시진행률을 보여 간헐외사시 수술군이 의미 있게 근시진행이 빨랐다(각각 p=0.04, p=0.02). 간헐외사시교정군과 비교정군 간 억제 효과 차이는 없었다. 결론: 간헐외사시 수술력이 있어도 저농도 아트로핀의 근시진행 억제 효과는 유사하였지만, 점안 초기 우세안에서는 억제 효과가 적었다. Purpose: To evaluate the effect of low-dose atropine on myopia control in children with a history of surgery for intermittent exotropia (IXT). Methods: We retrospectively reviewed the medical records of children who used 0.05% atropine for ≥ 1 year to control myopia progression. This group included 45 patients with a history of IXT surgery and 57 patients with no such history. The annual changes in spherical equivalent and axial length were compared 6 months before, 6 months after, and 1 year after atropine instillation between the IXT surgery group and myopia controls. In this comparison, the dominant eye was paired with the right eye and the non-dominant eye with the left eye. We also analyzed the difference between IXT surgery cases corrected within versus not within 10 prism diopters (PD) at the start of low-dose atropine treatment. Results: A total of 102 patients had an average of -3.81 ± 1.53 diopters (D) and used low-dose atropine for an average of 16.8 months from a mean age of 8.2 years. On average, the IXT surgery group underwent muscle surgery for 28.1 PD of IXT at 7.8 years. A year after instillation, the myopia progression rate was -0.52 ± 0.89 D/year and 0.27 ± 0.40 mm/year in the IXT surgery group compared to -0.47 ± 0.83 D/year and 0.31 ± 0.24 mm/year in the myopia control group with no significant differences. However, after 6 months of instillation, the dominant eye in the IXT surgery group exhibited a significantly faster myopia progression rate than the right eye in the myopia control group (-0.84 ± 1.61 D/year vs. -0.56 ± 0.80 D/year, p = 0.04; 0.27 ± 0.33 mm/year vs. 0.22 ± 0.21 mm/year, p = 0.02). No difference was found in the myopia control effect between corrected and uncorrected cases in the IXT surgery group. Conclusions: The effect of low-dose atropine on myopia control in children after IXT surgery was similar to that in myopia controls. However, it was less effective in the dominant eye during the early treatment period.

Gafchromic EBT3 필름 dosimetry 시스템의 개발 : Development of Gafchromic EBT3 film dosimetry system

박달 ; 박하령 부산대학교 병원 암연구소 2014 부산대병원학술지 Vol.- No.36

골반부 암 치료 시 초음파검사를 통한 방광체적과 CBCT영상 방광체적의 비교

손성호,박하령,백정진,손종기,최민호,Son, Seong Ho,Park, Ha Ryung,Baek, Jung Jin,Son, Jong Ki,Choi, Min Ho 대한방사선치료학회 2019 대한방사선치료학회지 Vol.31 No.2

목 적: 골반부 방사선 치료 시 방광체적에 따라 방사선 조사범위가 달라지기 때문에 방광체적을 조절하여 치료를 진행한다. 따라서 본 연구에서는 초음파펄스진단장치(BVI 6100, (주)메디칼써프라이)를 이용하여 방광체적 변화를 추적하여 BVI의 정확성을 평가하고자 한다. 대상 및 방법: 2017년 1월부터 2018년 9월까지 부산대학교병원에서 골반부 방사선 치료를 받은 환자 19명을 대상으로 하였다. 치료 시 BVI를 이용하여 획득한 방광체적과 CBCT영상에서 획득한 방광체적을 구간별로 비교한 후 그 유의성을 평가하였다. 결 과: 전체 체적 구간에서의 BVI와 CBCT는 r=0.773의 유의한 상관관계가 나타났으나 치료계획영상에서의 방광체적을 기준으로 p값이 125~175cc에서는 0, 175~275cc에서는 0.05보다 낮게, 그리고 275~375cc에서는 0.05보다 높게 나타났다. 결 론: 본 연구에서는 방광체적이 275cc 이상의 환자의 경우 BVI와 CBCT영상 간의 방광체적이 유의성이 있으나 방광을 비우는 환자의 경우 BVI측정의 신뢰성이 떨어진다고 판단할 수 있었다. 따라서 175~275cc 환자에 대해서는 BVI의 보정값을 이용하여 적절한 체적오차허용범위를 사용하면 유의한 값을 얻을 수 있을 것이다. Purpose: During the pelvic radiation therapy, it is performed with controlling bladder volume because the range of irradiation is changed depending on the bladder volume. Therefore in this study, we evaluate the accuracy of BVI by tracing the change of bladder volume using ultrasonic pulse diagnosis equipment(BVI 6100, Medical supply Co. LTD) Material and Methods: From January 2017 to September 2018, 19 patients who received pelvic radiation therapy at Pusan National University Hospital were included. To treat the patient, we compared that the bladder volume obtained from the BVI and the bladder volume obtained from the CBCT image then we evaluated for significance. Results: There was a significant correlation of r=0.773, BVI and CBCT in the whole volume section. However, based on the bladder volume in the RTP Image the p value was shown to be 0 at 125~175cc and lower than 0.05 at 175~275cc, And more than 0.05 at 275~375cc. Conclusions: In this study, the patient whose bladder volume is above than 275cc, there is a significance of bladder volume between BVI and CBCT image. However, we could make a decision to be undermined the reliability of BVI measurement in the case of the patient with emptied his urine. Therefore, it is possible to acquire a significant value for 175~275cc patients to use the correction value of BVI and the appropriate tolerance of volume.

Effect of the Collimator Angle on Dosimetric Verification of Volumetric Modulated Arc Therapy

김용호,박하령,김원택,김동원,기용간,이주혜,배진숙,박달,전호상,남지호 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.1

The collimator is usually rotated when planning volumetric modulated arc therapy (VMAT) due to the leakage of radiation between the multi-leaf collimator (MLC) leaves. We studied the effect of the collimator angle on the results of dosimetric verification of VMAT plans for head and neck patients. We studied VMAT plans for 10 head and neck patients. We made two sets of VMAT plans for each patient. Each set was composed of 10 plans with collimator angles of 0, 5, 10, 15, 20, 25, 30, 35, 40, 45 degrees. Plans in the first set were optimized individually, and plans in the second set shared the 30-degree collimator-angle optimization. The two sets of plans were verified by using the 2-dimensional ion chamber array MatriXX (IBA Dosimetry, Germany). The comparisons between the calculation and the measurements were made by using a -index analysis. The -index (2%/2 mm) and (3%/3 mm) passing rates had negative correlations with the collimator angle. The maximum difference between -index (3%/3 mm) passing rates of different collimator angles for each patient ranged from 1.46% to 5.60% with an average of 3.67%. There were significant differences (maximum 5.6%) in the passing rates for different collimator angles. The results suggested that the accuracy of the delivered dose depended on the collimator angle. These findings are informative when choosing a collimator angle for VMAT plans.

Effect of Collimator Angles on the Dosimetric Results of Volumetric Modulated Arc Therapy Planning for Patients with a Locally-Advanced Nasopharyngeal Carcinoma

김용호,박달,박하령,김원택,김동현,배진석,전계록,노정훈,기용간 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.5

In volumetric modulated arc therapy (VMAT) planning, usually the collimator is rotated to minimize interleaf leakage and the tongue-and-groove effect. The objective of this study was to evaluate the effect of collimator angle on the dosimetric results of VMAT plans for patients with a locallyadvanced nasopharyngeal carcinoma (LA-NPC). VMAT treatment planning sets were generated using the same planning parameters, but with different collimator angles for 11 LA-NPC patients. Each set was composed of 10 plans with collimator angles at 0, 5, 10, 15, 20, 25, 35, 40, and 45 degrees. Dosimetric parameters, such as target coverage, organs at risk (OAR), and dose conformity, were analyzed at various collimator angles. With increasing collimator angles, the absorbed doses to the optic apparatus were increased by up to 35% comparing to that at a collimator angle of 0. The best value of the conformity index (CI) was 0.971 ± 0.023 at collimator angles of 20 and 30. The worst value of CI was 0.917 ± 0.051 at a collimator angle of 0. The homogeneity index (HI)95 and HI98 had the best values of 0.106 ± 0.040 and 0.079 ± 0.031, respectively, at a collimator angle of 25. The worst values of HI95 and HI98 were 0.136 ± 0.039 and 0.105 ± 0.032, respectively, at a collimator angle of of 0. The maximum doses for some OARs (body, ear, parotid gland, mandible, and brainstem) and the HI did not show any statistically significant differences. However, the mean doses had positive correlations (r = 0.449 0.773, p < 0.001) with the irradiated volume. The CI had a weak positive correlation (r = 0.316, p < 0.001) with the irradiated volume. Other comparison parameters were evaluated as functions of the collimator angle. These findings will give useful information for choosing the collimator angle in VMAT plans for patients with a LA-NPC.