• 한국의학물리학회지:의학물리
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• 제28권4호
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• pp.218-225
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• 2017

Effects on skin caused by the dose from linear accelerator (LINAC) opposing portal irradiation and TomoDirect 3-D modeling treatment according to the radiation devices and treatment methods were measured, and a comparative analysis was performed. Two groups of 10 patients each were created and measurements were carried out using an optically stimulated luminescence dosimeter. These patients were already receiving radiation treatment in the hospital. Using the SPSS statistical program, the minimum and maximum average standard deviations of the measured skin dose data were obtained. Two types of treatment method were selected as independent variables; the measured points and total average were the dependent variables. An independent sample T-test was used, and it was checked whether there was a significance probability between the two groups. The average of the measured results for the LINAC opposing portal radiation was 117.7 cGy and PDD 65.39% for the inner breast, 144.7 cGy and PDD 80.39% for the outer breast, 143.2 cGy and PDD 79.56% for the upper breast, 151.4 cGy and PDD 84.11% for the lower breast, 149.6 cGy and PDD 83.11% for the axilla, and 141.32 cGy and PDD 78.51% for the total average. In contrast, for TomoDirect 3-D conformal radiotherapy, the corresponding measurement values were 137.6 cGy and PDD 76.44%, 152.3 cGy and PDD 84.61%, 148.6 cGy and PDD 82.56%, 159.7 cGy and PDD 88.72%, and 148.6 cGy PDD 82.56%, respectively, and the total average was 149.36 cGy and PDD 82.98%. To determine if the difference between the total averages was statistically significant, the independent sample T-test of the SPSS statistical program was used, which indicated that the P-value was P=0.024, which was 0.05 lower than the significance level. Thus, it can be understood that the null hypothesis can be dismissed, and that there was a difference in the averages. In conclusion, even though the treatment dose was similar, there could be a difference in the dose entering the body surface from the radiation treatment plan; however, depending on the properties of the treatment devices, there is a difference in the dose affecting the body surface. Thus, the absorbed dose entering the body surface can be high. During breast cancer radiotherapy, radiation dermatitis occurs in almost all patients. Most patients have a difficult time while undergoing treatment, and therefore, when choosing a radiotherapy treatment method, minimizing radiation dermatitis is an important consideration.

• 디지털융복합연구
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• 제12권10호
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• pp.425-431
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• 2014

본 연구는 ATOM Phantom을 이용하여 선량, 화질을 비교 분석 하여 Volume mode의 유용성 밝혀 소아 CT 검사에 적극적으로 사용하기 위함이다. Helical mode Noise와 Volume mode의 Noise, HU, SNR은 p>0.05 이므로 통계적으로 유이한 차이가 없음을 알 수 있었다. 각 부위별 선량값은 모두 p>0.05 이므로 통계적 유이한 차이가 없었으나 DLP값이 Helical mode보다 Volume mode가 더 낮게 측정되었다. 유효선량 역시 Volume mode가 Helical mode 보다 낮음을 알 수 있었다. 정성적 분석에서는 Mode에 따른 조건 별로 각각 Helical: 2.6, 3.3, 4.36 Volume: 2.8, 3.64, 4.44, Mode별 Follow up 영상평가 결과로는 Helical mode가 3.8 Volume mode가 3.83점으로 큰 차이가 없는 것으로 나타났다. 5세 이하의 소아 CT검사에 있어서 640-MDCT Volume scan이 Helical mode와 비교해 낮은 선량으로 영상의 질이 큰 차이가 없기에 소아 CT 검사에는 유용 하다고 생각된다.

• International Journal of Contents
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• 제8권2호
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• pp.52-59
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• 2012

This study uses digital imaging and communications in medicine (DICOM) files acquired after CT scan to obtain the absorbed dose distribution inside the body by using the patient's actual anatomical data; uses geometry and tracking (Geant)4 as a way to obtain the accurate absorbed dose distribution inside the body. This method is easier to establish the radioprotection plan through estimating the absorbed dose distribution inside the body compared to the evaluation of absorbed dose using thermo-luminescence dosimeter (TLD) with inferior reliability and accuracy because many variables act on result values with respect to the evaluation of the patient's absorbed dose distribution in diagnostic imaging and the evaluation of absorbed dose using phantom; can contribute to improving reliability accuracy and reproducibility; it makes significance in that it can implement the actual patient's absorbed dose distribution, not just mere estimation using mathematical phantom or humanoid phantom. When comparing the absorbed dose in polymethly methacrylate (PMMA) phantom measured in metal oxide semiconductor field effect transistor (MOSFET) dosimeter for verification of Geant4 and the result of Geant4 simulation, there was $0.46{\pm}4.69%$ ($15{\times}15cm^2$), and $-0.75{\pm}5.19%$ ($20{\times}20cm^2$) difference according to the depth. This study, through the simulation by means of Geant4, suggests a new way to calculate the actual dose of radiation exposure of patients through DICOM interface.

• 대한방사선치료학회지
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• 제28권1호
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• pp.47-55
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• 2016

동적 세기조절방사선치료 시 선량률 변화에 따른 다엽콜리메이터의 엽의 위치를 반영하는 선량학적엽간격과 다엽콜리메이터 투과계수 변화를 분석하여 다엽콜리메이터의 정확성을 평가하고자 하였다. Millennium 120 MLC 시스템이 장착된 선형가속기의 6 MV와 10 MV X선으로 물 팬텀의 깊이 10 cm에서 CC13과 FC-65G 전리함을 이용하여 선량률을 200, 300, 400, 500, 600 MU/min으로 변화시켜 선량학적엽간격과 다엽콜리메이터 투과계수를 측정하였다. 400 MU/min의 선량률 기준으로 200, 300, 400, 500, 600 MU/min으로 선량률을 변경하여 선량학적엽간격 값을 측정한 결과, 6 MV의 경우 각각 -2.59, -1.89, 0.00, -0.58, -2.89%의 차이가 나타났고, 10 MV에서는 각각 ?2.52, -1.69, 0.00, +1.28, -1.98%의 차이가 나타났다. 다엽콜리메이터 투과계수는 두 종류의 에너지와 모든 선량률에서 약 ${\pm}1%$ 이내의 범위로 측정되었다. 본 연구는 동적 세기조절방사선치료 시 선량률 변화에 대하여 다엽콜리메이터의 선량학적엽간격과 투과계수 변화를 평가하였다. 선량률 변화에 따라서 다엽콜리메이터의 투과계수의 차이는 미미했지만, 선량학적엽간격의 차이는 큰 것으로 확인하였다. 따라서 동적 세기조절방사선치료 시 임의로 선량률을 변경하면 종양에 전달되는 선량에 많은 영향을 미치므로 치료 중에 선량률을 변화시키지 않는 것이 더욱 정확한 방사선치료 방법이라 사료된다.

• 대한방사선치료학회지
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• 제30권1_2호
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• pp.83-95
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• 2018

목 적 : 폐암의 호흡동조방사선치료(Respiratory Gated Radiotherapy, RGRT)계획수립 후 표적 주변에 위치하고 있는 정상장기의 경우에는 움직임과 용적변화가 고려되지 않은 상태에서 선량평가가 이루어지는 경우가 많다. 본 연구에서는 적응형방사선치료(Adaptive Radiotherapy, ART)에서 많이 사용되는 변형영상정합(Deformable Image Registration, DIR)을 이용하여 호흡동조방사선치료 시 특정 위상에서의 정상장기의 움직임을 반영한 4차원-선량평가를 진행하였으며, 3차원 선량평가와의 차이를 연구하였다. 또한, 폐암의 치료계획평가 시 환자 호흡에 따른 정상장기의 움직임과 용적변화에 대한 분석 및 고려가 필요한 지 알아보고자 한다. 대상 및 방법 : 호흡동조방사선치료를 받은 폐암 환자 10명을 대상으로 하였다. Eclipse(Ver 13.6 Varian, USA)로 최고 위상 CT영상에 그려진 구조물을 모든 위상영상에 Propagation($Eclipse^{TM}$)이나 Segmentation Wizard($Eclipse^{TM}$)의 메뉴로 동일하게 설정하였으며, Center-to-Center 방식으로 구조물의 움직임 및 용적을 분석하였다. 또한, 4차원 선량평가를 위해 VELOCITY 프로그램(VELOCITY Ver 4.0, Varian, USA)을 이용하여 각 위상의 영상과 선량분포를 최고 위상 CT영상에 변형하였으며, 선량을 합산하여 정상장기의 4차원 선량평가를 실시하고, 3차원 선량평가와 비교분석을 하였다. 또한, 4차원 선량분포의 검증을 위해 $QUASAR^{TM}$ Phantom(Modus Medical Devices)과 $GAFCHROMIC^{TM}$ EBT3 Film(Ashland, USA)을 사용하여 4차원 감마분석을 시행하였다. 결 과 : 들숨과 날숨 구간의 움직임은 우측 폐가 축 방향 $0.989{\pm}0.34cm$로 가장 컸으며, 척수가 측 방향 -0.001 cm로 가장 작았다. 30~70 % 구간의 움직임은 식도가 축 방향 $0.52{\pm}0.21cm$로 가장 컸으며, 척수가 전후방향 $0.013{\pm}0.01cm$로 가장 작았다. 용적은 우측 폐가 33.5 %로 가장 큰 변화율을 보였다. 3차원 선량평가와 4차원 선량평가에서의 PTV 선량균질지수(Conformity Index, CI) 값과 처방선량지수(Homogeneity Index, HI) 값의 차이는 각각 최대 0.076, 0.021, 최소 0.011, 0.0으로 평가되었다. 정상장기의 경우 4차원 선량평가에서 0.0045~2.76 % 차이를 보였다. 모든 환자의 4차원 감마통과율은 평균 $98.1{\pm}0.42%$로 확인되었고, 모두 기준 95 %를 통과하였다. 결 론 : 모든 환자의 PTV 선량균질지수 값은 4차원 선량평가 시 더 유의한 값임을 확인할 수 있었으며, 처방 선량지수는 두 선량평가에서 차이를 보이지 않았다. 호흡에 의한 움직임이 고려된 4차원 선량분포에서 PTV 경계부분이 채워져 3차원 선량분포에서보다 선량이 더욱 균질한 것을 확인할 수 있었다. 정상장기의 4차원 선량평가에서 0.004~2.76 % 차이가 있었으며, 척수를 제외한 모든 정상장기에서 두 평가방법의 차이유의를 확인할 수 있었다. 정상장기의 3차원 선량평가 시 과소평가가 이루어 질 수 있다는 사실을 본 연구를 통해 알 수 있었으며, 호흡에 의한 정상장기의 선량변화가 예상되는 경우 변형영상정합을 이용한 4차원 선량평가를 고려할 수 있을 것이다. 변형영상정합을 이용한 4차원 선량평가는 환자의 호흡에 의한 정상장기의 움직임과 용적 변화를 반영하는 조금 더 현실적인 선량평가방법이 될 것이라고 사료된다.

• 한국의학물리학회지:의학물리
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• 제19권1호
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• pp.9-13
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• 2008

다이오드 측정기(diode)와 유리 선량계(glass dosimeter)를 이용하여 체표면 선량측정을 시행하고 실제 방사선조사 영역에 조사되는 방사선량을 치료계획 시스템에서 계산된 방사선량과 비교하여 유리 선량계를 체표면 측정기로 활용할 수 있는 가능성을 확인하고자 하였다. 이를 위하여 유방암 치료로 방사선을 조사받는 환자 27명을 대상으로 다이오드 측정기와 유리 선량계를 같은 부위에 부착하여 각각의 위치에서 조사되는 방사선량을 측정하였다. 여기서 사용된 유리 선량계는 총 40개 중 재현성이 3% 이내인 28개의 소자만을 사용하였다. 환자의 치료 셋업 위치에 따라 네 부위에 각각 선량계를 부착하여 각 위치에서의 선량값을 측정하였다. 연구에 참여한 27명의 환자 모두에 대하여 180 cGy/fraction의 방사선을 조사하였다. 이때 같은 부위에 부착한 두 측정기가 나타내는 선량값의 차이는 최대 3.2%였으며, 치료계획 된 선량값과 비교했을 때 다이오드 측정기의 경우 평균 2.3%의 차이를 보였으며, 유리선량계의 경우 평균 3.4%의 차이를 나타내었다. 이로써 유리 선량계는 체표면 측정기로 활용할 수 있는 가능성을 보였다. 치료계획에서 계산된 선량값에 비해 두 종류 측정기로 측정한 선량값이 모두 적은 값을 나타내었으나, 이는 각각의 선량계가 가지고 있는 특성 오차의 영향과 선량계를 부착한 부위가 고정되기 쉽지 않고 움직이기 쉬운 부분이라는 신체적 특성의 영향에 따른 차이라 생각된다.

• 한국의학물리학회지:의학물리
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• 제30권4호
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• pp.104-111
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• 2019

Purpose: Online magnetic resonance-guided adaptive radiotherapy (MRgART), an emerging technique, is used to address the change in anatomical structures, such as treatment target region, during the treatment period. However, the electron density map used for dose calculation differs from that for daily treatment, owing to the variation in organ location and, notably, air pockets. In this study, we evaluate the dosimetric effect of electron density override on air pockets during online ART for pancreatic cancer cases. Methods: Five pancreatic cancer patients, who were treated with MRgART at the Seoul National University Hospital, were enrolled in the study. Intensity modulated radiation therapy plans were generated for each patient with 60Co beams on a ViewrayTM system, with a 45 Gy prescription dose for stereotactic body radiation therapy. During the treatment, the electron density map was modified based on the daily MR image. We recalculated the dose distribution on the plan, and the dosimetric parameters were obtained from the dose volume histograms of the planning target volume (PTV) and organs at risk. Results: The average dose difference in the PTV was 0.86Gy, and the observed difference at the maximum dose was up to 2.07 Gy. The variation in air pockets during treatment resulted in an under- or overdose in the PTV. Conclusions: We recommend the re-contouring of the air pockets to deliver an accurate radiation dose to the target in MRgART, even though it is a time-consuming method.

• Asian Pacific Journal of Cancer Prevention
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• 제17권12호
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• pp.5107-5111
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• 2016

Background: Epidemiological studies have indicated an increasing incidence of radiation induced secondary cancer (SC) in breast cancer patients after radiotherapy (RT), most commonly in the contra-lateral breast (CLB). The present study was conducted to estimate the SC risk in the CLB following 3D conformal radiotherapy techniques (3DCRT) including wedge field and forward intensity modulated radiotherapy (fIMRT) based on the organ equivalent dose (OED). Material and Methods: RT plans treating the chest wall with conformal wedge field and fIMRT plans were created for 30 breast cancer patients. The risks of radiation induced cancer were estimated for the CLB using dose-response models: a linear model, a linear-plateau model and a bell-shaped model with full dose response accounting for fractionated RT on the basis of OED. Results: The plans were found to be ranked quite differently according to the choice of model; calculations based on a linear dose response model fIMRT predict statistically significant lower risk compared to the enhanced dynamic wedge (EDW) technique (p-0.0089) and a non-significant difference between fIMRT and physical wedge (PW) techniques (p-0.054). The widely used plateau dose response model based estimation showed significantly lower SC risk associated with fIMRT technique compared to both wedge field techniques (fIMRT vs EDW p-0.013, fIMRT vs PW p-0.04). The full dose response model showed a non-significant difference between all three techniques in the view of second CLB cancer. Finally the bell shaped model predicted interestingly that PW is associated with significantly higher risk compared to both fIMRT and EDW techniques (fIMRT vs PW p-0.0003, EDW vs PW p-0.0032). Conclusion: In conclusion, the SC risk estimations of the CLB revealed that there is a clear relation between risk associated with wedge field and fIMRT technique depending on the choice of model selected for risk comparison.

• 대한두개안면성형외과학회지
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• 제18권3호
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• pp.162-165
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• 2017

Background: It is controversial issue that heparin decreases thrombosis for microsurgical anastomosis, and its effective role is under discussion. This study is for proving whether low-dose heparin is preventing thrombosis in free flap reconstruction. Methods: Through chart reviews of 134 patients, using low-dose heparin for free tissue transfer from 2011 to 2016, retrospective analysis was performed. 33 patients received low-dose heparin therapy after surgery. And 101 patients received no-heparin therapy. Complications included flap necrosis, hematoma formation, dehiscence and infection. Results: In no-heparin therapy group, comparing the flap necrosis revealed 16 cases (15.84%). And, flap necrosis was 6 cases (18.18%) in low-dose heparin therapy group. The statistical analysis of flap necrosis rate showed no significant difference (p=0.75). The results showed that there was no significant difference of flap necrosis rate between two groups. Conclusion: In this study, patients in the low-dose heparin group had no significantly lower rates of flap failure compared with no-heparin group. This suggests that low-dose heparin may not prevent thrombosis and subsequent flap failure to a significant extent.

• 대한방사선기술학회지:방사선기술과학
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• 제45권4호
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• pp.305-312
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• 2022

The proportion and testing of portable radiation tests, which are limited at the request of the doctor, are gradually increasing only for patients in emergency situations and difficulties in moving. However, as there are many limiting factors compared to fixed devices, this study intends to measure and analyze the distortion of images according to the angle of the detector and the change in dose according to the position of the subject. For distortion experiments using a mobile radiation generator used in Hospital A, the SID was tilted by 110 cm, 14"×17" wireless FPD detector to 0°, -5°, -10°, -15°, -20°, and -35° to measure the change in area. The dose according to the location of the detector was analyzed on average by measuring the central dose at 110 cm of the SID and measuring the dose of 9 locations three times each. The analysis result of distortion by location according to the angle of the detector showed a statistically significant difference (f=58.74, p<0.000). Therefore, it can be seen that the angle of the detector and the tube is closely related to the distortion of the image. The difference in dose by location of the detector increased with respect to the center - pole, and decreased with the + pole. Tests using mobile radiation generators will require careful efforts by clinicians to position patients in the center of the detector for accurate diagnosis, and efforts will be made to level the angle between the mobile radiation generators and the detector.