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Original Article

Korean Journal of Medical Physics 2012; 23(1): 62-69

Published online March 25, 2012

Copyright © Korean Society of Medical Physics.

Improvement of the Dose Calculation Accuracy Using MVCBCT Image Processing

Megavoltage Cone-Beam CT 영상의 변환을 이용한 선량 계산의 정확성 향상

Min-Joo Kim*, Woong Cho*, Young-Nam Kang, Tae-Suk Suh*

김민주*ㆍ조웅*ㆍ강영남ㆍ서태석*

*Department of Biomedical Engineering, Research Institute of Biomedical Engineering, The Catholic University of Korea College of Medicine, Department of Radiation Oncology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Korea

가톨릭대학교 의과대학 *의공학교실, 생체의공학연구소, 가톨릭대학교 서울성모병원 방사선종양학과

Abstract

The dose re-calculation process using Megavoltage cone-beam CT images is inevitable process to perform the Adaptive Radiation Therapy (ART). The purpose of this study is to improve dose re-calculation accuracy using MVCBCT images by applying intensity calibration method and three dimensional rigid body transform and filtering process. The three dimensional rigid body transform and Gaussian smoothing filtering process to MVCBCT Rando phantom images was applied to reduce image orientation error and the noise of the MVCBCT images. Then, to obtain the predefined modification level for intensity calibration, the cheese phantom images from kilo-voltage CT (kV CT), MVCBCT was acquired. From these cheese phantom images, the calibration table for MVCBCT images was defined from the relationship between Hounsfield Units (HUs) of kV CT and MVCBCT images at the same electron density plugs. The intensity of MVCBCT images from Rando phantom was calibrated using the predefined modification level as discussed above to have the intensity of the kV CT images to make the two images have the same intensity range as if they were obtained from the same modality. Finally, the dose calculation using kV CT, MVCBCT with/without intensity calibration was applied using radiation treatment planning system. As a result, the percentage difference of dose distributions between dose calculation based on kVCT and MVCBCT with intensity calibration was reduced comparing to the percentage difference of dose distribution between dose calculation based on kVCT and MVCBCT without intensity calibration. For head and neck, lung images, the percentage difference between kV CT and non-calibrated MVCBCT images was 1.08%, 2.44%, respectively. In summary, our method has quantitatively improved the accuracy of dose calculation and could be a useful solution to enhance the dose calculation accuracy using MVCBCT images.

KeywordsDose calculation, Megavoltage Cone-beam CT, Adaptive radiation therapy

Korean Society of Medical Physics

Vol.35 No.4
December 2024

pISSN 2508-4445
eISSN 2508-4453
Formerly ISSN 1226-5829

Frequency: Quarterly

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