1991 Fiscal Year Final Research Report Summary
Development of a CT Scanner for Patient Set-Up Using Linear Accelerator Megavoltage Treatment Beam.
| Project/Area Number |
01870046
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| Research Category |
Grant-in-Aid for Developmental Scientific Research
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| Allocation Type | Single-year Grants |
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| Research Field |
Radiation science
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| Research Institution | University of Tokyo |
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Principal Investigator |
AOKI Yukimasa University of Tokyo, Department of Radiology, Associate Professor, 医学部(病), 講師 (40143474)
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| Co-Investigator(Kenkyū-buntansha) |
KIKUCHI Hiroshi Mitsubishi Electric Co., Department of Linac Technology, Chief, 医療機器課, 主任研究員
KAWAKAMI Hideyuki Mitsubishi Electric Co., Department of Linac Technology, Engineer, 加速器技術課, 研究員
KARASAWA Katsuyuki University of Tokyo, Department of Radiology, Staff, 医学部(病), 助手 (80177617)
NAKAGAWA Keiichi University of Tokyo, Department of Radiology, Staff, 医学部(病), 助手 (80188896)
AKANUMA Atsuo National Institute for Radiological Sciences, Division of Radiation Health, Dire, 障害臨床研究部, 部長
NAKATSU Yoshihiko Mitsubishi Electric Co., Department of Computer Software, Engineer
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| Project Period (FY) |
1989 – 1991
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| Keywords | Treatment beam CT / Megavoltage CT / Radiotherapy / Treatment planning / Verification / 治療計画 / 線量計算 / CT |
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| Research Abstract |
Megavoltage CT scanning using 4 MV and 6 MV radiotherapy beams has been developed and applied to verify errors in patient positioning. A detector system composed of 120 pairs of cadmium tungstate scintillators with photodiodes is mounted to the treatment unit at a distance of 160 cm from the beam source. Image reconstruction is performed with a standard filtered back projection algorithm. Scanning time and reconstruction time for a slice is approximately 35 s and 60 s respectively. Although spatial resolution is as large as 4 mm, it has sufficient image quality to be applied for treatment planning and verification. The delivered dose with 4 MV and 6 MV is about 1.4 cGy and 2.8 cGy respectively. When a megavoltage CT image is taken in treatment position, the positioning errors are easily detected by comparing it with diagnostic CT sections for treatment planning. We have investigated a new method to detect positioning errors in a quantitative manner. Furthermore megavoltage CT can be utilized for patient positioning directly. With this technique the patient is lying down on the treatment couch till treatment planning is completed and strict reproducibility in positioning is assured. A dose calculation algorithm using relative electron density distribution for therapy beam has investigated. It increases accuracy of dose calculation in treatment planning, which contributes to increase local control rate. The megavoltage CT scanning enhances the availability of the high precision radiation therapy.
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