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TH‐C‐BRC‐05: A CMOS‐Based Digital Imager Integrated with An Orthovoltage X‐Ray Therapy Unit for Guidance of Precise Small Animal Irradiation
Author(s) -
Wang Z,
Saito N,
Podgorsak MB
Publication year - 2009
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3182619
Subject(s) - imaging phantom , nuclear medicine , irradiation , materials science , image resolution , frame rate , medical imaging , biomedical engineering , optics , medicine , physics , radiology , nuclear physics
Purpose: Orthovoltage x‐ray units are commonly used in experimental irradiation of small animal models. However, the irradiation of targets that are deep‐seated within the animal is rather problematic without an image‐guidance system. This study was aimed at evaluating the use of a CMOS‐based portal‐imaging system to provide image‐guidance for small animal irradiation using an orthovoltage unit. Method and Materials: The imaging system consists of a CMOS‐based x‐ray sensor and a frame grabber connected to a PC. A fast frame rate (20 frame/sec, 50 ms/frame exposure, 96 m pixel size) was used to minimize image saturation due to the relatively high output of a typical therapeutic x‐ray unit (Phillips RT‐250). We first evaluated the imaging system with a contrast and resolution phantom. A pilot animal study with this system was then carried out for experimental thoracic irradiation of mice to induce pulmonary fibrosis. We used 75‐kVp beam for imaging, and 250‐kVp beam for the treatment, while keeping the same irradiation geometry setup. Based on image findings, radiation shields to protect the critical organs were custom‐made. Results: The 8‐mm diameter contrast discs in the testing phantom, with a minimum contrast of 0.9%, are all visible in the images. The spatial resolution based on bar‐pattern findings is at least 4.0 lp/mm. Mouse anatomical structures are clearly visible in the images. The portal images provided sufficient information for target localization and shield placement in the mice lung irradiation experiments. Conclusion: The CMOS‐based imaging system provides high quality images. It is convenient to use in comparison to the use of x‐ray films. We expect more accurate small animal irradiation results under the portal‐imaging guidance. Development of future applications of the imager may include multi‐directional imaging guidance and 3‐dimentional cone‐beam CT guidance for animal irradiation. (Acknowledgment: Rad‐icon Imaging Corp. graciously provided the Shod‐o‐box™ imager for evaluation.)