Nada Tomic1, Pavlos Papaconstadopoulos2, Saad Aldelaijan3, Juha Rajala4, Jan Seuntjens5, Slobodan Devic6. 1. Medical Physics Unit, McGill University, Montréal, Québec, Canada; Department of Radiation Oncology, SMBD Jewish General Hospital, Montréal, Québec, Canada. Electronic address: nada.tomic@mcgill.ca. 2. Medical Physics Unit, McGill University, Montréal, Québec, Canada; Department of Radiation Oncology, SMBD Jewish General Hospital, Montréal, Québec, Canada. 3. Medical Physics Unit, McGill University, Montréal, Québec, Canada; Department of Radiation Oncology, SMBD Jewish General Hospital, Montréal, Québec, Canada; Biological & Biomedical Engineering Department, Montreal Neurological Institute, Montréal, Québec, Canada; Biomedical Physics Department, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia. 4. Radiotherapy Department, Vaasa Central Hospital, Vaasa, Finland. 5. Medical Physics Unit, McGill University, Montréal, Québec, Canada. 6. Medical Physics Unit, McGill University, Montréal, Québec, Canada; Department of Radiation Oncology, SMBD Jewish General Hospital, Montréal, Québec, Canada; Segal Cancer Centre, Jewish General Hospital, McGill University, Montréal, Québec, Canada.
Abstract
PURPOSE: We compare image quality parameters derived from phantom images taken on three commercially available radiotherapy CT simulators. To make an unbiased evaluation, we assured images were obtained with the same surface dose measured using XR-QA2 model GafChromic™ film placed at the imaging phantom surface for all three CT-simulators. METHODS: Radiotherapy CT simulators GE LS 16, Philips Brilliance Big Bore, and Toshiba Aquilion LB were compared in terms of spatial resolution, low contrast detectability, image uniformity, and contrast to noise ratio using CATPHAN-504 phantom, scanned with Head and Pelvis protocols. Dose was measured at phantom surface, with CT scans repeated until doses on all scanners were within 2%. RESULTS: In terms of spatial resolution, the GE simulator appears slightly better, while Philips CT images are superior in terms of SNR for both scanning protocols. The CNR results show that Philips CT images appear to be better, except for high Z material, while Toshiba appears to fit in between the two simulators. CONCLUSIONS: While the image quality parameters for three RT CT simulators show comparable results, the scanner bore size is of vital importance in various radiotherapy applications. Since the image quality is a function of a large number of confounding parameters, any loss in image quality due to scanner bore size could be compensated by the appropriate choice of scanning parameters, including the exposure and by balancing between the additional imaging dose to the patient and high image quality required in highly conformal RT techniques.
PURPOSE: We compare image quality parameters derived from phantom images taken on three commercially available radiotherapy CT simulators. To make an unbiased evaluation, we assured images were obtained with the same surface dose measured using XR-QA2 model GafChromic™ film placed at the imaging phantom surface for all three CT-simulators. METHODS: Radiotherapy CT simulators GE LS 16, Philips Brilliance Big Bore, and Toshiba Aquilion LB were compared in terms of spatial resolution, low contrast detectability, image uniformity, and contrast to noise ratio using CATPHAN-504 phantom, scanned with Head and Pelvis protocols. Dose was measured at phantom surface, with CT scans repeated until doses on all scanners were within 2%. RESULTS: In terms of spatial resolution, the GE simulator appears slightly better, while Philips CT images are superior in terms of SNR for both scanning protocols. The CNR results show that Philips CT images appear to be better, except for high Z material, while Toshiba appears to fit in between the two simulators. CONCLUSIONS: While the image quality parameters for three RT CT simulators show comparable results, the scanner bore size is of vital importance in various radiotherapy applications. Since the image quality is a function of a large number of confounding parameters, any loss in image quality due to scanner bore size could be compensated by the appropriate choice of scanning parameters, including the exposure and by balancing between the additional imaging dose to the patient and high image quality required in highly conformal RT techniques.
Authors: Richard Y Wu; Tyler D Williamson; Narayan Sahoo; Trang Nguyen; Shane M Ikner; Amy Y Liu; Paul G Wisdom; MingFu Lii; Rachel A Hunter; Paola E Alvarez; G Brandon Gunn; Steven J Frank; Yoshifumi Hojo; X Ronald Zhu; Michael T Gillin Journal: Phys Imaging Radiat Oncol Date: 2020-03-26