Journal of medical physics · 2023
Evaluation of In-room Volumetric Imaging Doses for Image-guided Radiotherapy: A Multi-institutional Study.
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Sakai Yusuke, Monzen Hajime, Takei Yoshiki, Kosaka Hiroyuki, Nakamura Kenji, Yanagi Yuya, Wakabayashi Kazuki, Hosono Makoto, Nishimura Yasumasa
Аннотация
AIMS: We investigated imaging dose and noise under clinical scan conditions at multiple institutions using a simple and unified method, and demonstrated the need for diagnostic reference levels in image-guided radiotherapy (IGRT).
MATERIALS AND METHODS: Nine cone-beam and helical computed tomography (CT) scanners (Varian, Elekta, Accuray Inc., and BrainLAB) from seven institutions were investigated in this study. The weighted cone-beam dose index (CBDIw) was calculated for head and pelvic protocols using a 100 mm pencil chamber under the conditions used in actual clinical practice at each institution. Cone-beam CT image noise was evaluated using polymethylmethacrylate head and body phantoms with diameters of 16 and 32 cm, respectively.
RESULTS: For head and pelvic protocols, CBDIw values ranged from 0.94-6.59 and 1.47-20.9 mGy, respectively. Similarly, standard deviation (SD) values ranged from 9.3-34.0 and 26.9-97.4 HU, respectively. The SD values tended to increase with decreasing imaging dose (r = -0.33 and -0.61 for the head and pelvic protocols, respectively).
CONCLUSIONS: Among the nine machines, the imaging dose for high imaging dose institutions was approximately 20 mGy to the pelvic phantom, and there was a 14-fold difference in dose compared with the other institutions. These results suggest the need to establish DRLs for IGRT to guide clinical decision-making.
MATERIALS AND METHODS: Nine cone-beam and helical computed tomography (CT) scanners (Varian, Elekta, Accuray Inc., and BrainLAB) from seven institutions were investigated in this study. The weighted cone-beam dose index (CBDIw) was calculated for head and pelvic protocols using a 100 mm pencil chamber under the conditions used in actual clinical practice at each institution. Cone-beam CT image noise was evaluated using polymethylmethacrylate head and body phantoms with diameters of 16 and 32 cm, respectively.
RESULTS: For head and pelvic protocols, CBDIw values ranged from 0.94-6.59 and 1.47-20.9 mGy, respectively. Similarly, standard deviation (SD) values ranged from 9.3-34.0 and 26.9-97.4 HU, respectively. The SD values tended to increase with decreasing imaging dose (r = -0.33 and -0.61 for the head and pelvic protocols, respectively).
CONCLUSIONS: Among the nine machines, the imaging dose for high imaging dose institutions was approximately 20 mGy to the pelvic phantom, and there was a 14-fold difference in dose compared with the other institutions. These results suggest the need to establish DRLs for IGRT to guide clinical decision-making.