Imaging Dose From Radixact ClearRT Kilovoltage Imaging
Presentations
PO-GePV-M-185 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: To assess the in-field and peripheral dose from kilovoltage (kV) imaging of the Accuray Radixact system. The kV imaging is a new addition to the Radixact system, complementing its megavoltage imaging capability
Methods: Imaging dose from various protocols was measured in standard CTDI head and body phantoms and compared to values measured on a Varian TrueBeam CBCT and a Philips CT scanner. In addition, 3D printed slices of the Rando phantom with an ionization chamber insert were utilized to measure the dose within phantom for a number of protocols. Out-of-field dose measurements were done by imaging the Rando phantom and measuring the dose at 10 cm from imaging field edge in solid water. The Rando phantom measurements were also repeated for the Varian and Philips systems.
Results: Imaging dose scales linearly with the ClearRT scan parameters: “body size” and “mode”. The field of view change from 270 to 440 cm increases the dose by a factor of two. The CTDI values are, in general, comparable to Varian CBCT ones. In-field measurements in phantom are a better indicator of organ dose and are highly dependent on the protocol used. The ClearRT out-of-field dose is generally higher than the other two systems. Measurements in Rando phantom indicate a range of values between 1 and 4 cGy for an 18 cm long scan, depending on the protocol used.
Conclusion: The in-field Radixact kV imaging dose is consistently higher than that of Varian TrueBeam CBCT scans in head and neck and less than the Philips CT. In the thorax and pelvis, it could be higher or lower depending on the protocol used. The out-of-field dose of this system is generally higher than TrueBeam CBCT and Philips CT. The imaging dose increases with the “body size” selection and choosing finer modes, as expected.
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