Investigation of KV Imaging Dose in Accelerated Partial Breast Irradiation (APBI)
Y Song1*, X Zhai2, Y Liang3, B Mueller4, D Guttmann5, D Roth O'Brien6, L Braunstein7, (1) Memorial Sloan Kettering Cancer Center, Bergen, NJ,(2) Memorial Sloan Kettering Cancer Center, Bergen, NJ,(3) Memorial Sloan Kettering Cancer Center, Bergen, NJ,(4) Memorial Sloan Kettering Cancer Center, Bergen, NJ,(5) Memorial Sloan Kettering Cancer Center, Bergen, NJ,(6) Memorial Sloan Kettering Cancer Center, Bergen, NJ,(7) Memorial Sloan-Kettering Cancer Center, New York, NY
Presentations
PO-GePV-T-94 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: Daily kV imaging with matching on surgical clips is a standard component of the setup procedure for accelerated partial breast irradiation (APBI). Daily kV imaging contributes non-therapeutic radiation dose and may have long-term toxicity implications. Therefore, we evaluated kV imaging dose in comparison to both treatment dose and linear accelerator head leakage dose.
Methods: kV imaging doses were measured with a diagnostic ionization chamber for three Varian TrueBeam linear accelerators. The default Thorax Arms Up kV imaging protocol was used with acquisition parameters: 100kVp, 10mAs, and large body size. Three measurements were taken for each machine. To assess head leakage dose produced by a typical APBI plan, a test plan was created with X-jaw = 9.7cm, Y-jaw = 9.3cm, total MU = 443 (the mean values among 20 clinical APBI plans). Measurements were made at isocenter, 10cm, and 20cm to the right and inferior directions, respectively.
Results: Mean kV imaging doses at the isocenter were 0.1405cGy, 0.1155cGy, and 0.1198cGy for three independent machines. In comparison to the APBI treatment dose of 400cGy/fraction, these doses represent 0.02995%, 0.03513%, and 0.02888%. Mean head leakage doses were 2.738cGy at isocenter, 0.284cGy at 10cm-right, 0.173cGy at 20cm-right, 0.5468cGy at 10cm-inferior, and 0.2779cGy at 20cm-inferior.
Conclusion: Daily kV imaging contributes minutely to overall dose from a course of APBI, conferring less than one-tenth of the head leakage dose. This amount of non-therapeutic radiation exposure is not expected to have significant adverse clinical effects.
Funding Support, Disclosures, and Conflict of Interest: This research was funded in part by the NIH/NCI Cancer Center Support Grant P30 CA008748, The Lois Green Fund, and The Rose-Margulies Family Research Fund
Keywords
Breast, X Rays, Radiation Risk
Taxonomy
IM- Radiation Dose and Risk: General (Most Aspects)
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