Abstract
Purpose: To investigate the dosimetric characteristics of a low energy photon intra-operative radiotherapy (IORT) system and explore its potential limitation in clinical application. Methods: A special water phantom, a parallel-plate ionization chamber and an electrometer were used to measure the depth dose rate, isotropy of dose distribution in X/Y plane, dosimetry reproducibility of bare probe and spherical applicators of different size which were used in comparison with the system data. Results: The difference in depth dose rate between the measurement and system data for bare probe is -2.16% ± 1.36%, the range of the relative deviation for isotropy in the X/Y plane is between -1.9% and 2.1%. The difference in depth dose rate, transfer coefficient, isotropy in X/Y plane between the measurement and system data for the whole set of spherical applicators is -10.0% - 2.3%, -8.9% - 4.2% and -1.6% - 2.6%, respectively. Higher surface dose rate and steeper gradient depth dose are observed in smaller spherical applicators. The depth dose rate and isotropy for bare probe and spherical applicators have been shown good reproducibility. The uncertainty of measurement is associated with the positioning accuracy, energy response, noise current and correction function f’(R). Conclusions: Thorough commissioning of the low energy photon IORT system helps us better understand the dosimetry characteristics, verify the system data, obtain adequate data for clinical application and routine quality assurance. The steep gradient depth dose and limited treatment range may restrain its potential in clinical application.
Highlights
Intra-operative radiotherapy (IORT) delivers single high dose radiation directly to the tumor bed within a relative short period of treatment time during the surgical operation, which requires a higher surface dose to protect the deep normal tissues
For patients enrolled at 33 centers in 11 countries, 1721 patients were randomised to targeted intraoperative radiotherpay (TARGIT) and 1730 to external beam radiotherapy (EBRT)
TARGIT-B is an ongoing multicenter randomised controlled trial that began in 2013, which is testing the replacement of EBRT boost to the tumor bed by a TARGIT boost given during surgery
Summary
Intra-operative radiotherapy (IORT) delivers single high dose radiation directly to the tumor bed within a relative short period of treatment time during the surgical operation, which requires a higher surface dose to protect the deep normal tissues. It often uses high energy electron beam or low energy photon beam. Vaidya J.S. et al have analysis overall survival of using as single-dose targeted intraoperative radiotherpay (TARGIT) versus fractionated external beam radiotherapy (EBRT) for breast cancer. TARGIT-B (for boost, ISRCTN43138042) is an ongoing multicenter randomised controlled trial that began in 2013, which is testing the replacement of EBRT boost to the tumor bed by a TARGIT boost given during surgery. An ongoing open registry study, TARGIT-R (for registry, ISRCTN91179875), began in 2013, aiming to monitor the long-term effectiveness and safety of the patients treated with TARGIT following breast conserving surgery for early breast cancer [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
