(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: A viable method for treating nonmelanoma skin cancers is surface-applicator based electronic brachytherapy. The devices are easily implementable in clinical settings without the need for stringent radiation safety protocols such that are necessary in alternative brachytherapy programs. Defining characteristics of quality unit performance, however, can be complicated by several factors including: lack of literature for this application, manufacturer specifications defined for averages of many sources that are difficult to interpret on a source-by-source basis, and implementation of the technology in scenarios that may lack resources of expertise and equipment to properly evaluate meaningful device operation. It is for these reasons that a revisitation of the commissioning of a surface applicator-based electronic brachytherapy program is conducted with the end-goal of providing a source by-use robust and practical analysis mechanism.
Methods: The results are relegated to commissioning measurements conducted following acceptance testing but prior to first patient treatment. They include general device performance tests including evaluations of: ramp-up performance and beam and output stability. Also conducted are surface-applicator specific tests including evaluations of: dose-rate calibration, percentage depth dose, half-value layer, effective inverse-square, and flatness and symmetry.
Results: Effective ramp-up time was determined to be 1.93 seconds via linear regression with zero intercept. Beam stability was determined to vary from 0.13% during a typical treatment delivery. Output stability as a function of iterated calibrations showed adherence to initial calibration and subsequent expectations asserted by the source manufacturer. TG-61-based dose rate calibrations resulted in nominal surface dose rate in water standard deviations ranging from 0.013 to 0.06 gray per minute. Flatness varied dramatically from source-to-source with maximum observed ranging values on the order of ±15%.
Conclusion: Surface-applicator based electronic brachytherapy can provide an easy to implement and effective treatment; however, commissioning baselines should be evaluated on a source-by-source basis.
Keywords
Taxonomy
TH- Brachytherapy: Calibration & Quality Assurance
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