Dose Distribution Evaluation and Independent Quality Check of Spherical INTRABEAM™ Applicators via Radiochromic EBT2 Film Measurement

Introduction: The present study was conducted to implement a simple practical independent quality check of depth dose and isotropy of the Intrabeam™ therapeutic X-ray machine using radiochromic EBT2 film. Material and Methods: The independent quality check of 1.5, 3.5, and 5-cm spherical Intrabeam™ applicators was accomplished using particular EBT2 film cutting pieces with internal rounded edges in a water phantom. Prior to this measure, the film was calibrated at three distances from the 5-cm applicator in water to clarify the effects of beam spectrum and dose rate alteration on film response. To this end, three calibration curves were plotted. Results: The results of the one-way analysis of variance showed a critical difference between film pieces receiving equal doses at various distances (P<0.05). Therefore, depth dose curves were designed using all three calibration curves. Smaller applicators represented steeper dose fall-off, compared to the larger sizes. In this regard, 14.97%, 17.59%, and 30.92% of the relative mean doses were measured at 1 cm depth of 1.5-cm, 3.5-cm, and 5-cm applicators, respectively. A 10%/1mm gamma index was satisfied for the lateral dose evaluation of corresponding depth relative to Z-direction. Conclusion: The approach implemented in this study could be carried out as a rapid monthly quality check method for the dose distribution evaluation of the Intrabeam device.