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Determination of Source Positions in HDR Applicators for Commissioning/QA Using An Image Plate Device, Raven QA

I Bernstein*, B Yi , university of Maryland School Of Medicine, Baltimore, MD


(Wednesday, 8/1/2018) 10:00 AM - 10:30 AM

Room: Exhibit Hall | Forum 4

Purpose: A task to identify source positions in HDR applicators, such as ring- or tandem-GYN applicators is challenging. Conventional methods use the intensity distribution of the source in the applicator tightly attached to film or an imager. A novel jig has been developed which enables the user to calculate the source positions in the applicator by analyzing the marker positions of the jig projected from the HDR source onto an imager. This study is to test the performance of the jig for QA and commissioning HDR applicators.

Methods: The jig consists of three layers of plates which are 3-cm apart each; the top layer for the HDR applicator (6-7 cm above the imager). Radio-opaque 1-mm markers are located at the mid and bottom plates. The jig is placed on the image receptor plate of the RavenQA (LAP Laser, Germany). The RavenQA is a commercially available QA tool for TG-142 tasks, which consists of a fluorescent image receptor, a mirror system and a camera. The source moves in the applicator while the Raven QA system collects images in all dwell positions. The source position of each dwell position is calculated from the motion of the mid-plate marker positions in the image.

Results: The dummy source positions could be determined either from a CT image set or calculated from the autoradiograph using a HDR source located above the jig. All of the markers were visible and it was possible to separate the markers of mid plate and those of the bottom plate from the images. The bottom markers correct the image distortion and mid plate markers determined the source positions within 1.2mm precision. The total QA time took 10 minutes.

Conclusion: Source locations in the applicators can be determined using the jig developed in this study with the RavenQA system.

Funding Support, Disclosures, and Conflict of Interest: This project is supported in part by Maryland Industrial Partnership Program.


HDR, Quality Assurance, Commissioning


TH- Brachytherapy: Calibration & Quality Assurance

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