Author: Robert A. Dahl 👨🔬
Affiliation: Mayo Foundation 🌍
Purpose: To develop tools to simplify/accelerate the quality assurance testing of the Mobetron mobile linear accelerator and increase safety when moving it to different OR’s.
Methods: The Mobetron does not have a field light or crosshairs which makes QA setup more time consuming. Alignment caps which have a pin at the isocenter location were manufactured for the different style of applicators in use (circular 0°/30°, rectangular 0°/20°).
Since the Mobetron is non-isocentric and has no accessory mount, a method of testing the output/flatness/symmetry at various gantry angles is needed. A plastic applicator cap that holds five electron IBA diodes (CA, +/- in-plane/cross-plain) was manufactured to fit the 10cm circular applicator.
Five OR’s and the Gamma Knife suite are configured to allow Mobetron treatments or QA testing. A camera system was developed to allow visualization of the area in front of the Mobetron while moving to or from the storage location.
Results: When used with a water phantom the pin on the alignment caps protrudes into the water by 1/8” which allows the center of the scanning chamber to be positioned at “isocenter”. The alignment can also be done on a solid plastic phantom block.
The electron scanning diodes are connected to a Scanditronix DPD-12pc electrometer which allows simultaneous readouts of the five diodes. The diode readings are entered into an Excel sheet for calculation.
A GoPro HERO12 Black camera with an Ultra Wide Lens (177° FOV) is mounted on the front of the Mobetron and connected via Bluetooth to the GoPRO Quik software on an Apple iPad which is mounted on the back of the Mobetron.
Conclusion: The QA tools developed allow for quicker equipment setup and can reduce MU’s needed for testing. Visualization of the front of the Mobetron while moving increases personnel safety.