Room: Exhibit Hall | Forum 6
Purpose: In conventional total body irradiation (TBI), therapeutic beams and films are usually used during simulation and treatment setup for lung block delineation and positioning. However, film developing prolongs the procedure, particularly when multiple films are needed to guide lung block positioning. This is not favorable because patient needs to hold still in treatment position during the entire process. Besides, using therapeutic beam for imaging exposes much dose to patients. This clinical project is to commission a Philips mobile X-ray unit to replace the use of film in TBI.
Methods: Our commissioning was performed in four steps. First, we tested the imaging capability of the mobile x-ray unit at extended source-to-detector distance (SDD) required for general TBI setup. Then we established a procedure to accurately position the x-ray unit, such that its focal spot is at the same position as the linac target at TBI treatment beam angles (usually around 270Â°). The third step was to verify the x-ray focal spot position can represent the position of linac target for a general TBI setup. As such, we placed two objects along beam path at different distances, and measured their sizes and relative distances using both film and x-ray image. At last, an end-to-end test on a lung phantom was performed to evaluate the feasibility of using the x-ray unit for lung block delineation and positioning.
Results: The measurements of the two objects on the film and x-ray images show a good agreement, demonstrating the accurate position of x-ray tube. The x-ray images and films taken during the end-to-end test present a high similarity, demonstrating the feasibility of using mobile x-ray unit for TBI.
Conclusion: We have successfully commissioned a mobile x-ray unit for TBI use, which not only shorten the procedure but also reduce imaging dose exposed to patients.