Author: Edwin Quashie, Yun Wang 👨🔬
Affiliation: Indiana University Medical School, Indiana University School of Medicine, Department of Radiation Oncology 🌍
Purpose: To provide a formal evaluation for the TrueBeam linac matching process before, during and after the commission of the newly installed TrueBeam linac which we want to match to an existing TrueBeam linac.
Methods: As the preparation of the linac matching (before the commission of the new linac), A through quality assurance check was performed on the existing linac. Special attention was paid to the isocenter checks, jaw calibrations, MLC position accuracy, DLG verification, and the RapidArc QA checks. The same beam scan system used to scan both machines, so we can compare them side by side. The existing machine was scanned first, and then used as the baselines to tune up the new machine. A comparison of the PDD, Sc,p, beam profiles are performed. This two machines are setup as the machine equivalent group in the RT Administration, and they share the same beam modes in the Beam Configuration. A full set of comparison plans are treatment delivered on both machines and the results are compared. To maintain the quality of the machine matching, the same physicist performs the monthly QA (after the commission) on the matched machines to ensure that both still have the same beam characteristics and the same absolute outputs within the tight tolerance. A test IMRT plans are also treatment delivered at both machines and the results are compared.
Results: The evaluation of the matching process before, during and after the commission provided the insurance of the matching quality. The results are tabulated, and the procedures are presented.
Conclusion: To have a formal evaluation of the machine matching process is important to ensure the quality of the treatment for the patients who are transferred from one machine to another.