04/03/2024
By Erno Sajo

The Kennedy College of Sciences, Department of Physics & Applied Physics, invites you to attend a Master’s thesis defense by Samantha Maragioglio on "Longitudinal assessment of on-board imaging systems performance for re-evaluation of linear accelerator imaging qa requirements."

Candidate Name: Samantha Maragioglio
Degree: MS
Defense Date: Wednesday, April 10
Time: 11 a.m.-12:30 p.m.
Location: This will be a virtual defense via Zoom. Please contact the candidate at Samantha_Maragioglio@student.uml.edu
Thesis Title: Longitudinal assessment of on-board imaging systems performance for re-evaluation of linear accelerator imaging qa requirements

Committee:

  • Advisor Yulia Lyatskaya, Ph.D., Chief of Dosimetry and Quality Assurance, Radiation Oncology, Brigham & Women's Hospital/Harvard Medical School
  • Erno Sajo, Ph.D.
  • Mark Tries, Ph.D., Radiological Sciences

Abstract: The requirements for linear accelerator (linac) quality assurance (QA) are described in several AAPM publications (TG-142, TG-198, MPPG-8a, MPPG-2b); however disagreements exist on the frequency and types of tests recommended for on-board imaging (OBI). Maintenance and routine QA are essential for reducing downtime and ensuring smooth operations in clinic, but the current substantial time commitment of 1.75-2.75 hours required for monthly imaging QA calls for better definition of QA standards. This study uses in-house software to examine data on OBI performance and characterize the frequency, severity, and reporting pattern of technical issues on linac OBI to aid in defining data-driven recommendations for optimal OBI QA. Logs of reports related to linac issues or events from 2013-2023 were extracted from the central database of a single radiation oncology department with 7 linacs. Out of 32,543 total reports, 925 reports were identified as related to actionable linac OBI issues. 17%, 53%, and 30% of those actionable reports were categorized as severity level 1, 2, and 3, respectively. Reports of mechanical issues were predominant (34%), followed by software/communication issues (20%), image quality issues (13%), and imager alignment issues (2%). 54%, 32% and 14% of reports were filed by engineers, therapists and physicists, respectively. Results were consistent between different linacs and different years. Only 2% of reports were related to issues found during monthly QA; therapists and engineers report the majority of issues. These findings indicate that the nature of OBI behavior is unpredictable and generally not detectable during routine QA. The efficiency and efficacy of physics monthly imaging QA appears to be relatively low. These results support recommendations of MPPG2.b on preferential QA of mechanical parameters and potentially reducing frequency of image quality checks for on-board imaging. This may help departments with decisions related to the allocation of resources.