Author: Alyssa Capizzi, John J Dombrowski, Nabil N. Khater 👨🔬
Affiliation: Saint Louis University 🌍
Purpose: To evaluate a mask-less adaptable headrest (MAHR) prototype for head-and-neck IMRT designed to reduce random and systematic shifts of patients’ setups. MAHR complements current image-guidance systems e.g., CBCT. MAHR was evaluated for setup time, tolerance, and pitch adjustment under optical surface monitoring systems (OSMS) guidance.
Methods: The testing was performed after IRB approval for human subjects (n=10) on two mask-less headrest systems developed in-house; MAHR - adjustable via pneumatic control, capable of correcting the head, spine and shoulder positions based on OSMS-guidance, and Headrest-2 (HR2) - rigid and conventional. The tests evaluate positioning reproducibility and the subjects’ tolerance for both headrests. The testing was performed by the radiotherapy team as follows: Position the subject and acquire an OSMS reference surface (RF); reposition the subject, record the setup time, for a duration of 5 minutes adjust the setup using MAHR to bring the current optical surface to match RF; capture the OSMS pitch real-time-data and a surface picture every minute; monitor the subject for 5 additional minutes to assess the subject’s tolerance. Comfort questionnaire was collected.
Results: The average setup times for all subjects: 163(135) sec (MAHR) vs. 51(23) sec (HR2) (p = 0.0044.) Questionnaire: 90% of subjects felt comfortable and 10% felt some pressure using MAHR vs. 50% and 50% respectively using HR2. During the 5-minute alignment time, MAHR reduced the initial OSMS pitch error to near-zero, placing the subject’s surface within +/- 3mm of RF.
Conclusion: MAHR helped minimizing the OSMS pitch error. It was tolerated by all subjects for 10 minutes (typical treatment time) and felt more comfortable than the conventional HR2. MAHR eliminates the use of mask known to be claustrophobic and to cause gag in some patients, while allowing exposure the head-and-neck topology for favorable optical guidance. Further clinical evaluation of MAHR is justified.