Room: AAPM ePoster Library
To quantify the improvement in head and neck (H&N) patient setup reproducibility following 2 cycles of process improvement at the immobilization and simulation stages of the RT process.
The head and neck positioning verification at our centre requires daily CBCT imaging with 6 degree-of-freedom 3D/3D matching. A second CBCT is required when any applied rotation = 2 degrees. At implementation, H&N immobilization consisted of a choice of standard headrest (6 styles available) coupled with a 5-point thermoplastic mask formed in the cast and mould room. Three months following the implementation of the policy, the location of manufacture of thermoplastic masks, still made by the cast and mould staff, was moved to the CT-Sim. Four months later custom headrests were introduced, replacing standard headrest. Throughout the process, the reproducibility of the patient positioning was assessed by quantifying the percentage of repeat CBCTs required per patient to reach treatment position. The percentage of patients requiring a replan during the treatment course was also assessed as a secondary metric.
Data was collected for 2468 H&N fractions representing 95 patients between March and December 2019. Baseline data shows that patients (n=25 patients) received 21% repeat CBCTs. With thermoplastic masks being formed at CT-Sim (n=49 patients), 19% repeat CBCTs were performed. After the introduction of custom headrests (n=21 patients), only 14% repeat CBCTs were performed. The percentage of patients requiring replans decreased from 48%, to 35%, to 19% from baseline to each cycle of process improvement, respectively.
Incremental improvement to the immobilization and simulation of H&N patients has resulted in marked decrease in the amount of CBCT exposure needed to reach treatment position. Coupled with a dramatic decrease in the amount of replans required, this resulted in more efficient use of simulation, planning, and treatment resources.