Room: Exhibit Hall | Forum 9
Purpose: To evaluate the impact of using a surface imaging system, AlignRT, on the number of portal images acquired during setup for breast cancer patients.
Methods: The number of portal images acquired during initial and weekly setups was evaluated for 530 consecutive breast cancer patients since July 2015. Patients were treated at two locations, L1 and L2, which started using AlignRT in March 2016 and September 2017 respectively. We recorded the number of fields (as a measure of treatment complexity), laterality (to assess the effect of breath hold), and couch displacement between first and last port (to evaluate initial setup error).
Results: 207 patients were set up using AlignRT and 323 were not. The number of excess ports beyond minimum (i.e., one per field) showed a statistically significant decrease of 2-3 ports for initial setups (median, Mann-Whitney U test, pL1=0.003 and pL2<0.0001) and 1 port for weekly setups (p<0.0001) when using AlignRT. The benefit was greater for more complicated cases. For breath hold cases at L2, the median decrease in ports was double that of non-breath hold cases when using AlignRT. At L1, 2 additional ports (median, Mann-Whitney U test, pL1=0.041) were required when not using AlignRT for two-field plans, but this number jumped to 4 additional ports (median, Mann Whitney U test, pL1=0.018) for three-field plans. The magnitude of couch correction needed in all three directions between first and last ports was also 4-7 mm smaller using AlignRT (median, Mann-Whitney U test, pL1=0.0003 and pL2<0.0001).
Conclusion: The use of surface imaging, on average, reduced the number of portal images acquired during breast cancer patient setup.