This was completed for all clinical plans and ring gantry plans for the PTV and brain structures to compare the 2 sets of plans.
PURPOSE OF MULTILEAF COLLIMATOR IN RADIOTHERAPY SOFTWARE
In all cases, DVH data was exported for comparison using in-house developed software to compare groups of patients by calculating the median and inner fences of the DVH distributions across groups of plans. Wilcoxon signed-rank testing was used to compare the 2 paired data sets. Box and swarm plots of each parameter for both the original clinical plans and the ring gantry plans were created. A summary of these metrics and our departmental standards is given in Table 2. For all cases the conformity index (CI = V30 Gy/volume of PTV), gradient index (GI = V15 Gy/V30 Gy), gradient measure (GM = distance between equivalent spheres of the 30 Gy isodose to the 15 Gy isodose), homogeneity index (HI = max dose/30 Gy), R50 = V15 Gy/volume of PTV, and monitor unit ratio (MUR = total MU/3000 cGy) were collected.
ConclusionsĪnd quantitatively by collecting plan quality metrics and DVH data. RGLA plans showed a median reduction in delivery time of ≈50%. All plans were able to meet the departmental quality assurance requirements and were delivered under image guidance on an end-to-end phantom with measurements agreeing within 3% of the expected value. The population-based dose-volume histograms showed target coverage and organ-at-risk sparing similar to that of the clinical plans. These differences were not believed to be clinically significant because they met clinical goals. There were statistically significant increases in conformity and gradient indices, with median values of 1.09 versus 1.11 and 2.82 versus 3.13, respectively, for the c-arm versus RGLA plans. There were no statistically significant differences in the homogeneity index or number of monitor units between the 2 systems. RGLA plans showed increases in the 50% isodose in the axial plane but decreases in the sagittal and coronal planes. The RGLA plans were able to meet departmental standards for target coverage and organ-at-risk sparing and showed plan quality similar to the clinical plans.
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