RAdiotherapy Dose Accumulation Routine (RADAR)-A Novel Dose Accumulation Script With Built-In Uncertainty

Purpose: To incorporate uncertainty into dose accumulation for reirradiation.

Methods and materials: The RAdiotherapy Dose Accumulation Routine (RADAR) script for the Eclipse treatment planning system (Varian Medical Systems) is described, and the voxel-wise ellipsoid search algorithm is introduced as a means of incorporating uncertainty. RADAR is first demonstrated on a test patient reirradiated to the spine, illustrating the effect of the uncertainty algorithm. A summary of initial evaluation testing conducted by 11 users, each of whom ran a separate spine reirradiation case, follows. Finally, RADAR run times are reported for various conditions.

Results: In the demonstration case in which a 3-mm ellipsoid search was used, the maximum RADAR 2-Gy equivalent (EQD2) accumulated spinal cord dose increased from 7244 to 12,689 cGy because the ellipsoid search pulled dose from closer to the adjacent target structure. When the ellipsoid search was restricted to voxels within the spinal cord, the maximum accumulated cord dose was reduced to 6523 cGy and did not exceed the sum of the maximum EQD2 spinal cord doses of the individual plans (6730 cGy). In the evaluation cases, the RADAR EQD2 maximum dose for the spinal cord increased by an average of 31.6% with uncertainty applied compared to a conventional dose accumulation and decreased by an average of 16.7% compared to a conventional dose accumulation when the uncertainty calculation was restricted to voxels within the spinal cord. RADAR run times vary depending on the number of plans added and the type of uncertainty used.

Conclusions: RADAR offers a novel way to directly account for uncertainty in dose accumulation through a voxel-wise ellipsoid search algorithm. EQD2 dose accumulation with and without dose discounts is also available.