Radiotherapy Dose Accumulation Routine (RADAR)- A novel dose accumulation script with built-in uncertainty.

Purpose: To incorporate uncertainty into dose accumulation for reirradiation.

Methods: The RADAR script for the Eclipse treatment planning system (Varian Medical Systems, Palo Alto, CA) 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 by 11 users, each of whom ran a separate spine reirradiation case, follows. Finally, RADAR run times are reported for different conditions.

Results: In the demonstration case in which a 3mm ellipsoid search was used, maximum RADAR 2 Gy equivalent (EQD2) accumulated spinal cord dose increased from 7244 cGy to 12689 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 an average of 31.6% with uncertainty applied compared to a conventional dose accumulation and decreased 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 depend on the number of plans being added and the type of uncertainty being used.

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