SU-E-T-526: Evaluation of Dose Mapping Errors via Use of a Volume-Based Dose Mapping Method

Autor: W Watkins, H Chen, F. J. Salguero, N Saleh-Sayah, Jeffrey V. Siebers, E Heath, C Yan
Rok vydání: 2017
Předmět:
Zdroj: Medical physics. 39(6Part18)
ISSN: 2473-4209
Popis: Purpose: To quantify dose mapping errors (DMEs) of a point‐based dose mapping method for 4D lung treatment plans. Methods: Point‐based dose mapping methods utilize deformation vector fields (DVFS) to interpolate dose from a deformed image. Volume‐based dose mapping methods consider the volume overlap between deformed and reference voxels; defining dose as the integral energy divided by the integral mass of the voxel, and conserving integral dose . DME is defined as the dose differences between volume‐based and point‐based mapped dose (DME=( DpointBased‐DvolumeBased)/DRx). The DME for a 4D lung case is compared with a bitmap DME method, both using a Pinnacle research version 8.1y DVF. DME is computed for ten 4D lung cases (five 10 phases, five 3 phase) with Pinnacle research version 9.100 DVFs. Multi‐phase accumulated 4D DMEs are also evaluated. Results: For all cases, the largest DMEs are located in the dose/density gradient regions. With Pinnacle 8.1y DVF, mapping dose from phase 9 to phase 0, results in a DME=−0.2%±6.1% (range of −76%∼112%). The same case with Pinnacle 9.100 DVFs, DME=0.3%±4.8%(−41%∼32%). Locations of large DME are consistent with those from the bitmap method. For the ten 4D lung cases, accumulated mean DME are within ±0.07% (std. deviations: 1∼5%, range −102%∼64%). Maximum tumor DMEs are less than 30cGy (DRx=7200cGy) for all patients. Conclusions: Due to its inherent integral dose conservation, volume‐based dose mapping methods can quantify errors in point‐based dose mapping methods. While mean DME values are small for the cases tested, standard deviations near 5% indicate that a substantial number of voxels have ∼5% dose mapping errors, however these dose errors do not occur in the target structures. Work supported by NIH P01CA116602
Databáze: OpenAIRE
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