A dose based metric to assess the accuracy of image registration

The relationship between dose mapped using two mapping methods (energy mapping method and voxel warping method) and registration error was examined. The correlation between the difference in doses mapped using these methods, defined as dose mapping difference (DMD), and landmark distance to agreement for a realistic lung patient plan using registrations of varying accuracy was examined. Results showed no correlation between DMD and landmark error. Further investigation on simple dose mapping geometries revealed a correlation of DMD with fractional volume (FVC) change induced by registration errors. A formula for DMD as a function of FVC was derived. Results of this formula agreed with simulated values of DMD with percentage differences less than 3.5% in regions of uniform dose. However, no agreement was found in regions containing a dose gradient. Further work is required in order to extend this formula to regions of dose gradients and scenarios that emulate realistic deformations.