The limitations of dose reconstruction without treatment imaging

Dose reconstruction (DR) is a radiotherapy process in which the full three-dimensional dose actually delivered to a patient is computed. The calculation is performed on a CT of the patient in the actual treatment position using the actual energy fluence obtained from delivery verification (DV). This provides valuable information regarding the efficacy of a treatment. Specifically, this is the basis for fraction-by-fraction adaptive radiotherapy. However, dose reconstruction is only as accurate as the inputs to the computation, namely the verified fluence and the CT. Studies were conducted regarding the effects of positional errors and internal anatomy changes for a canine nasopharyngeal treatment and a prostate treatment on an abdominal phantom, respectively. It was found that energy fluence errors may or may not be detected in DV. However, even if an error was detected, the authors show that the potential effects on outcome could not possibly be addressed without a CT at the time of delivery.