A method for acquiring random range uncertainty probability distributions in proton therapy.

A method for acquiring random range uncertainty probability distributions in proton therapy. Phys Med Biol. 2017 Oct 20;: Authors: Holloway SM, Holloway MD, Thomas SJ Abstract In treatment planning we depend upon accurate knowledge of geometric and range uncertainties. If the uncertainty model is inaccurate then the plan will produce under-dosing of the target and/or overdosing of OAR. We aim to provide a method for which centre and site-specific population range uncertainty due to inter-fraction motion can be quantified to improve the uncertainty model in proton treatment planning.
 
 Daily volumetric MVCT data from previously treated radiotherapy patients has been used to investigate inter-fraction changes to water equivalent path-length (WEPL). Daily image-guidance scans were carried out for each patient and corrected for changes in CTV position (using rigid transformations). An effective depth algorithm was used to determine residual range changes, after corrections had been applied, throughout the treatment by comparing WEPL within the CTV at each fraction for several beam angles. 
 
 As a proof of principle this method was used to quantify uncertainties for inter-fraction range changes for a sample of head and neck patients of Σ=3.39mm, σ = 4.72mm and overall mean = -1.82mm. For prostate Σ=5.64mm, σ = 5.91mm and overall mean = 0.98 mm. The choice of beam angle for head and neck did not affect...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research