Improvement of single detector proton radiography by incorporating intensity of time-resolved dose rate functions.

Improvement of single detector proton radiography by incorporating intensity of time-resolved dose rate functions. Phys Med Biol. 2017 Nov 08;: Authors: Zhang R, Jee KW, Cascio EW, Sharp GC, Flanz JB, Lu HM Abstract Proton radiography, which images patients with the same type of particles as what they are to be treated with, is a promising approach to image guidance and water equivalent path length (WEPL) verification in proton radiation therapy. We have shown recently that proton radiographs could be obtained by measuring time-resolved dose rate functions (DRF) using an x-ray amorphous silicon flat panel. The WEPL values were derived solely from the root-mean-square (RMS) of DRFs while the intensity information in the DRFs was filtered out. In this work, we explored the use of such intensity information for potential improvement in WEPL accuracy and imaging quality. Three WEPL derivation methods based on, respectively, the RMS only, intensity only, and the intensity weighted RMS were tested and compared in terms of the quality of obtained radiograph images and the accuracy of WEPL values. A Gammex CT calibration phantom containing inserts made of various tissue substitute materials with independently measured relative stopping powers (RSP) were used to assess the imaging performances. Improved image quality with enhanced interfaces was achieved while preserving the accuracy by utilizing intensity information in the calibration. Othe...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research