PubMed · 13033217
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L LE BOUFFANT, J L SOULE. 1952-11-17. [An automatic procedure for granulometric analysis].. https://pubmed.ncbi.nlm.nih.gov/13033217/
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PURPOSE: In breast radiotherapy, delivery of manually-calculated electron boosts limits retrospective dose-response analyses as dose distribution is unavailable. This work evaluates the feasibility of reconstructing dose distributions from manually planned electron boosts in breast-conserving radiotherapy. METHODS: Only 72 out of 198 breast cancer patients had complete stored dose distributions from sequential electron boosts in the REQUITE study. Arbitrary data from 70/72 patients were used to develop and validate dose reconstruction method. Twenty patients were used to determine optimal parameters for Monte-Carlo-based (MC) electron dose reconstruction on RayStation (v.11B-R), considering CT-calibration curve, MC-history number, andcalculation grid resolution. Remaining 50 patients were used to quantify dose reconstruction accuracy. The similarity between reconstructed and stored dose was evaluated using 3D-gamma index and dosimetric parameters extracted from breast and tumour bed contours. Dose difference location was evaluated using dose-location histogram. RESULTS: Calculation grid resolution significantly impacted electron dose distribution (p < 0.01), where the finest grid (0.15 cm) showed highest similarity to stored doses. CT-calibration curve and MC-history number had a negligible influence on dose reconstruction. Dosimetric difference between reconstructed and stored doses was < 1 Gy for breast and tumour bed. Reconstructed dose was achieved > 90% gamma passing rate in the validation set. However, around 2.5 Gy dose differences were observed at the skin and tissue interface regions. CONCLUSIONS: Retrospective electron boost dose reconstruction is feasible with acceptable accuracy, and could increase data completeness in large cohort studies. Caution is advised when assessing dose near tissue interface and further validation is needed outside the REQUITE dataset.
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Microdosimetric distributions of protons, from 19 to 65 MeV, were measured using an A150-walled Low Pressure Proportional Counter at the cyclotron facility in the National Institute of Radiological Sciences. The measured distributions were found to be very different from the spectra assumed by the Continuous Slowing Down Approximation. The measurements consisted of determining the energy deposition by direct incident protons, by secondary electrons produced in the wall of the detector and by scattered protons at the wall. The secondary electron and the scattered proton distributions were studied using analytical functions and the MCNPX Monte Carlo code, respectively.