PubMed · 14874656
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J H TABOR. 1951. Electron microscopy.. https://pubmed.ncbi.nlm.nih.gov/14874656/
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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.
The aim of our study is the development of a method for calculating the interface of dimerization of protein-protein complexes based on simplified medium-resolution structures. In particular, we wished to evaluate if the existing concepts for the computation of the Solvent-Accessible Surface Area (SASA) of macromolecules could be applied to medium-resolution models. Therefore, we selected a set of 140 protein chains and computed their reduced representations by topological analysis of their electron density maps at 2.85 A crystallographic resolution. This procedure leads to a limited number of critical points (CPs) that can be identified and associated to backbone and side-chain parts. To evaluate the SASA and interfaces of dimerization of the reduced representations, we chose and modified two existing programs that calculate the SASA of atomic representations, and tested (1) several radii tables of amino acids, (2) the influence of the backbone and side-chain points, and (3) the radius of the solvent molecule, which rolls over the surface. The results are shown in terms of relative error compared to the values calculated on the corresponding atomic representations of the proteins.
PURPOSE: To determine the relationships between electron beam depth dose characteristics, depth of maximum dose (d(max)), depth of 80% dose (d(80)), and depth of 50% dose (d(50)), and the nominal energy designation of electron beams from multiple linear accelerators for the purpose of electron beam treatment planning and quality assurance. METHODS: The Radiological Physics Center Staff, during its on-site dosimetry review visits to institutions participating in clinical trials, measured depth dose characteristics for more than 2000 electron beams. Measurements were performed on Varian, Siemens, and Elekta/Philips accelerators generating beams with nominal energy values ranging from 4-22 MeV. The depth dose data were determined at the nominal source-to-skin distance with the reference cone size in accordance with recommendation of the American Association of Physicists in Medicine Task Group 25 report. RESULTS: The important depth dose characteristics d(max), d(80), and d(50) varied in a predictable fashion when plotted against the true beam quality indicator, R(50). However, d(80) and d(50) values overlapped considerably when plotted against the manufacturers' nominal electron energy values. For a specific nominal electron energy value, the values of d(max), d(80), and d(50) varied by as little as 3 mm for low energy levels to nearly as much as 20 mm for high energies. CONCLUSIONS: The manufacturer's nominal electron energy value does not adequately describe the depth dose characteristics of an electron beam for treatment planning purposes. Clinicians and physicists should determine and use only the specific depth dose data for their clinical beams and not the manufacturer's nominal value.