PubMed · 13880167
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D C COGAN. 1961. Electron microscopy.. https://doi.org/10.1001/archopht.1961.00960010774002
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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.
Five multilevel model chemistries (CBS-QB3, G3B3, G3MP2B3, MCG3/3, and MC-QCISD/3) and seven hybrid density functional methods (PBE0, B1B95, B3LYP, MPW1KCIS, PBE1KCIS, and MPW1B95) have been applied to the calculation of gas-phase basicity and proton affinity values for a series of 17 molecules relevant to the study of biological phosphoryl transfer. In addition, W1 calculations were performed on a subset of molecules. The accuracy of the methods was assessed and the nature of systematic errors was explored, leading to the introduction of a set of effective bond enthalpy and entropy correction terms. The multicoefficient correlation methods (MCG3/3 and MC-QCISD), with inclusion of specific zero-point scale factors, slightly outperform the other multilevel methods tested (CBS-QB3, G3B3, and G3MP2B3), with significantly less computational cost, and in the case of MC-QCISD, slightly less severe scaling. Four density functional methods, PBE1KCIS, MPW1B95, PBE0, and B1B95 perform nearly as well as the multilevel methods. These results provide an important set of benchmarks relevant to biological phosphoryl transfer reactions.
A comprehensive survey of computational methods: semiempirical (ZINDO/S), Time-Dependent Hartree-Fock (TD-HF), Configuration Interaction Singles (CIS), and several approximate functionals within the Time-Dependent Density Functional Theory (TD-DFT) has been carried out for the description of vertical excitation energies and oscillator strengths of retinal and related polyenals. ZINDO and TD-DFT computations showed the best agreement with the experimental data. In particular, hybrid functionals including approximately 25% of exact exchange (B3LYP, B3P86, and PBE0) were found to perform best with these highly conjugated polyenes. A systematic average error of 0.18-0.22 eV has been found after a simple one-parameter correction. Thus, 0.18 eV might be considered the upper limit of accuracy for current one-determinant methods in the computation of vertical excitation energies. The consideration of adiabatic excitations, conformational sampling, solvation, and nondynamic correlation should describe this processes more accurately, but this leads to highly demanding methods beyond feasibility for these large polyenes. The trends observed, particularly the good performance of the ZINDO/S method, should pave the way for the prediction of excited states properties in natural and artificial photoreceptor proteins, thus advancing towards the description of their light-transducing biological role in Nature.