Lead shielding for electrons.

F M Khan; B L Werner; F C Deibel

doi:10.1118/1.594841

Home/Archive/PubMed

PubMed · 7290024

Lead shielding for electrons.

F M Khan·B L Werner·F C Deibel

View original source ↗Export metadata ↓

Abstract

Using a 13 MeV electron beam as an example, transmission curves for various thicknesses of lead were measured. The data indicated that the choice of shielding thickness depends greatly on the depth at which the measurements are made. The importance of this reference depth and criteria for shield design when shields of minimum thickness are required is discussed.

Explore related subjects

Electrons Evaluation Studies as Topic Lead Radiation Dosage Radiation Protection Radiotherapy Journal Article Research Support, U.S. Gov't, P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

F M Khan, B L Werner, F C Deibel. Lead shielding for electrons.. https://doi.org/10.1118/1.594841

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2026

Technical note: reconstructing dose distributions from manually planned electron boosts in breast radiotherapy.

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.

Electrons↗

PubMed2002

Dosimetry characteristics of degraded electron beams investigated by Monte Carlo calculations in a setup for intraoperative radiation therapy.

Degraded electron beams, as used for intraoperative radiation therapy (IORT) or similar complicated dosimetric situations, have different characteristics compared to conventional electron therapy beams. If international dosimetry protocols are applied in a direct manner to such degraded beams, uncertainties will be introduced in the absorbed dose determination. The Monte Carlo method has been used to verify experimentally determined relative absorbed dose distributions and output factors in an IORT geometry. Monte Carlo generated dose distributions are mostly within +/-2% or +/-2 mm of measured data. The simulated output variation between the IORT cones (relative output factors) are mostly within 2% of measured values. By comparing IORT and conventional electron beam characteristics (e.g. energy spectra, angular distributions and the contributions of different system components to these quantities) limitations and uncertainties of commonly used dosimetric techniques in IORT electron fields are quantified. The intraoperative treatment field contains a larger amount of scattered electrons, which leads to a broader energy spectrum as well as a wider angular distribution of electrons at the phantom surface. The dose from the scattered electrons can contribute up to 40% of the total dose at a depth of dose maximum, compared to approximately 10% for standard beams. A study of the energy spectra at the reference depth reveals that an uncertainty of the order of 1% can be introduced if ionization chamber based dosimetry is used to determine output factors for the investigated IORT system. We recommend that relative absorbed dose distributions and output factors in IORT electron beams and for similar complicated dosimetric situations should be determined with detectors having a small energy and angular dependence (e.g. diamond detectors or p-Si diodes).

Electrons↗

PubMed2002

Dielectric behaviour of gap junction connected cells: a microscopic approach.

The dielectric behaviour of interconnected cells is simulated by taking into account the 'real' shape. In previous work, we derived the polarizability of non-spherical, shelled, particles by solving the related integral equation using a spectral decomposition. The permittivity and impedance modulus spectra of gap junction connected cells are compared with those provided by a suspension of ellipsoids (prolate spheroids) having the same shape as the individual cells connected through gap junction, and the same volume fraction. This approach aims to provide a microscopic hint on the effect of the closing of gap junctions reported on the dielectric behaviour of ischaemic tissues, as well as to offer a rough approximation of a tissue by considering high concentrations of oriented gap junction connected cells.

Electrons↗