To study the dosimetric effect of Qfix kVue Calypso-compatible couch top and rails for spine stereotactic body radiation therapy (SBRT) patients treated with intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques. Materials/Methods: The computed tomography (CT) dataset for Qfix kVue Calypso-compatible couch top with rails were imported into the treatment planning system (TPS). Ten patients who underwent spine SBRT at our institution were selected for this study. The patients were treated initially on a stereotactic linear accelerator without the couch being part of the dose calculation. Eight patients were treated with static IMRT posterior fields and 2 patients were treated using the VMAT technique. Couch top and rails were added to the structures as support devices and the dose was recalculated for (a) couch top and rails (CR) (b) couch-top and no rails (CNR), then the results were compared the results to no couch-top no-rails (NCNR). Dose covering 100% of the target volume (D100%), dose covering 99% of the target volume (D99%), dose covering 95% of the target volume (D95%), dose covering 90% of the target volume (D90%), volume receiving 100% of the prescription dose (V100%), conformal index (CI), dose gradient index (DGI), and spinal cord threshold and maximum doses were compared to the initial plan with NCNR.
Purpose: GATE, a Geant4 based application for use in emission tomography, is a powerful package that permits realistic Monte Carlo simulations of both, the scanner geometry and the digitization chain. The main problem when using GATE in practice is its slow simulation speed. The purpose of this investigation is to improve the efficiency of PET related simulations. Method and Materials: An EGSnrc based radiation transport tool, referred to as egs_pet, is developed. egs_pet can be used together with GATE in two modes: In mode 1, egs_pet performs the simulation of radiation transport in the phantom and passes exiting particles to GATE for further transport through the scanner geometry and for digitization. In mode 2, egs_pet performs the entire simulation and writes energy depositions in the detectors to a file. GATE is modified to be able to read this file when performing the digitization. Results: The correct operation of egs_pet within GATE is validated using benchmark calculations of a source within a water phantom and a detailed model of the GE Advance PET scanner. In mode 1, the number of singles and coincidences are found to agree with GATE within the statistical uncertainties (0.2% for singles). Differences of about 0.5% are observed in mode 2, which can be attributed to differences between Geant4 and EGSnrc when modeling binding effects for photon interactions in BGO. For a 4 mm voxel phantom, the simulation efficiency is increased by a factor of 4 in mode 1, and by a factor of 130 or 44 with digitization excluded or included in mode 2. Conclusion: A new Monte Carlo tool for PET simulations based on EGSnrc is developed and incorporated into GATE. Significant gains in simulation efficiency are achieved. Results from egs_pet simulations agree with GATE at the 1% level.
The simulation of the transport of characteristic x rays plays an important role, if an accurate modeling of a PET scanner system is to be achieved. The simulation time decreases slowly with the increase of the cut which, combined with the accuracy loss at high cuts, means that the usage of high photon energy cuts is not recommended for the acceleration of MC simulations.
This work describes an algorithm for automatic counting of alpha tracks in scanned images of electrochemically etched CDs and DVDs. It is demonstrated that the algorithm copes with the specific problems encountered in retrospective 222 Rn measurements with CDs and DVDs; it reliably separates overlapping tracks and ignores artifacts in the image. The algorithm is validated by comparison to manual counting and a very good correlation is found. The measurement range of 222 Rn concentrations in dwellings and soil gas is estimated. It is shown that the wide span of track densities that can be covered by the algorithm combined with the specific advantages of the compact disc method can provide reliable measurements in the whole range of 222 Rn concentrations of practical interest. For retrospective measurements of 222 Rn in dwellings the estimated range is from 10 Bq m 3 to 100 kBq m 3 for five years exposure time. For 222 Rn in soil gas the estimated range is from 1 kBq m 3 to 10 MBq m 3 for ten days exposure time.
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