When a linear accelerator is unavailable for treatment, a clinical decision is imminent regarding whether a patient should be treated on a linear accelerator other than the machine the patient was scheduled on, or whether treatment should be postponed until the original Linac becomes available. This work investigates the feasibility of switching patients to different accelerators for intensity-modulated radiation therapy (IMRT). We have performed Monte Carlo simulations of photon beams from different Linac models and vendors.
View Article and Find Full Text PDFAustralas Phys Eng Sci Med
March 2016
Ratio of percentage depth dose (PDD) at two depths, PDD at a depth of 10 cm (PDD10), and beam flatness are monitored regularly for radiotherapy beams for quality assurance. The purpose of this study is to understand the effects of changes in one of these parameters on the other. Is it possible to monitor only the beam flatness and not PDD? The investigation has two components.
View Article and Find Full Text PDFJ Appl Clin Med Phys
July 2014
The purpose of this study is to characterize and understand the long-term behavior of the output from megavoltage radiotherapy linear accelerators. Output trends of nine beams from three linear accelerators over a period of more than three years are reported and analyzed. Output, taken during daily warm-up, forms the basis of this study.
View Article and Find Full Text PDFPurpose: The goal of this work is to evaluate planning target volume (PTV)-to-skin proximity versus plan quality as well as the effects of calculation voxel size on dose uncertainty in the surface region.
Methods And Materials: A right-sided clinical target volume with the lateral border 5 mm from the surface was delineated on the computed tomographic data of a head-and-neck phantom. A 5-mm PTV expansion was generated except laterally where distances of 0-5 mm were used.
Int J Radiat Oncol Biol Phys
May 2012
Purpose: Magnetic resonance stereoscopic imaging (MRSI) of the prostate is an emerging technique that may enhance targeting and assessment in radiotherapy. Current practices in radiotherapy invariably involve image guidance. Gold seed fiducial markers are often used to perform daily prostate localization.
View Article and Find Full Text PDFIncreasing the dose rate offers time saving for IMRT delivery but the dosimetric accuracy is a concern, especially in the case of treating a moving target. The objective of this work is to determine the effect of dose rate associated with organ motion and gated treatment using step-and-shoot IMRT delivery. Both measurements and analytical simulation on clinical plans are performed to study the dosimetric differences between high dose rate and low dose rate gated IMRT step-and-shoot delivery.
View Article and Find Full Text PDFIntensity modulated radiation therapy (IMRT) offers a method of delivering radiation dose conforming to the shape of targets while minimizing the dose to the surrounding tissue and nearby critical organs. One popular device is the NOMOS MIMiC Collimator coupled to the CORVUS treatment planning system. The MIMiC collimator, mounted on a linac head, opens and closes one or more of its 40 small leaves as determined by the planner while the linac delivers radiation and the gantry rotates.
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