J Appl Clin Med Phys
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J Appl Clin Med Phys · Jan 2014
Quality assurance measurements for high-dose-rate brachytherapy without film.
The purpose of this study was to develop new and modified tools that allow HDR brachytherapy quality assurance tests to be carried out efficiently without film, video cameras, stopwatches, and mechanical rulers; and to devise methods that use these new tools for daily and quarterly check procedures, which are efficient and provide increased accuracy compared to previous methods. The HDR brachytherapy system tested was the GammaMedplus iX, Ir-192 HDR. Various catheters and treatment applicators designed for this system were tested. ⋯ Timer linearity and accuracy can be determined. Source strength can be confirmed. Measurement efficiency is improved compared to previous methods that used film, video cameras, mechanical rulers, and stopwatches.
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J Appl Clin Med Phys · May 2013
Volumetric-modulated arc therapy for the treatment of a large planning target volume in thoracic esophageal cancer.
Recently, volumetric-modulated arc therapy (VMAT) has demonstrated the ability to deliver radiation dose precisely and accurately with a shorter delivery time compared to conventional intensity-modulated fixed-field treatment (IMRT). We applied the hypothesis of VMAT technique for the treatment of thoracic esophageal carcinoma to determine superior or equivalent conformal dose coverage for a large thoracic esophageal planning target volume (PTV) with superior or equivalent sparing of organs-at-risk (OARs) doses, and reduce delivery time and monitor units (MUs), in comparison with conventional fixed-field IMRT plans. We also analyzed and compared some other important metrics of treatment planning and treatment delivery for both IMRT and VMAT techniques. ⋯ The key benefit for VMATI was the reduction in treatment delivery time and MUs, and improvement in dose conformality. In our study, we found no significant difference in VMATII over single-arc VMATI for PTV coverage or OARs doses. However, we observed significant increase in delivery time for VMATII compared to VMATI.
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J Appl Clin Med Phys · Jan 2013
Comparative StudyValidation of three deformable image registration algorithms for the thorax.
Deformable image registration (DIR) has been proposed for lung ventilation calculation using 4D CT. Spatial accuracy of DIR can be evaluated using expert landmark correspondences. Additionally, image differences between the deformed and the target images give a degree of accuracy of DIR algorithms for the same image modality registration. ⋯ For the DD algorithm, 71% of the voxels were within 50 HU, and 87% within a difference of 100 HU. These data suggest that the three DIR methods perform accurate registrations in the thorax region. The mean TRE for all three DIR methods was less than two voxels suggesting that the registration performed by all methods are equally accurate in the thorax.
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J Appl Clin Med Phys · Nov 2012
Six degrees of freedom CBCT-based positioning for intracranial targets treated with frameless stereotactic radiosurgery.
Frameless radiosurgery is an attractive alternative to the framed procedure if it can be performed with comparable precision in a reasonable time frame. Here, we present a positioning approach for frameless radiosurgery based on in-room volumetric imaging coupled with an advanced six-degrees-of-freedom (6 DOF) image registration technique which avoids use of a bite block. Patient motion is restricted with a custom thermoplastic mask. ⋯ This system is inexpensive compared to a couch-based 6 DOF system, improves patient comfort compared to systems that utilize a bite block, and is ideal for the treatment of pediatric patients with or without general anesthesia, as well as of patients with dental issues. From this study, it is clear that only adjusting for 4 DOF may, in some cases, lead to significant compromise in PTV coverage. Since performing the additional match with 6 DOF in our registration system only adds a relatively short amount of time to the overall process, we advocate making the precise match in all cases.
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J Appl Clin Med Phys · Jan 2012
A light field-based method to adjust rounded leaf end MLC position for split shape dose calculation correction in a radiation therapy treatment planning system.
We present an analytical and experimental study of split shape dose calculation correction by adjusting the position of the round leaf end position in an intensity-modulated radiation therapy treatment planning system. The precise light field edge position (Xtang.p ) was derived from 50% of the central axis dose created by nominal light field using geometry and mathematical methods. Leaf position (Xmlc.p), defined in the treatment planning system for monitor unit calculation, could be derived from Xtang.p. ⋯ The monitor unit calculation could provide underdosage or overdosage of 7.5% per mm without offset correction. Calibration could be performed at a certain SSD to fit all SSD offset corrections. With careful measurement and an accurate offset correction, it is possible to achieve the dose calculation with 0.5% error for the adjusted MLC leaf edge location in the treatment planning system.