Tissue–air ratios for narrow gamma‐ray beams

Nizin, Paul S.; Mooij, Rob

doi:10.1118/1.598319

Cited by 23 publications

(12 citation statements)

References 14 publications

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“…Some institutions have developed in‐house computer programs to verify the treatment shot times from the planning system for a prescribed dose 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 . These programs usually perform a point‐dose calculation based on tissue–air ratio (TAR) lookup table for narrow 60 Co beams (12) and an algorithm for patient skull geometry reconstruction 13 , 14 , 15 . At other institutions, this independent check has been done simply by comparing the reported dose rate from the planning system with that obtained from a precalculated decay table, under the assumption that the dose calculation in the planning system should always be accurate provided a correct dose rate of the Gamma Knife unit is used.…”

Section: Introductionmentioning

confidence: 99%

Two‐year experience with the commercial Gamma Knife Check software

Bhatnagar

Bednarz

et al. 2016

J Applied Clin Med Phys

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The Gamma Knife Check software is an FDA approved second check system for dose calculations in Gamma Knife radiosurgery. The purpose of this study was to evaluate the accuracy and the stability of the commercial software package as a tool for independent dose verification. The Gamma Knife Check software version 8.4 was commissioned for a Leksell Gamma Knife Perfexion and a 4C unit at the University of Pittsburgh Medical Center in May 2012. Independent dose verifications were performed using this software for 319 radiosurgery cases on the Perfexion and 283 radiosurgery cases on the 4C units. The cases on each machine were divided into groups according to their diagnoses, and an averaged absolute percent dose difference for each group was calculated. The percentage dose difference for each treatment target was obtained as the relative difference between the Gamma Knife Check dose and the dose from the tissue maximum ratio algorithm (TMR 10) from the GammaPlan software version 10 at the reference point. For treatment plans with imaging skull definition, results obtained from the Gamma Knife Check software using the measurement‐based skull definition method are used for comparison. The collected dose difference data were also analyzed in terms of the distance from the treatment target to the skull, the number of treatment shots used for the target, and the gamma angles of the treatment shots. The averaged percent dose differences between the Gamma Knife Check software and the GammaPlan treatment planning system are 0.3%, 0.89%, 1.24%, 1.09%, 0.83%, 0.55%, 0.33%, and 1.49% for the trigeminal neuralgia, acoustic neuroma, arteriovenous malformation (AVM), meningioma, pituitary adenoma, glioma, functional disorders, and metastasis cases on the Perfexion unit. The corresponding averaged percent dose differences for the 4C unit are 0.33%, 1.2%, 2.78% 1.99%, 1.4%, 1.92%, 0.62%, and 1.51%, respectively. The dose difference is, in general, larger for treatment targets in the peripheral regions of the skull owing to the difference in the numerical methods used for skull shape simulation in the GammaPlan and the Gamma Knife Check software. Larger than 5% dose differences were observed on both machines for certain targets close to patient skull surface and for certain targets in the lower half of the brain on the Perfexion, especially when shots with 70 and/or 110 gamma angles are used. Out of the 1065 treatment targets studied, a 5% cutoff criterion cannot always be met for the dose differences between the studied versions of the Gamma Knife Check software and the planning system for 40 treatment targets.PACS number(s): 87.55.Qr, 87.56.Fc

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Section: Introductionmentioning

confidence: 99%

Two‐year experience with the commercial Gamma Knife Check software

Bhatnagar

Bednarz

et al. 2016

J Applied Clin Med Phys

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“…The TPR values of the Gamma Knife beam in WFPs were close to those of a 1.86-cm diameter circular beam (14) or a 2 Â 2 cm 2 square beam in water (13), as shown in Fig. 5.…”

Section: Absorbed Dose Rate To Water and Tprmentioning

confidence: 78%

“…The solid circles denote the measured values; the solid line is a fitted curve. (13), the solid line denotes the circular beam data with diameter of 1.86 cm taken from previous work (14), the dash-dotted line denotes a 2 Â 2 cm 2 square beam, and the dotted line denotes a 4 Â 4 cm 2 square beam, both data sets are taken from previous work (13). All the single beam data were measured or calculated in water.…”

Section: Uncertainty Analysismentioning

confidence: 99%

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Determination of the Absorbed Dose Rate to Water for the 18-mm Helmet of a Gamma Knife

Chung

Hyun

Choi

et al. 2011

International Journal of Radiation Oncology*Biology*Physics

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“…There are numerous dose models in the literature, with the gold standard being a Monte Carlo technique that simulates each particle's path through the anatomy. We use an accurate 3D dose model developed in Nizin (1998) and Nizin and Mooij (1998). Positions within the anatomy where dose is calculated are called dose-points.…”

Section: Introductionmentioning

confidence: 99%

The influence of dose grid resolution on beam selection strategies in radiotherapy treatment design

Acosta

Ehrgott

Holder

et al.

Optimization in Medicine

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. (2008). The influence of dose grid resolution on beam selection strategies in radiotherapy treatment design. In C. J. S. Alves, P. M. Pardalos, & L. N. Vicente (Eds.), Springer AbstractThe design of a radiotherapy treatment includes the selection of beam angles (geometry problem), the computation of a fluence pattern for each selected beam angle (intensity problem), and finding a sequence of configurations of a multilef collimator to deliver the treatment (realization problem). While many mathematical optimization models and algorithms have been proposed for the intensity problem and (to a lesser extent) the realization problem, this is not the case for the geometry problem. In clinical practice, beam directions are manually selected by a clinician and are typically based on the clinician's experience. Solving the beam selection problem optimally is beyond capability of current optimization algorithms and software. However, heuristic methods have been proposed. In this paper we compare various heuristic approaches on a clinical case. In particular, we study the influence of dose point resolution on the performance of these heuristics. We also compare the solutions obtained by the heuristics with those achieved by a clinician using a commercial planning system.

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Tissue–air ratios for narrow gamma‐ray beams

Cited by 23 publications

References 14 publications

Two‐year experience with the commercial Gamma Knife Check software

Two‐year experience with the commercial Gamma Knife Check software

Determination of the Absorbed Dose Rate to Water for the 18-mm Helmet of a Gamma Knife

The influence of dose grid resolution on beam selection strategies in radiotherapy treatment design

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