Monte Carlo calculated correction factors for the PTW microDiamond detector in the Gamma Knife‐Model C

Barrett, J. Carl; Knill, Cory

doi:10.1118/1.4940790

Cited by 11 publications

(13 citation statements)

References 41 publications

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“…The PTW 60019 microDiamond detector has been extensively studied for small field dosimetry. [24][25][26][27][28]37,38 For the 4 mm diameter cone used in this study, the ROF calculated using the zero area extrapolation technique was in good agreement to the ROF measured with the microDiamond detector. As such, we believe this agreement shows the suitability of using a zero area technique for these smaller fields in film dosimetry.…”

Section: Scan Resolutionsupporting

confidence: 69%

“…A best fit extrapolation technique was applied to the results to determine the zero area output factor utilizing a second order polynomial or linear function based on cone size and data requirements. Relative output factor measurements determined with a PTW 60019 microDiamond detector [24][25][26][27][28] (PTW, PTW-Freiburg, Germany) have also been included for comparison with the extrapolated Gafchromic EBT3 results. These measurements were made under the same geometrical conditions as the measurements for the Gafchromic EBT3 film.…”

Section: A Film Dosimetry Techniquementioning

confidence: 99%

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An experimental extrapolation technique using the Gafchromic EBT3 film for relative output factor measurements in small x-ray fields

et al. 2016

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This work shows that for very small fields such as 4.0 mm cone sizes, a measureable difference can be seen in the relative output factor based on the circular ROI and the size of the area of analysis using radiochromic film dosimetry. The authors recommend to scan the Gafchromic EBT3 film at a resolution of 1200 dpi for cone sizes less than 7.5 mm and to utilize an extrapolation technique for the output factor measurements of very small field dosimetry.

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Section: Scan Resolutionsupporting

confidence: 69%

Section: A Film Dosimetry Techniquementioning

confidence: 99%

An experimental extrapolation technique using the Gafchromic EBT3 film for relative output factor measurements in small x-ray fields

et al. 2016

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“…The results of one study investigating RapidArc (arc modulated delivery, Varian Medical Systems) for SRS indicated that for a 0.4 cm 3 target, their measured dose was 20% higher than the treatment planning system (TPS)-planned dose even when using a 1.25-mm dose calculation grid. 78 For PFX, 42,43,[79][80][81][82][83][84] CK with cone inserts, 56,[85][86][87][88][89][90][91][92][93][94] or linac with cone inserts, small-field dosimetry is also challenging; however, the discrete nature of the fixed collimator sizes in such dedicated systems minimizes the risk of user-dependent beam modeling error and focuses more user attention to verifying a finite set of dosimetric properties rather than modeling them. The clinical relevance of over-or underdosing in the context of multiple metastases SRS is unknown, as there are limited outcome data available; however, a factor when considering systems may be how susceptible a given system is to dosimetric error.…”

Section: Multiple (>4) Metastasesmentioning

confidence: 99%

Stereotactic radiosurgery alone for multiple brain metastases? A review of clinical and technical issues

Sahgal

Ruschin

et al. 2017

Neuro-Oncology

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Over the past three decades several randomized trials have enabled evidence-based practice for patients presenting with limited brain metastases. These trials have focused on the role of surgery or stereotactic radiosurgery (SRS) with or without whole brain radiation therapy (WBRT). As a result, it is clear that local control should be optimized with surgery or SRS in patients with optimal prognostic factors presenting with up to 4 brain metastases. The routine use of adjuvant WBRT remains debatable, as although greater distant brain control rates are observed, there is no impact on survival, and modern outcomes suggest adverse effects from WBRT on patient cognition and quality of life. With dramatic technologic advances in radiation oncology facilitating the adoption of SRS into mainstream practice, the optimal management of patients with multiple brain metastases is now being put forward. Practice is evolving to SRS alone in these patients despite a lack of level 1 evidence to support a clinical departure from WBRT. The purpose of this review is to summarize the current state of the evidence for patients presenting with limited and multiple metastases, and to present an in-depth analysis of the technology and dosimetric issues specific to the treatment of multiple metastases.

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“…If the machine is incapable of producing such a field, a machine-specific reference (MSR) field is used instead, taken to be the largest available field (e.g., 60 mm diameter circular field for CyberKnife). This formalism has been applied extensively for 55 individual field configurations, with several authors having calculated k f clin ,fmsr Q clin ,Qmsr correction factors in small individual fields (Cranmer-Sargison et al 2012, Ralston et al 2012, Scott et al 2012, Czarnecki & Zink 2013, Bassinet et al 2013, Azangwe et al 2014, Benmakhlouf et al 2014, Francescon, Beddar, Satariano & Das 2014, Francescon, Kilby & Satariano 2014, Moignier et al 2014, Barrett & Knill 2016.…”

Section: Introductionmentioning

confidence: 99%

Small composite field correction factors for the CyberKnife radiosurgery system: clinical and PCSR plans

et al. 2017

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A formalism has been proposed for small and non-standard photon fields in which [Formula: see text] correction factors are used to correct dosimeter response in small fields (indiviual or composite) relative to that in a larger machine-specific reference (MSR) field. For clinical plans consisting of several fields, a plan-class specific reference (PCSR) plan can also be defined, serving as an intermediate calibration field between the MSR and clinical plans within a certain plan-class. In this work, the formalism was applied in the calculation of [Formula: see text] for 21 clinical plans delivered by the [Formula: see text] radiosurgery system, each plan employing one or two of the smallest diameter collimators: 5 mm, 7.5 mm, and 10 mm. Three detectors were considered: the Exradin A16 and A26 micro chambers, and the W1 plastic scintillator. The clinical plans were grouped into 7 plan-classes according to commonly shared characteristics. The suitability of using a PCSR plan to represent the detector response of each plan within the plan-class was investigated. Total and intermediate correction factors were calculated using the [Formula: see text] Monte Carlo user code. The corrections for the micro chambers were large, primarily due to the presence of the low-density air cavity and the volume averaging effect. The correction for the scintillator was found to be close to unity for most plans, indicating that this detector may be used to measure small clinical plan correction factors in any plan except for those using the 5 mm collimator. The PCSR plan was shown to be applicable to plan-classes comprising isocentric plans only, with plan-classes divided according to collimator size. For non-isocentric plans, the variation of [Formula: see text] as a function of the point of measurement within a single plan, as well as the high inter-plan-class variability of the correction factor, precludes the use of a PCSR plan.

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Monte Carlo calculated correction factors for the PTW microDiamond detector in the Gamma Knife‐Model C

Cited by 11 publications

References 41 publications

An experimental extrapolation technique using the Gafchromic EBT3 film for relative output factor measurements in small x-ray fields

An experimental extrapolation technique using the Gafchromic EBT3 film for relative output factor measurements in small x-ray fields

Stereotactic radiosurgery alone for multiple brain metastases? A review of clinical and technical issues

Small composite field correction factors for the CyberKnife radiosurgery system: clinical and PCSR plans

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