An algorithm for independent verification of Gamma Knife™ treatment plans

Beck, James F.; Berndt, Anita

doi:10.1118/1.1786532

Cited by 9 publications

(14 citation statements)

References 6 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 .…”

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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“…To accomplish an exact, safe and rigorous treatment, independent verification methods have been developed by many scientists 1,2,4,6,7) . One of the key issues not addressed by the previous methods is how to calculate the radiation depth from 201 beamlets.…”

Section: Discussionmentioning

confidence: 99%

“…To acquire each radiation depth, the patient's skull geometry has to be simulated. All of the prior efforts were made based upon the 24 point measurements using the bubble plastic helmet 1,2,4,6,7) . This measurement is a part of the routine Gamma Knife procedure to simulate the skull geometry.…”

Section: Discussionmentioning

confidence: 99%

“…Several efforts to determine the dose from the primary LGP designs were made in the literature. 1,2,4,6,7) However, prior studies calculated the dose for a single matrix point out of 29,791 matrix points. The matrix point of interest was either given by the LGP 4,6,7) or the coordinate of the maximal dose was not available.…”

Section: Introductionmentioning

confidence: 99%

“…The matrix point of interest was either given by the LGP 4,6,7) or the coordinate of the maximal dose was not available. 1,2) Furthermore, no study has been done to prove its accuracy on the effective treatment volume. These parameters are also important to minimize the injury to the critical structure, such as the optic pathway, optic lenses and the brain stem.…”

Section: Introductionmentioning

confidence: 99%

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The Variable Ellipsoid Modeling Technique as a Verification Method for the Treatment Planning System of Gamma Knife Radiosurgery

Hur

Choi

Sung

et al. 2010

J Korean Neurosurg Soc

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Objective : The secondary verification of Leksell Gamma Knife treatment planning system (LGP) (which is the primary verification system) is extremely important in order to minimize the risk of treatment errors. Although prior methods have been developed to verify maximum dose and treatment time, none have studied maximum dose coordinates and treatment volume. Methods : We simulated the skull shape as an ellipsoid with its center at the junction between the mammillary bodies and the brain stem. The radiation depths of the beamlets emitted from 201 collimators were calculated based on the relationship between this ellipsoid and a single beamlet expressed as a straight line. A computer program was coded to execute the algorithm. A database system was adopted to log the doses for 31×31×31 or 29,791 matrix points allowing for future queries to be made of the matrix of interest. Results : When we compared the parameters in seven patients, all parameters showed good correlation. The number of matrix points with a dose higher than 30% of the maximal dose was within ± 2% of LGP. The 50% dose volume, which is generally the target volume, differs maximally by 4.2%. The difference of the maximal dose ranges from 0.7% to 7%. Conclusion : Based on the results, the variable ellipsoid modeling technique or variable ellipsoid modeling technique (VEMT) can be a useful and independent tool to verify the important parameters of LGP and make up for LGP.

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Development and validation of a comprehensive patient‐specific quality assurance program for a novel stereotactic radiation delivery system for breast lesions

Becker

Niu

Mutaf

et al. 2019

J Applied Clin Med Phys

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Purpose: The GammaPod is a dedicated prone breast stereotactic radiosurgery (SRS) machine composed of 25 cobalt-60 sources which rotate around the breast to create highly conformal dose distributions for boosts, partial-breast irradiation, or neo-adjuvant SRS. We describe the development and validation of a patient-specific quality assurance (PSQA) system for the GammaPod. Methods: We present two PSQA methods: measurement based and calculation based PSQA. The measurements are performed with a combination of absolute and relative dose measurements. Absolute dosimetry is performed in a single point using a 0.053-cc pinpoint ionization chamber in the center of a polymethylmethacrylate (PMMA) breast phantom and a water-filled breast cup. Relative dose distributions are verified with EBT3 film in the PMMA phantom. The calculationbased method verifies point doses with a novel semi-empirical independent-calculation software.Results: The average (± standard deviation) breast and target sizes were 1263 ± 335.3 cc and 66.9 ± 29.9 cc, respectively. All ion chamber measurements performed in water and the PMMA phantom agreed with the treatment planning system (TPS) within 2.7%, with average (max) difference of -1.3% (−1.9%) and −1.3% (−2.7%), respectively. Relative dose distributions measured by film showed an average gamma pass rate of 97.0 ± 3.2 when using a 3%/1 mm criteria. The lowest gamma analysis pass rate was 90.0%. The independent calculation software had average agreements (max) with the patient and QA plan calculation of 0.2% (2.2%) and −0.1% (2.0%), respectively. Conclusion:We successfully implemented the first GammaPod PSQA program.These results show that the GammaPod can be used to calculate and deliver the predicted dose precisely and accurately. For routine PSQA performed prior to treatments, the independent calculation is recommended as it verifies the accuracy of the planned dose without increasing the risk of losing vacuum due to prolonged waiting times.---

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An algorithm for independent verification of Gamma Knife™ treatment plans

Cited by 9 publications

References 6 publications

Two‐year experience with the commercial Gamma Knife Check software

Two‐year experience with the commercial Gamma Knife Check software

The Variable Ellipsoid Modeling Technique as a Verification Method for the Treatment Planning System of Gamma Knife Radiosurgery

Development and validation of a comprehensive patient‐specific quality assurance program for a novel stereotactic radiation delivery system for breast lesions

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