Effect of skull shape approximations in Gamma Knife dose calculations

Berndt, Anita; Beck, James F.

doi:10.1120/jacmp.v8i3.2377

Cited by 6 publications

(3 citation statements)

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“…The TMR dose calculation algorithm and the 24‐point measurement‐based manual skull definition method have been the basis of the Gamma Knife radiosurgery treatment planning for many years (1‐2) . The manual skull definition method is a convenient approach for modeling the shape of a human head for dose calculation (3) . The water‐based TMR algorithm provides a fast dose calculation method for real‐time interactive treatment planning in Gamma Knife radiosurgery.…”

Section: Introductionmentioning

confidence: 99%

“…Many studies have been done to evaluate the performance of the TMR dose calculation algorithm and the manual skull definition method (3‐11) . The TMR algorithm is demonstrated to work better for targets located at the center of the brain than for those in the peripheral and/or heterogeneous regions (2,4‐9) .…”

Section: Introductionmentioning

confidence: 99%

“…The TMR algorithm is demonstrated to work better for targets located at the center of the brain than for those in the peripheral and/or heterogeneous regions (2,4‐9) . The manual skull definition method is in general considered a good approximation owing to the fact that the Gamma Knife dose calculation is relatively insensitive to the local variations in the skull contour (3,10‐11) …”

Section: Introductionmentioning

confidence: 99%

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Gamma Knife radiosurgery with CT image‐based dose calculation

Bhatnagar

Bednarz

et al. 2015

J Applied Clin Med Phys

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The Leksell GammaPlan software version 10 introduces a CT image‐based segmentation tool for automatic skull definition and a convolution dose calculation algorithm for tissue inhomogeneity correction. The purpose of this work was to evaluate the impact of these new approaches on routine clinical Gamma Knife treatment planning. Sixty‐five patients who underwent CT image‐guided Gamma Knife radiosurgeries at the University of Pittsburgh Medical Center in recent years were retrospectively investigated. The diagnoses for these cases include trigeminal neuralgia, meningioma, acoustic neuroma, AVM, glioma, and benign and metastatic brain tumors. Dose calculations were performed for each patient with the same dose prescriptions and the same shot arrangements using three different approaches: 1) TMR 10 dose calculation with imaging skull definition; 2) convolution dose calculation with imaging skull definition; 3) TMR 10 dose calculation with conventional measurement‐based skull definition. For each treatment matrix, the total treatment time, the target coverage index, the selectivity index, the gradient index, and a set of dose statistics parameters were compared between the three calculations. The dose statistics parameters investigated include the prescription isodose volume, the 12 Gy isodose volume, the minimum, maximum and mean doses on the treatment targets, and the critical structures under consideration. The difference between the convolution and the TMR 10 dose calculations for the 104 treatment matrices were found to vary with the patient anatomy, location of the treatment shots, and the tissue inhomogeneities around the treatment target. An average difference of 8.4% was observed for the total treatment times between the convolution and the TMR algorithms. The maximum differences in the treatment times, the prescription isodose volumes, the 12 Gy isodose volumes, the target coverage indices, the selectivity indices, and the gradient indices from the convolution and the TMR 10 calculations are 14.9%, 16.4%, 11.1%, 16.8, 6.9%, and 11.4%, respectively. The maximum differences in the minimum and the mean target doses between the two calculation algorithms are 8.1% and 4.2% of the corresponding prescription doses. The maximum differences in the maximum and the mean doses for the critical structures between the two calculation algorithms are 1.3 Gy and 0.7 Gy. The results from the two skull definition methods with the TMR 10 algorithm agree either within ± 2.5% or 0.3 Gy for the dose values, except for a 4.9% difference in the treatment times for a lower cerebellar lesion. The imaging skull definition method does not affect Gamma Knife dose calculation considerably when compared to the conventional measurement‐based skull definition method, except in some extreme cases. Large differences were observed between the TMR 10 and the convolution calculation method for the same dose prescription and the same shot arrangements, indicating that the implementation of the convolution algorithm in routine clinical use might be ...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%