Monte carlo simulation of the Leksell Gamma Knife: II. Effects of heterogeneous versus homogeneous media for stereotactic radiosurgery
| Autor: | Marcus E. Randall, Vadim Moskvin, Phil H. Dittmer, Robert Timmerman, Lech Papiez, Colleen DesRosiers, Paul M. DesRosiers |
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| Rok vydání: | 2004 |
| Předmět: |
Quality Assurance
Health Care medicine.medical_treatment Monte Carlo method Radiation Dosage Radiosurgery Models Biological Sensitivity and Specificity Secondary electrons Imaging phantom Radiation Protection medicine Dosimetry Humans Radiology Nuclear Medicine and imaging Computer Simulation Radiation treatment planning Radiometry Simulation Physics Models Statistical Radiological and Ultrasound Technology Phantoms Imaging Attenuation Radiotherapy Planning Computer-Assisted Skull Brain Reproducibility of Results Computational physics Mockup Anisotropy Monte Carlo Method Algorithms |
| Zdroj: | Physics in medicine and biology. 49(21) |
| ISSN: | 0031-9155 |
| Popis: | The absence of electronic equilibrium in the vicinity of bone-tissue or air-tissue heterogeneity in the head can misrepresent deposited dose with treatment planning algorithms that assume all treatment volume as homogeneous media. In this paper, Monte Carlo simulation (PENELOPE) and measurements with a specially designed heterogeneous phantom were applied to investigate the effect of air-tissue and bone-tissue heterogeneity on dose perturbation with the Leksell Gamma Knife®. The dose fall-off near the air-tissue interface caused by secondary electron disequilibrium leads to overestimation of dose by the vendor supplied treatment planning software (GammaPlan®) at up to 4 mm from an interface. The dose delivered to the target area away from an air-tissue interface may be underestimated by up to 7% by GammaPlan® due to overestimation of attenuation of photon beams passing through air cavities. While the underdosing near the air-tissue interface cannot be eliminated with any plug pattern, the overdosage due to under-attenuation of the photon beams in air cavities can be eliminated by plugging the sources whose beams intersect the air cavity. Little perturbation was observed next to bone-tissue interfaces. Monte Carlo results were confirmed by measurements. This study shows that the employed Monte Carlo treatment planning is more accurate for precise dosimetry of stereotactic radiosurgery with the Leksell Gamma Knife® for targets in the vicinity of air-filled cavities. |
| Databáze: | OpenAIRE |
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