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Analysis of R50% location dependence on LINAC-based VMAT cranial stereotactic treatments
Ivan L Cordrey1, Dharmin D Desai1, E Lee Johnson2
1Department of Radiation Oncology, CHI Memorial Hospital, Chattanooga, TN 37404 USA.
Summary
Stereotactic radiosurgery (SRS) and stereotactic radiation therapy (SRT) are advanced treatments for brain tumors. This study found that lesion location within the cranium has minimal impact on treatment dose conformity.
Area of Science:
- Neurosurgery
- Radiation Oncology
- Medical Physics
Background:
- Stereotactic radiosurgery (SRS) and stereotactic radiation therapy (SRT) are established techniques for treating intracranial targets.
- Advances in linear accelerator (LINAC) technology, including multi-leaf collimators and volumetric arc therapy, enhance SRS/SRT delivery.
- Clinical applications span diverse pathologies like metastases, meningioma, glioblastoma, arteriovenous malformations, and trigeminal neuralgia.
Purpose of the Study:
- To prospectively investigate the influence of intracranial lesion location on dose conformality in SRS/SRT.
- To assess dose conformality using the R50% index while controlling for lesion volume, shape, prescription dose, and isodose surface.
- To determine if lesion location explains the variability in dose conformity observed in previous SRS/SRT studies.
Main Methods:
- Prospective study design evaluating nine strategically placed intracranial lesions.
- Measurement of intermediate dose conformality using the R50% index.
- Analysis controlled for lesion volume, shape, prescription dose, and isodose surface.
- Inclusion of both single and single isocenter multiple target plans.
- Assessment of critical structure doses against AAPM Task Group report 101 recommendations.
Main Results:
- A weak correlation was observed between lesion location and intermediate dose conformality (R50%).
- Proximity to critical structures showed a minimal effect on reducing dose conformality.
- All evaluated critical structure doses remained within recommended safety limits.
- Lesion location was not identified as a significant factor in the variability of dose conformity.
Conclusions:
- Intracranial lesion location is not a major determinant of dose conformality variations in SRS/SRT.
- While critical structure proximity can slightly impact conformity, its effect is generally minimal.
- The findings suggest other factors may be more influential in the observed dispersion of dose conformity indices in SRS/SRT literature.
