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Radiation Medicine Commons

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Radiation Medicine Faculty Publications

R50%

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Full-Text Articles in Radiation Medicine

A Measure Of Srs/Srt Plan Quality: Quantitative Limits For Intermediate Dose Spill (R50%) In Linac-Based Delivery, Dharmin D. Desai, Ivan L. Cordrey, Ellis L. Johnson Mar 2022

A Measure Of Srs/Srt Plan Quality: Quantitative Limits For Intermediate Dose Spill (R50%) In Linac-Based Delivery, Dharmin D. Desai, Ivan L. Cordrey, Ellis L. Johnson

Radiation Medicine Faculty Publications

Stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) of multiple cranial targets using a single isocenter on conventional C-arm linear accelerators are rapidly developing clinical techniques. However, no universal guidelines for acceptable intermediate dose spill limits are currently available or widely accepted. In this work, we propose an intermediate dose spill guidance range for cranial SRS/SRT delivered on C-arm linacs with MLC collimation for single PTV plans and single isocenter multiple target plans with PTV volumes in the range 0.02–57.9 cm3. We quantify intermediate dose spill with the R50% metric (R50% = volume of 50% of prescription isodose cloud …


An Analytical Expression For R50% Dependent On Ptv Surface Area And Volume: A Cranial Srs Comparison, Dharmin D. Desai, Ellis Lee Johnson, Ivan L. Cordrey Jan 2021

An Analytical Expression For R50% Dependent On Ptv Surface Area And Volume: A Cranial Srs Comparison, Dharmin D. Desai, Ellis Lee Johnson, Ivan L. Cordrey

Radiation Medicine Faculty Publications

The intermediate dose spill for a stereotactic radiosurgery (SRS) plan can be quantified with the metric R50%, defined as the 50% isodose cloud volume (VIDC50%) divided by the volume of the planning target volume (PTV). By coupling sound physical principles with the basic definition of R50%, we derive an analytical expression for R50% for a spherical PTV. Our analytical expression depends on three quantities: the surface area of PTV (SAPTV), the volume of PTV (VPTV), and the distance of dose drop-off to 50% (Δr). The value of ∆r was obtained from a simple set …