PTV margin
Also written as: PTV — Planning Target Volume margin
The additional margin added around the clinical target volume to account for setup uncertainties and organ motion during radiation therapy.
Full Definition
The Planning Target Volume (PTV) margin is a geometric expansion applied around the Clinical Target Volume (CTV) to ensure adequate radiation dose coverage despite daily setup variations, patient positioning errors, and organ motion. PTV margins are institution-specific and depend on immobilization techniques, image guidance capabilities, and anatomical site. Standard margins range from 3-10mm but may be reduced with advanced positioning and verification systems. Proper PTV margin selection is crucial for treatment efficacy while minimizing normal tissue complications.
Usage
Usage note: Distinguish from CTV (clinical target volume) and PRV (planning organ at risk volume) margins
In Context
- "A 5mm PTV margin was applied to account for respiratory motion in lung treatments." — Treatment planning report
- "Daily CBCT imaging allowed reduction of PTV margins from 10mm to 5mm." — Protocol documentation