CTV to PTV expansion
Geometric margin added to clinical target volume to account for setup uncertainties and organ motion.
Full Definition
CTV to PTV expansion refers to the systematic enlargement of the Clinical Target Volume (CTV) to create the Planning Target Volume (PTV) in radiation therapy planning. This margin accounts for day-to-day setup variations, patient positioning errors, organ motion, and treatment delivery uncertainties. The expansion is typically uniform in all directions but may be asymmetric based on anatomical considerations and immobilization techniques. Typical expansions range from 3-10mm depending on the treatment site, immobilization, and image guidance protocols. Modern techniques like IGRT allow for reduced margins while maintaining target coverage.
Usage
Usage note: Be precise about which margin is being described - GTV to CTV margins serve different purposes than CTV to PTV expansions.
In Context
- "A 5mm CTV to PTV expansion was applied for the prostate treatment plan." — radiation oncology report
- "The CTV to PTV expansion was reduced to 3mm due to daily cone-beam CT guidance." — treatment planning documentation