Common Terminology Used in Radiation Therapy
| Term | Definition |
|---|---|
| Gross tumor volume (GTV) | Macroscopic tumor volume as detected by clinical examination and anatomic imaging (ultrasound, CT, MRI, PET) |
| Clinical target volume | GTV with margin added for subclinical microscopic spread |
| Planning target volume | Clinical target volume with margin added for organ motion and setup inaccuracy |
| Treatment volume | Tissue volume treated to substantial radiation dose (typically larger than planning target volume) |
| Metabolic tumor volume | Metabolically active tumor volume as detected by biologic imaging, for example, 18F-FDG PET |
| Hypoxic tumor volume | Hypoxic tumor volume as detected by biologic imaging, that is, hypoxia or hypoxia-related PET tracers (18F-FMISO, 18F-fluoroazomycin arabinoside, 18F-fluoroerythronitroimidazole), or blood oxygen level–dependent MRI |