Defining Radiotherapy Target Volumes Using 18F-Fluoro-Deoxy-Glucose Positron Emission Tomography/Computed Tomography: Still a Pandora's Box?

The fluctuations in tumor volume using different quantitative PET thresholding approaches did not depend on the thresholding method used. They originated from the nature of functional imaging in general and PET imaging in particular. Functional imaging will eventually be used for biologically tailored target radiotherapy volume definition not as a replacement of CT- or magnetic resonance imaging-based anatomic gross tumor volumes but with the methods complementing each other in a complex mosaic of distinct biologic target volumes.