ABSTRACT
Radiobiological descriptions of normal tissue and tumor response to radiation are often limited to fitting the mean or median of population-based data with little to no consideration of patient-specific variability of tumor or normal tissue properties that modulate this response. Biological imaging, including both molecular and functional imaging, noninvasively investigates properties that are spatially localized either to cancerous or functional tissue and that may dynamically vary with time. Within precision radiation therapy, quantitative biological imaging can define treatment-planning targets, define functional avoidance regions, and assess the response of targets and functional tissues during and after therapy. To use biological imaging for therapeutic applications, such as treatment planning and treatment response evaluation of spatial and temporal variations in biological properties that are unique to each individual patient, quantitative imaging biomarkers must be established. Quantitative imaging biomarkers may be associated with clinical endpoints, and they may complement tissues biomarkers, both potentially driving precision medicine.
