baseline /bās″līn/ [Gk, basis + L, linea] , 1. a known value or quantity with which an unknown is compared when measured or assessed (e.g., baseline vital signs). 2. the patient’s initial information at diagnosis or assessment against which later tests will be compared; level of performance or aggregate findings before therapy. 3. (in radiology) any of several basic anatomical planes or locations used for positioning purposes. They include the orbitomeatal, infraorbitomeatal, acanthomeatal, and glabellomeatal lines.
