Isocenter in aerial photography: it is a point where a line cuts an angle of 90 degree of tier/2.
The two are closely related but differ in terms of their functionality and working in Space.
Isocenter definition in Radiotherapy: The point in space relative to the treatment machine about which various components of the linac rotate.
The treatment collimators also rotate about an axis pointing through the isocentre.
The source to isocenter distance (SIsoD) can be an important parameter to control in determining patient exposure and image quality in diagnostic computed tomography and fluoroscopy.