A radio therapy apparatus (100) includes a tissue of interest tracker (124) that receives a first image of tissue of interest and a second later acquired spectral image of the tissue of interest and tracks a change in a geometry and/or location of the tissue of interest based at least on the first and second images and generates a signal indicative of the change. The second image is generated based on a first spectral signal corresponding to an output of an energy-resolving radiation sensitive detector array for a first predetermined energy range and a second spectral signal corresponding to an output of the energy-resolving radiation sensitive detector array for a second predetermined energy range and visually enhances scanned structure corresponding to the first or second signals while visually suppressing scanned structure corresponding to the other of the first or second signals. An adaptive planner (126) updates a radiotherapy treatment plan based on the signal.