The invention comprises a method and apparatus for using a multi-layer multi-color scintillation based detector element to image a tumor of a patient using a process of determining residual energies of positively charged particles after passing through the patient, the process comprising the steps of: (1) transmitting the positively charged particles at known energies through the patient and into a multi-layer detector element; (2) detecting first and second secondary photons, resultant from passage of the positively charged particles, respectively from a first layer of a first scintillation material and a second layer of a second scintillation material at two respective layer depths, where the first wavelength range differs from the second wavelength range; (4) determining residual energies of the positively charged particles, using output from the step of detecting; and (5) relating the residual energies to body densities to generate an image.