  We propose an innovative method for proton radiography based on nuclear
emulsion film detectors, a technique in which images are obtained by measuring
the position and the residual range of protons passing through the patient's
body. For this purpose, nuclear emulsion films interleaved with tissue
equivalent absorbers can be used to reconstruct proton tracks with very high
accuracy. This is performed through a fully automated scanning procedure
employing optical microscopy, routinely used in neutrino physics experiments.
Proton radiography can be used in proton therapy to obtain direct information
on the average tissue density for treatment planning optimization and to
perform imaging with very low dose to the patient. The first prototype of a
nuclear emulsion based detector has been conceived, constructed and tested with
a therapeutic proton beam. The first promising experimental results have been
obtained by imaging simple phantoms.
