3D dosimetry of proton beams and influences on response

Abstract

Proton beams offer the ability to conform dose distributions exquisitely to target volumes, allowing radiation oncologists to avoid exceeding tolerance doses to sensitive normal tissues. Several volumetric dosimeters have shown potential in conventional radiotherapy modalities, but suffer from dose under-responding, or signal quenching, in proton therapy. This reduced response has been seen with gels as well as with radiochromic plastics and may result from dependences on dose rate and linear energy transfer (LET). Investigations have shown that the under-response is affected by the chemical concentration of the active components of PRESAGE®, and changes to the composition have been shown to reduce quenching. It is not clear if similar changes can be made to gels. This report reviews studies into the impact of formulation changes on signal quenching, and the degree to which mathematical corrections might still be needed to achieve accurate dosimetry.