Room: Exhibit Hall | Forum 7
Purpose: In the last few decades, proton therapy (PT) has been an increasingly popular method of radiotherapy for malignant tumors. One of the advantages of PT over conventional photon therapy is its characteristic dose profile with a reduced entrance dose, which could increase the tumor control probability while minimizing the dose to healthy tissues. One of the disadvantages of PT is the unnecessary irradiation of a larger-than-necessary tumor volume due to uncertainties in the stopping powers of protons in tissue. We would like to address this limitation using a new range-verification technique.
Methods: During typical PT treatment, most gamma ray radiation is promptly emitted by tissue and bone. However, if a tumour marker is administered in or close to a tumor, a small fraction of beam particles will undergo direct nuclear and fusion-evaporation reactions with the marker to produce beta-delayed characteristic gamma rays. The successful detection of these gamma rays provides verification that the beam particle interacted with the tumor and its energy, allowing adjustment of the beam position and range during the treatment.
Results: The proposed method of range verification was initially tested in an experiment at the PT Facility at TRIUMF, Vancouver, Canada. In this experiment, several tumour markers, such as Mo, were irradiated with various proton beam energies, and the resulting gamma rays detected using fast LaBrâ‚ƒ(Ce) scintillators. Several observed gamma ray lines were identified, consistent with beta-delayed gamma rays emitted from the products of (p,n) and (p,d) reactions on â?¹Â²Mo, indicating the irradiation of the tumour marker and measuring the proton energy.
Conclusion: Using our high-precision range-verification technique, we have successfully measured prompt and beta-delayed gamma radiation from various tumour markers. This technique may be a promising new method to significantly reduce uncertainties in PT treatment of difficult-to-treat cancers.
Not Applicable / None Entered.