Photon Interaction Coefficients for the Colorectal Cancer Tissue

PURPOSE: The application of radiotherapy to the treatment of cancer requires the knowledge of photon interaction coefficients such as mass attenuation (μ(m)) and mass energy-absorption coefficients (μ(en)/ρ). Although these coefficients have been determined for different tissues, it is lacking for the colorectal cancer (CRC) tissue in the literature. This study determines the μ(m) and μ(en)/ρ for the CRC tissue within the radiotherapy energy range. MATERIALS AND METHODS: The CRC tissue from autopsy patients was freeze-dried, grounded into a fine powder, and made into pellets of 1 cm thickness. The elements detected in the CRC tissue using Rutherford backscattering spectrometry were used in XCOM to determine the theoretical values of μ(m) and μ(en)/ρ. The CRC tissue was again exposed to X-rays of energies of 6 and 15MV, respectively, to determine its experimental values of μ(m) and μ(en)/ρ. RESULTS: Elements detected included carbon, oxygen and nitrogen making up 96.67%, high atomic number and trace elements making up the remaining 3.33% fraction of the CRC tissue. CONCLUSION: The theoretical and experimental μ(m) and μ(en)/ρ values showed a good agreement of about 2% difference between them. These values can be used to simulate the CRC tissue with respect to μ(m) and μ(en)/ρ.