Characterization of backscatter factors for various tissue substitutes in diagnostic radiology: a Monte Carlo...

Accurate assessment of backscatter factors (BSFs) is critical in medical dosimetry to precisely quantify the increase in surface dose caused by photon scattering, particularly in the low-energy kilovoltage X-ray beams used in diagnostic radiology. This study aimed to conduct a comprehensive evaluation of BSF values for diagnostic X-ray beams through Monte Carlo simulations. The interactions of BSFs with widely used tissue substitutes, including water, ICRU tissue, polyester, polymethyl methacrylate (PMMA), and nylon, were examined across a range of conditions, including half-value layer (HVL), field size, and energy spectra. The results demonstrate that BSF values consistently increase with larger field sizes and higher beam energies/HVLs, highlighting the significant impact of these parameters on scatter contributions. Comparative analysis of the materials revealed that water most closely approximates the BSF behaviour of ICRU tissue, with deviations of -2.08-8% across the studied energy range and field sizes. Polyester and PMMA also showed promising agreement, converging to within ± 5% of ICRU tissue at higher energies and larger field sizes. In contrast, nylon exhibited more substantial deviations, particularly in smaller field sizes and lower energies. These findings provide essential insights to improve the accuracy of dosimetric models and enhance radiation safety in diagnostic radiology applications.