Document Type: Original Article
Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
National Institute of Nuclear Physics, Section of Torino, Torino, Italy
Clinical Department, Fondazione CNAO, Pavia, Italy
Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
Introduction: Gamma cameras are proposed for online range verification and treatment monitoring in proton therapy. An Analytical formula was derived and validated for sensitivity of a slit collimator based on the photon fluence concept.
Methods: Fluence formulation was generalized for photons distribution function and solved for high-energy point sources. The effect of the collimator slit size and source off-axis position on the sensitivity of the collimator were included in the formula.
Results: The analytically calculated sensitivities of the slit collimator were in good agreement with Monte Carlo results according to the Bland-Altman agreement test and Pearson correlation (r =0.998) statistical analysis with . The mean relative error between calculated sensitivities with the derived formula and Monte Carlo was up to 0.8%. Moreover, we found that under certain conditions, the established formula is converted to the Anger equation for the pinhole collimator.
Conclusion: The analytical formula developed in this research can estimate the slit collimator sensitivity with an acceptable accuracy. The derived closed-form sensitivity formula can be applied in KE collimator design and optimization studies.