The effect of gamma ray penetration on angle‐dependent sensitivity for pinhole collimation in nuclear medicine

摘要: The sensitivity of a pinhole collimator for gamma ray imaging in nuclear medicine is dependent on the angle incidence rays. effect penetration near aperture angle-dependent was investigated using experimental measurements and numerical modeling. Projection data were acquired with Tc-99m I-131 point sources tungsten inserts 1.0 to 4.0 mm diameter apertures. Curves form sinx theta, where theta incident surface detector crystal, fit from projection data. Experimentally measured x values between 3.3 4.1 5.1 7.2 I-131. Penetration modeled (1) an expression effective that generalization Anger's formula normally photons (2) photon transport simulation code. exponents new previously reported observations within 15% by simulations. For modeling generalized average error 1.4% standard deviation 7.7%. code 1.5% also design parameters high resolution apertures greater 364 keV than 140 small diameters, acceptance angles, large channel heights. These results provide theoretical justification incorporating corrections, value 3 impenetrable pinhole, filtered back iterative reconstruction algorithms single emission computed tomography (SPECT) imaging. Simulated SPECT studies uniformly active cylinders showed activity concentrations underestimated toward outside when sin3 rather correct correction applied image reconstruction.