The geometric transfer function component for scintillation camera collimators with straight parallel holes

Abstract

A theoretical approach has been developed that allows the geometric transfer function component for conventional scintillation camera collimators to be predicted in closed form. If transfer function analysis is to be useful in describing imaging system performance, the image of a point source must not depend on source position in a plane parallel to the detection plane. This shift invariance can be achieved by analysis of system response in terms of an effective point spread function, defined as the normalised image of a point source that would be obtained if the camera collimator were uniformly translated (but not rotated) during image formation. The geometric component of the corresponding effective transfer function is shown to be expressed simply by the absolute square of the two-dimensional Fourier transform of a collimator hole aperture, with the spatial frequency plane scaled by a factor which depends on collimator length, source-to-collimator distance, and collimator-to-detection plane distance. Closed form algebraic expressions of the geometric transfer function have been obtained for all four common hold shapes (circular, hexagonal, square and triangular). Monte Carlo simulations and experimental measurements have shown these theoretical expressions to be highly accurate.

Collimator design for single photon emission tomography

“…These authors demonstrated small differences between the PSFs and MTFs of triangular and hexagonal hole shapes. Metz et al (1980) derived exact expressions for the geometric component of the collimator MTF for any hole shape which confirmed these results and, additionally, treated circular and square holes. Both of these analyses used response functions averaged over the appropriate periodic "cell size" of the collimator structure.…”

Recent developments and future prospects of SPECT myocardial perfusion imaging

“…During each iteration, reconstructed image data are updated for each subset and spatial resolution increases with each update provided adequate noise suppression is incorporated during iterative reconstruction. Most of the current algorithms have incorporated scatter and attenuation compensation and resolution recovery techniques to minimize image blurring caused by collimators [14].…”

Advances in technical aspects of myocardial perfusion SPECT imaging

“…In addition, resolution recovery techniques can be incorporated to correct for losses in spatial resolution due to image blurring by the collimator. 36 The current algorithms simultaneously address these problems by modeling the instrumentation and imaging parameters used for a specific application in order to eliminate the degrading physical effects and suppress noise in the image reconstruction process. The resolution recovery aspects of these algorithms can be emphasized to provide significant improvements in spatial resolution and MPS image quality, and the noise suppression aspects can be emphasized to decrease imaging times.…”

“…Their approach includes modeling of the integrated collimator and detector response function (CDR) in an iterative reconstruction algorithm and performs image resolution recovery 43 based on these parameters. This technique has been described in detail by DePuey et al 44 The OSEM-RR modeling includes basic collimator geometric response function for round-hole-shaped collimators 36,45 which can be applied with good approximation to hexagonal holes.…”