Abstract
An efficient postprocessing method to compensate for the scattering and blurring effects in inhomogeneous medium in SPECT is proposed. A two-dimensional point spread function (2D-PSF) was estimated in the image domain to model the combination of these two physical effects. This 2D-PSF in the inhomogeneous medium is fitted with an asymmetric Gaussian function based on Monte Carlo simulation results. An efficient further blurring and deconvolution method was used to restore images from the spatially variant 2D-PSF kernel. The compensation is performed using a computer-simulated NCAT phantom and a flanged Jaszczak experimental phantom. The preliminary results demonstrate an improvement in image quality and quantity accuracy with increased image contrast (25% increase compared to uncompensated image) and decreased error (40% decrease compared to uncompensated image). This method also offers an alternative to compensate for scatter and blurring in a more time efficient manner compared to the popular iterative methods. The execution time for this efficient postprocessing method is only a few minutes, which is within the clinically acceptable range.
Highlights
Single photon emission computed tomography (SPECT) images are degraded by attenuation, collimator and detector blurring, and photon scatter
We model the 2D-PSF h in (3) as a Gaussian function with five variables: the magnitude of the Gaussian A0, full width at half-maximum in the long-axis direction FWHMl, full width at half-maximum in the short-axis direction FWHMs, and the center (x0, y0) of the Gaussian: h x0, y0; x, y = A0 exp
In our previous study of the 2D-PSF [40], we discovered that in homogeneous scattering media, the 2D-PSF is rotationally symmetric with respect to the rotation center, which means that the 2D-PSF with a constant radial distance has the same shape for all angles but is rotated by a certain angle
Summary
Single photon emission computed tomography (SPECT) images are degraded by attenuation, collimator and detector blurring, and photon scatter. Several studies have shown that compensations for these degradations can improve the quantitative accuracy and clinical lesion detectability [1,2,3,4,5,6]. The goal of this study is to develop a new method that can compensate for the scatter and blurring effects and improve the quantitative and qualitative accuracy of clinically realistic SPECT images. The main problem with this iterative compensation method is its heavy computational burden. Preprocessing procedures have been investigated to compensate for these physical degradations. The blurring is compensated in a preprocessing procedure such as using the frequency-distance principle [21,22,23,24]. The scatter is corrected using energy-distribution-based methods [25,26,27]
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