J. Liow and S. Strother, "Practical tradeoffs between noise, quantita- tion and number of iterations for maximum likelihood-based reconstruc- tions," IEEE Trans. Med. Imag, vol. 13, pp. 6014309, Dec., 1994.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....PET. I. INTRODUCTION p OSITRON emission tomography (PET) images can be re constructed by an iterative process whereby the iterates maximize a Poisson likelihood objective function. Maximum likelihood (ML) reconstructions have been reported to improve both variance [56] and resolution [36] compared with filtered backprojection reconstructions, in studies characterized by poor counting statistics. In transmission tomography, for example, where the scan duration is often short and the count rate is there fore low, ML reconstructions based on a Poisson model of the observations have ....

J. Liow and S. Strother, "Practical tradeoffs between noise, quantita- tion and number of iterations for maximum likelihood-based reconstruc- tions," IEEE Trans. Med. Imag, vol. 13, pp. 6014309, Dec., 1994.

....domain copies, centered at 2k and 2k . maximum count [75] RC values for reconstructions of uniform count density discs with varying diameters have been used to examine the effects of point response and to estimate properties of the ML EM algorithm for systems with stationary point responses [79]. To generate RC values, we first created a set of 2 D Gaussian test objects of varying fwhms. Eleven Gaussians, with fwhms ranging from 1 to 11 pixels in one pixel increments, were created using a sampling rate of 0.16mm Gamma1 . Each Gaussian was scaled to a maximum count of 100. As discussed ....

J.-S. Liow and S. C. Strother, "Practical tradeoffs between noise, quantitation, and number of iterations for maximum likelihood-based reconstructions," IEEE Trans. Med. Imaging, vol. 10, no. 4, pp. 563--571, 1991.

....here. EM can also incorporate the resolution limitations of the detection system into the reconstruction model and thereby remove the partial volume effect inherent in FBP [4] Liow and Strother have reported moderately improved noise in EM reconstructions at matched resolutions relative to FBP [11]. In this investigation we compare 2D FBP and 3DRP reconstructions with 2D EM and 3D EM reconstructions for an opposed mode NaI(Tl) PET scanner with very fine sampling. Hudson and Larkin have reported that ordered subset EM (OSEM) with k subsets taken to n k iterations can produce reconstructions ....

J. Liow and S. Strother, "Practical tradeoffs between noise, quantitation and number of iterations for maximum likelihood-based reconstructions," IEEE Trans. Med. Imag., vol. 10, pp. 563-571, 1991.

....ridge estimators [6] are used to reduce variance of the ordinary least squares estimator. The quantitative study of estimator bias and variance has been useful for characterizing statistical performance for many statistical signal processing applications including: tomographic reconstruction [7], 8] 9] functional imaging [10] non linear and morphological filtering [11] 12] and spectral estimation of time series [13] 14] However, the plane parameterized by the bias and variance b and oe 2 is not useful for studying fundamental tradeoffs since an estimator can always be ....

J.-S. Liow and S. C. Strother, "Practical tradeoffs between noise, quantitation, and number of iterations for maximum likelihoodbased reconstructions," IEEE Trans. on Medical Imaging, vol. 10, no. 4, pp. 563--571, 1991.

....def = crc j p var j : 30) Assuming that the reconstructions are locally ergodic (i. e the ensemble variances approximated using the expression above are close to the spatial variances of a local region computed from an individual reconstruction) then the CNR is equivalent to the SNR used in [29, 35], which has been shown to be correlated with both human and machine observers for cold spot detectability. From (18) and (22) we know that the CNRs are different for each voxel location, so the hyperparameter fi needs to be spatially variant in order to maximize the ratio. The maximum ....

J.-S. Liow and S. C. Strother, "Practical tradeoffs between noise, quantitation, and number of iterations for maximum likelihood-based reconstructions," IEEE Transactions on Medical Imaging, vol. 10, no. 4, pp. 563--571, 1991.

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