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ABSTRACT: Dynamic cardiac SPECT using Tc-99m labeled teboroxime can provide
kinetic parameters (washin, washout) indicative of myocardial blood
flow. A time-consuming and subjective step of the data analysis is
drawing regions of interest to delineate blood pool and myocardial
tissue regions. The time-activity curves of the regions are then used to
estimate local kinetic parameters. In this work, the appropriate regions
are found automatically, in a manner similar to that used for
calculating maximum count circumferential profiles in conventional
static cardiac studies. The drawbacks to applying standard static
circumferential profile methods are the high noise level and high liver
uptake common in dynamic teboroxime studies. Searching along each ray
for maxima to locate the myocardium does not typically provide useful
information. Here we propose an iterative scheme in which constraints
are imposed on the radii searched along each ray. The constraints are
based on the shape of the time-activity curves of the circumferential
profile members and on an assumption that the short axis slices are
approximately circular. The constraints eliminate outliers and help to
reduce the effects of noise and liver activity. Kinetic parameter
estimates from the automatically generated regions were comparable to
estimates from manually selected regions in dynamic canine teboroxime
studies
IEEE Transactions on Nuclear Science 07/1997; · 1.45 Impact Factor
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ABSTRACT: Rotation-based projectors and backprojectors offer unique
trade-offs between accuracy, computational complexity, and smoothing.
The authors analyzed six different rotation methods for generating
projections and iterative reconstructions of tomographic data. Nearest
neighbor, upsampled nearest neighbor, bilinear interpolation, and
bicubic interpolation were all used to determine the values at rotated
grid points. A decomposition of the rotation transformation matrix into
three components was also investigated. Linear and cubic interpolation
were used in the three-pass method. For all of the methods, mean
normalized square errors were computed. The authors' results demonstrate
the tradeoffs associated with the different methods and suggest that the
three-pass method with cubic interpolation offers a computationally
efficient approach with accuracy between that of bilinear and bicubic
interpolation
IEEE Transactions on Nuclear Science 01/1997; · 1.45 Impact Factor
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ABSTRACT: Kinetic parameters (washin, washout) of dynamic SPECT teboroxime data sets may provide a more sensitive measure of coronary artery disease than conventional (T1, MIBI) static myocardial perfusion studies. A time-consuming and subjective step of the data analysis is drawing regions of interest to delineate blood pool and myocardial tissue regions. The time-activity curves for the regions are then used to estimate local kinetic parameters. In this work, the appropriate time-activity curves are found automatically, in a manner similar to that used for calculating circumferential profiles in conventional static cardiac studies. The drawbacks to applying standard static circumferential profile methods are the high noise level and high liver uptake common in dynamic studies. Searching along each ray for maxima to locate the myocardium does not always provide useful information. Here, the authors propose an iterative scheme in which constraints are imposed on the radii searched. The constraints are based on the shape of the time-activity curve of the circumferential profile members and on an assumption that the short axis slices are approximately circular. The constraints eliminate outliers and help to reduce the effects of the noise and the liver activity. Kinetic parameter estimates from the automatically generated regions were comparable to estimates from manually selected regions in canine dynamic teboroxime studies
Nuclear Science Symposium, 1996. Conference Record., 1996 IEEE; 12/1996
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ABSTRACT: We estimated that in 75%-90% of PET 82Rb patients the left lung appeared to wrap around the anterior aspect of the left ventricle. We used clinical PET 82Rb myocardial perfusion studies as the input to a SPECT computer simulation model to determine if patients with left lung wrap-around displayed consistent artifacts in reconstructed SPECT images. In particular, we sought an explanation for the hot lateral wall seen in SPECT images from normal female and male patients.
Attenuated SPECT 201Tl emission data were simulated from a mid-ventricular slice in 10 randomly selected clinical PET 82Rb studies with left lung wrap-around. In these same cases, the influence of left lung wrap-around was removed by assigning the left lung an attenuation coefficient which matched that of the heart. Five randomly selected clinical PET 82Rb studies without left lung wrap-around were also processed with our model.
In all 10 cases with left lung wrap-around, reconstructed SPECT images showed the hot lateral wall artifact with a mean septal-to-lateral wall count ratio of 0.86. With left lung wrap-around removed in the same 10 patients, reconstructed images did not show hot lateral wall (mean septal-to-lateral wall count ratio = 1.07). The 5 cases without left lung wrap-around did not show hot lateral wall (mean septal-to-lateral wall count ratio = 1.04) and the ratios changed little with the filling of the left lung (mean septal-to-lateral wall count ratio = 1.05).
Results of our PET-to-SPECT computer simulation model showed that the hot lateral wall artifact found in SPECT myocardial perfusion images was related to the orientation and positions of the left ventricle and the left lung.
Journal of Nuclear Medicine 12/1996; 37(11):1891-6. · 6.38 Impact Factor
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ABSTRACT: Rotation-based approaches to iterative reconstruction algorithms offer unique trade-offs between accuracy, computational complexity, and smoothing. We analyzed six different rotation methods for generating projections and reconstructions of simulated and clinical data. Nearest neighbor, upsampled nearest neighbor, bilinear interpolation, and bicubic interpolation were all used to determine the values at rotated grid points. A decomposition of the rotation transformation matrix into three components was also investigated. Linear and cubic interpolation were used in the three pass method. For all of the methods, mean normalized square errors were computed as was a measure of smoothness. Our results demonstrate the trade-offs associated with the different methods and suggest that the method of shears with cubic interpolation offers a computationally efficient approach with accuracy between that of bilinear and bicubic interpolation
Nuclear Science Symposium and Medical Imaging Conference Record, 1995., 1995 IEEE; 11/1995
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ABSTRACT: In normal dogs, SPECT Tc-99m Sestamibi (MIBI) Tl-201 myocardial perfusion images reconstructed with filtered backprojection (FBP) show a large decrease of counts in the septal wall (S) compared to the lateral wall (L). We evaluated the iterative method of Chang at 0 and 1 iterations (Chang0 and Chang1), and the Maximum Likelihood-Expectation Maximization with attenuation compensation (ML-EM-ATN) algorithm on data acquired from 5 normal dogs and from simulated projection data using a homogeneous count-density model of a normal canine myocardium in the attenuation field measured in one dog. Mean counts in the S and L regions were calculated from maximum-count circumferential profile arrays. Our results demonstrate that ML-EM-ATN and Chang1 result in improved uniformity, as measured by the S/L ratio
Nuclear Science Symposium and Medical Imaging Conference, 1994., 1994 IEEE Conference Record;
