PubMed · 9420798
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D S Berman, G Germano, H Kiat, J Friedman. Simultaneous perfusion/function imaging.. https://doi.org/10.1016/s1071-3581(05)80065-0
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Accuracy and limitation of energy-window based scatter correction techniques have been evaluated for myocardial 201Tl SPECT by means of Monte Carlo simulation. In particular, projection view-dependency of energy distribution of the scattered photons was evaluated. Two geometrical configurations were simulated: namely a homogeneous cylindrical radioactivity located asymmetrically in a homogeneous cylindrical phantom, and a homogeneous ring radioactivity positioned at the myocardial region of a human thorax phantom. Energy spectra were recorded for each projection, and accuracy of the triple-energy window (TEW) method was then evaluation for both phantoms. The energy distribution of the scattered photons was apparently dependent on the projection view. TEW also demonstrated systematic overcorrection for the scatter because of multiple photo peaks around 80 KeV, and more importantly, the error was highly dependent on the projection view. The error reached to 35-38% for the view that is the closest to the 201Tl radioactivity (anterior view in case of the myocardial ring phantom), and was approximately 20% in the opposite view. This view-dependency of the error remained for other energy window settings, and was found to cause significant artifact in the reconstructed myocardial images, typically causing a defect in the anterior myocardial wall. Thus, this study demonstrated the need for optimizing the window settings for each projection view in all energy window-based scatter correction methods.
The differentiation of viable from non viable myocardium is a key issue in the current era of revascularization. Several methods have been used to assess myocardial viability. The radionuclide detection of dysfunctional but viable myocardium depends upon the use of radiotracers whose uptake and trapping are related to presence and amount of living cells. The choice of the diagnostic technique to be applied in clinical practice depends on accuracy of the method and availability of resources. SPECT imaging with TI-201 and Tc-99m-myocardial perfusion tracers are widely available diagnostic tools. Several studies have documented their reliability to detect myocardial segments which may improve in both perfusion and function after revascularization. Positron emission tomography after injection of glucose analogues is a more sophisticated and accurate technology to detect viability, whose utilization is at present limited to few centers due to its high cost. Therefore an accurate selection of patients requiring viability studies is needed in order to identify the most appropriate diagnostic test.