Imaging of cardiac 18 F-FDG uptake is used in the diagnostic evaluation of residual viable myocardium. Although, originally, hibernating myocardium was identified by a mismatch between perfusion defect and relatively preserved 18 F-FDG uptake, at present several studies propose that 18 F-FDG distribution can also be used alone for this purpose. Nevertheless, even severe myocardial 18 F-FDG uptake defects are frequently observed in cancer patients without any cardiac disease. The aim of this study was to retrospectively analyze global and regional 18 F-FDG cardiac images of 49 consecutive cancer patients free of cardiac diseases who submitted to 3 PET scans under fasting conditions. Methods: Images were acquired with a high-resolution PET/CT scanner. Three-dimensional regions of interest were drawn on the fused PET/CT images to measure the maximal standardized uptake value of the left ventricular myocardium (SUV Myo ) as well as the average SUV of the left ventricular blood (SUV LV ) and of the liver (SUV Liver ). Analysis of regional myocardial 18 F-FDG uptake was performed on a subsample of 26 patients by an automatic recognition of endocardial and epicardial borders and subdividing the left ventricle in 20 segments. Regional 18 F-FDG distribution was defined as the percentage of SUV Myo in each region. Results: SUV Myo as well as SUV LV and SUV Liver did not change on average throughout the studies. This stability was not caused by a persistent pattern of myocardial 18-FDG distribution. Rather, it was associated with important variations in both directions over time. Regional 18 F-FDG distribution was largely heterogeneous in all 3 studies, with a variation coefficient in each patient of 18% 6 7%, 18% 6 5%, and 17% 6 5%, respectively. An 18 F-FDG uptake of ,50% occurred in 78, 102, and 69 of 468 segments, although it disappeared in 55% of instances at subsequent examinations. Regional temporal variability was also marked: The absolute value of the difference in percent uptake was 10.1% 6 7.3% from test 1 to test 2, 8.0% 6 7.0% from test 1 to test 3, and 9.2% 6 6.9% from test 2 to test 3. Overall from one test to another, uptake increased or decreased by .10% in 76 and in 116 of 468 segments, respectively. Conclusion: The large spatial and temporal heterogeneity of the myocardial metabolic pattern, in cancer patients free of any disease, suggests a word of caution on the use of 18 F-FDG alone as a diagnostic tool for myocardial viability.
The major findings of the present work are the demonstration of additivity of subset and iteration in OSEM over noise, with the possibility of defining an EM equivalent iteration number, and the superiority of OSEM with respect to FBP in terms of spatial resolution.
This is the first study comparing the relative performance of different, commercially available, IRR software, over a wide range of count statistics; the additional effect of scatter and attenuation corrections, alone or in combination, was also evaluated. Our results confirm that IRR algorithms produce substantial benefits with respect to conventional FBP or OSEM reconstruction methods, as assessed through different figures of merit, in particular when SC and/or SCAC are also included.
Our results show that D-SPECT and D530c have different performances. The lack of differences in the image performance indices along the range of count statistics explored, indicates that there is the possibility for a further reduction in the injected activity and/or the acquisition time, for both systems.
These preliminary results are in agreement with the few previous scientific contributions available on this topic and indicate that it is possible to reduce the extent and duration of surgery and necessary to reevaluate the conventional sites of lymphatic drainage.
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