Spatial and Temporal Heterogeneity of Regional Myocardial Uptake in Patients Without Heart Disease Under Fasting Conditions on Repeated Whole-Body 18F-FDG PET/CT

摘要

id="p-1">Imaging of cardiac 18F-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 18F-FDG uptake, at present several studies propose that 18F-FDG distribution can also be used alone for this purpose. Nevertheless, even severe myocardial 18F-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 18F-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 18F-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 18F-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 18F-FDG distribution was largely heterogeneous in all 3 studies, with a variation coefficient in each patient of 18% ?± 7%, 18% ?± 5%, and 17% ?± 5%, respectively. An 18F-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% ?± 7.3% from test 1 to test 2, 8.0% ?± 7.0% from test 1 to test 3, and 9.2% ?± 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 18F-FDG alone as a diagnostic tool for myocardial viability.