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.

BackgroundFDG-PET/CT imaging has an emerging role in staging and treatment planning of various tumor locations and a number of literature studies show that also the carcinoma of the anal canal may benefit from this diagnostic approach. We analyzed the potential impact of FDG-PET/CT in stage definition and target volume delineation of patients affected by carcinoma of the anal canal and candidates for curative radiotherapy.MethodsTwenty seven patients with biopsy proven anal carcinoma were enrolled. Pathology was squamous cell carcinoma in 20 cases, cloacogenic carcinoma in 3, adenocarcinoma in 2, and basal cell carcinoma in 2. Simulation was performed by PET/CT imaging with patient in treatment position. Gross Tumor Volume (GTV) and Clinical Target Volume (CTV) were drawn on CT and on PET/CT fused images. PET-GTV and PET-CTV were respectively compared to CT-GTV and CT-CTV by Wilcoxon rank test for paired data.ResultsPET/CT fused images led to change the stage in 5/27 cases (18.5%): 3 cases from N0 to N2 and 2 from M0 to M1 leading to change the treatment intent from curative to palliative in a case.Based on PET/CT imaging, GTV and CTV contours changed in 15/27 (55.6%) and in 10/27 cases (37.0%) respectively. PET-GTV and PET-CTV resulted significantly smaller than CT-GTV (p = 1.2 × 10-4) and CT-CTV (p = 2.9 × 10-4). PET/CT-GTV and PET/CT-CTV, that were used for clinical purposes, were significantly greater than CT-GTV (p = 6 × 10-5) and CT-CTV (p = 6 × 10-5).ConclusionsFDG-PET/CT has a potential relevant impact in staging and target volume delineation of the carcinoma of the anal canal. Clinical stage variation occurred in 18.5% of cases with change of treatment intent in 3.7%. The GTV and the CTV changed in shape and in size based on PET/CT imaging.

No abstract

The whole-body DWIBS protocol provided a fast whole-body examination with high specificity and NPV. One major bias of the study was the inclusion of patients with diffuse disease and advanced disease stage and the heterogeneity of the neoplastic diseases included.

The aim of our work is to describe the way in which physical figures of merit such as contrast-to-noise ratio (CNR) behave when varying acquisition parameters such as emission scan duration (ESD) or activity at the start of acquisition (A(acq)) that in clinical practice can be selected by the user, or object properties such as target dimensions or target-to-background (T/B) ratio, which depend uniquely on the intrinsic characteristics of the object being imaged. Figures of merit, used to characterize image quality and quantitative accuracy for a 3D-LSO based PET/CT scanner, were studied as a function of ESD and A(acq) for different target sizes and T/B ratios using a multivariate approach in a wide range of conditions approaching the ones that can be encountered in clinical practice. An annular ring of water bags of 3 cm thickness was fitted over an IEC phantom in order to obtain counting rates similar to those found in average patients. The average scatter fraction (SF) of the modified IEC phantom was similar to the mean SF measured on patients with a similar scanner. A supplemental set of micro-hollow spheres was positioned inside the phantom. The NEMA NU 2-2001 scatter phantom was positioned at the end of the IEC phantom to approximate the clinical situation of having activity that extends beyond the scanner. The phantoms were filled with a solution of water and 18F (12 kBq/mL) and the spheres with various T/B ratios of 22.5, 10.3, and 3.6. Sequential imaging was performed to acquire PET images with varying background activity concentrations of about 12, 9, 6.4, 5.3, and 3.1 kBq/mL, positioned on the linear portion of the phantom's NECR curve, well below peak NECR of 61.2 kcps that is reached at 31.8 kBq/mL. The ESD was set to 1, 2, 3, and 4 min/bed. With T/B ratios of 3.6, 10.3, and 22.5, the 13.0, 8.1, and 6.5 mm spheres were detectable for the whole ranges of background activity concentration and ESD, respectively. The ESD resulted as the most significant predictor of CNR variance, followed by T/B ratio and the cross sectional area of the given sphere. Only last comes A(acq) with a weight more than halved with respect to ESD. Thus, raising ESD seems to be much more effective than raising A(acq) in order to obtain higher CNR, which is the physical figure of merit closely related with target detectability, at least in the simple task of the signal known exactly background known exactly model.