Background: PET scans using FDG and somatostatin receptor imaging agents have both been used to study neuroendocrine tumours. Most reports have documented the sensitivity and specificity of each radiopharmaceutical independently, and even suggested the superiority of one over the other for different grades of disease.Aim: The aim of this work was to develop a grading scheme that describes the joint results of both the FDG and somatostatin receptor imaging PET scans in staging subjects with neuroendocrine tumours in a single combined parameter. The grading scheme that has been developed is referred to as the NETPET grade.Methods: This is a retrospective study which assessed subjects who had both FDG and somatostatin receptor PET imaging at our institution within 31 days of each other. The NETPET grade was assigned by experienced nuclear medicine physicians and compared with other clinical data such as WHO grade and overall survival.Results: In the period 2011-2015 we were able to recruit 62 subjects with histologically proven metastatic neuroendocrine tumour for review. The NETPET grade incorporating both the FDG and somatostatin receptor imaging results was significantly correlated with overall survival by univariate analysis (p=0.0018), whereas in this cohort the WHO grade at the time of diagnosis did not correlate with survival.Conclusions: The NETPET grade has promise as a prognostic imaging biomarker in neuroendocrine tumours. It permits the capturing of the complexity of dual radiotracer imaging in a single parameter which describes the subjects' disease and is readily amenable to use in patient management and further research.

Learning Objectives: On successful completion of this activity, participants should be able to describe (1) advantages and shortcomings of planar versus SPECT V/Q scanning, (2) advantages and disadvantages of CT pulmonary angiography versus V/Q SPECT in the investigation of pulmonary embolism, and (3) an overview of image acquisition, processing, display, and reporting of V/Q SPECT studies.Financial Disclosure: The authors of this article have indicated no relevant relationships that could be perceived as a real or apparent conflict of interest. CME Credit: SNMMI is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to sponsor continuing education for physicians. SNMMI designates each JNM continuing education article for a maximum of 2.0 AMA PRA Category 1 Credits. Physicians should claim only credit commensurate with the extent of their participation in the activity. For CE credit, participants can access this activity through the SNMMI Web site (http:// www.snmmi.org/ce_online) through September 2016.Planar ventilation-perfusion ( V/Q) scanning is often used to investigate pulmonary embolism; however, it has well-recognized limitations. SPECT overcomes many of these through its ability to generate 3-dimensional imaging data. V/Q SPECT has higher sensitivity, specificity, and accuracy than planar imaging and a lower indeterminate rate. SPECT allows for new ways to display and analyze data, such as parametric V/Q ratio images. Compared with CT pulmonary angiography, SPECT has higher sensitivity, a lower radiation dose, fewer technically suboptimal studies, and no contrast-related complications. Any nuclear medicine department equipped with a modern hybrid scanner can now perform combined V/Q SPECT with CT (using low-dose protocols) to further enhance diagnostic accuracy. V/Q SPECT (with or without CT) has application in other pulmonary conditions and in research. Si nce its first description by Wagner et al. in 1964 (1), the planar lung scan has been one of the most commonly performed studies in nuclear medicine. It is, however, a test with significant limitations, which have had an adverse impact on its reputation (2,3). Because planar imaging is a 2-dimensional technique, it has inherent limitations, especially related to overlap of anatomic segments. Assigning defects to specific lung segments is often difficult, and the variability in segment size and shape between patients makes accurate determination of the extent of embolic involvement in individual segments a challenge (2). Embolic defects may not be detected if there is shine-through from underlying lung segments with normal perfusion, thus resulting in an underestimation of the extent of perfusion loss (4). Furthermore, the medial basal segment of the right lower lobe is often not visualized on planar scans (2,5). Added to these factors is the widespread use of probabilistic reporting criteria, and a relatively high indeterminate rate, both of which have caused significant dissatisfaction among referring physicians (6,7). ...

Objective Positron emission tomography/computed tomography (PET/CT) has not been well studied as a first‐line test for giant cell arteritis (GCA), due, in part, to historical limitations in visualizing the cranial arteries. The Giant Cell Arteritis and PET Scan (GAPS) study was therefore carried out to assess the accuracy of a newer generation PET/CT of the head, neck, and chest for determining a diagnosis of GCA. Methods In the GAPS study cohort, 64 patients with newly suspected GCA underwent time‐of‐flight PET/CT (1‐mm slice thickness from the vertex to diaphragm) within 72 hours of starting glucocorticoids and before undergoing temporal artery biopsy (TAB). Two physicians with experience in PET reviewed the patients’ scans in a blinded manner and reported the scans as globally positive or negative for GCA. Tracer uptake was graded across 18 artery segments. The clinical diagnosis was confirmed at 6 months’ follow‐up. Results In total, 58 of 64 patients underwent TAB, and 12 (21%) of the biopsies were considered positive for GCA. Twenty‐one patients had a clinical diagnosis of GCA. Compared to TAB, the sensitivity of PET/CT for a diagnosis of GCA was 92% (95% confidence interval [95% CI] 62–100%) and specificity was 85% (95% CI 71–94%). The negative predictive value (NPV) was 98% (95% CI 87–100%). Compared to clinical diagnosis, PET/CT had a sensitivity of 71% (95% CI 48–89%) and specificity of 91% (95% CI 78–97%). Interobserver reliability was moderate (κ = 0.65). Among the enrolled patients, 20% had a clinically relevant incidental finding, including 7 with an infection and 5 with a malignancy. Furthermore, 5 (42%) of 12 TAB‐positive GCA patients had moderate or marked aortitis. Conclusion The high diagnostic accuracy of this PET/CT protocol would support its use as a first‐line test for GCA. The NPV of 98% indicates the particular utility of this test in ruling out the condition in patients considered to be at lower risk of GCA. PET/CT had benefit over TAB in detecting vasculitis mimics and aortitis.