Detection of moderate hepatic steatosis on contrast-enhanced dual-source dual-energy CT: Role and accuracy of virtual non-contrast CT.

PURPOSE: To investigate diagnostic accuracy of virtual non contrast (VNC) images, based on dual-source dual-energy CT (dsDECT), for detection of at least moderate steatosis and to define a threshold value to make this diagnosis on VNC. METHODS: This single-institution retrospective study included patients who had multi-phasic protocol dsDECT. Regions of interests were placed in different segments of the liver and spleen on true non-contrast (TNC), VNC, and portal-venous phase (PVP) images. At least moderate steatosis was defined as liver attenuation (LHU) < 40 HU on TNC. Diagnostic performance of VNC to detect steatosis was determined and the new threshold was tested in a validation cohort. RESULTS: 236 patients were included in training cohort. Mean liver attenuation values were 51.3 ±â€¯10.8 HU and 58.1 ±â€¯11.5 HU for TNC and VNC (p < 0.001), with a mean difference (VNC - TNC) of 6.8 ±â€¯6.9 HU. Correlation between TNC and VNC was strong (r = 0.81, p < 0.001). The AUCs of LHU on VNC for detection of hepatic steatosis were 0.92 (95 % Cl: 0.86-0.98), 0.92 (95 % Cl: 0.87-0.97), 0.92 (95 % Cl: 0.86-0.99), 0.91 (95 % Cl: 0.84-0.97), and 0.87 (95 % Cl: 0.80-0.95) for entire liver, left lateral, left medial, right anterior, and right posterior segments, respectively. VNC had sensitivity/specificity of 100 % /42 % when using a threshold of 40 HU; they were 69 % and 95 %, respectively, when using optimized threshold of 46 HU. This threshold showed similar performance in validation cohort (n = 80). CONCLUSIONS: Hepatic attenuation on VNC has promising performance for detection of at least moderate steatosis. Proposed threshold of 46 HU provides high specificity and moderate sensitivity to detect steatosis.

Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia and Granulomatous Inflammation Mimicking High-Grade Malignancy on FDG-PET/CT.

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a rare form of preinvasive lung lesion associated with indolent carcinoid tumor formation. This disease is characterized by multiple small pulmonary nodules with low SUVmax on F-FDG PET. Biopsy and immunohistochemical staining for neuroendocrine markers confirm diagnosis. There is no consensus for treatment, which typically involves surgical excision or management of symptoms with steroid-based therapies. We report an unusual case of DIPNECH colocalizing with necrotizing granulomatous inflammation mimicking high-grade aggressive malignancy on FDG-PET and a typical case of DIPNECH for comparison with low FDG avidity.