Rapid advances in techniques of contrast material-enhanced magnetic resonance (MR) angiography have enabled evaluation of the entire aorta and the main arteries. Dynamic subtraction MR angiography consists of first-pass imaging of long segments of arteries by using a three-dimensional fast field echo sequence with multiple rapid bolus injections of a small dose of gadopentetate dimeglumine. Subtraction enables clear demonstration of the enhanced vascular lumen by eliminating background signal. Improved temporal resolution and repeated sequences after gadopentetate dimeglumine administration allow demonstration of arteries and veins separately. Double subtraction postprocessing can be used to eliminate arterial enhancement in demonstration of the portal and systemic veins. Additional postprocessing can be used to demonstrate arteries in a single image in patients with aortic dissection or a prolonged circulation time. To optimize the examination, the pulse sequence, injection dose, injection rate, timing of the start of data acquisition, imaging time, breath holding, section thickness, and coil selection should be considered. This technique is flexible enough to be applied in a variety of clinical settings, including atherosclerotic occlusive disease, aneurysm of aortoiliac arteries, bypass graft, Takayasu arteritis, aortic dissection, antiphospholipid antibody syndrome, renal artery disease, pelvic vascular disease, and the portomesenteric venous system.
Although dual-time point PET/CT scan enhances the difference of FDG uptake between FDG-avid metastatic and benign LNs and improves the differentiation when compared with a single scan, biopsy procedure may be still required for accurate assessment of LN status in patients with NSCLC and possible etiologies showing intensive FDG uptake in benign LNs.
The aim of this study was to assess the probability of malignancy in one or two small nodules 1 cm or less coexisting with potentially operable lung cancer (coexisting small nodules). The preoperative helical CT scans of 223 patients with lung cancer were retrospectively reviewed. The probability of malignancy of coexisting small nodules was evaluated based on nodule size, location, and clinical stage of the primary lung cancers. Seventy-one coexisting small nodules were found on conventional CT in 58 (26%) of 223 patients, and 14 (6%) patients had malignant nodules. Eighteen (25%) of such nodules were malignant. The probability of malignancy was not significantly different between two groups of nodules larger and smaller than 0.5 cm ( p=0.1). The probability of malignancy of such nodules within primary tumor lobe was significantly higher than that in the other lobes ( p<0.01). Metastatic nodules were significantly fewer in clinical stage-IA patients than in the patients with the other stage ( p<0.01); however, four (57%) of seven synchronous lung cancers were located in the non-primary tumor lobes in the clinical stage-I patients. Malignant coexisting small nodules are not infrequent, and such nodules in the non-primary tumor lobes should be carefully diagnosed.
Although delayed PET/CT scan enhances the difference of FDG uptake between FDG-avid NSCLC and benign lesions, and the use of delayed SUVmax > 5.5 appears to improve the differentiation of these hypermetabolic lesions compared with an early scan, careful interpretation and management for correct differentiation are still required.
A 72-year-old woman with Mikulicz disease with pathogically proven sclerosing sialadenitis showed systemic abnormal F-18 FDG uptake in the bilateral lacrimal and submandibular glands, pancreas, abdominal aortic wall, and a retroperitoneal fibroid mass on PET/CT scan, with marked elevation of the serum IgG4 level. This case supports Mikulicz disease being included as 1 of the disorders associated with a new clinical entity of systemic IgG4-related plasmacytic syndrome. A whole-body FDG-PET/CT scan can be expected as a useful tool for detecting systemic involvement in systemic IgG4-related plasmacytic syndrome.
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