Is 18F-FDG PET/CT useful for distinguishing between primary thyroid lymphoma and chronic thyroiditis?

PURPOSE: This study aims to investigate the usefulness of (18)F-FDG PET/CT for distinguishing between primary thyroid lymphoma (PTL) and chronic thyroiditis. METHODS: We retrospectively reviewed the data of 196 patients with diffuse (18)F-FDG uptake of the thyroid gland and enrolled patients who were diagnosed as having PTL or chronic thyroiditis based on the medical records, pathological findings, and laboratory data. The enrolled patients comprised 10 PTL patients (M/F = 4:6) and 51 chronic thyroiditis patients (M/F = 8:43). Images had been acquired on a PET/CT scanner at 100 minutes after intravenous injection of (18)F-FDG. RESULTS: The PTL group consisted of 7 patients with diffuse large B-cell lymphoma (DLBCL) and 3 with mucosa-associated lymphoid tissue (MALT) lymphoma. The maximum standardized uptake value (SUV(max)) was significantly higher in the PTL group than that in the chronic thyroiditis group (25.3 ± 8.0 and 7.4 ± 3.2, P < 0.001). On the other hand, the CT density (Hounsfield unit: HU) was significantly lower in the PTL group than that in the chronic thyroiditis group (46.1 ± 7.0 HU and 62.1 ± 6.9 HU, P < 0.001). Within the PTL group, the SUV(max) was significantly higher in the cases of DLBCL than in those of MALT lymphoma (29.0 ± 6.4 and 16.7 ± 2.3, P = 0.017). CONCLUSIONS: The SUV(max) was significantly higher and the CT density was significantly lower in PTL as compared with those in chronic thyroiditis. Thus, (18)F-FDG PET/CT may be useful for distinguishing between PTL and chronic thyroiditis.

Long-term changes of aortic 18F-FDG uptake and calcification in health-screening subjects.

BACKGROUND: We investigated long-term changes in aortic (18)F-fluorodeoxyglucose ((18)F-FDG) uptake and calcification in health-screening subjects and their relation with atherogenic risk factors. METHODS AND RESULTS: A total of 94 consecutive subjects (72 men, 22 women; age 47-85 years, mean 57.9 years) participating in a health-screening protocol were evaluated retrospectively. All subjects had follow-up PET/CT scans 3.0-5.8 years (mean 4.1 years) later. We measured (18)F-FDG uptake (maximum SUV) and calcium score (Agatston score) of the ascending, descending thoracic and infrarenal abdominal aorta on PET/CT images. (18)F-FDG uptake and calcium score of the whole aorta (FUWA and CSWA) increased significantly in the follow-up study compared with the initial study (p = 0.02 and p < 0.0001, respectively). Multiple regression analysis showed that the change in FUWA per year was significantly associated with visceral fat area, while the change of CSWA per year was significantly associated with age and smoking habit. The degrees of (18)F-FDG uptake and calcium score increases were significantly greater in the abdominal aorta than in the thoracic aorta (p = 0.05 and p < 0.0001, respectively). CONCLUSIONS: Our data demonstrated the longitudinal progressions of vascular inflammation and calcification of health-screening subjects. Inflammation and calcification were observed to progress significantly faster in the abdominal aorta than in the thoracic aorta. The progressions of vascular inflammation and calcification may be associated with different atherogenic risk factors.

Normal variants of bowel FDG uptake in dual-time-point PET/CT imaging.

OBJECTIVE: To evaluate the normal variants of the physiological bowel 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) uptake in dual-time-point positron emission tomography/computed tomography (PET/CT). METHODS: We performed a retrospective review of 206 consecutive asymptomatic subjects who underwent whole-body FDG PET/CT for medical checkup in our institution. The criteria for exclusion of the subjects from this study were as follows: history of abdominal surgeries or endoscopic mucosal resection, history of any malignant tumors, symptoms of diarrhea or constipation, a positive fecal occult blood test, elevated serum carcinoembryonic antigen (CEA) level, and hyperglycemia (more than 110 mg/dl). A total of 39 subjects (32 males, 7 females, mean age 58.1 years old) were enrolled in this retrospective study. Two radiologists evaluated the dual-time-point FDG PET/CT images of these 39 subjects, retrospectively. FDG uptakes in 5 areas (small bowel (SB), cecum and ascending colon (AC), transverse colon (TC), descending colon (DC), and rectosigmoid colon (RS)) were scored visually in comparison with the activity in the liver (0 = no uptake, 1 = activity less than that in the liver, and 2 = activity equal to or greater than that in the liver) in the early and delayed image. The scores decided by two radiologists were averaged and this average score was defined as the bowel uptake score (BUS). For 34 areas with the BUS of 2 in either the early or delayed images, the maximum standardized uptake values (SUV(max)) were measured for semiquantitative analysis. Wilcoxon's signed rank test and paired t test were adopted for the statistical analyses. RESULTS: The average BUS in the early/delayed images was 1.19/1.17 (SB), 0.81/1.23 (AC), 0.10/0.35 (TC), 0.35/0.59 (DC), and 1.17/1.54 (RS), respectively. The average SUV(max) of the 34 areas with a score of 2 was 3.11 in the early images and 3.76 in the delayed images. The scores in the AC, TC, DC and RS, and the SUV(max) were significantly higher in the delayed images (p < 0.05). CONCLUSIONS: Physiological FDG uptake in the colon increases significantly from the early to the delayed phase in dual-time-point PET/CT imaging, which should be carefully taken into consideration in the diagnosis of bowel diseases.

Bilateral renal angiomyolipoma in a patient with tuberous sclerosis treated with resection of one kidney and transarterial embolization of other kidney using CT during selective arteriography: a case report.

Renal AML complicating tuberous sclerosis shows a rapid growth and its rupture is frequently associated with hemorrhagic shock as a result of profuse retroperitoneal bleeding, necessitating an aggressive therapeutic approach. This report describes the long-term clinical progress of 28 year-old woman with tuberous sclerosis with a ruptured giant AML that underwent unilateral nephrectomy, who has been followed up after treatment with concomitant application of computed tomography during selective arteriography to conserve the remaining normal renal parenchyma, and in whom the need for initiation of dialysis has been successfully avoided, with conspicuous reduction of the tumor size.

Potential extraperitoneal space continuous with the peri-intestinal space: CT evidence and anatomical evaluation in patients with pneumatosis intestinalis without intestinal ischemia.

PURPOSE: Extraperitoneal spaces, such as the mesenteric space and the retroperitoneal space, can serve as areas that enable a reduction in the pressure exerted by extraperitoneal fluid collection and infiltrating diseases. In clinical practice, understanding the existence of these decompression spaces (or pathways) is very important for making accurate diagnoses. Here, we evaluated potential anatomical extraperitoneal spaces based on the extraluminal gas distribution in patients with pneumatosis intestinalis without intestinal ischemia. METHODS: The computed tomography scans of ten patients with pneumatosis intestinalis without intestinal ischemia were reviewed, and the anatomic location of the extraluminal gas distribution was investigated. RESULTS: Four patients were diagnosed as having pneumatosis intestinalis of the small intestine and six were diagnosed as having pneumatosis intestinalis of the large intestine. Mesenteric pneumatosis was observed in nine (90%) of the ten patients. The potential anatomical extraperitoneal spaces (or decompression pathways) were classified as follows: mesenteric (n = 3), retroperitoneal (n = 4), and direct (n = 5). CONCLUSIONS: The distributions of the extraluminal gas were classified into three categories, and each location may characterize a different decompression pathway. The existence of a potential extraperitoneal space continuous with the peri-intestinal space was confirmed in living subjects.

Increased subcutaneous fat accumulation has a protective role against subclinical atherosclerosis in asymptomatic subjects undergoing general health screening.

PURPOSE: To evaluate the clinical role of subcutaneous fat accumulation in subclinical arteriosclerosis, using computed tomography (CT), we measured the subcutaneous fat area (SFA), the visceral fat area (VFA) and the VFA/SFA ratio and compared these with the calcium score of the whole aorta (CSWA) in asymptomatic subjects who were undergoing general health screening. METHODS: 122 consecutive asymptomatic subjects (40 female, mean age 56.2+/-8.4 years) were analyzed. Whole-body low-dose CT scan (mAs=50, slice thickness=5 mm) was performed. The SFA and VFA were measured at the umbilical level. Calcification of whole aorta was defined as an area with >90 HU and 1 mm(2), and CSWA was calculated using the modified Agatston method. RESULTS: Mean+/-SD of SFA, VFA and log CSWA were 158+/-67.1 cm(2), 94.0+/-44.8 cm(2), and 7.93+/-1.08, respectively. SFA was significantly and inversely correlated with log CSWA (r=-0.219, P=0.015) but VFA was not (r=0.105, P=0.250) and as a result, the VFA/SFA ratio was significantly and positively correlated with log CSWA (r=0.221, P=0.015). Subsequently, all predictor variables were used in a stepwise multiple regression model with log CSWA as dependent variable, and age, SFA and fasting plasma glucose significantly influenced log CSWA (P<0.001) by the multiple regression formula Y=0.046X1***-0.005X2**+0.015X3*+4.426, (***P<0.001, **P<0.01, and *P<0.05) where Y=log CSWA, X1=age, X2=SFA, and X3=fasting plasma glucose). CONCLUSIONS: SFA was significantly and inversely associated with log CSWA, in an independent fashion. These results suggest that subcutaneous fat accumulation might have a protective role against atherosclerosis in asymptomatic subjects.