Impact of 18F-FDG PET/CT on treatment of patients with differentiated thyroid carcinoma, negative 131I whole body scan and elevated serum thyroglobulin.

OBJECTIVES: 18F-FDG PET/CT is increasingly performed in patients with differen-tiated thyroid cancer. The aim of this study was to assess the clinical impact of 18F-FDG PET/CT on the management of patients with differentiated thyroid carcinoma who had elevated serum thyroglobulin (Tg) and negative 131I whole body scan (WBS). METHODS: 67 patients with differentiated thyroid carcinoma were included in this study. The findings of 18F-FDG PET/CT imaging were compared with histo-pathology, follow up imaging, or clinical follow-up results. The diagnostic accuracy of 18F-FDG PET/CT was evaluated for the entire patient group and for those patients with stimulated serum thyroglobulin levels of less than 5, 5-10, and more than 10 pmol/L as well as for local recurrences and metastases sites. The impact of 18F-FDG PET/CT on therapeutic management was also evaluated. RESULTS: 30/67 patients had positive findings on 18F-FDG PET/CT; 28 were true-positive and 2 were false-positive. 18F-FDG PET/CT results were true-negative in 36 patients and false-negative in 1 patient. The overall sensitivity, specificity, accuracy, PPV and NPV of 18F-FDG PET/CT were, 96.5%, 94.5%, 95.5%, 93.3%, and 97.2% respectively. Positive 18F-FDG PET/CT findings were directly correlated with stimulated serum thyroglobulin levels, 7.1% had Tg between 5-10, and 92.9% had Tg greater than 10 pmol/L. 18F-FDG PET/CT had a high or moderate impact on treatment management in 28 (41.8%) of patients. CONCLUSION: 18F-FDG PET/CT is able to improve diagnostic accuracy and have management impact in a therapeutically relevant way in patients with differentiated thyroid carcinoma who present with rising thyroglobulin level, negative 131I WBS, and clinical suspicion of recurrent disease.

Unusual location of recurrent mantle cell lymphoma on fluorodeoxyglucose-positron emission tomography despite complete metabolic resolution of previous sites of disease.

This case report presents a patient with recurrent pleomorphic mantle cell lymphoma (MCL), which is a relatively rare but aggressive type of lymphoma. A positron emission tomography/computed tomography scan performed to assess treatment response demonstrated a complete metabolic response in the sites of primary disease while also revealing new subcutaneous lesions, which were biopsy-proven recurrent disease. This case illustrates the importance of the different biological behavior of MCL, whereby new sites of metabolically active lesions can represent recurrent disease, even though there is a complete metabolic response at sites of primary disease.

Effect of blood glucose level on standardized uptake value (SUV) in 18F- FDG PET-scan: a systematic review and meta-analysis of 20,807 individual SUV measurements.

OBJECTIVES: To evaluate the effect of pre-scan blood glucose levels (BGL) on standardized uptake value (SUV) in 18F-FDG-PET scan. METHODS: A literature review was performed in the MEDLINE, Embase, and Cochrane library databases. Multivariate regression analysis was performed on individual datum to investigate the correlation of BGL with SUVmax and SUVmean adjusting for sex, age, body mass index (BMI), diabetes mellitus diagnosis, 18F-FDG injected dose, and time interval. The ANOVA test was done to evaluate differences in SUVmax or SUVmean among five different BGL groups (< 110, 110-125, 125-150, 150-200, and > 200 mg/dl). RESULTS: Individual data for a total of 20,807 SUVmax and SUVmean measurements from 29 studies with 8380 patients was included in the analysis. Increased BGL is significantly correlated with decreased SUVmax and SUVmean in brain (p < 0.001, p < 0.001,) and muscle (p < 0.001, p < 0.001) and increased SUVmax and SUVmean in liver (p = 0.001, p = 0004) and blood pool (p = 0.008, p < 0.001). No significant correlation was found between BGL and SUVmax or SUVmean in tumors. In the ANOVA test, all hyperglycemic groups had significantly lower SUVs compared with the euglycemic group in brain and muscle, and significantly higher SUVs in liver and blood pool. However, in tumors only the hyperglycemic group with BGL of > 200 mg/dl had significantly lower SUVmax. CONCLUSION: If BGL is lower than 200 mg/dl no interventions are needed for lowering BGL, unless the liver is the organ of interest. Future studies are needed to evaluate sensitivity and specificity of FDG-PET scan in diagnosis of malignant lesions in hyperglycemia.

Normal range of osteoblastic activity in total hip arthroplasties on single-photon emission computed tomography bone scintigraphy.

AIM: Knowledge of the normal range of periprosthetic osteoblastic activity around total hip arthroplasties is required for rational diagnosis of complications. The aim of this study was to establish such a normal range for single-photon emission computed tomography (SPECT). Clinical utility of such a range is confident differentiation of normal from abnormal arthroplasties. METHODS: A total of 122 asymptomatic acetabular cups (age: 0-22 years) and 71 femoral stems (age: 0-20 years) were scanned with SPECT/CT. Two acetabular and three femoral activity ratios to normal reference bone were defined [acetabular axial (AA/RA), acetabular coronal (AC/RA), RA=reference acetabulum; femoral calcar (FC/RF), femoral mid-stem (FM/RF), femoral stem tip (FS/RF), RF=reference femur]. Upper cut-off of normal was defined as mean +3 SD (rounded). Two time breakpoints were analysed (12 and 24 months). RESULTS: The upper cut-off for the normal range was 1.0 for AA/RA, 1.5 for AC/RA and 2.2 for all thee of FC/RF, FM/RF and FS/RF. AA/RA, FM/RF and FS/RF showed no statistically significant temporal trends. AC/RA showed stabilization of activity after 12 months and FC/RF after 24 months. CONCLUSION: Measured activity ratios that fall within our normal range are likely to represent normal periprosthetic osteoblastic activity. Measured activity ratios that fall above the upper cut-offs of our normal range are likely to be abnormal. The cut-offs are robust in clinical practice and have utility in discriminating normal from abnormal stabilized arthroplasties where visual interpretation is ambiguous. Elevated AC/RA under 12 months and FC/RF under 24 months may represent normal periprosthetic activity and should be interpreted with caution.

Reference range for intrapatient variability in blood-pool and liver SUV for 18F-FDG PET.

UNLABELLED: (18)F-FDG PET qualitative tumor response assessment or tumor-to-background ratios compare targets against blood-pool or liver activity; standardized uptake value (SUV) semiquantitation has artifacts and is validated by a stable normal-tissue baseline. The aim of this study was to document the normal intrapatient range of scan-to-scan variation in blood-pool SUV and liver SUV and to identify factors that may adversely affect it (increase its spread). METHODS: Between July 2009 and June 2010, 132 oncology patients had 2 PET/CT scans. Patient preparation, acquisition, and reconstruction protocols were held stable, uniform, and reproducible. Mean SUV (body weight) values were obtained from 2-dimensional regions of interest in the aortic arch blood pool and in the right lobe of the liver. RESULTS: Of the 132 patients, 65 had lymphoma. Their mean age was 62.5 y. The group's mean serum glucose level was 6.0 mmol/L at the first visit and 5.9 mmol/L at the second visit. The mean (18)F-FDG dose was 4.1 MBq/kg at the first visit and 4.0 at the second. At the first visit, the group's mean blood-pool SUV was 1.55 (SD, 0.38); at the second, 1.58 (SD, 0.37)-not statistically different. The group's mean liver SUV was 2.17 (SD, 0.44) at the first visit and 2.29 (SD, 0.44) at the second (P = 0.005). Visit-to-visit intrapatient variation in blood-pool and liver SUVs had gaussian distributions. The variation in blood-pool SUV had a mean of 0.03 and SD of 0.42. The variation in liver SUV had a mean of 0.12 and SD of 0.50. Using 95th percentiles, the reference range in our patient population for intrapatient variation was -0.8 to 0.9 for blood pool SUV and -0.9 to 1.1 for liver SUV. Subanalysis by cancer type and chemotherapy suggested that the rise in liver SUV between the 2 visits was largely due to the commencement of chemotherapy, but no factors were identified as systematically affecting intrapatient variation, and no factors were identified as increasing its spread. CONCLUSION: In our patient cohort, the reference range for intrapatient variation in blood-pool and liver SUVs is -0.8 to 0.9 and -0.9 to 1.1, respectively.