Detection of metastatic lesions from malignant pheochromocytoma and paraganglioma with diffusion-weighted magnetic resonance imaging: comparison with 18F-FDG positron emission tomography and 123I-MIBG scintigraphy.

OBJECTIVE: To investigate the diagnostic features of whole-body diffusion-weighted magnetic resonance imaging (DWI) as compared with 2-[(18)F]-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) and (123)I-meta-iodo-benzyl guanidine scintigraphy (MIBG) on metastatic lesions of patients with malignant pheochromocytoma or paraganglioma. METHODS: We prospectively studied 11 patients with histologically confirmed pheochromocytoma/paraganglioma and possible metastatic lesions. FDG-PET, MIBG, and DWI examinations were performed within 1 week, and the images were visually interpreted. Abnormal positive uptake either on MIBG or on FDG-PET was considered as metastases. Abnormal high signal intensities on DWI were considered as metastases using conventional T1-and T2-weighted images as reference. RESULTS: FDG-PET and DWI demonstrated metastatic lesions in all 11 patients, but MIBG showed no metastatic lesions in two patients. The numbers of lymph node metastases depicted on FDG-PET, MIBG, and DWI were 19, 6, and 39; bone metastases were 50, 49, and 60; liver metastases were 9, 9, and 15; lung metastases were 5, 7, and 5, respectively. MIBG failed to demonstrate many metastatic lesions, which were demonstrated on FDG-PET or DWI, although two mediastinal lymph node metastases, three lung metastases, and six bone metastases, which were not seen on DWI, were clearly demonstrated on MIBG. DWI showed 15 liver metastases, but 6 of them were not seen on FDG-PET or MIBG. CONCLUSIONS: DWI may be particularly advantageous in depicting lymph node and liver metastases and may have a higher rate of detecting metastatic lesions when compared with MIBG or FDG-PET. The limitations of DWI were possible false-positive finding, and probable lower detectability of mediastinal lymph node and lung metastasis.

Early diagnosis of recurrent hepatocellular carcinoma with 18F-FDG PET after radiofrequency ablation therapy.

The aim of this study was to evaluate the role of positron emission tomography (PET) with 18F-fluoro-2-deoxy-D-glucose (18F-FDG) in the restaging of hepatocellular carcinoma (HCC) treated with radiofrequency ablation (RFA). This study was performed on 33 lesions in 24 patients with HCC. 18F-FDG PET and computed tomography (CT) studies were performed in all patients before treatment. PET acquisition was started 50-60 min after injection of 18F-FDG (5-6 MBq/kg). Semi-quantitative analysis using Standardized Uptake Value (SUV) was measured for the evaluation of tumour 18F-FDG uptake. All patients underwent RFA treatment and were followed up at least 2 years with 18F-FDG PET, CT and clinical evaluation in the interval of every 3 months in the first year and every 6 months in the second year. 18F-FDG PET detected recurrence earlier than CT between 4-6 months in 2 patients and between 7-9 months in 6 patients whereas CT was positive in 4 patients. Overall detection rate of recurrence with 18F-FDG PET was 92% which was higher than that of CT (75%). Statistically significant difference in the SUV was observed between well and moderately differentiated HCC (p=0.033) and also between well and poorly differentiated HCC (p=0.037). The size of tumours showed a significant correlation with the time of recurrence (p<0.00033, r=0.8601, n=12). The results of this study indicate that 18F-FDG PET could detect recurrence earlier in patients with HCC treated with RFA, as compared with CT and could diagnose extrahepatic lesions. SUV showed a significant correlation with time of recurrence after RFA. 18F-FDG PET may be a dominant imaging modality as a follow-up procedure of HCC after RFA, in terms of early detection of recurrence.

Body diffusion-weighted MR imaging using high b-value for malignant tumor screening: usefulness and necessity of referring to T2-weighted images and creating fusion images.

RATIONALE AND OBJECTIVES: To evaluate the potential usefulness of high b-value body diffusion-weighted images (DWIs) as a screening tool in the depiction of abdominal malignant tumors. MATERIALS AND METHODS: We selected 110 abdominal magnetic resonance examinations (1.5 T; 60 men; age range, 25-90 years) with and without malignant tumors (n = 37 and n = 73, respectively). Axial DWIs were obtained by single-shot spin-echo (SE) type echo planar imaging (EPI) sequence with inversion pulse (repetition time, 6,800 msec; echo time, 100 msec; T1, 150 msec; b value, 1,000 sec/mm(2)) without breath-holding. Two radiologists independently interpreted the DWIs, T2-weighted images (T2-WI), all three types of images including DWIs, T2-WIs, and fusion images at the same time (DWIs + T2-WIs + fusion) with 7-14 days' interval, and the diagnostic confidence for each patient was scored. RESULTS: The area under the curve (AUC) of the composite receiver operating characteristic (ROC) curve of DWIs + T2-WIs + fusion (0.904) was significantly higher than those of DWIs (0.720; P < .001) and T2-WIs (0.822; P < .05). Both sensitivity and specificity were higher in DWIs + T2-WIs + fusion (89.5% and 81.9%, respectively) compared with those of DWIs (72.4% and 59.0%; P < .01 and P < .001, respectively). CONCLUSIONS: Abdominal high b-value DWIs have a high sensitivity and specificity for malignant tumors when T2-WIs are referred and image fusion technique is employed, suggesting that it may potentially be a new screening tool.

Perfusion CT of breast carcinoma: arterial perfusion of nonscirrhous carcinoma was higher than that of scirrhous carcinoma.

RATIONALE AND OBJECTIVES: Our goals were to apply perfusion CT technique to breast tumor and to evaluate the correlation between arterial perfusion value and other tumor characteristics. MATERIALS AND METHODS: Thirty-one female patients with primary breast tumors were included in this study. A single-slice dynamic CT was performed after an intravenous bolus injection of contrast material (40 ml; 370 mg I/ml) at 8 ml/sec. The parameters were calculated on a pixel-by-pixel basis by using maximum slope method, and quantitative maps of arterial perfusion were created. Statistical correlation between tumor size, patient age, and perfusion were assessed. Differences in perfusion between scirrhous and nonscirrhous carcinoma were also assessed. RESULTS: Perfusion CT images were successfully created for 24 patients (mean age, 55.9 years old; range, 36-85 years). In five patients, dynamic CT was not performed due to lack of visualization of the breast tumor on unenhanced CT. In two patients, reliable perfusion CT image could not be created because of motion artifact. The mean perfusion for 24 tumors was 33.1 +/- 16.9 ml/min/100 ml (mean +/- SD; range, 14-78), and the tumor perfusion did not correlate with patient's age or tumor size (21.0 +/- 10.2 mm; range, 10-45 mm). The mean perfusion of nonscirrhous carcinoma (45.8 ml/min/100 ml; n = 11) was higher than that of scirrhous carcinoma (22.7 ml/min/100 ml; n = 11; P < .001). CONCLUSION: Determination of the perfusion of breast carcinoma is feasible by dynamic CT and can be performed during a routine CT study without much supplementary burden on the patient. There are differences in blood flow between scirrhous and nonscirrhous breast carcinoma, and further research is needed to determine the impact of this finding.

Inverse correlation between tumor perfusion and glucose uptake in human head and neck tumors.

RATIONALE AND OBJECTIVES: We sought to determine the relationship between tumor blood flow and glucose uptake in head and neck tumors using perfusion computed tomography (PCT) and fluorine-18-fluorodeoxyglucose (FDG) positron emission tomography (PET). MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained for this study. Sixteen patients (mean age, 67 years; age range, 36-89 years) who had known or suspected head and neck tumors (15 malignant tumors and one schwannoma) underwent PCT and FDG PET examinations. Tumor area was measured on conventional CT images. The PCT data were postprocessed using maximum slope method analysis, and standardized uptake value (SUV) was measured on FDG PET. RESULTS: Mean arterial perfusion of the tumors was 61.56 mL/min/100 mL (range 22.17-102.7 mL/min/100 mL), and mean FDG SUV was 7.48 (range 2.74-17.1). A significant negative correlation between arterial perfusion and FDG SUV was found for malignant tumors (r = -0.538, P = .04, n = 15). CONCLUSION: There was an inverse relationship between arterial perfusion and glucose uptake of head and neck malignant tumors, suggesting that the malignant tumors may depend on anaerobic glycolysis.