Aisheng Dong

18F-FDG PET/CT in Differentiating Acute Tuberculous From Idiopathic Pericarditis: Preliminary Study

Purpose The aim of this study was to evaluate retrospectively the diagnostic capability of 18F-FDG PET/CT in differentiating acute tuberculous from idiopathic pericarditis. Methods FDG PET/CT findings were reviewed in 15 patients with acute tuberculous (n = 5) or idiopathic pericarditis (n = 10). The maximal thickness and SUVmax of the pericardium and the number, size, and SUVmax of the mediastinal and supraclavicular lymph nodes with increased FDG uptake were measured. Results All patients had small-to-large amount of pericardial effusion. The patients with acute tuberculous pericarditis (n = 5) showed diffuse (n = 3) or multifocal (n = 2) FDG uptake in the pericardia. The patients with acute idiopathic pericarditis (n = 10) showed diffuse (n = 6) or regional (n = 4) FDG uptake in the pericardia. The mean (SD) pericardial thickness and SUVmax of acute tuberculous pericarditis were significantly higher than those of acute idiopathic pericarditis (5.1 [1.0] vs 3.4 [0.9], P < 0.05; 13.5 [3.9] vs 3.0 [0.7], P < 0.05, respectively). A total of 69 mediastinal and supraclavicular lymph nodes with increased FDG uptake were observed in all 15 patients (44 in patients with acute tuberculous pericarditis and 25 in patients with acute idiopathic pericarditis). The mean (SD) SUVmax of mediastinal and supraclavicular lymph nodes of acute tuberculous pericarditis (5.3 [1.8]) was significantly higher than that of acute idiopathic pericarditis (2.8 [0.6], P < 0.05). There was no significant difference in the mean size of the mediastinal and supraclavicular lymph nodes between acute tuberculous and idiopathic pericarditis. Conclusions The degrees of FDG uptake in the pericardium and the mediastinal and supraclavicular lymph nodes are useful for differentiating acute tuberculous from idiopathic pericarditis. Familiarity with the FDG uptake patterns of acute tuberculous and idiopathic pericarditis may be helpful for successful (especially timely) diagnosis and treatment.

MRI and FDG PET/CT findings of hepatic epithelioid hemangioendothelioma.

Purpose The aim of this study was to evaluate retrospectively magnetic resonance imaging (MRI) and 18F fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) findings of hepatic epithelioid hemangioendothelioma (HEH). Patients and Methods MRI and FDG PET/CT findings were reviewed in 6 patients with HEH confirmed by pathology. All patients underwent magnetic resonance (MR) examination. Early PET/CT scans were performed 1 hour after FDG injection in all 6 patients. After an interval of 1 hour, delayed PET/CT scans were performed in 4 patients. Results A total of 60 lesions were detected in all 6 patients. MRI features of HEH included multifocal hepatic disease, predominantly subcapsular location, coalescence of lesions, and capsular retraction. T2-weighted MR images frequently showed a target-like configuration of the lesions. Contrast-enhanced MR images showed variable degrees of peripheral rim enhancement with delayed central enhancement. Forty lesions (67%) with increased FDG uptake and 20 lesions (33%) with FDG uptake similar to the surrounding liver parenchyma were found in all 6 patients. The mean maximum standardized uptake value (SUVmax) of all lesions was 3.6 ± 1.1, with a low variability of SUVmax among lesions ranging from 1.7 to 6.6. There was no relationship between lesion sizes and corresponding SUVmax. Some larger lesions demonstrated a hypermetabolic peripheral rim reflecting hypercellular tumor regions and a relatively hypometabolic central area corresponding to hypocellular stroma. Eleven lesions with increased FDG uptake on the delayed PET/CT images were found in 3 patients, and 19 lesions with decreased FDG uptake were found in all 4 patients with total 32 lesions. Conclusions MRI demonstrated morphological features of HEH and FDG PET/CT reflected the histopathological composition of the tumors. FDG uptake of HEH may be related to tumor cellularity, but not the tumor size. Dual-time-point imaging may be not useful for differentiating benign lesions from HEH. Familiarity with the morphological and functional imaging findings of HEH is useful for recognition of this rare hepatic tumor.

Inflammatory myofibroblastic tumor: FDG PET/CT findings with pathologic correlation.

Purpose The aim of this study was to evaluate retrospectively 18F-FDG PET/CT findings of inflammatory myofibroblastic tumor (IMT) and their correlation with the pathologic findings. Patients and Methods FDG PET/CT findings were reviewed in 5 patients with IMT and 1 patient with spindle cell sarcoma transformed from IMT. PET/CT scans were performed in all 6 patients before surgery. Follow-up FDG PET/CT scan was performed in 1 patient. The location, size, maximal standardized uptake value (SUVmax), and pathologic findings of the tumors were reviewed. The correlation between the FDG uptake and pathologic findings were analyzed. Results A total of 10 lesions were detected in all 6 patients. The tumor locations were liver (n = 3), retroperitoneum (n = 2), spleen (n = 1), lung (n = 1), and bone (n = 3). Seven IMTs and 1 spindle cell sarcoma transformed from IMT were confirmed by pathology. The mean SUVmax of the pathologically proven tumors was 10.9 ± 5.5, with a high variability of SUVmax among tumors ranging from 3.3 to 20.8. The tumors (n = 7) with high cellularity had stronger FDG uptake, while the tumors (n = 1) with low cellularity had relatively low FDG uptake. The tumors with nuclear atypia and relatively high proliferative index had very strong FDG uptake, while those with low proliferative index or negative Ki-67 staining had relatively lower FDG uptake. One small tumor with abundant plasma cells showed high FDG uptake, while 1 large tumor with focal inflammatory cell infiltrate showed lower FDG uptake. One patient developed local recurrences and distant metastases revealed by the second FDG PET/CT scan 7 months after resection. Conclusions FDG uptake in IMTs varied from low to high FDG uptake, which may be due to tumor cellularity, biological behaviors of the tumor cells, the composition and the proportion of inflammatory cells, and the extent of activation of the inflammatory cells. FDG PET/CT may be useful for detection of the primary tumors, local recurrences, and distant metastases.

FDG PET/CT findings of solid pseudopapillary tumor of the pancreas with CT and MRI correlation.

Purpose The aim of this study was to evaluate retrospectively 18F-FDG PET/CT findings of solid pseudopapillary tumor of the pancreas (SPTP). Patients and Methods FDG PET/CT findings were reviewed in 8 patients with SPTP confirmed by pathology. Early PET/CT scans were performed 1 hour after FDG injection in all 8 patients. After an interval of 1 hour, delayed PET/CT scans were performed in 6 patients. All patients underwent enhanced CT and 4 patients underwent MRI. Results A total of 8 tumors were detected in all 8 patients. CT and MRI findings included encapsulation (n = 2), solid and cystic components (n = 4), focal calcification (n = 7), and weak enhancement during the arterial phase on enhanced CT or MRI and increasing enhancement during the portal venous phase (n = 8). All the tumors showed increased FDG uptake. The mean SUVmax of all tumors was 8.9, with a high variability of SUVmax among lesions ranging from 2.5 to 29.1. The tumors (n = 6) with high cellularity had stronger FDG uptake, whereas the tumors (n = 2) with low cellularity had relatively low FDG uptake. The tumors (n = 6) with pancreatic parenchymal, vascular, or perineural invasions had intense FDG uptake, whereas the tumors (n = 2) without invasions had slight-to-moderate FDG uptake. Two tumors with relatively high proliferative index had very strong FDG uptake, whereas those (n = 6) with low proliferative index or negative Ki-67 staining result had relatively lower FDG uptake. On delayed FDG PET/CT images, The SUVmax of SPTP increased in 4 patients and slightly decreased in 2 patients. Conclusions CT or MRI demonstrated morphological features of SPTP and FDG PET/CT that reflected the histopathological composition of the tumors. FDG uptake of SPTP may be related to tumor cellularity, proliferative index, or histological malignancy. Familiarity with the morphological and functional imaging findings of SPTP may be helpful for correct diagnosis and appropriate treatment.

Hypermetabolic mesenteric brown adipose tissue on dual-time point FDG PET/CT in a patient with benign retroperitoneal pheochromocytoma.

Intense FDG uptake of the mesenteric brown adipose tissue (BAT) is rare. We present a case of benign retroperitoneal pheochromocytoma showing multiple hypermetabolic regions corresponding with common locations of BAT. Furthermore, the mesenteric region showed intense FDG uptake, with SUVmax of 10.6. FDG PET/CT findings of this case supports the previous theories that the incidence of BAT may be higher in patients with pheochromocytoma than in patients without, and the intra-abdominal fat of human adults, including the omental fat, which is brown adipose tissue in infancy, becomes reactivated in the presence of high circulating noradrenaline concentrations.

FDG PET/CT and enhanced CT imaging of tumor heterogeneity in hepatocellular carcinoma: imaging-pathologic correlation.

Tumor heterogeneity is used to define the appearance of different histological differentiation within a single neoplasm. We present a case of single hepatocellular carcinoma showing both low and high FDG uptake areas. The low FDG uptake area was corresponding to low-grade HCC, and the high FDG uptake area was corresponding to high-grade HCC. This case indicates that the tumor grades affect intratumoral heterogeneity in FDG distribution. FDG PET/CT can be useful for guiding tissue sampling of the HCC with heterogeneous histological differentiations, and obviating overestimation or underestimation of the proportion of the higher-risk cell population.

Hypermetabolic lesions of the pancreas on FDG PET/CT.

Purpose Interpretation of 18F-FDG PET/CT studies in the pancreas is challenging owing to nonspecific FDG uptake in various benign and malignant pancreatic lesions. The purpose of this atlas article was to demonstrate features of various pancreatic lesions encountered at our institution, both benign and malignant, which can result in hypermetabolism on FDG PET/CT imaging. Patients and Methods We presented FDG PET/CT studies of 13 patients with various pancreatic lesions. All patients underwent abdominal enhanced CT before FDG PET/CT. Results We described these cases under the following categories: exocrine pancreatic cancer, cystic tumors, solid pseudopapillary tumor, neuroendocrine tumor, lymphoma, pancreatitis (focal acute and chronic pancreatitis, mass forming pancreatitis, and autoimmune pancreatitis), and infection. Conclusions Knowledge of a wide spectrum of hypermetabolic pancreatic lesions on FDG PET/CT is essential in accurate reading of FDG PET/CT.

FDG PET/CT in primary pulmonary lymphoepithelioma-like carcinoma.

Primary pulmonary lymphoepithelioma-like carcinomas are extremely rare tumors with better prognosis than other types of non-small cell lung cancer. An 83-year-old man presented with cough and hemoptysis for 2 weeks. Chest CT images showed a cylinder-shaped lesion in the right upper lung. F-FDG PET/CT showed strong FDG uptake (SUVmax, 34.5) of the tumor with ipsilateral hilar lymph node metastases. Video-assisted thoracoscopic lobectomy was performed. Histopathologically, the tumor was composed of epithelial tumor cells with high proliferation index (80%) and abundant lymphoplasmacytic cells, consistent with lymphoepithelioma-like carcinoma.

F-18 FDG uptake in borderline intraductal papillary neoplasms of the bile duct.

Intraductal papillary neoplasm of the bile duct (IPN-B) has been recently proposed as the biliary counterpart of intraductal papillary mucinous neoplasm of the pancreas. Histologically, IPN-B can be classified into adenoma, borderline, carcinoma in situ, and invasive carcinoma. Two patients with suspected intraductal tumor underwent fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography. One patient showed an FDG-avid tumor in the right liver with SUVmax of 9.4 in early images and 11.3 in delayed images. The patient underwent complete tumor resection. Adenoma with high-grade dysplasia was confirmed by pathology. The other patient showed an FDG-avid polypoid lesion at the distal common bile duct with SUVmax of 5.4. The lesion was endoscopically resected. Histopathologic findings showed adenoma with low-grade dysplasia. These two cases highlight that IPN-B should be included in the differential diagnosis of abnormal biliary intraductal FDG accumulation along with carcinoma, and inflammatory and infectious processes.

Organized urachal abscess mimicking urachal carcinoma on FDG PET/CT.

Urachal inflammation is rarely seen in adults. Two patients with suspected abdominal tumor underwent FDG PET/CT. One patient showed an irregular hypermetabolic mass anterosuperior to the bladder. The other patient showed a thick-walled cystic mass with strong FDG uptake extending from the bladder dome to the anterior abdominal wall. Urachal carcinomas were suspected based on imaging findings. Both patients underwent complete resection of the masses. However, both masses were organized urachal abscesses confirmed by pathological examination. These two cases highlight that differentiation between organized urachal abscess and carcinoma is difficult on the basis of imaging.