F-18 FDG positron emission tomography findings in primary pancreatic lymphoma

The usefulness of F-18 2'-deoxy-2-fluoro-D-glucose (FDG) positron emission tomography (PET) has been well established for lymphoma staging. Although involvement of the pancreas occurs in more than one third of patients with non-Hodgkin lymphoma, primary lymphoma of the pancreas accounts for less than 1% of extranodal non-Hodgkin lymphomas. Because patients with primary pancreatic lymphoma require a different therapeutic approach and have a better prognosis than those with pancreatic adenocarcinoma, the accurate diagnosis is important. However, conventional imaging modalities cannot differentiate between adenocarcinoma and other less common neoplasms such as lymphoma. We report a 67-year-old man who had a primary pancreatic lymphoma in which FDG PET imaging revealed round, intense FDG uptake in the center of the midabdomen.     

Pituitary adenoma detected on FDG positron emission tomography in a patient with mucosa-associated lymphoid tissue lymphoma

A 52-year-old woman with a history of treated non-Hodgkin's lymphoma, B-cell type, was examined for a right eyelid mass proved on excision to be a mucosa-associated lymphoid tissue lymphoma. She was referred for F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging of the whole body, including the brain, to identify the possible presence or recurrence of lymphoma. The FDG-PET images revealed focal marked FDG uptake in the pituitary gland but no evidence of abnormal metabolic sites in the rest of the body, including the orbital regions. Magnetic resonance imaging and computed tomography confirmed a 1.8 x 1.5 cm intrasellar mass. Surgery was performed, and histologic examination revealed a nonfunctional adenoma that was negative for leukocyte common antigen staining, an antigen that is positive in lymphoma but negative in pituitary adenoma. This case provides evidence for avid uptake of FDG on PET imaging of pituitary adenomas.     

Fluorine-18 fluorodeoxyglucose positron emission tomography correlated with computed tomographic scan and magnetic resonance imaging in a case of hematometrocolpos

A 12-year-old girl had intense abdominal pain that had increased in the past 3 months and was accompanied by weight loss. An ultrasound examination revealed large cystic masses in the abdomen. A computed tomographic scan could not conclusively rule out a malignant condition. The hymen was normal on physical examination, but magnetic resonance imaging confirmed that the abnormalities corresponded to dilated cavities of the vagina, uterus, and fallopian tubes, with an appearance suggestive of hematometrocolpos. Fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography was requested concurrently with the magnetic resonance image to assess the metabolic activity of the lesions and to exclude the presence of distant metastases. Large defects without FDG accumulation were noted in the areas corresponding to the cystic masses. Vaginal atresia with hematometrocolpos was confirmed at surgery. This rare case involving F-18 FDG positron emission tomographic imaging in hematometrocolpos illustrates that this diagnosis should be considered in the presence of symmetric hypometabolic masses in the pelvis.     

Effect of dietary intake before F-18 FDG positron emission tomographic scanning on the evaluation of a solitary pulmonary nodule

The uptake of fluorine-18 fluorodeoxyglucose (F-18 FDG) by a malignant tumor depends on the blood glucose level. The authors present a striking case that illustrates the importance of blood glucose measurement in F-18 FDG positron emission tomographic (PET) imaging in a patient with a solitary pulmonary nodule. With the emergence of freestanding imaging centers, this case emphasizes the importance of using an objective method, such as a glucometer, to measure blood glucose levels before F-18 FDG PET imaging. Results of the initial scan were equivocal (the patient had eaten before the scan), whereas a hypermetabolic focus was clearly identified on a second scan obtained 2 days later.     

Fluorine-18 deoxyglucose uptake in sarcoidosis measured with positron emission tomography

Regional pulmonary glucose metabolism (MR_glu; mol h^–1 g^–1), extravascular lung density (D_EV; g cm^–3) and vascular volume (V_B; ml cm^–3) were measured in a single midthoracic transaxial slice (2 cm thick) using positron emission tomography (PET) in seven patients with histologically proven sarcoidosis. The measurements were repeated 1–7 months later after steroid therapy (in two cases, no treatment) in order to assess MR_glu as an index of inflammation and relate it to routine pulmonary function tests, chest radiography and serum angiotensin converting enzyme (SACE) levels. MR^glu was computed from serial lung scans and peripheral venous blood samples for 60 min following an i.v. injection of¹⁸F-2-fluoro-2-deoxy-D-glucose (¹⁸FDG). Both MR_gu (which was increased in six of seven patients) and elevated SACE levels returned to normal in those patients treated with high-dose steroids. Regional vascular volume was normal in six of seven cases and did not change significantly with therapy. The high tissue density measured in all patients decreased significantly in two of three patients treated with 40 mg prednisolone daily. The abnormal MR& observed in active sarcoidosis becomes normal pari passu with SACE levels during high-dose steroid therapy. We conclude that MR^glu measured with¹⁸FDG and PET may reflect disease activity in sarcoidosis in quantitative terms (per gram lung tissue) and in respect of disease distribution.     

Fluorine-18-fluorodeoxyglucose positron emission tomography to evaluate recurrent gastric cancer after surgical resection: a systematic review and meta-analysis

We aimed to explore the diagnostic accuracy of ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) for detection of gastric cancer recurrence after surgical resection through a systematic review and meta-analysis. “PubMed”, EMBASE, Web of Knowledge and Springer, from the beginning of 2002 to Feb 2015, were searched for studies evaluating the diagnostic performance of 18F-FDG PET in detecting recurrent gastric cancer. We calculated sensitivities, specificities, diagnostic odds ratios and likelihood ratios, and constructed summary receiver operating characteristic curves. Fourteen studies (828 patients) were included. On a per-patient basis, the forest plots showed that the pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio and diagnostic odds ratio of ¹⁸F-FDG PET or PET/CT were 0.85 [95 % confidence interval (CI) 0.75–0.92], 0.78 (95 % CI 0.72–0.84), 3.9 (95 % CI 2.9–5.4), 0.19 (95 % CI 0.11–0.34), and 21 (95 % CI 9–47), respectively. On a per-lesion basis, the pooled sensitivity was 0.75 (95 % CI 0.61–0.86). The area under the SROC curve of PET/CT on the basis of per-patient was 0.86. ¹⁸F-FDG PET had great value in the detection of gastric cancer recurrence after surgical resection. The sensitivities of ¹⁸F-FDG PET were 85 and 75 %, respectively, on per-patient basis and on per-lesion basis.     

Characteristics of myocardial18F-fluorodeoxyglucose positron emission computed tomography in dilated cardiomyopathy and ischemic cardiomyopathy

Myocardial 18F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) has been used to assess myocardial ischemia and viability, but few studies have conducted on FDG-PET for dilated cardiomyopathy (DCM). We investigated myocardial FDG uptake in patients with DCM in comparison with ischemic cardiomyopathy (ICM). Twenty-four patients with heart failure were included in this study. Fourteen of them were diagnosed as DCM and the other 10 were ICM. All of them underwent myocardial FDG-PET at fasting and after glucose loading the same day. FDG uptake was quantified by the ratio of the counts at the heart to those at the liver (H/L ratio). Left ventricular (LV) function was measured by echocardiography. We classified FDG distribution patterns in the myocardium in the fasting state into 3 types (faint uptake, regional uptake and diffuse uptake). In DCM patients, 5 had faint uptake, 7 had regional uptake, and the other 2 had diffuse uptake. On the other hand, all ICM patient had regional uptake (p < 0.05). In DCM, there were no significant relationships between the patterns and LV functions. On the other hand, there were close correlation between the H/L ratio after glucose loading and the left ventricular ejection fraction (r = 0.680, p < 0.01). The changes in PET images caused by glucose loading were classified into 2 types (non-reversing and reversing patterns). DCM significantly showed a non-reversing pattern (86%, 12 of 14 patients) whereas ICM showed mainly a reversing pattern (70%, 7 of 10 patients; p < 0.05). In conclusion, myocardial FDG uptake after glucose loading may indicate a myocardial viable mass although FDG uptake at fasting was not evidently related to LV function. The change in the pattern of the FDG image from fasting to glucose loading may be useful in differentiating DCM from ICM.     

FDG positron emission tomographic, radioiodine, and MIBI imaging in a patient with poorly differentiated insular thyroid carcinoma.

Poorly differentiated insular thyroid carcinoma is now classified as a separate entity among other tumors of the thyroid gland. Its histologic pattern and its clinical course are regarded as intermediate between well differentiated and anaplastic thyroid cancer. Insular carcinoma accumulates I-131, but no data exist regarding its fluorodeoxyglucose (FDG) positron emission tomographic (PET) uptake. The authors report F-18 FDG PET, Tc-99m MIBI, and radioiodine imaging features in a 63-year-old patient with metastatic insular thyroid carcinoma. After total thyroidectomy (for poorly differentiated insular carcinoma pT3a), the patient was referred for radioiodine ablation. No signs of recurrence were present until 16 months later, when thyroglobulin levels increased. An I-131 scan showed a single lesion in the right lung, and further radioiodine treatment was administered (cumulative dose [530 mCi], 19,610 MBq I-131). Three years after the initial diagnosis, FDG-PET and Tc-99m MIBI scans were performed within 5 days during thyroxine treatment. After that, thyroxine substitution was withdrawn; 6 weeks later, an I-131 whole-body scan was performed. Both radioiodine and MIBI images showed increased tracer uptake in the known lung lesion. However, FDG PET showed a normal tracer distribution. Magnetic resonance and computed tomographic imaging confirmed a 12-mm lesion in the right upper lobe. These findings support the concept of the "flip-flop phenomenon" in insular thyroid carcinoma, an alternating pattern of metastases with either I-131 or FDG-uptake. Despite poorly differentiated histologic findings, glucose metabolism was not increased in this patient with an insular tumor.