Cheng-Pei Chang

PET imaging of brain astrocytoma with 1-11C-acetate

PurposeThe purpose of this study was to assess the use of 1-11C-acetate (ACE) as a metabolic tracer for the detection and characterisation of astrocytomas.MethodsPositron emission tomography (PET) studies with ACE and 2-18F-fluoro-2-deoxy-D-glucose (FDG) were performed sequentially in 26 patients with primary astrocytomas. Images were analysed by visual interpretation and determination of the tumour to cortex ratio (T/C ratio) and standardised uptake value (SUV). The tumour uptake was visually scored into three grades as compared with the contralateral cortex: clearly lower (–), almost equal (+) and clearly higher (++).ResultsThere were 85% of astrocytomas with ++ ACE uptake, 15% with + ACE uptake and none with – ACE uptake. Only 19% of astrocytomas had ++ FDG uptake. Thirty-seven percent of high-grade astrocytomas had + FDG uptake and 37% had – FDG uptake. The sensitivity and specificity of the FDG T/C ratio in discriminating high-grade from low-grade astrocytomas were 79% and 100%, respectively, at the cutoff value of 0.75. Using 2.33 as the cutoff value of the ACE T/C ratio, the sensitivity and specificity were 42% and 86%, respectively. FDG was better than ACE in discriminating high-grade from low-grade astrocytomas. T/C ratios and SUVs of FDG uptake of tumours correlated with the histological grades, but those of ACE uptake did not.ConclusionACE appears to be a promising tracer for use in the detection of primary astrocytomas, but is of limited value in the differentiation of high- and low-grade astrocytomas. ACE is complementary to FDG for the diagnosis and characterisation of astrocytoma.

The feasibility of 11C-methionine-PET in diagnosis of solitary lung nodules/masses when compared with 18F-FDG-PET

ObjectiveTo differentiate between benign and malignant lesions of the lung, 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) has limitations such as a lower specificity in cases of non-specific inflammation. The positive predictive value is unsatisfactory in countries where inflammatory lung disorders are prevalent. We present the preliminary results of the usefulness of combining 11C-methionine-PET and 18F-FDG-PET in this context.MethodsFifteen patients with indeterminate solitary pulmonary nodules/masses (10 men, 5 women; average age 64.7 ± 14.0 years, ranging from 25 to 87 years) were studied using 11C-methionine- and 18F-FDG-PET. Interpretations were primarily made on visual analysis with five-point scale and a consensus of two nuclear medicine physicians, using standardized uptake value as an accessory reference. Foci of abnormal radiotracer uptake were subsequently correlated with clinical follow-up, imaging modalities such as chest radiography, chest computed tomography (CT), serial PET studies, and pathology results from bronchoscopic biopsy and/or surgical specimen.ResultsDiagnoses were established in 14 patients. The 11C-methionine-PET and 18F-FDG-PET studies were both true positive in two cases of adenocarcinoma and true negative in two cases of clinical benign nodules. In one case of lymphoid hyperplasia both 11C-methionine-PET and 18F-FDG-PET showed false-positive findings. Discordant results were obtained in nine cases. In spite of the false-positive results of 18F-FDG-PET, 11C-methionine-PET was true negative in four cases with chronic inflammatory nodules and three cases of pulmonary tuberculosis. Furthermore, 11C-methionine-PET was true positive in one case of lung metastasis of thyroid cancer, and in another with recurrence of gastric cancer, respectively, for which 18F-FDG-PET imaging was false negative.ConclusionsOur experience indicates that 11C-methionine-PET seems more specific and sensitive when compared with 18F-FDG-PET for the purpose of differentiating benign and malignant thoracic nodules/masses. The possibility of an FDG-avid lesion being malignant is decreased if it shows a negative result by 11C-methionine-PET.

F-18 FDG PET/CT in evaluation of pulmonary sclerosing hemangioma.

Purpose: Pulmonary sclerosing hemangioma (PSH), or the alternative name of “sclerosing pneumocytoma,” is a rare benign neoplasm. PSH is often asymptomatic and presents as a solitary pulmonary nodule on radiologic imaging studies. Few articles have been reported to describe the FDG PET findings about PSH. We reported FDG PET findings of 6 cases of PSH and reviewed the literatures. Materials and Methods: FDG PET and PET/CT imaging studies of 6 patients with proven PSH were reviewed. The relation between the degree of FDG uptake and tumor size was analyzed. Results: All 6 tumors were detected by FDG PET or PET/CT. Mean diameter of these tumors was 2.9 cm. Mean standard uptake value was 2.45 (range, 1.8–3.93). The maximal standard uptake value of FDG uptake was positively correlated with the tumor size (R = 0.9694, P < 0.05). Conclusions: PSH demonstrates low to moderate uptake on FDG PET imaging. The larger PSH has higher uptake and might be misrecognized as a malignancy. The possibility of false-positive result caused by PSH should be considered while interpreting FDG PET images of solitary pulmonary nodules.

The Clinical Relevance of Thyroid Incidentalomad Detected by 18F-Fluorodeoxyglucose Positron Emission Tomography

Backgrounds: Incidentally discovered thyroid nodules may be noted on positron emission tomography(PET)for reasons unrelated to thyroid pathology The nature of such thyroid incidentalomas can be source of considerable anxiety for individual patients. The aim of this retrospective study is to assess the clinical relevance of the thyroid incidentalomas detected by 18F-fluorodeoxyglucose (FDG)PET Methods: Four hundred and seventy-seven patients(261 male,216 female; age: mean±SD,52.4±12.9years,ranging from 10～90 years),free of thyroid disease history and palpable neck mass, were studied by FDG PET scan for the purpose of cancer screening or surveillance of recurrent malignancies. Images were analyzed by visual interpretation. Patients found to have focal thyroid uptake were subsequently correlated with thyroid ultrasonography, fine needle aspiration cytology or pathology of the specimen from surgical excision. Standard uptake value(SUV)of each focal abnormal thyroid uptake was calculated. Results: Solitary focal thyroid uptake was disclosed in twelve patients(2.5%).Final diagnosis was available in ten cases. One had well-differentiated papillary carcinoma and one had follicular adenoma with partial capsular invasion, both proved by pathology of surgical specimen. Another had a hemorrhagic cyst, and the remaining seven cases had benign nodules based on ultrasound foundlings, fine needle aspiration cytology and relative clinical evidences. The average SUVs of the ten nodules ranged from 1.1 to 2.1.The average SUVs of papillary carcinoma, follicular adenoma and hemordagic cyst were 1.6,1.7 and 1.8 respectively. The average SUVs of remaining seven benign nodules were 1.1,1.7,1.7,2.0,1.4,2.1 and 1.8.Conclusion:Thyroid incidentalomas was found by FDG PET in 2.5% of patients without known thyroid disease or palpable thyroid mass. Only one out of ten hypermetabolic incidentalomas was malignant neoplasm. SUV of FDG uptake by the solitary nodule did not differentiate benign from malignant nodule.

Unilateral Thalamic Hypometabolism in Patients With Temporal Lobe Epilepsy

BACKGROUND/PURPOSE Interictal brain 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is useful for localizing the focus of a seizure, and thalamic hypometabolism has been observed in temporal lobe epilepsy (TLE). In this study, we aimed to investigate the prevalence of thalamic hypometabolism and to assess the usefulness of this supplementary finding for lateralizing epileptic foci on FDGPET scans in patients with TLE. METHODS This was a retrospective study of 47 patients who underwent anterior temporal lobectomy to treat medically intractable TLE. Other inclusion criteria were age older than 18 years, preoperative interictal FDG-PET, no structural abnormality (except for mesial temporal sclerosis) on preoperative magnetic resonance imaging, and seizure-free status (Engel class I) for at least 2 years after the operation. The presence and location of hypometabolism on FDG-PET scans were recorded. RESULTS Of the 47 patients examined, 12 were subsequently excluded. Concomitant hypometabolism in both the temporal lobe and the ipsilateral thalamus was observed on FDG-PET scans in seven (20%) of the remaining 35 patients. One patient had thalamic hypometabolism contralateral to the hypometabolic temporal lobe. CONCLUSION Ipsilateral thalamic hypometabolism is a supplementary finding on FDG-PET scans in patients with TLE and can aid in lateralizing epileptic foci during FDG-PET. However, in rare cases, hypometabolism of the contralateral thalamus can occur and cause false lateralization.

F-18 FDG PET and Ga-67 scintigraphy in a case of fever of unknown origin with underlying cutaneous diffuse large B-Cell lymphoma.

Ga-67 scintigraphy and FDG PET imaging were performed on a 60-year-old woman with fever of unknown (FUO). Abnormal FDG uptake scattered in the right-side chest wall was seen whereas Ga-67 scintigraphy yielded only ambiguous findings. Pathology revealed diffuse large B-cell lymphoma. Neoplasms account for 10 to 20% of all cases of FUO. Cutaneous diffuse large B-cell lymphoma is uncommon, and concomitant FDG PET and gallium images are scarcely reported.

Cerebral blood flow and glucose metabolism in an infant with Sturge-Weber syndrome.

A 15-month-old girl had Sturge-Weber syndrome associated with glaucoma in the left eye. No seizure or hemiparesis was present. Leptomeningeal angiomatosis was clearly shown by contrast-enhanced MRI and MR angiography. Positron emission tomography (PET) with 0-15 water and F-18 fluorodeoxyglucose (FDG) was used to study blood flow and glucose metabolism in the brain. The 0-15 water PET and FDG PET showed that the cerebral blood flow and glucose metabolism were dissimilar in the region of the leptomeningeal angiomatosis and the ipsilateral remote cerebral cortex.

The “Fisherman’s Waders” sign in a bone scan of inferior vena cava thrombosis associated with nephrotic syndrome

This paper presents a 61-year-old male patient with nephrotic syndrome, hypercoagulability and IVC thrombosis. Increased soft tissue uptake below the level of the mid chest was seen in his bone scan. The term “Fisherman’s Waders” sign is suggested for this finding, whose recognition may permit the identification of inferior vena cava obstruction in bone scans. The existence of a cavoportal shunt was also confirmed by dynamic scintigraphy.

Added Value of Dual-Time-Point 18F-FDG PET/CT With Delayed Imaging for Detecting Aortic Graft Infection: An Observational Study.

Abstract18F-FDG PET/CT is a promising tool in detecting aortic graft infection. Present study investigated the value of dual-time-point 18F-FDG PET/CT imaging (DTPI) with delayed imaging in assessing aortic graft infection.Twenty-nine patients with suspected aortic graft infection were prospectively enrolled in this DTPI study. Two nuclear medicine physicians read all the images and achieved consensus about the measurement of maximal standardized uptake value (SUVmax) and grading of image quality. The percentages of SUVmax change between initial and delayed images were recorded as retention index (RI); sensitivity, specificity, and accuracy were calculated based on reference standard.All the 5 infected aortic grafts had positive RIs, which were generally higher than that of noninfected grafts. Those noninfected grafts had variable RIs. Seven patients had improved image quality in delayed imaging. DTPI with delayed image detected all the infected grafts with improved specificity (88%) and accuracy (90%), providing conspicuous delineation of the infected graft extent.In conclusion, noninfected aortic grafts had more variable RIs than infected ones. DTPI might be useful for detecting aortic graft infection, improving image quality, and enhancing delineation of the infected aortic grafts.

Scintigraphic appearance of parosteal osteosarcoma.

Parosteal osteosarcoma is a rare form of bone tumor. The lesion is usually well differentiated and arises from the bone surface. It has a better prognosis than other osteosarcomas. Although the radiographic features of parosteal osteosarcoma have been well documented, the scintigraphic characteristics of this tumor have not been described in the English literature. The authors show the unique and distinctive scintigraphic appearance of this tumor.