Hung-Jen Hsieh

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 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.

Visualisation of impaired dopamine biosynthesis in a case of aromatic L-amino acid decarboxylase deficiency by co-registered 18F-FDOPA PET and magnetic resonance imaging.

Aromatic L-amino acid decarboxylase (AADC) converts L-dopa to dopamine and 5-hydroxytryptophan to serotonin. Deficiency of this enzyme, a rare autosomal recessive disorder, leads to decreased brain levels of these neurotransmitters and resultant developmental disorder. We present an 18-month-old female baby with AADC deficiency characterised by axial hypotonia, myoclonus epilepsy and frequent aspiration. CSF study revealed decreased homovanillic acid and 5-hydroxyindoleacetic acid with elevated L-dopa and noradrenaline levels. Nevertheless, non-invasive 18F-FDOPA positron emission tomography (PET) obtained at 2 h after intravenous injection of 44 MBq of 18F-DOPA and co-registered with magnetic resonance imaging indicated scarce dopamine biosynthesis in the striatum. In region of interest analysis, the average uptake ratio in relation to cerebellum was 1.1, 1.2, 1.0 and 1.3 for the right caudate nucleus, right putamen, left caudate nucleus and left putamen, respectively. L-Dopa and pyridoxine supplements had been withdrawn 48 h and 1 week, respectively, before this PET study. We suggest that PET study using distinctive radiotracers might serve as an informative tool for the evaluation of children suspected of having inborn metabolic disorders.

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.

Vertebroplasty using real-time, fluoroscopy-controlled, catheter-assisted, low-viscosity cement injection.

Study Design. Case series. Objective. Evaluation of new vertebroplasty technique. Summary of Background Data. Viscous polymethylmethacrylate cement is frequently used to avoid leakage in vertebroplasty. However, the large force required to inject the cement can require the use of special equipment or the direct injection of the cement without a cannula. In addition, injection under fluoroscopic guidance with a short or absent cannula is associated with a higher intraoperative radiation dose. A method using an angiographic catheter for thin cement injection is presented. Methods. Real-time, fluoroscopy-controlled, catheter-assisted, thin cement injection was used for 102 vertebroplasty sessions (84 patients, 148 vertebrae). Leakage was monitored in 85 procedures via computed tomography. Results. All vertebral bodies were successfully and satisfactorily filled with bone cement. Cement leakage was evident in 50% of the 85 asymptomatic cases (25 paraspinal, 29 epidural, and 30 intradisc space). On follow-up, new compression fractures were noted in the same (n = 5) or adjacent (n = 16) vertebral body, and elsewhere (n = 10). Vertebroplasty provided pain relief in >90% of cases. Recurrent compression fracture occurred in 5 vertebrae of 4 patients after vertebroplasty. New compression fractures occurred in 16 adjacent vertebral bodies of 11 patients and in 10 vertebral bodies remote from the site. One patient who developed osteomyelitis was successfully treated with antibiotics alone. Conclusion. Real-time, fluoroscopy-controlled, catheter-assisted, low-viscosity cement injection is a safe and feasible method for vertebroplasty, and produces a comparable outcome as high-viscosity cements.

Infected Aneurysm of the Abdominal Aorta Demonstrated on Gallium-67 Scintigraphy

Infected aneurysm is defined as a lesion of the arterial wall due to bacterial contamination. The authors show a distinctive scintigraphic appearance of infected aneurysm. A 76-year-old man was admitted to the hospital because of fever and back pain. 67Ga scan showed abnormal concentration in the region corresponding to the anatomical location of the abdominal aorta. Contrast-enhanced CT scan of the mid abdomen revealed an infra-renal aortic aneurysm.

Combining 11C-Acetate and 18F-FDG PET Studies: Experience in Patients with Hepatic Lesions

Background: Hepatic lesions may be found by conventional imaging tools in cases of cancer screening or for surveillance of treated cancers. Such hepatic lesions arouse much concern about the nature of disease and patient management. The aim of this study is to assess the possible benefit combing the use of 11C-acetate and 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET). Methods: Fifteen patients with focal hepatic lesions (11 male, 4 female; age average 54 years, ranging from 30~79 years) were studied by both 11C-acetate and 18F-FDG PET scans. Among the 15 patients, 6 were aimed for cancer screening without previous cancer history and 9 for surveillance of treated cancers (7 hepatocellular carcinoma (HCC), 1 cholangiocarcinoma and 1 colon cancer). Images were analyzed by visual interpretation. Foci of abnormal radiotracer uptake were subsequently correlated with imaging modalities such as CT, MRI or repeated PET, pathology from surgical specimen and long-term follow-up for more than 12 months. Results: The results were available in 14 patients. In the subgroup of patients without cancer history, 11C-acetate and 18F-FDG PET were concordantly true positive in 1 case of HCC and true negative in 1 case of focal nodular hyperplasia, 1 case of hemangioma and another of fatty infiltration. One case of HCC, however, was missed by 18F-FDG PET but could be detected by 11C-acetate PET. In the subgroup of patients for surveillance of treated cancers, 11C-acetate and 18F-FDG PET were concordantly true negative in 2 cases of HCC and 1 case of cholangiocarcinoma, but both false negative in 3 cases of recurrent HCC and 1 case of colon cancer with liver metastasis. In addition, two patients with recurrent HCC detected by 18F-FDG PET were overlooked by C-acetate PET. One of the two cases had lung metastases and died within 3 months after PET studies. Conclusion: In this study, C-acetate PET detected one more case of HCC than 18F-FDG PET in five cases with newly discovered hepatic lesions. However, in cases of treated HCC or other cancers, considerable proportion (4/9) of cases, in the existence of viable tumors, could be neglected even by combining 11C-acetate and 18F-FDG PET. Furthermore, in two cases of recurrent HCC readily diagnosed by 18F-FDG PET, 11C-acetate PET was false-negative.

Dual Time Point Fluorine-18-FDG PET in a Case of Idiopathic Bronchiolitis Obliterans Organizing Pneumonia Presenting as Single Pulmonary Nodule

Idiopathic bronchiolitis obliterans organizing pneumonia (idiopathic BOOP) is a rare clinicopathological entity with insidious causes. Cases with associated PET studies have been scarcely reported in the literature. We report a case of idiopathic BOOP whose 18F-FDG PET imaging is misleadingly false-positive for malignancy by definition of SUV even with comparing dual time point studies. Knowledgement of such possibility is valuable in the clinical patient management.