Yum-Kung Chu

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.

Epileptic negative myoclonus: SPECT, PET, and video/EEG studies and the dramatic effects of levetiracetam

An 18-year-old woman presented with epileptic negative myoclonus (ENM) as her major seizure pattern for 4years. Her seizures were characterized by intermittent postural lapse of the right limbs for a period of hours to 2 days. Ictal electroencephalography (EEG)-electromyography showed a silent period that was time-locked to generalized spike-wave discharges. Video/EEG monitoring demonstrated marked improvement of ENM after oral administration of levetiracetam. Cranial magnetic resonance imaging was normal, but 2-deoxy-2-[(18)F]fluoro-d-glucose positron emission tomography during frequent ENM showed hypometabolism in the left frontoparietal cortex. Technetium-99m-ethyl cysteinate dimer single-photon emission computed tomography revealed hyperperfusion over the left parietal cortex and putamen. Here, we document the short-term effects of levetiracetam in this subject with nearly isolated ENM and the neuroimaging results during ENM. Long-term follow-up is in progress to evaluate the clinical evolution and long-term effects of levetiracetam on ENM.

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.

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.

Superscan in patients with nasopharyngeal carcinoma

Bone scintigraphy plays an important role in the early detection of bone metastases in patients with nasopharyngeal carcinoma and serial scans may aid the clinician to assess the therapeutic response. A superscan is a pattern described as abnormal bone scan, indicating extensive bony metastases associated with various neoplastic diseases. Bone scans from 407 patients with nasopharyngeal carcinoma were reviewed retrospectively. Only six superscans (1.5%) were found. The appearance of a superscan is frequently accompanied by an abnormal titer of serological markers IgG-VCA and IgA-VCA, liver metastases, and poor survival. Although a superscan rarely occurs in nasopharyngeal carcinoma, its appearance may represent a poor prognosis in these patients.

RBC volume deficiency in patients with excessive orthostatic decrease in cerebral blood flow velocity.

Background: Orthostatic intolerance (OI) is common but heterogeneous. There is a subgroup of OI patients who have excessive decrease in cerebral blood flow velocity (CBFV) of bilateral middle cerebral arteries (MCAs) during head‐up tilt without systemic blood pressure change. This study evaluated the role of blood volume reduction in such patients. Methods: Patients with idiopathic OI who had excessive orthostatic decrease (>20% of the supine level) in mean CBFV of bilateral MCAs and who also received blood volume determination were collected. The chromium (51Cr) dilution method was used for red blood cell (RBC) volume determination in these patients. The blood volume was expressed as a percentage of the expected volume. These patients were further divided into two groups, those with postural tachycardia syndrome (POTS group) and those without (non‐POTS group). The data of RBC volume were compared between the two groups. Besides, we used multivariate linear regression to evaluate the factors that predict RBC volume. Results: Twenty‐five patients (13 females, median age = 28 years) were enrolled in this study. Nine of these patients had POTS (5 females, median age = 26 years) and 16 did not (8 females, median age = 29.5 years). Compared with the expected volume, the RBC volume was significantly reduced in all patients (median = 82% of the expected volume). Moreover, the RBC volume was significantly lower in the POTS group than that in the non‐POTS group (78% vs. 85% of the expected volume, p = 0.013). The orthostatic decrease of MCA flow velocity was 28.3% in the POTS group and 32.5% in the non‐POTS group (p = 0.140). The orthostatic pulsatility index increment was 15.4% in the POTS group and 20.5% in the non‐POTS group (p = 0.438). Moreover, basic demography and hemoglobin levels were not different between the two groups. After multivariate linear regression (dependent variables including age, sex, body surface, and groups), only the presence of POTS significantly predicted the RBC volume (p = 0.006). Conclusion: The results of our study indicated that low RBC volume may play an important role in the pathophysiology of OI in this group of patients. Moreover, its role seems even more relevant in patients with POTS than in those without. Further studies for mechanistic evaluation are needed in the future.

Unusual site of metastasis detected with FDG PET/CT in a case of recurrent rectosigmoid cancer.

Metastatic colon cancers to the oral cavity are unusual, involving a majority of the mandible rather than the oral soft tissues. We describe a rare site of gingival metastasis in a case of rectosigmoid cancer. The patient was a 74-year-old woman who developed swelling and persistent bleeding of the right mandibular gingiva after tooth extraction. A PET/CT using 18F-FDG depicted multiple metastatic lesions in the neck, lung, abdominal wall, and mandibular gingiva. Histologic study of the gingival lesion confirmed the diagnosis of gingival metastasis from colon adenocarcinoma.

Zollinger-Ellison syndrome: Revelation of the gastrinoma triangle

Zollinger-Ellison syndrome is a complex condition in which one or more tumors form in the patients pancreas or upper duodenum. These tumors, called gastrinomas, secrete excessive amounts of gastrin, and almost all develop ulcers. The vast majority of gastrinomas are present within the “gastrinoma triangle,” which is composed of the porta hepatis, duodenal sweep, and pancreatic head. As surgery remains the treatment of choice, localization of the primary lesion is often challenging but essential. We present a 50-year-old man with a tentative diagnosis of Zollinger-Ellison syndrome. His In-111 pentetreotide scan, fused onto a Tc-99m abdomen image, revealed an avid lesion adjacent to the duodenal loop. Operative resection was performed, and a primary pancreatic gastrinoma was diagnosed by immunohistochemical staining. The neuroendocrine tumors have somatostatin receptors upon them. Therefore, a penteteotide scan, using In-111 radiolabelled somatostatin analogues, is the current technique of choice. This dual-isotope display permits a visual perception of anatomic landmarks around the lesion.

Bisphosphonate-related osteonecrosis of the jaw complicated by Ludwig's angina

Ludwigs angina is a life-threatening cellulitis that involves the submandibular and sublingual spaces. It often occurs after an infection of the roots of the teeth. However, modern dental care and use of antibiotics for oral infections have made Ludwigs angina rare. We present here a cancer patient exhibiting the sequential features of bisphosphonate related osteonecrosis of the jaw on bone scan complicating with Ludwigs angina. This report highlights the need for medical practitioners to be alert to these rare combinations in the compromised patient after bisphosphonate therapy. To the best of our knowledge, no case of Ludwigs angina secondary to osteonecrosis of the jaw has been reported.

Compartment syndrome following robotic-assisted prostatectomy: rhabdomyolysis in bone scintigraphy.

Major urologic surgery performed in the lithotomy position sometimes results in the serious complication of rhabdomyolysis. A 56-year-old man was admitted to the hospital for prostate adenocarcinoma. A whole-body bone scan was performed to exclude bony metastases, which demonstrated no bone lesions but showed intense soft-tissue activity in gluteus maximus muscles, findings suggestive of a myopathy. He had just undergone right nerve-sparing radical prostatectomy in the lithotomy position for 6 hours and presented with swollen bilateral thighs. Elevation of creatine kinase level confirmed muscle injury.