Bang-Hung Yang

1-11C-Acetate Versus 18F-FDG PET in Detection of Meningioma and Monitoring the Effect of γ-Knife Radiosurgery

This study aimed to define the potential of 1-11C-acetate PET, compared with 18F-FDG, in detecting meningiomas and monitoring the effect of γ-knife radiosurgery. Methods: Twenty-two patients with the neuroradiologic diagnosis of meningioma were examined by 1-11C-acetate and 18F-FDG PET on the same day. There were 12 cases of histopathologically proven meningioma (8 grade I, 2 grade II, and 2 grade III), 1 of tuberculous granuloma, and 1 of degenerative tissue. 1-11C-acetate PET scans of fasting patients were obtained 10 min after intravenous administration of 740 MBq of 1-11C-acetate. 18F-FDG PET was performed at 2 h after 1-11C-acetate scanning. The PET images were evaluated by a qualitative method and semiquantitative analysis using standardized uptake value and tumor-to-cortex ratio. Results: The 18F-FDG PET study revealed a hypometabolic focus in 17 meningiomas (8 grade I, 1 grade II, and 8 unknown grade) and hypermetabolism in 1 grade II and 2 grade III meningiomas. High uptake of 1-11C-acetate was observed in all 20 meningiomas, in contrast to the low uptake in surrounding normal brain tissue, allowing a clearer demarcation of the tumor boundary than that provided by 18F-FDG. Dissociation of regional accumulation of 1-11C-acetate and 18F-FDG within the tumor was also noted on the coregistered images. The standardized uptake value for 1-11C-acetate was not different from that for 18F-FDG (mean ± SD, 3.16 ± 1.75 vs. 3.22 ± 1.50, P = 0.601), but the tumor-to-cortex ratio for 1-11C-acetate was higher than that for 18F-FDG (3.46 ± 1.38 vs. 0.93 ± 1.08, P < 0.005). 18F-FDG was able to differentiate grade I from grade II–III meningiomas, whereas 1-11C-acetate was unable to do so. Tuberculous granuloma had a high 1-11C-acetate and 18F-FDG uptake similar to that of grade II/III meningioma. Five patients received 1-11C-acetate and 18F-FDG PET before and after γ-knife surgery. 1-11C-acetate performed better than did 18F-FDG in monitoring the response of tumor metabolism to radiosurgery. Conclusion: 1-11C-acetate was found to be useful for detecting meningiomas and evaluating the extent of meningiomas and potentially useful for monitoring tumor response to radiosurgery. However, 1-11C-acetate was not useful for evaluating the tumor grade. 18F-FDG was found to be less useful than 1-11C-acetate for evaluating the extent of meningiomas and the response to radiosurgical treatment but may be useful for differentiating benign from malignant meningiomas. 18F-FDG and 1-11C-acetate are complementary for assessing diverse cell metabolism of meningioma.

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.

SPECT myocardial blood flow quantitation toward clinical use: a comparative study with 13N-Ammonia PET myocardial blood flow quantitation

ObjectivesThe aim of this study was to evaluate the accuracy of myocardial blood flow (MBF) quantitation of 99mTc-Sestamibi (MIBI) single photon emission computed tomography (SPECT) compared with 13N-Ammonia (NH3) position emission tomography (PET) on the same cohorts.BackgroundRecent advances of SPECT technologies have been applied to develop MBF quantitation as a promising tool to diagnose coronary artery disease (CAD) for areas where PET MBF quantitation is not available. However, whether the SPECT approach can achieve the same level of accuracy as the PET approach for clinical use still needs further investigations.MethodsTwelve healthy volunteers (HVT) and 16 clinical patients with CAD received both MIBI SPECT and NH3 PET flow scans. Dynamic SPECT images acquired with high temporary resolution were fully corrected for physical factors and processed to quantify K1 using the standard compartmental modeling. Human MIBI tracer extraction fraction (EF) was determined by comparing MIBI K1 and NH3 flow on the HVT group and then used to convert flow values from K1 for all subjects. MIBI and NH3 flow values were systematically compared to validate the SPECT approach.ResultsThe human MIBI EF was determined as [1.0-0.816*exp(−0.267/MBF)]. Global and regional MBF and myocardial flow reserve (MFR) of MIBI SPECT and NH3 PET were highly correlated for all subjects (global R2: MBF = 0.92, MFR = 0.78; regional R2: MBF ≥ 0.88, MFR ≥ 0.71). No significant differences for rest flow, stress flow, and MFR between these two approaches were observed (All p ≥ 0.088). Bland-Altman plots overall revealed small bias between MIBI SPECT and NH3 PET (global: ΔMBF = −0.03Lml/min/g, ΔMFR = 0.07; regional: ΔMBF = −0.07 − 0.06 , ΔMFR = −0.02 − 0.22).ConclusionsQuantitation with SPECT technologies can be accurate to measure myocardial blood flow as PET quantitation while comprehensive imaging factors of SPECT to derive the variability between these two approaches were fully addressed and corrected.

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.

Evolutional Characterization of Photochemically Induced Stroke in Rats: a Multimodality Imaging and Molecular Biological Study.

Photochemically induced cerebral ischemia is an easy-manipulated, reproducible, relatively noninvasive, and lesion controllable model for translational study of ischemic stroke. In order to longitudinally investigate the characterization of the model, magnetic resonance imaging, 18F-2-deoxy-glucose positron emission tomography, fluorescence, and bioluminescence imaging system were performed in correlation with triphenyl tetrazolium chloride (TTC), hematoxylin-eosin staining, and immunohistochemistry examinations of glial fibrillary acidic protein, CD68, NeuN, von willebrand factor, and α-smooth muscle actin in the infarct zone. The results suggested that the number of inflammatory cells, astrocytes, and neovascularization significantly elevated in peri-infarct region from day 7 and a belt of macrophage/microglial and astrocytes was formed surrounding infarct lesion at day 14. Both vasogenic and cytotoxic edema, as well as blood brain-barrier leakage, occurred since day 1 after stroke induction and gradually attenuated with time. Numerous cells other than neuronal cells infiltrated into infarct lesion, which resulted in no visible TTC negative regional existence at day 14. Furthermore, recovery of cerebral blood flow and glucose utilization in peri-infarct zone were noted and more remarkably than that in infarct core following the stroke progression. In conclusion, these characterizations may be highly beneficial to the development of therapeutic strategies for ischemic stroke.

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.

Quantitative Measurement of the Thyroid Uptake Function of Mouse by Cerenkov Luminescence Imaging

Cerenkov luminescence imaging (CLI) has been an evolutional and alternative approach of nuclear imaging in basic research. This study aimed to measure the 131I thyroid uptake of mouse using CLI for assessment of thyroid function. Quantification of 131I thyroid uptake of mice in euthyroid, hypothyroid and hyperthyroid status was performed by CLI and γ-scintigraphy at 24 hours after injection of 131I. The 131I thyroid uptake was calculated using the equation: (thyroid counts − background counts)/(counts of injected dose of 131I) × 100%. Serum T4 concentration was determined to evaluate the thyroid function. The radioactivity of 131I was linearly correlated with the CL signals in both in vitro and in vivo measurements. CLI showed a significant decrease and increase of 131I thyroid uptake in the mice in hypo- and hyperfunctioning status, respectively, and highly correlated with that measured by γ-scintigraphy. However, the percent thyroid uptake measured by CLI were one-fifth of those measured by γ-scintigraphy due to insufficient tissue penetration of CL. These results indicate that CLI, in addition to nuclear imaging, is able to image and evaluate the 131I thyroid uptake function in mice in preclinical and research settings.

Effects of the Acute and Chronic Ethanol Intoxication on Acetate Metabolism and Kinetics in the Rat Brain

BACKGROUND Ethanol (EtOH) intoxication inhibits glucose transport and decreases overall brain glucose metabolism; however, humans with long-term EtOH consumption were found to have a significant increase in [1-11 C]-acetate uptake in the brain. The relationship between the cause and effect of [1-11 C]-acetate kinetics and acute/chronic EtOH intoxication, however, is still unclear. METHODS [1-11 C]-acetate positron emission tomography (PET) with dynamic measurement of K1 and k2 rate constants was used to investigate the changes in acetate metabolism in different brain regions of rats with acute or chronic EtOH intoxication. RESULTS PET imaging demonstrated decreased [1-11 C]-acetate uptake in rat brain with acute EtOH intoxication, but this increased with chronic EtOH intoxication. Tracer uptake rate constant K1 and clearance rate constant k2 were decreased in acutely intoxicated rats. No significant change was noted in K1 and k2 in chronic EtOH intoxication, although 6 of 7 brain regions showed slightly higher k2 than baseline. These results indicate that acute EtOH intoxication accelerated acetate transport and metabolism in the rat brain, whereas chronic EtOH intoxication status showed no significant effect. CONCLUSIONS In vivo PET study confirmed the modulatory role of EtOH, administered acutely or chronically, in [1-11 C]-acetate kinetics and metabolism in the rat brain. Acute EtOH intoxication may inhibit the transport and metabolism of acetate in the brain, whereas chronic EtOH exposure may lead to the adaptation of the rat brain to EtOH in acetate utilization. [1-11 C]-acetate PET imaging is a feasible approach to study the effect of EtOH on acetate metabolism in rat brain.

Using 3-D OFEM for movement correction and quantitative evaluation in dynamic cardiac NH3 PET images

Various forms of cardiac pathology, such as myocardial ischemia and infarction, can be characterized with 13NH3-PET images. In clinical situation, polar map (bullseye image), which derived by combining images from multiple planes (designated by the circle around the myocardium in the above images), so that information of the entire myocardium can be displayed in a single image for diagnosis. However, image artifact problem always arises from body movement or breathing motion in image acquisition period and results in indefinite myocardium disorder region shown in bullseye image. In this study, a 3-D motion and movement correction method is developed to solve the image artifact problem to improve the accuracy of diagnostic bullseye image. The proposed method is based on 3-D optical flow estimation method (OFEM) and cooperates with the particular dynamic imaging protocol, which snaps serial PET images (5 frames) in later half imaging period. The 3-D OFEM assigns to each image point in the visual 3-D flow velocity field, which associates with the non-rigid motion of the time-varying brightness of a sequence of images. It presents vectors of corresponding images position between frames for motion correction. To validate the performance of proposed method, 10 normal and 20 abnormal whole-body dynamic PET imaging studies were applied, and the results show that the bullseye images, which generated by corrected images, present clear and definite tissue region for clinical diagnosis.