Laszlo Pavics

Regional cerebral blood flow single-photon emission tomography with 99mTc-HMPAO and the acetazolamide test in the evaluation of vascular and Alzheimer's dementia

Abstract. The diagnostic potential of technetium-99m hexamethylpropylene amine oxime (HMPAO) following systemic administration of the cerebral vasodilator acetazolamide (acetazolamide test) was evaluated by regional cerebral blood flow (rCBF) single-photon emission tomography (SPET) in patients with Alzheimer’s disease (AD) or vascular dementia (VD). An initial, high-resolution SPET study was performed with 99mTc-HMPAO, and after 2 days the patients were re-evaluated with 99mTc-HMPAO following systemic administration of acetazolamide. Reconstructed SPET slices were evaluated visually and semiquantitatively by a semi-automatic rCBF map method. When 99mTc-HMPAO alone was used, bilateral hypoperfusion was found in the temporal and/or parietal regions in 33% (6/18) of the VD patients and in 70% (23/33) of the AD patients. The corresponding data obtained by quantitative evaluation were 41% (7/17) and 71% (15/21), respectively. The vascular reserve capacity, as determined with the acetazolamide test, was preserved visually in 22% (4/18) and quantitatively in 29% (5/17) of the VD patients, but in 73% (24/33) and 76% (16/21) of the AD patients. The differences in the perfusion patterns between the VD and AD patients were statistically significant (P<0.01, Fischer’s exact test). Of the VD patients with hypoperfusion (bilateral temporal and/or parietal), 4/6 (67%, visual evaluation) and 4/7 (57%, quantitative evaluation) had a decreased vascular reserve capacity as determined with the acetazolamide test. In the AD group of patients the corresponding results were 3/23 (13%) and 4/15 (27%). It is concluded that the acetazolamide test is promising in rCBF SPET to differentiate VD from AD.

The relevance of interictal rCBF brain SPECT in temporal lobe epilepsy: Diagnostical value and effects of spatial resolution

Interictal rCBF-SPECT is frequently being used as an adjunctive method for localization of an epileptogenic area during presurgical evaluation of patients suffering from medically refractory temporal lobe epilepsy. This study retrospectively evaluates interictal rCBF-SPECT using Tc-99m-HMPAO in comparison to the results of MRI. The final results of surface EEG and ECoG and the postsurgical clinical results as to seizure frequency were used as a ‘gold-standard’ for the evaluation of both imaging procedures.As spatial resolution is discussed to be the major reason for higher sensitivity of F-18-DG-PET compared to rCBF-SPECT, special attention has been paid to the spatial resolution of the different SPECT systems being used in this study. In 55 patients the complete data set could be obtained retrospectively, 36 of them being evaluated using SPECT systems with relatively low spatial resolution (Picker Dyna 2000, Elscint Helix) and 19 pt. being evaluated using moderateto highresolution SPECT systems (ADAC Genesys, DSI Ceraspect). Overall sensitivity of the interictal rCBF-SPECT was 75%, with 69% for low-resolution systems and 84% for high-resolution systems. Approximately at the same time when our institution installed the ADAC Genesys, the MRI equipment was changed from the 1.5 T Philips Gyroscan S15 to the 1.5 T Philips Gyroscan ACS II, the latter allowing superior imaging opportunities. Overall sensitivity of MRI was 60%, with 56%, for the Gyroscan S15 and 68% for the Gyroscan ACS II. The overall positive predictive value (PPV) was 87% for the interictal rCBF-SPECT and 87% for the MRI. Due to the lack of true negative studies in this population specificity was not calculated. False lateralization using rCBF-SPECT occurred in 5 pt. (9%), however in 3 pt. the area of hypoperfusion correlated with a detectable MRI pathology, yet EEG/ ECoG revealed the epileptogenic focus to be elsewhere. In conclusion, the interictal rCBF-SPECT revealed reasonable sensitivity and PPV in pt. suffering from focal temporal lobe epilepsy and modern SPECT systems showed significantly improved results. Since there is a variety of possible reasons for regional cortical hypoperfusion, the interictal SPECT could add significant information prior to the application of ECoG. This specially appeared to be useful in patients with a normal MRI scan. Furthermore, in patients presenting with a clear pathology on MRI and a corresponding EEG focus, ECoG could be avoided if the interictal rCBF-SPECT additionally showed localized and singular involvement of the affected temporal lobe. ECoG was mainly applied in those patients with relatively wide-spread hypoperfusion additionally involving frontal or parietal cortical areas.

Effect of nitric oxide on gallbladder motility in patients with acalculous biliary pain: A cholescintigraphic study

The aim of the present study was to evaluate the influence of the exogenous nitric oxide donor glyceryl trinitrate on cerulein-induced gallbladder contraction in patients with acalculous biliary pain. Quantitative hepatobiliary scintigraphy was performed on 33 patients. From the 60th min cerulein (1 ng/kg body wt/min for 10 min intravenous) then from the 90th min the same dose of cerulein plus glyceryl trinitrate (0.5 mg sublingually) (21 patients) or placebo (12 patients) were administered and the gallbladder ejection fraction was measured repeatedly. After the first dose of caerulein, the gallbladder ejection fraction was less than 35% in 23 of 33 patients (nonresponders), while it was more than 35% in the remaining 10 patients (responders). After the second dose of cerulein in 16 nonresponder patients glyceryl trinitrate administration significantly increased the previously impaired gallbladder ejection fraction while in 7 nonresponder patients placebo administration had no effect. In conclusion, normalization of the gallbladder ejection fraction in the majority of patients following glyceryl trinitrate administration suggests that impairment of gallbladder emptying is caused by a functional motility disorder rather than any organic disease.

Our policy in diagnosis and treatment of hydrocephalus

The authors present the policy they have worked out for hydrocephalus patients with special reference to the pressure measurement and test methods and to rCBF, SPECT and transcranial Doppler sonography (TDC) studies. For diagnosis, the protocol proposed by Gjerris and Borgesen was followed in 75 cases: besides other methods (CT, radionuclide cisternography, MRI) the intracranial pressure waves routinely recorded and analyzed by means of ventricular catheters for 24 h. The patients were roughly divided into groups in terms of diagnosis, baseline pressure, compliance, results of infusion tests and of surgery. In 13 patients the investigations were supplemented by rCBF SPECT and in 42 patients by TCD studies before and after CSF shunting or withdrawal to analyze the acute effects on cerebral circulation. Clinical follow-up shows that need for shunting was indicated fairly well by the common results of baseline ICP, compliance and infusion loading. The rCBF SPECT studies revealed a significant increase of the cerebral perfusion at the basal ganglia after shunting while, on the basis of CBF velocity changes three types of vasoregulatory response could be defined with TCD. In our hands, monitoring of the pressure and craniospinal capacity has proved to be a valuable aid in decisions on surgery; however, for a more precise (and beneficial) appreciation of whether surgery is indicated the vasoregulatory responses should also be taken into account in future.

The Possible Place of FDG-PET Investigations in the Differential Diagnosis of Focal Pancreatic Lesions

The values of different diagnostic modalities (measurement of the CA 19-9 level, abdominal ultrasonography (US) and computed tomography (CT), endoscopic retrograde cholangiopancreatography (ERCP) investigations and fluorodeoxyglucose positron emission tomography (FDG-PET)) were analysed retrospectively in the differential diagnosis of focal pancreatic lesions. FDG-PET was found to be the most effective tool for differentiation between malignant and benign focal pancreatic lesions. It is suggested that in cases where focal pancreatic lesions detected by CT or US, and there is a simultaneously elevated CA 19-9 level, FDG-PET should be the next step in the diagnostic strategy.

The Department of Nuclear Medicine, Szeged, on the Internet

In response to the demand of an easy-to-use information system at the Department of Nuclear Medicine, Szeged, a complete web-site has been developed. The web pages are in HTML 3.0 language, which is well known by all Internet browsers. The system covers almost all aspects of the departmental activities. However, students and nuclear medicine scientists can profit most from it.