[Position paper nuclear cardiology: update 2008]. / Positionsbericht Nuklearkardiologie Update 2008: Aktueller Stand der szintigraphischen Methodik.

Nuclear cardiology is well established in clinical diagnostic algorithms for many years. This is an update 2008 of the first common position paper of the German Association of Nuclear Medicine and the German Association of Cardiology, Heart and Circulation Research published in 2001 aiming at an overview of state-of-the-art scintigraphic methods.

Positron emission tomography study of regional cerebral metabolism during general anesthesia with xenon in humans.

BACKGROUND: The precise mechanism by which the gaseous anesthetic xenon exerts its effects in the human brain remains unknown. Xenon has only negligible effects on inhibitory gamma-aminobutyric acid receptors, one of the putative molecular targets for most general anesthetics. Instead, xenon has been suggested to induce anesthesia by inhibiting excitatory glutamatergic signaling. Therefore, the authors hypothesized that xenon, similar to ketamine and nitrous oxide, increases global and regional cerebral metabolism in humans. METHODS: The regional cerebral metabolic rate of glucose (rcMRGlu) was sequentially assessed in two groups of six volunteers each, using F-fluorodeoxyglucose as tracer. In the xenon group, rcMRGlu was determined at baseline and during general anesthesia induced with propofol and maintained with 1 minimum alveolar concentration xenon. In the control group, rcMRGlu was measured using the identical study protocol but without administration of xenon. rcMRGlu was assessed after the plasma concentration of propofol had decreased to subanesthetic levels (< 1.0 microg/ml). rcMRGlu was quantified in 10 cerebral volumes of interest. In addition, voxel-wise changes in rcMRGlu were analyzed using statistical parametric mapping. RESULTS: Xenon reduced whole-brain metabolic rate of glucose by 26 +/- 7% (from 43 +/- 5 micromol x 100 g x min to 31 +/- 3 micromol x 100 g x min; P < 0.005) and significantly decreased rcMRGlu in all volumes of interest compared with the control group receiving propofol only. Voxel-based analysis revealed metabolic depression within the orbitofrontal, frontomesial, temporomesial, occipital, dorsolateral frontal, and lateral temporal cortices and thalami. No increases in rcMRGlu were detected during xenon anesthesia. CONCLUSIONS: Xenon induces metabolic depression in the human brain, suggesting that the inhibition of the glutamatergic system is likely to be of minor significance for the anesthetic action of xenon in vivo.

pO(2) Polarography versus positron emission tomography ([(18)F] fluoromisonidazole, [(18)F]-2-fluoro-2'-deoxyglucose). An appraisal of radiotherapeutically relevant hypoxia.

BACKGROUND AND PURPOSE: The aim of the present study was to validate ([(18)F] fluoromisonidazole (FMISO) and [(18)F]-2-fluoro-2'-deoxyglucose (FDG) positron emission tomography (PET) for determination of radiotherapeutically relevant hypoxia by the gold standard for measuring tissue oxygenation in human tumors, the computerized polarographic needle electrode system (pO(2) histography). PATIENTS AND METHODS: Up to now, a total of 16 patients with a metastatic neck lymph node from a primary squamous carcinoma of the head and neck underwent pO(2) and PET measurements. Tumor tissue pO(2) was measured with polarographic needle electrodes using a pO(2) histograph (Eppendorf). Under CT control, the needle electrode was placed in the tumor without general or local anesthesia. To assess the biological and clinical relevance of oxygenation measurement, the relative frequency of pO(2) readings, with values < or = 2.5, < or = 5.0, and < or = 10.0 mmHg, as well as mean and median pO(2) were recorded. All PET studies were carried out using an ECAT EXACT 922/47 scanner with an axial field of view of 16.2 cm. FMISO PET consisted of one static scan of the relevant region, performed 120 min after intravenous administration. The acquisition and reconstruction parameters were as follows: 15-min emission scanning and 4-min transmission scanning with (68)Ge rod sources. FDG PET of the lymph node metastasis was performed 68 +/- 11 min after intravenous administration, applying the whole-body tool with 8-min emission scanning and 4-min transmission scanning per bed position. RESULTS: In order to detect possible relations between the different relevant polarographically measured parameters of tumor hypoxia and FMISO PET data-based oxygenation values, the Pearson correlation coefficient was calculated. Average (r > 0.5) to high correlation (r > 0.7) was found between tumor-to-muscle ratio of FMISO after 2 h and parameters of hypoxic fraction (pO(2) readings with values