Positron emission tomography sensitivity

Positron emission tomography (PET) is a high-resolution, sensitive, functionalimaging technique in nuclear medicine that permits repeated, non-invasive... 

A recent positron emission tomography (PET) study in which the radiolabeled serotonin precursor alpha C methyl tryptophan was used provides empirical evidence of decreased 5-HT synthesis in frontal and thalamic regions and increased 5-HT synthesis in contralateral cerebellar dentate regions (Chugani et al., 1997). These findings are consistent with findings of increased 5-HTm inhibitory autoreceptor sensitivity in adult autistic patients (Hollander et al., 2000 Novotny et al., 2000), since these receptors are prevalent in frontal and thalamic, but not cerebellar, regions. 

Neuroimaging techniques assessing cerebral blood flow (CBF] and cerebral metabolic rate provide powerful windows onto the effects of ECT. Nobler et al. [1994] assessed cortical CBE using the planar xenon-133 inhalation technique in 54 patients. The patients were studied just before and 50 minutes after the sixth ECT treatment. At this acute time point, unilateral ECT led to postictal reductions of CBF in the stimulated hemisphere, whereas bilateral ECT led to symmetric anterior frontal CBE reductions. Regardless of electrode placement and stimulus intensity, patients who went on to respond to a course of ECT manifested anterior frontal CBE reductions in this acute postictal period, whereas nonresponders failed to show CBF reductions. Such frontal CBF reductions may reflect functional neural inhibition and may index anticonvulsant properties of ECT. A predictive discriminant function analysis revealed that the CBF changes were sufficiently robust to correctly classify both responders (68% accuracy] and nonresponders (85% accuracy]. More powerful measures of CBF and/or cerebral metabolic rate, as can be obtained with positron-emission tomography, may provide even more sensitive markers of optimal ECT administration. 

Distribution in vivo could be studied by positron emission tomography (PET). Positron emission tomography is a sensitive and specific functional non invasive 3-D imaging method that permits rapidly and directly measurement of the total radioactivity from a drug labelled with a positron-emitting radionuclide (Gupta). 

Since the doses are very small, conventional LC-MS techniques are sometimes not sensitive enough to assay samples from microdosing studies. Often accelerator mass spectrometry (AMS) and positron emission tomography (PET) are required for obtaining PK and distribution information, respectively. As described in Section 5.4, although AMS is capable of quantifying 14C-labeled compounds with attomole (10 18M) sensitivity, the technique is not useful for distinguishing between an NCE... 

In the future, it will be necessary to investigate asymptomatic lesions of the nervous system using high-sensitivity tests such as, single photon emission computed tomography (SPECT) and positron emission tomography (PET). 

The natural stable isotope of fluorine, fluorine-19 (19F), with a spin of one-half and a chemical shift range of around 300 ppm, is a sensitive and useful probe in nuclear magnetic resonance (NMR) studies. Fluorine substitution may be a very effective method for studying the fate of bioactive molecules. Since there are few natural fluorinated materials to create background signals, the analyses are freed from the complications often associated with proton NMR spectroscopy (65). An artificially prepared useful short-lived isotope, fluorine-18 (18F), decays by positron emission. Positron emission tomography (PET) is an especially useful non-invasive... 

---