Data obtained from animal and human brain imaging studies indicate that frontal cortex and medial temporal lobe are involved in experiencing and controlling fear and anxiety. We tested the hypothesis that benzodiazepine receptor binding is decreased in the left temporal pole and increased in the right prefrontal area among patients suffering from anxiety. We studied 10 drug-naive female patients with generalized anxiety disorder (GAD) and 10 age- and gender-matched healthy controls with MRI and with SPET by using a new (123)I-labelled specific benzodiazepine receptor radioligand, NNC 13-8241. Blindly analyzed results showed that the benzodiazepine receptor binding of [(123)I]NNC 13-8241 was significantly decreased in the left temporal pole among patients with GAD when compared with age- and sex-matched healthy controls. This hemispheric asymmetry was studied further with a fractal analysis of the SPET images. The fractal dimension of the left hemispheric benzodiazepine receptor binding in patients with GAD was significantly higher than that of controls (1.28 +/- 0.09 and 1.17 +/- 0.07, respectively), whereas the intercept was decreased by 43 +/- 23% reflecting more homogeneous cerebral benzodiazepine receptor density distribution in patients with GAD. The finding is analogous to the decreased heterogeneity of myocardial blood flow observed in patients with ischemic heart disease. The results are consistent with the general hypothesis that high regional heterogeneity of perfusion, metabolism and receptor density is necessary to maintain adaptation ability in the living organism.

Adult↗

PubMedDate not supplied

Altered frontal lobe function suggested by source analysis of event-related potentials in impulsive violent alcoholics.

Scalp-recorded event-related potentials (ERPs) are sensitive indicators of subtle alterations in cerebral processes. We assessed automatic auditory adaptation and detection of novel stimuli in violent and non-violent alcoholics and normal subjects. Source analysis of ERPs revealed active medial temporal and frontal regions in all subjects. Frontal lobe processed alerting tones in violent alcoholics, whereas non-violent alcoholics and normal subjects processed them in medial temporal brain areas. Detection of deviant tones appeared simultaneously in frontal and temporal areas in violent alcoholics, but sequentially in other groups. These findings imply alterations in arousal and involuntary adaptive processes in cortical networks associated with violent behaviour and alcoholism.

Adult↗

PubMedDate not supplied

Dopamine receptors in pituitary adenomas: PET visualization with 11C-N-methylspiperone.

Two patients with pituitary tumors were examined with positron emission tomography (PET) after intravenous administration of 11C-N-methylspiperone. In repeat studies the patients were given 1 mg of intravenous haloperidol prior to the administration of the radioligand to block the dopamine receptors. High uptakes of the radiolabeled ligand were seen in one of the tumors. With haloperidol pretreatment the uptake was lower, probably mainly showing the remaining unspecific binding. The most marked uptake and the largest effect of haloperidol pretreatment was seen in a patient with a hormonally active prolactinoma. Dopamine receptor binding in pituitary tumors can be demonstrated in vivo with PET, and quantification of this binding is possible using a compartmental model. This technique may be useful in improving our understanding of the variable response to medical treatment of prolactinomas with dopamine agonists as well as in the prediction of the effect of such treatment.

Adenoma↗

PubMedDate not supplied

Deep-frozen biologic phantom for performance evaluation of CT scanners.

A test method with use of a biologic phantom--a deep-frozen specimen of a human cadaver--was developed in an attempt to simulate the clinical setting in CT of the spine. The quality of both soft tissue and bone images in the absence of motion artifacts was evaluated for seven scanner models. Special attention was paid to identification of the pattern and extent of artifacts. The phantom consisted of a spine with surrounding muscles. The images were evaluated subjectively and comparisons were made between the different scanners. Examples of these results are presented. A biologic phantom is a valuable supplement to artificial phantoms and increases the ability to evaluate and compare the performance of CT scanners.

Cadaver↗