[en] PET and SPECT enable the direct measurement of components of the dopaminergic and other systems in the living human brain and offer unique opportunity for the in vivo quantification on the dopaminergic function in PD and other movement disorders. The need to establish the early and differential diagnosis of PD is increasingly important given the recent evidence that early pharmacologic intervention may slow progression of this progressive degenerative disease. Accordingly, imaging with PET and SPECT using specific neuro markers has been increasingly important to biochemically identify the loss of specific neurotransmitters, their synthesizing enzymes and their receptors in movement disorders. Through the parallel development of new radiotracers, kinetic models and better instruments, PET and SPECT technology is enabling investigation of increasingly more complex aspects of the human brain neurotransmitter systems. This paper summarizes the results of different PET-SPECT studies used to evaluate the various elements of the dopamine system in the human brain with PET and intends to introduce the newly emerging specific tracers and their applications to clinical research in movement disorders

[en] This paper concerns application of genetic algorithm in maximum likelihood image reconstruction in emission tomography. The example of genetic algorithm for image reconstruction is presented. The genetic algorithm was based on the typical genetic scheme modified due to the nature of solved problem. The convergence of algorithm was examined. The different adaption functions, selection and crossover methods were verified. The algorithm was tested on simulated SPECT data. The obtained results of image reconstruction are discussed. (author)

[en] PET and SPECT neuro receptor imaging techniques combined with pharmacological challenges have been introduce to measure acute fluctuations of synaptic dopamine (DA) concentrations in the living human brain. Changes in the in vivo binding of radioligands following manipulation of transmitter levels are generally believed to be driven by binding competition between the radioligand and neurotransmitter. This imaging modality has been very successful in the study of DA transmission at D2 receptors. Yet, the extension of this technique to the study of other neurotransmitter systems has proven difficult. This paper reviews recent evidence suggesting that simple binding competition might not be the only phenomenon regulating transmitter-radioligand interactions in vivo, and examines emerging data indicating that receptor trafficking might also be involved. A better understanding of the mechanisms underlying these interactions should facilitate the development of PET and SPECT radiotracers suitable for the reporting of synaptic transmitter levels

[en] Functional neuroimaging with positron and single photon emitter-labeling has added considerably to the understanding of epileptic seizure activity and of the postictal and interictal cerebral dysfunctions that accompany many epilepsies. Some of these functional alterations cannot be studied in humans by any other technique, and in other instances the information is complementary to that provided by other techniques, some of which are invasive or even require tissue destruction. Available radiotracer imaging techniques have yet to be fully applied to several important epileptic syndromes (including the Lennox-Gastaut syndrome and other secondary generalized epilepsies), to physiological aspects of the natural history of temporal lobe epilepsy or any other commonly occurring epilepsy, and to the assessment of mechanism of action and adverse effects of antiepileptic drugs and other epilepsy therapies. New radiotracers should be developed to permit study of specific excitatory amino acid receptors and other receptor sites that are known to be relevant to the development of epilepsy, to the onset of individual seizures, and to interical dysfunctions

[en] An emission type computed tomography apparatus is claimed. It comprises: a detector for producing a signal corresponding to radiation incident on a detecting surface; means for holding the detector at a predetermined angle with respect to a tangential line to a circle centered on an axis perpendicular to a tomogram plane; rotating means for rotating the detector about the axis through the holding means; and means for processing an output signal from the detector in accordance with rotational movement of the detector to produce a representation of radioactive distribution in the tomogram plane

[en] Emission computed tomography provides an opportunity to quantify neurotransmitter-neuro receptor systems in vivo. In order to do so, very high image quality and quantitative accuracy are required. Quantitation of receptor systems involves considerations of physical effects (such as finite spatial resolution, scatter, and attenuation), instrumentation design (such as spatial sampling), image processing (such as filtering), and data analysis (such as kinetic modeling). Appropriate application of these considerations can lead to useful results, but emerging approaches promise even greater levels of accuracy and precision

[en] Atherosclerosis still represents killer number one in industrialized nations, and is starting to have increased impact in developing countries. Atherosclerotic plaques are the net result of a complex interplay between vascular cholesterol deposition, inflammatory activity and extracellular matrix formation. The result is luminal narrowing of arteries, which may ultimately lead to compromised blood flow to essential body organs, most notoriously to the heart. Most of the cardiovascular events that are caused by atherosclerosis, such as acute myocardial infarction or stroke, are the result of a transition of so-called stable atherosclerotic plaques to vulnerable plaques, that are prone to rupture. The direct consequence of atherosclerotic plaque rupture is exposure of thrombogenic plaque constituents to the blood, leading to instant local thrombus formation. The formation of this localized thrombus may ultimately result in sudden obstruction of blood flow and consequent infarction of distal tissue. Clinical risk profiling methods, such as the Framingham and Procam risk scores, are reasonable predictors of myocardial infarction over a 10-year time-span. However, the challenge remains to identify those patients with a very high risk of suffering from myocardial infarction in the coming months. Imaging may provide the necessary diagnostic information to identify such individuals. The transition of stable atherosclerotic plaques to vulnerable plaques is typically heralded by inflammation, thinning of the overlying fibrous cap, and the presence of a large necrotic core. Apoptosis is linked to all of these features of plaque vulnerability, and may, therefore, provide uniquely useful targets for the identification of plaque vulnerability. In recent years, a number of molecular imaging technologies have been developed to image apoptosis, which will be discussed in this review. Further development of apoptosis imaging technologies may aid, in the years to come, in the quest to identify patients with critical cardiovascular risks, to treat myocardial infarction in its imminent, instead of its evident phase.

[en] Non-invasive radioligand imaging methods for brain receptor studies use either short-lived positron-emitting radionuclides such as ¹¹C and ¹⁸F for positron emission tomography (PET) or single photon-emitting radionuclides such as ¹²³I for single photon emission computed tomography (SPECT). PET and SPECT use radioligands which are injected intravenously into experimental animals, human volunteers or patients. The main applications of radioligands in brain research concern human neuro psychopharmacology and the discovery and development of novel drugs to be used in the therapy of neurological and psychiatric disorders. A basic problem in PET and SPECT brain receptor studies is the lack of useful radioligands with appropriate binding characteristics. Prerequisite criteria need to be satisfied for a radioligand to reveal target binding sites in vivo. This section will discuss these important criteria and also review recent examples in neuro receptor radioligand development such as selective radioligands for brain monoamine transporters

[en] Pathophysiology od cerebrovascular disease has been studied by measuring cerebral blood flow and energy metabolism using single photon emission computed tomography (SPECT) and positron emission tomography (PET). These parameters are measures for brain tissue consisting of heterogeneous components such as neurons, glial cells, and blood vessels. It is still difficult to evaluate brain damages specifically involving either neurons or other components. Several trials were recently conducted to visualize neuron-specific injury in cerebrovascular disease by means of ¹¹C flumazenil for PET and ¹²³I-iomazenil for SPECT. These tracers selectively bind to central benzodiazepine receptor which is purely neuronal. A reduced accumulation of these ligands was found in the area surrounding the complete infarction and in the cortex remote from putaminal hemorrhage, indicating the existence of neuron specific injury not visualized by CT and MR. Neurological deficits were well correlated with the loss of cortical accumulation of these ligands. These preliminary studies indicated a potential of neurochemical imaging in cerebrovascular disease. Vulnerability to ischemia which may differ among brain tissue components, among subpopulations of neurons, and among pre-synaptic and post-synaptic functions can be more precisely examined. Neurochemical imaging can be also applied to reveal releases and re-organization of each neurotransmitter-acceptor system after stroke

[en] Algorithms that calculate maximum likelihood (ML) and maximum a posteriori solutions using expectation-maximization have been successfully applied to SPECT and PET. These algorithms are appealing because of their solid theoretical basis and their guaranteed convergence. A major drawback is the slow convergence, which results in long processing times. This paper presents two new heuristic acceleration methods for maximum likelihood reconstruction of ECT images. The first method incorporates a frequency-dependent amplification in the calculations, to compensate for the low pass filtering of the back projection operation. In the second method, an amplification factor is incorporated that suppresses the effect of attenuation on the updating factors. Both methods are compared to the one-dimensional line search method proposed by Lewitt. All three methods accelerate the ML algorithm. On the test images, Lewitt's method produced the strongest acceleration of the three individual methods. However, the combination of the frequency amplification with the line search method results in a new algorithm with still better performance. Under certain conditions, an effective frequency amplification can be already achieved by skipping some of the calculations required for ML