Progress in nuclear medicine最新文献

Some recent methodological improvements of the 133Xe-inhalation method for determination of the rCBF are reviewed. Improvements of the classical (Obrist) method of analysis involving routines for correction of background, remaining activity and contamination from 133Xe in the air passages are described. Advantages and limitations of the ISI as compared to the bi-exponential flow parameters are discussed as well as different ways to determine technical quality and reliability of the flow calculations. Finally, a new method of curve analysis based on Fourier transforms is described. This method allows use of the full curve from start of 133Xe breathing and offers improved methods for correction of influence from air passages and arteries. Its advantages in terms of greater sensitivity and validity are discussed.

The initial clinical application of PET has demonstrated intriguing aspects in ischaemic cerebrovascular disease and epilepsy. A few observations on migraine have also been published, and studies on extrapyramidal disorders are currently underway at the UCLA and the Hammersmith Hospital. The development of PET centres in the USA and Europe will result in larger clinical studies. The capacity for accurate and reliable quantitation of physiological parameters now opens the door to serial measurements in individual patients. Quantitation in absolute units of flow or consumption of a metabolite means that correlations and comparisons can be made between patients, and between studies in individual patients. This means that the natural history of cerebral disease in pathophysiological terms is open to study and, in turn, the effects of therapeutic interventions can be monitored. In this way, with the formulation of appropriate clinical research questions, significant advances in the understanding of cerebral disease and its treatment can be expected. Though the clinical results from PET studies are as yet scanty or preliminary, sufficient data exists to indicate that PET is the most promising tool for the exploration of functional and metabolic processes in the central nervous system in vivo.

CA and RA were performed in 140 patients suffering either from TIAs (n = 43; mean age 59 +/- 9.7 years) or from RIND (n = 97; mean age 58 +/- 13 years). Completed stroke was excluded from this study. Criteria of abnormality of RA were determined from a normal control group (n = 100; mean age 37 +/- 17 years). Overall detection rate of extracranial carotid artery lesions of any size was 63% (42:66). False negative results were reviewed. Within the same group of patients, DU was positive in 76%. The addition of RA and DU enhanced the detection rate to 88%. In the subgroup with normal extracranial carotid arteries, RA accounted for 6.7% of false positive results. Intracranially, RA was able to demonstrate a significant asymmetry of perfusion in good correlation with clinical examination in 65% of the cases (91: 140), whereas CA was found positive in only 26% of the patients. It is concluded that RA is best suited for documentation of intracranial carotid artery territory disease and for studying intracranial consequences of extracranial lesions. In contrast, DU is preferred for detection of extracranial lesions. However, the addition of both techniques enhances the power of non-invasive detection of carotid artery stenosis and obstruction.

Different imaging modalities can operate on basically different object (biologic) parameters. In addition to an understanding of the intrinsic differences among modalities, it is useful to also understand how these differences translate into information on the output image. Thus, given a defined diagnostic situation, it is important to estimate the confidence (or signal-to-noise level) with which a particular abnormality is observed. For this purpose, we have extended the Rose model for characterization of signal to noise in images by taking into account the sources of degradation of contrast found in diagnostic imaging instrumentation. The model is not only useful in comparing different instruments applied to the identical physiologic state, but can also be used to compare signal to noise in images resulting from different instruments imaging the same subject under different conditions (for instance, positron and planar imaging in the head). The model can also be formulated so as to compare the signal to noise in images obtained from the same object by totally different modalities. A particularly useful feature of this model is its ability to yield an understanding of the intrinsic limitations of any one modality.

This review describes recent advances in the application of rCBF measurements by the 133Xe-inhalation method to neuropsychological and psychiatric research. Studies mapping cortical activity, as indicated by flow variations during visual, auditory and tactile tasks of varying complexity are described. The bilateral rCBF measurements do also offer information concerning lateralization of mental processes. Some clinical applications in psychiatry are finally reviewed demonstrating the use of the technique in differential diagnosis of dementia of organic ethiology (Alzheimer's disease, multi-infarct dementia) against pseudodementia due to psychosis. The method is also very useful in the study of cases with toxic influence by alcohol and other agents.

A rapidly rotating single photon tomograph is described for atraumatic and three-dimensional measurements of rCBF in ml/100 g/min. The instrument has a high sensitivity permitting the recording of the uptake and washout of xenon-133 from the human brain during and after inhalation of the gas at a concentration of 10 mCi/l for 1 min. The algorithm used to calculate rCBF is described, and clinical results in particular in stroke cases are presented. The rapidly rotating tomograph is better suited for the study of focal cerebral ischemia than the conventional stationary detectors because superposition of tissue layers is avoided.