Neuro-SPECT: On the development and function of brain emission tomography in the Copenhagen area.

This review describes the development of single-photon emission tomography (SPECT) in the Copenhagen area under the leadership of the internationally renown scientist, Niels A. Lassen, and the history leading up to construction of the tomograph. Measurements of global cerebral blood flow (CBF) in the 1940s and 1950s were performed by Kety & Schmidt and Lassen & Munck. Determination of regional cerebral blood flow (rCBF) by intra-arterial injection of 133 Xe and measurement with a 254-multicrystal scintillation detector and a computer system was a major step forward in the study of physiology and pathophysiology of cortical cerebral blood flow. Tomography with radioisotope ligands, including non-invasive administration, was advanced in different centres during the 1970s. An emission tomograph, the Tomomatic 64, was developed as a result of a multidisciplinary Danish and international collaboration. It was the first emission tomograph to provide dynamic data that could produce cross-sectional rCBF images. The present description of the construction and function of the Tomomatic 64 includes comparison with other contemporary and later brain-dedicated SPECT systems. Basic and clinical application of the Tomomatic 64 in Copenhagen resulted in several hundred important scientific publications and improved diagnostics for patients with a variety of neurological disorders. It is concluded that the development of the Tomomatic 64 was a major step forward in the study and examination of rCBF and brain function related to several brain disorders, in addition to vascular diseases.

Regulation of cerebral blood flow in patients with autonomic dysfunction and severe postural hypotension.

BACKGROUND: Whether cerebral blood flow (CBF) autoregulation is maintained in autonomic dysfunction has been debated for a long time, and the rather sparse data available are equivocal. The relationship between CBF and mean arterial blood pressure (MABP) was therefore tested in eight patients with symptoms and signs of severe cardiovascular autonomic dysfunction. PATIENTS AND METHODS: Eight patients were included, three of whom had Parkinson's disease, three diabetes, one pure autonomic failure and the last one had multiple system atrophy. By the use of two techniques, the arteriovenous oxygen [(a-v)O2] method and xenon-inhalation with single photon emission tomography, 15 measurements (range 10-20) and three to four CBF measurements, respectively, were obtained in each patient. Following CBF measurements during baseline, MABP was raised gradually using intravenous noradrenaline infusion, and then lowered by application of lower body negative pressure. From the (a-v)O2 samples the CBF response to changes in MABP was evaluated using a computer program fitting one or two regression lines through the plot. RESULTS AND CONCLUSION: Preserved autoregulation was observed in three patients, while the remaining five patients showed a linear relationship between CBF and MABP. Comparison of the results of the tomographic CBF measurements to the (a-v)O2 data demonstrated that it is not possible to assess whether CBF is autoregulated or not with only three to four pairs of data.

Effect of ECT on Cerebral Blood Flow in Melancholia Assessed with SPECT.

Ten endogenously depressed patients were studied before, during, and after electroconvulsive therapy. The nature and severity of depression was measured using the Newcastle Rating and Hamilton Depression Scales. The mean number of treatments administered was 12, and all patients recovered. Regional cerebral blood flow was studied using single photon emission computerized tomography (SPECT) with inhalation of (133)Xe. The mean values dropped by 8% after session three and a further 13% after the last session. The flow values of untreated patients was significantly higher than those found in 10 healthy volunteers. The values in patients following the last treatment session did not differ from those in the control group. There were no changes in the regional distribution of blood flow between controls and among patients in the three situations studied. No correlation was found between the physiological data and single items from the rating scales used. Increased cerebral blood flow values found in the treatment situation are due to the presence of depressive illness as such and not to agitation or anxiety. The parallel between flow data and clinical data points to the normalization taking place after, and not during, electroconvulsive therapy.