¹³³Xe-DSPECT: Normalwerte von zerebraler Ruhedurchblutung und Reservekapazität

Using the ¹³³Xe-DSPECT technique, quantitative measurements of regional cerebral blood flow (rCBF) were performed before and after provocation with acetazolamide (Diamox) i. v. in 32 patients without evidence of brain disease (normals). In 6 cases, additional studies were carried out to establish the time of maximal rCBF increase which was found to be approximately 15 min p. i. 1 g of Diamox increases the rCBF from 58 ±8 at rest to 73±5 ml/100 g/min. A Diamox dose of 2 g (9 cases) causes no further rCBF increase. After plotting the rCBF before provocation (rCBF_R) and the Diamox-induced rCBF increase (reserve capacity, Δ rCBF) the regression line was Δ rCBF = −0,6 x rCBF_R +50 (correlation coefficient: r = −0,77). In normals with relatively low rCBF values at rest, Diamox increases the reserve capacity much more than in normals with high rCBF values before provocation. It can be expected that this concept of measuring rCBF at rest and the reserve capacity will increase the sensitivity of distinguishing patients with reversible cerebrovascular disease (even bilateral) from normals.

Zusammenfassung

Mit der dynamischen Single-Photon-Emissions-Computertomographie nach Inhalation von ¹³³Xe-Gas (¹³³Xe-DSPECT) wurde die regionale Hirndurchblutung (rCBF) vor und nach Provokation mit dem Carboanhydrasehemmer Azetazolamid (Diamox) bei 32 Patienten ohne intrakranielle Erkrankungen gemessen. In 2 Sitzungen wurden Ruhedurchblutung und Diamox-induzierbarer rCBF-Anstieg ermittelt. rCBF-Messungen vor und in unterschiedlichen Abständen nach Diamox-Provokation (6 Fälle) belegten ein Maximum des rCBF-Anstiegs nach etwa 15 min. Durch Provokation mit 1 g Diamox stieg der rCBF von einem Ausgangswert von 58 ± 8 auf 73 ± 5 ml/100 g/min an (relative Zunahme: 25%). Eine Dosiserhöhung auf 2 g Diamox führte zu keiner weiteren rCBF-Steigerung. Auffallend war die geringere Streubreite der rCBF- Werte nach Diamox-Provokation (l g) im Vergleich zu den Ruhewerten. In erster Näherung bestand ein linearer Zusammenhang zwischen Ruhedurchblutung (rCBF_R) und Diamox-induzierbarem rCBF-Anstieg (Reservekapazität, ΔrCBF): ΔrCBF = −0,60 rCBF_R +50 (Korrelationskoeffizient: r = −0,77). Auf der Basis einer kombinierten Bewertung von Ruhedurchblutung und Reservekapazität ist eine Verbesserung der Sensitivität zur Erfassung von Patienten mit reversiblen zerebrovaskulären Erkrankungen zu erwarten.

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