Estimation of regional cerebral blood flow using N-isopropyl-p-¹²³I iodoamphetamine acquisition data from the lungs and brain

Summary

Aim: Previously, we devised a method for estimating ¹²³I labeled N-isopropyl-p-iodo- amphetamine (¹²³I IMP) arterial blood activity at 10 minutes after intravenous injection of ¹²³I IMP (Ca10) without any blood sampling using ¹²³I IMP autoradiography (ARG) acquisition data, and verified its usefulness for quantification of regional cerebral blood flow (rCBF). In this study, we attempted to develop an improved noninvasive method for estimating rCBF. Patients, methods: ¹²³I IMP studies with 23 patients and ¹⁵O-H₂O positron emission tomography (PET) ARG studies with 20 patients were evaluated. Multiple regression analysis was used to estimate an integral of the arterial blood counts during the time after injection of ¹²³I (JCa) using parameters from the time series of the lung counts and brain counts as the explanatory variables and the fraction [brain single-photon emission computed tomography (SPECT) average count / the mean of rCBFs (mean CBF) measured by ¹⁵O-H₂O PET ARG method] as the objective variable. Results: The regression equation was as follows: Estimated JCa = (7.09x10^-3 · Cb12) - (1.57x10^-4 · CbpreSPECT) + (9.48x10^-5 · CbpostSPECT) + (1.35x10^-4· L15) - (6.95x10^-4· L33) + (7.61x10^-4· L81) - (0.417), where Cb12: brain count at 12 minutes, Cbpre-SPECT: brain count before SPECT, Cbpost-SPECT: brain count after SPECT, L15, L33, and L81: lung count at 15, 33, and 81 seconds, respectively. The mean CBF values (ml/min/100g) calculated using the estimated JCa values more closely correlated with those measured by ¹⁵O-H₂O PET ARG method (r = 0.833, p < 0.01) than those obtained by our previous method (r = 0.590, p < 0.01). Conclusion: The rCBFs obtained by this method approximated more accurately to the values measured by ¹⁵O-H₂O PET ARG method than those obtained by our previous method.

Zusammenfassung

Ziel: In einer früheren Arbeit wurde eine Methode vorgestellt, ohne Blutentnahmen die Aktivität von ¹²³I-markiertem N-Isopropyl- p-Iodamphetamin (¹²³I-IMP) im arteriellen Blut 10 Minuten nach intravenöser Injektion abzuschätzen (Ca10), und deren Nutzen zur Quantifizierung des regionalen zerebralen Blutflusses (rCBF) mittels ¹²³I-IMP-Autoradio- graphie (ARG) verifiziert. In dieser Studie wurde versucht, eine verbesserte, nicht-inva- sive Methode zur Schätzung des rCBF zu entwickeln. Patienten, Methoden: Untersuchungen mit ¹²³I-IMP an 23 Patienten und ¹⁵O-H₂O-Positronenemissionstomographie (PET) ARG an 20 Patienten wurden evaluiert. Zur Abschätzung des Zeitintegrals der Zählrate im arteriellen Blut (JCa) nach Injektion von ¹²³I wurde eine multiple Regressionsanalyse durchgeführt. Dabei wurden Parameter aus den Aufnahmeserien über der Lunge und dem Gehirn als erklärende Variablen verwendet. Zielvariable war der Quotient aus der durchschnittlichen Zählrate des Gehirns in der Einzelphotonen-Emissionscomputertomographie (SPECT) und dem Mittelwert der rCBFs (mittlerer CBF) gemessen mittels ¹⁵O-H₂O-PET-ARG. Ergebnisse: Die Regressionsgleichung lautete: geschätztes JCa = (7,09x10^-3 · Cb12) - (1,57x10^-4 · CbpreSPECT) + (9,48x10^-5 · CbpostSPECT) + (1,35x10^-4 · L15) - (6,95x10^-4 · L33) + (7,61x10^-4· L81) - (0,417). Dabei ist Cb12 die Zählrate für das Gehirn 12 Minuten p. i., Cbpre-SPECT und Cbpost-SPECT sind die Zählraten des Gehirns vor bzw. nach SPECT, sowie L15, L33 bzw. L81 die Zählraten über der Lunge 15, 33 bzw. 81 Sekunden nach Injektion. Die anhand der geschätzten jCa- Werte berechneten mittleren CBF-Werte (ml/min/100 g) korrelierten stärker mit den Werten, die mittels der ¹⁵O-H₂O-PET-ARG gemessen wurden (r = 0,833, p < 0,01), als die mit der früher beschriebenen Methode bestimmten Werte (r = 0,590, p < 0,01). Schlussfolgerung: Im Vergleich mit den gemessenen rCBF-Werten der ¹⁵O-H₂O-PET- ARG liefert die Abschätzung mit der vorgestellten Methode eine bessere Näherung als das früher beschriebene Verfahren.

Keywords

Cerebral blood flow - ¹²³I IMP - ¹⁵O-H₂O - SPECT - PET

Schlüsselwörter

¹²³I IMP - ¹⁵O-H₂O - SPECT - PET

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