Rapid calculation of regional cerebral blood flow and distribution volume using iodine-123-iodoamphetamine and dynamic SPECT.
Iodine-123-iodoamphetamine (IMP) is commonly used as a flow tracer for SPECT due to its large first-pass extraction fraction. Significant clearance from the brain, however, causes changes in distribution and underestimation of CBF values when a conventional microsphere model is applied to prolonged data acquisition. We have developed a rapid method to calculate CBF images in which clearance effects are taken into account.


METHODS
A dynamic SPECT scan was obtained from five subjects (four patients with cerebral infarctions and one healthy volunteer) following intravenous injection of IMP lasting 1 min. The arterial input function was obtained by frequent blood sampling and measurement of the octanol extraction ratio. The dynamic images were weighted and integrated so that the look-up table procedures yielded values of CBF and distribution volume (Vd) simultaneously.


RESULTS
Calculated values for CBF and Vd were consistent with those determined by nonlinear least squares fitting [CBF: Y = 1.03X-0.30 (ml/100 ml/min), r = 0.998, p < 0.001; Vd: Y = 0.99X-0.11 (ml/ml), r = 0.99, p < 0.001] and calculated CBF correlated significantly with CBF measured by PET [Y = 0.85X-0.15 (ml/100 ml/min), r = 0.92, p < 0.001].


CONCLUSIONS
This technique is valid for estimating CBF.
Ito
H
H
Department of Radiology, Research Institute for Brain and Blood Vessels, Akita, Japan.
Iida
H
H
Bloomfield
P M
PM
Murakami
M
M
Inugami
A
A
Kanno
I
I
Fukuda
H
H
Uemura
K
K
D000662:Amphetamines; D001921:Brain / Q000000981:diagnostic imaging*; D002544:Cerebral Infarction / Q000000981:diagnostic imaging*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007457:Iodine Radioisotopes; D020367:Iofetamine; D016018:Least-Squares Analysis; D008875:Middle Aged; D008954:Models, Biological; D013997:Time Factors; D014055:Tomography, Emission-Computed; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
D000662:Amphetamines; D007457:Iodine Radioisotopes; D020367:Iofetamine