A comparative study of simple methods to measure regional cerebral blood flow using iodine-123-IMP SPECT.
The aim of this study was to compare the accuracy and reliability of simple methods of quantifying regional cerebral blood flow (rCBF) with 123I-labeled N-isopropyl-p-iodoamphetamine (IMP) and SPECT and to determine which method was best.


METHODS
Four methods were examined: (a) the microsphere method with continuous withdrawal of arterial blood, which was based on a microsphere model using the SPECT image obtained 5 min after tracer injection, (b) the microsphere method with one-point sampling, which was the same as the first method except that one-point sampling was used instead of continuous withdrawal, (c) the modified microsphere method with one-point sampling, which was the same as the second method except that a later SPECT image (30-min postinjection) with correction was used and (d) a table look-up method based on a two-compartment model with one-point arterial blood sampling and two SPECT scans obtained 40- and 180-min postinjection. The accuracy of these methods was validated by comparing the rCBF values with those obtained by nonlinear least squares fitting analysis based on the two-compartment model in 15 subjects.


RESULTS
Regional cerebral blood flow values obtained by the first method correlated most closely with those obtained by nonlinear least squares fitting analysis (error, 6.8%). The second method estimated rCBF with a mean error of 10.4%. The third method estimated rCBF with a mean error of 13.1%, even though it tended to slightly overestimate rCBF. The fourth method was inclined to underestimate rCBF with a mean error of 17.1%, and it greatly overestimated regional distribution volume.


CONCLUSIONS
The first method was the most accurate and reliable. For less invasiveness, the first method should be combined with one-point sampling instead of continuous withdrawal, which was used in the second method. When using a delayed SPECT image with a conventional SPECT scanner, the third method was considered to be superior to the fourth method.
Ohkubo
M
M
Department of Radiological Technology, College of Biomedical Technology, Niigata University, Japan.
Odano
I
I
Takahashi
M
M
D000328:Adult; D000368:Aged; D000662:Amphetamines; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D020367:Iofetamine; D008297:Male; D008863:Microspheres; D008875:Middle Aged; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
D000662:Amphetamines; D007457:Iodine Radioisotopes; D020367:Iofetamine