A quantitative approach to technetium-99m ethyl cysteinate dimer: a comparison with technetium-99m hexamethylpropylene amine oxime

To develop non-invasive regional cerebral blood flow (rCBF) measurements using technetium-99m ethyl cysteinate dimer (^99mTc-ECD) and single-photon emission tomography (SPET), the same graphical analysis as was described in our previous reports using technetium-99m hexamethylpropylene amine oxime (^99mTc-HMPAO) was applied to time-activity data for the aortic arch and brain hemispheres after intravenous injection of^99mTc-ECD. Hemispherical brain perfusion indices (BPI) for^99mTc-ECD showed a highly significant correlation (n = 22,r = 0.935,P = 0.0001) with those for^99mTc-HMPAO in 11 patients who underwent both tracer studies. Using both linear regression line equations between^99mTc-ECD BPI and^99mTc-HMPAO BPI and between^99mTc-HMPAO BPI and mean cerebral blood flow (CBF) values obtained from a xenon-133 inhalation SPET method in a previous study,^99mTc-ECD BPI was converted to¹³³Xe CBF values (y = 2.60x + 19.8). Then raw SPET images of^99mTc-ECD were converted to rCBF maps using Lassen's correction algorithm. In this algorithm, the correction factor a was fixed to 1.5, 2.6 and infinite. In the comparison of rCBF values for^99mTc-ECD SPET with those for^99mTc-HMPAO SPET in 396 regions of interest in the aforementioned 11 patients, the fixed correction factor of 2.6 gave nearly the same rCBF values for^99mTc-ECD (50.1 ± 16.9 ml/100 g/min, mean ± SD) as for^99mTc-HMPAO (49.9 ± 17.3 ml/100 g/min). In conclusion, the same non-invasive method as has been used in^99mTc-HMPAO studies is applicable to a^99mTc-ECD study for the measurement of rCBF without any blood sampling.