[Quantitative measurements of cerebral blood flow using 99mTc-ECD radionuclide angiography, SPECT and one-point...

We quantified regional cerebral blood flow using 99mTc-bicisate ethyl cysteinate dimer (ECD) radionuclide (RN) angiography, one-point arterial sampling and static SPECT in 12 patients. The tracer was injected as a bolus into the right antecubital vein, and time-activity curves over the cerebrum and the aortic arch were sequentially recorded for 300 s with 3 s intervals in a 128 x 128 format with a large-field of view gamma camera equipped with a low-energy collimator. Blood was obtained from the femoral artery immediately after stopping the RN angiography and the arterial concentration of 99mTc-ECD was calculated. Thereafter, the SPECT data acquisition was started with the subject's head immobilized. We applied a three-compartment kinetic model: The influx constant of 99mTc-ECD from blood to brain (K1) and the transfer of ECD from diffusible compartment to nondiffusible one in the blood (k5). The K1 value was compared with the global cerebral blood flow value (Fa) measured by the 133Xe clearance technique. From the kinetic analysis, the following parameter values could be calculated: K1 = 0.21 +/- 0.05 (ml/ml/min), k5 = 0.66 +/- 0.15 (/min), Fa = 0.32 +/- 0.09 (ml/ml/min) and the extraction fraction E = K1/Fa = 0.65 +/- 0.05. There was a strong correlation between K1 and Fa (Y = 0.53X + 3.7; rs = 0.91). By combining the K1 and E values in the whole-brain, we can obtain the absolute global flow value and regional 99mTc-ECD CBF maps if the average concentration of the tracer in the whole-brain is used as a reference. Our method is less invasive and suitable for quantitation of cerebral blood flow in patients with brain disorders.