Quantification of regional cerebral blood flow with continuous infusion of technetium-99m-ethyl cysteinate dimer

We propose a new method to quantify regional cerebral blood flow (rCBF) with continuous infusion of 99mTc-ethyl cysteinate dimer (ECD) and dynamic SPECT.

Thirteen subjects were studied. Seven subjects had SPECT and PET studies, and the other six subjects were involved in the measurement of blood clearance of 99mTc-ECD. During constant infusion of 99mTc-ECD (740 MBq) over 10 min, dynamic SPECT scans were obtained every 1 min by means of a triple-head rotating SPECT camera. Intermittent arterial blood sampling with octanol extraction was performed every 1 min to estimate the arterial input function. Influx constant (Ku) obtained by Gjedde-Patlak graphical plot method was compared with rCBF measured by PET using 15O CO2 steady state method. In order to simplify the procedure, arterial input function in each subject was estimated by calibration of the arterial blood sampled at the end of the scan to the standard arterial input function estimated from the blood clearance rate in six subjects.

Ku was linearly correlated with rCBF (Ku = 0.09 + 0.62 rCBF, r = 0.85, p < 0.05). Ku calculated with the estimated input function (Ku') and rCBF also demonstrated a linear relationship (Ku' = 0.05 + 0.65 rCBF, r = 0.84, p < 0.05).

The proposed method with one-point arterial sampling is a simple, clinically feasible tool for quantitative measurement of rCBF with 99mTc-ECD.