Extraction and retention of technetium-99m-ECD in human brain: dynamic SPECT and oxygen-15-water PET studies.
The kinetic behavior of 99mTc-ethyl cysteinate dimer (99mTc-ECD) in the human brain was investigated in six normal volunteers.


METHODS
Dynamic SPECT and a three-compartmental model were used to estimate the rate constants of 99mTc-ECD in normal human brain. Extraction fraction (E), retention fraction (R) and permeability surface area product (PS product) of 99mTc-ECD were calculated using the rate constants. Regional cerebral blood flow (rCBF) was measured by PET with 15O-water.


RESULTS
The rate constants in the cerebral cortex were estimated as 0.307 +/- 0.021 for K1 (influx constant), 0.201 +/- 0.047 for k2 (backdiffusion rate constant), 0.547 +/- 0.103 for k3 (lipophilic-to-hydrophilic conversion constant) and 0.0028 +/- 0.0012 for k5 (rate constant from lipophilic compartment to blood) at rCBF of 0.509 +/- 0.055 ml/g/min (mean +/- s.d.). The first-pass extraction, retention fraction and PS product were calculated as 0.608 +/- 0.069, 0.734 +/- 0.047 and 0.477 +/- 0.060, respectively. The first-pass extraction of 99mTc-ECD decreased significantly with increases in rCBF. The retention fraction and PS product of 99mTc-ECD did not show significant changes within the normal range of rCBF. The net extraction of 99mTc-ECD calculated from the static SPECT image obtained from 20 to 40 min was 0.358 +/- 0.039 in the cortex.


CONCLUSIONS
Technetium-99m-ECD has a fairly high brain extraction, and its retention fraction and PS product appear to be independent of rCBF in the healthy human brain.
Ishizu
K
K
Department of Nuclear Medicine, Faculty of Medicine, Kyoto University, Japan.
Yonekura
Y
Y
Magata
Y
Y
Okazawa
H
H
Fukuyama
H
H
Tanaka
F
F
Hattori
N
N
Kitano
H
H
Fujita
T
T
Tamaki
N
N
Konishi
J
J
D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging*; D002560:Cerebrovascular Circulation; D003545:Cysteine / Q000031:analogs & derivatives*; D006801:Humans; D008297:Male; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics; D010104:Oxygen Radioisotopes; D014055:Tomography, Emission-Computed; D015899:Tomography, Emission-Computed, Single-Photon; D014867:Water
D015609:Organotechnetium Compounds; D010104:Oxygen Radioisotopes; D014867:Water; C059659:technetium Tc 99m bicisate; D003545:Cysteine