title: Extraction and retention of technetium-99m-ECD in human brain: dynamic SPECT and oxygen-15-water PET studies.
abstract: 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.
authors.affiliation: Department of Nuclear Medicine, Faculty of Medicine, Kyoto University, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ishizu
authors.forename: Y
authors.initials: Y
authors.lastname: Yonekura
authors.forename: Y
authors.initials: Y
authors.lastname: Magata
authors.forename: H
authors.initials: H
authors.lastname: Okazawa
authors.forename: H
authors.initials: H
authors.lastname: Fukuyama
authors.forename: F
authors.initials: F
authors.lastname: Tanaka
authors.forename: N
authors.initials: N
authors.lastname: Hattori
authors.forename: H
authors.initials: H
authors.lastname: Kitano
authors.forename: T
authors.initials: T
authors.lastname: Fujita
authors.forename: N
authors.initials: N
authors.lastname: Tamaki
authors.forename: J
authors.initials: J
authors.lastname: Konishi
mesh_terms: 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
chemical_list: D015609:Organotechnetium Compounds; D010104:Oxygen Radioisotopes; D014867:Water; C059659:technetium Tc 99m bicisate; D003545:Cysteine