title: Absolute quantitation of myocardial blood flow with (201)Tl and dynamic SPECT in canine: optimisation and validation of kinetic modelling.
abstract: OBJECTIVE
  201Tl has been extensively used for myocardial perfusion and viability assessment. Unlike 99mTc-labelled agents, such as 99mTc-sestamibi and 99mTc-tetrofosmine, the regional concentration of 201Tl varies with time. This study is intended to validate a kinetic modelling approach for in vivo quantitative estimation of regional myocardial blood flow (MBF) and volume of distribution of 201Tl using dynamic SPECT.
  
  
  METHODS
  Dynamic SPECT was carried out on 20 normal canines after the intravenous administration of 201Tl using a commercial SPECT system. Seven animals were studied at rest, nine during adenosine infusion, and four after beta-blocker administration. Quantitative images were reconstructed with a previously validated technique, employing OS-EM with attenuation-correction, and transmission-dependent convolution subtraction scatter correction. Measured regional time-activity curves in myocardial segments were fitted to two- and three-compartment models. Regional MBF was defined as the influx rate constant (K(1)) with corrections for the partial volume effect, haematocrit and limited first-pass extraction fraction, and was compared with that determined from radio-labelled microspheres experiments.
  
  
  RESULTS
  Regional time-activity curves responded well to pharmacological stress. Quantitative MBF values were higher with adenosine and decreased after beta-blocker compared to a resting condition. MBFs obtained with SPECT (MBF(SPECT)) correlated well with the MBF values obtained by the radio-labelled microspheres (MBF(MS)) (MBF(SPECT) = -0.067 + 1.042 x MBF(MS), p < 0.001). The three-compartment model provided better fit than the two-compartment model, but the difference in MBF values between the two methods was small and could be accounted for with a simple linear regression.
  
  
  CONCLUSIONS
  Absolute quantitation of regional MBF, for a wide physiological flow range, appears to be feasible using 201Tl and dynamic SPECT.
authors.affiliation: Department of Investigative Radiology, National Cardiovascular Center Research Institute, Fujishiro-dai, Suita City, Osaka 565-8565, Japan. iida@ri.ncvc.go.jp
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Iida
authors.forename: Stefan
authors.initials: S
authors.lastname: Eberl
authors.forename: Kyeong-Min
authors.initials: KM
authors.lastname: Kim
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Tamura
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Ono
authors.forename: Mayumi
authors.initials: M
authors.lastname: Nakazawa
authors.forename: Antti
authors.initials: A
authors.lastname: Sohlberg
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Zeniya
authors.forename: Takuya
authors.initials: T
authors.lastname: Hayashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watabe
mesh_terms: D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology*; D003198:Computer Simulation; D003326:Coronary Circulation / Q000502:physiology*; D003331:Coronary Vessels / Q000000981:diagnostic imaging* / Q000502:physiology*; D004285:Dogs; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007700:Kinetics; D008955:Models, Cardiovascular; D011786:Quality Control; D019275:Radiopharmaceuticals; D012212:Rheology / Q000379:methods; D013793:Thallium; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; C027549:thallium chloride; D013793:Thallium