title: 99mTc-HL91: "hot spot" detection of ischemic myocardium in vivo by gamma camera imaging.
abstract: BACKGROUND
  99mTc-HL91 is a new hypoxia imaging agent that demonstrates increased uptake and retention in globally hypoxic myocardium in vitro. The purpose of this study was to determine whether 99mTc-HL91 could detect regional ischemia in vivo by gamma camera imaging.
  
  
  RESULTS
  Eight open-chest dogs with left circumflex (LCx) stenoses were studied. Injection of 5 mCi of 99mTc-HL91 and microspheres was followed by imaging over 4 hours. Heart slices were imaged, then stained with triphenyltetrazolium chloride (TTC), and tissues were well-counted. TTC staining demonstrated no injury. Mean LCx blood flow was 0.32+/-0.04 mL x min(-1) x g(-1), and mean left anterior descending coronary artery (LAD) flow was 0.96+/-0.02 mL x min(-1) x g(-1) (ratio, 0.33). "Hot spots" were detected in 8 of 8 experiments in vivo within 60 minutes and improved over 4 hours. Region of interest analysis of LCx/LAD activity ratios demonstrated significant increases within 30 minutes (final ratio, 3.0; P<0.05). LCx and LAD washout curves demonstrated significant differences within 15 minutes. Washout curves were biexponential over 1 hour, followed by linear retention from 1 to 4 hours. Four-hour fractional retention was 0.12 for LAD and 0.44 for LCx (P<0.01). Myocardial flow versus tracer uptake demonstrated 2 phases: phase 1 (flow, 0.05 to 0.7 mL x min(-1) x g(-1)) had an inverse linear correlation (r= -0.80); phase 2, (flow, >0.7 mL x min(-1) x g(-1)) had no correlation. Ischemic heart/liver ratios remained near 1.0 for 4 hours.
  
  
  CONCLUSIONS
  99mTc-HL91 positively identifies regional myocardial ischemia in a canine model using 99mTc imaging. Quantitative techniques allowed identification of ischemic myocardium within 15 minutes of tracer administration.
authors.affiliation: William K. Warren Medical Research Institute of the University of Oklahoma Health Sciences Center, Tulsa 74136, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Okada
authors.forename: G
authors.initials: G
authors.lastname: Johnson
authors.forename: K N
authors.initials: KN
authors.lastname: Nguyen
authors.forename: Z
authors.initials: Z
authors.lastname: Liu
authors.forename: B
authors.initials: B
authors.lastname: Edwards
authors.forename: C M
authors.initials: CM
authors.lastname: Archer
authors.forename: T L
authors.initials: TL
authors.lastname: North
authors.forename: A C
authors.initials: AC
authors.lastname: King
authors.forename: J D
authors.initials: JD
authors.lastname: Kelly
mesh_terms: D000818:Animals; D003287:Contrast Media; D004285:Dogs; D015902:Gamma Cameras; D017202:Myocardial Ischemia / Q000175:diagnosis*; D015609:Organotechnetium Compounds; D010091:Oximes; D019275:Radiopharmaceuticals
chemical_list: D003287:Contrast Media; D015609:Organotechnetium Compounds; D010091:Oximes; D019275:Radiopharmaceuticals; C105527:technetium Tc 99m 4,9-diaza-3,3,10,10-tetramethyldodecan-2,11-dione dioxime