title: Noninvasive assessment of myocardial viability in a small animal model: comparison of MRI, SPECT, and PET.
abstract: Acute myocardial infarction (AMI) research relies increasingly on small animal models and noninvasive imaging methods such as MRI, single-photon emission computed tomography (SPECT), and positron emission tomography (PET). However, a direct comparison among these techniques for characterization of perfusion, viability, and infarct size is lacking. Rats were studied within 18-24 hr post AMI by MRI (4.7 T) and subsequently (40-48 hr post AMI) by SPECT ((99)Tc-MIBI) and micro-PET ((18)FDG). A necrosis-specific MRI contrast agent was used to detect AMI, and a fast low angle shot (FLASH) sequence was used to acquire late enhancement and functional images contemporaneously. Infarcted regions showed late enhancement, whereas corresponding radionuclide images had reduced tracer uptake. MRI most accurately depicted AMI, showing the closest correlation and agreement with triphenyl tetrazolium chloride (TTC), followed by SPECT and PET. In some animals a mismatch of reduced uptake in normal myocardium and relatively increased (18)FDG uptake in the infarct border zone precluded conventional quantitative analysis. We performed the first quantitative comparison of MRI, PET, and SPECT for reperfused AMI imaging in a small animal model. MRI was superior to the other modalities, due to its greater spatial resolution and ability to detect necrotic myocardium directly. The observed (18)FDG mismatch likely represents variable metabolic conditions between stunned myocardium in the infarct border zone and normal myocardium and supports the use of a standardized glucose load or glucose clamp technique for PET imaging of reperfused AMI in small animals.
authors.affiliation: Department of Radiology, University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Thomas
authors.forename: Harshali
authors.initials: H
authors.lastname: Bal
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Arkles
authors.forename: James
authors.initials: J
authors.lastname: Horowitz
authors.forename: Luis
authors.initials: L
authors.lastname: Araujo
authors.forename: Paul D
authors.initials: PD
authors.lastname: Acton
authors.forename: Victor A
authors.initials: VA
authors.lastname: Ferrari
mesh_terms: D000818:Animals; D003287:Contrast Media / Q000493:pharmacokinetics; D004195:Disease Models, Animal; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D019786:Gadolinium DTPA / Q000493:pharmacokinetics; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008665:Metalloporphyrins / Q000493:pharmacokinetics; D009203:Myocardial Infarction / Q000000981:diagnostic imaging* / Q000473:pathology*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013194:Staining and Labeling; D017256:Technetium Tc 99m Sestamibi / Q000493:pharmacokinetics; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
chemical_list: D003287:Contrast Media; C476926:Gadophrin-3; D008665:Metalloporphyrins; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D017256:Technetium Tc 99m Sestamibi; D019786:Gadolinium DTPA