Cine and tagged cardiovascular magnetic resonance imaging in normal rat at 1.5 T: a rest and stress study.
BACKGROUND
The purpose of this study was to measure regional contractile function in the normal rat using cardiac cine and tagged cardiovascular magnetic resonance (CMR) during incremental low doses of dobutamine and at rest.


METHODS
Five rats were investigated for invasive left ventricle pressure measurements and five additional rats were imaged on a clinical 1.5 T MR system using a cine sequence (11-20 phases per cycle, 0.28/0.28/2 mm) and a C-SPAMM tag sequence (18-25 phases per cycle, 0.63/1.79/3 mm, tag spacing 1.25 mm). For each slice, wall thickening (WT) and circumferential strains (CS) were calculated at rest and at stress (2.5, 5 and 10 microg/min/kg of dobutamine).


RESULTS
Good cine and tagged images were obtained in all the rats even at higher heart rate (300-440 bpm). Ejection fraction and left ventricular (LV) end-systolic volume showed significant changes after each dobutamine perfusion dose (p < 0.001). Tagged CMR had the capacity to resolve the CS transmural gradient and showed a significant increase of both WT and CS at stress compared to rest. Intra and interobserver study showed less variability for the tagged technique. In rats in which a LV catheter was placed, dobutamine produced a significant increase of heart rate, LV dP/dtmax and LV pressure significantly already at the lowest infusion dose.


CONCLUSIONS
Robust cardiac cine and tagging CMR measurements can be obtained in the rat under incremental dobutamine stress using a clinical 1.5 T MR scanner.
Daire
Jean-Luc
JL
Radiology Department, Faculty of Medicine, University of Geneva and Geneva University Hospital, CH-1211 Geneva 14, Switzerland. jlucdaire@yahoo.fr
Jacob
Jean-Pascal
JP
Hyacinthe
Jean-Noel
JN
Croisille
Pierre
P
Montet-Abou
Karin
K
Richter
Sophie
S
Botsikas
Diomidis
D
Lepetit-Coiffé
Matthieu
M
Morel
Denis
D
Vallée
Jean-Paul
JP
D000818:Animals; D002316:Cardiotonic Agents / Q000008:administration & dosage*; D004280:Dobutamine / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D005080:Exercise Test; D019028:Magnetic Resonance Imaging, Cine; D009200:Myocardial Contraction / Q000187:drug effects*; D015588:Observer Variation; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D013318:Stroke Volume / Q000187:drug effects; D016277:Ventricular Function, Left / Q000187:drug effects*; D017725:Ventricular Pressure / Q000187:drug effects
D002316:Cardiotonic Agents; D004280:Dobutamine