Small animal look-locker inversion recovery (SALLI)
Journal of Cardiovascular Magnetic Resonance volume 13, Article number: P24 (2011)
Introduction and purpose
Cardiac T1 mapping allows for quantitative analysis of myocardial tissue properties. Pulse sequences for human applications are not suitable for in-vivo studies in small animals.The aim of this study was to develop a single magnetic resonance imaging (MRI) approach for comprehensive assessment of cardiac function and tissue properties in small animals with high heart rates.
Small animal Look-Locker inversion recovery (SALLI) was implemented on a clinical 3 Tesla MRI system equipped with a 70 mm solenoid coil. SALLI combines a segmented, ECG-gated, IR-prepared Look-Locker type pulse sequence with a multimodal reconstruction framework. The pulse sequence scheme uses radial non-balanced steady-state free precession readout to minimize motion artifacts. Data acquisition can be accelerated through the use of temporal undersampling by a factor of R, where only a fraction of 1/R profiles is acquired for each heart phase while still allowing for reconstruction of fully sampled data sets. To assess T1 accuracy in-vitro, SALLI with different sequence settings was performed in 9 agarose gel phantoms. In-vivo, 10 Sprague-Dawley rats were studied to establish normal values pre- and post- injection of gadopentetate dimeglumine. One rat with surgically induced acute myocardial infarction was examined to test the potential of SALLI for the detection of acute myocardial injury.
Phantom studies demonstrated systematic behavior of T1 measurements. In-vitro T1 error could be reduced to 1.3±7.4% using a simple linear correction algorithm. Figure 1 shows a representative set of T1 maps from one of the wild-type rats at different time points. Pre- and post-contrast T1 of left-ventricular myocardium and blood showed narrow normal ranges. In the animal with surgical ligation of the left circumflex artery, SALLI demonstrated hypokinesia (cine images), myocardial edema (pre-contrast T1 map), and myocardial necrosis (post-contrast T1 map and late gadolinium enhancement) in the area of infarction
SALLI enables simultaneous generation of cardiac T1 maps, cine, and inversion recovery (IR)-prepared images at high heart rates. T1 measurements demonstrate high accuracy in-vitro and narrow normal ranges in-vivo. SALLI might allow for comprehensive qualitative and quantitative assessment of myocardial morphology and function in small animal models of myocardial injury.
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Messroghli, D., Nordmeyer, S., Buehrer, M. et al. Small animal look-locker inversion recovery (SALLI). J Cardiovasc Magn Reson 13 (Suppl 1), P24 (2011). https://doi.org/10.1186/1532-429X-13-S1-P24