Intravoxel Incoherent Motion applied to Cardiac diffusion weighted MRI using breath-hold acquisitions in healthy volunteers

Abstract

Background: Diffusion weighted imaging (DWI) gives rise to a unique method to evaluate perfusion and diffusion parameters of a tissue without the need of any contrast agent, with the introduction of the Intravoxel Incoherent Motion (IVIM) model (Le Bihan, Radiology 1988). Despite its relevance, cardiac DWI has so far been limited to low b-values primarily due to signal loss induced by physiological motion. Recently, an efficient cardiac DWI method was proposed where images were acquired at different time points of the cardiac cycle and where motion-induced signal-loss was removed by Principal Component Analysis (PCA) filtering and temporal MIP (tMIP) techniques (PCATMIP) (Rapacchi, Invest Radiol (Figure presented) 2011). We compared the IVIM parameters obtained at a single optimized diastolic time point of the cardiac cycle (1TD) to the results obtained with PCATMIP technique. Methods: Breath-hold DWI scans were performed on 12 volunteers for 10 trigger-delay values in diastole. 13 b-values ranged from 0 to 550 s/mm2 were used. Signal intensity (SI) of the LV myocardium was fitted with the IVIM model corrected for T1/T2 relaxation (Lemke, MRM 2010). Results: Figure 1 shows examples of DWI for 1TD and PCATMIP as well as maps of IVIM parameters. PCATMIP allowed the recovery of signal loss due to either intra-scan cardiac motion or RR variability over multiple breath-holds (see fig. 2). Perfusion fraction f, diffusion coefficient D and pseudo-diffusion coefficient Dnull were evaluated. The values of D measured for 1TD and for PCATMIP were similar (2.35(plus or minus)1.12x10-3 mm2/s and 2.35 (plus or minus)0.89x10-3 mm2/s respectively, p=0.999). However, f was lower with 1TD than with PCATMIP (0.118(plus or minus)0.067 and 0.163(plus or minus)0.056 respectively, p=0.0018). Average Dnull obtained was 0.106 mm2/s for 1TD and 0.0763 mm2/s for PCATMIP. Conclusions: This study demonstrates feasibility and reports for the first time cardiac IVIM parameters in normal humans. PCATMIP minimized the motion-induced signal loss which is the main problem in cardiac DWI. This study opens new perspectives for perfusion imaging without contrast media.