Injectable ice slurry for reducing pericardial adipose tissue.

OBJECTIVES: Excess pericardial adipose tissue (PAT) is associated with a higher risk of cardiovascular diseases. Currently, available methods for reducing PAT volume include weight loss through diet and exercise, weight loss with medications, and bariatric surgery. However, these methods are all limited by low patient compliance to maintain the results. We have developed an injectable ice slurry that could selectively target and reduce subcutaneous adipose tissue volume. The aim of this study was to investigate the feasibility and safety of using injectable slurry to selectively reduce PAT volume in a preclinical large animal model. METHODS: PAT in Yucatan swine was injected with slurry or room temperature control solution. All animals were imaged with baseline chest computed tomography (CT) before slurry injection and at 2 months after injection to quantify PAT volume. Specimens from injected and noninjected PAT were harvested for histology. RESULTS: Slurry treatment of PAT was well tolerated in all animals. Slurry-induced selective cryolipolysis in treated PAT. CT imaging showed decrease in PAT volume in treated area at 8 weeks posttreatment compared to baseline, that was significantly different from control solution treated group (median [range]: -29.66 [-35.07 to -27.92]% vs. -1.50 [-11.69 to 8.69]% in control animals respectively, p < 0.05). CONCLUSIONS: This study demonstrated that slurry injection into PAT is feasible in a large animal model. Slurry injection was safe and effective in inducing selective cryolipolysis in PAT and reducing PAT volume. Slurry reduction of PAT could potentially serve as a novel treatment for cardiovascular diseases.

Free-breathing 3D cardiac extracellular volume (ECV) mapping using a linear tangent space alignment (LTSA) model.

$\textbf{Purpose:}$ To develop a new method for free-breathing 3D extracellular volume (ECV) mapping of the whole heart at 3T. $\textbf{Methods:}$ A free-breathing 3D cardiac ECV mapping method was developed at 3T. T1 mapping was performed before and after contrast agent injection using a free-breathing ECG-gated inversion-recovery sequence with spoiled gradient echo readout. A linear tangent space alignment (LTSA) model-based method was used to reconstruct high-frame-rate dynamic images from (k,t)-space data sparsely sampled along a random stack-of-stars trajectory. Joint T1 and transmit B1 estimation was performed voxel-by-voxel for pre- and post-contrast T1 mapping. To account for the time-varying T1 after contrast agent injection, a linearly time-varying T1 model was introduced for post-contrast T1 mapping. ECV maps were generated by aligning pre- and post-contrast T1 maps through affine transformation. $\textbf{Results:}$ The feasibility of the proposed method was demonstrated using in vivo studies with six healthy volunteers at 3T. We obtained 3D ECV maps at a spatial resolution of 1.9$\times$1.9$\times$4.5 $mm^{3}$ and a FOV of 308$\times$308$\times$144 $mm^{3}$, with a scan time of 10.1$\pm$1.4 and 10.6$\pm$1.6 min before and after contrast agent injection, respectively. The ECV maps and the pre- and post-contrast T1 maps obtained by the proposed method were in good agreement with the 2D MOLLI method both qualitatively and quantitatively. $\textbf{Conclusion:}$ The proposed method allows for free-breathing 3D ECV mapping of the whole heart within a practically feasible imaging time. The estimated ECV values from the proposed method were comparable to those from the existing method. $\textbf{Keywords:}$ cardiac extracellular volume (ECV) mapping, cardiac T1 mapping, linear tangent space alignment (LTSA), manifold learning.