Julie Magat1,2, Arnaud Fouillet3,4, Marion Constantin3,4, Kylian Haliot3,4, Jérôme Naulin3,4, Dounia El Hamrani3,4, David Benoist3,4, Sabine Charron3,4, Richard Walton3,4, Olivier Bernus3,4, Bruno Quesson3,4. 1. IHU Liryc, Electrophysiology and Heart Modeling Institute, Foundation Bordeaux Université, Hopital Xavier Arnozan, Avenue du Haut Lévêque, 33604, Pessac cedex, France. julie.magat@ihu-liryc.fr. 2. Centre de Recherche Cardio-Thoracique de Bordeaux Inserm, U1045, Université de Bordeaux, 33000, Bordeaux, France. julie.magat@ihu-liryc.fr. 3. IHU Liryc, Electrophysiology and Heart Modeling Institute, Foundation Bordeaux Université, Hopital Xavier Arnozan, Avenue du Haut Lévêque, 33604, Pessac cedex, France. 4. Centre de Recherche Cardio-Thoracique de Bordeaux Inserm, U1045, Université de Bordeaux, 33000, Bordeaux, France.
Abstract
OBJECTIVES: We investigate the possibility to exploit high-field MRI to acquire 3D images of Purkinje network which plays a crucial role in cardiac function. Since Purkinje fibers (PF) have a distinct cellular structure and are surrounded by connective tissue, we investigated conventional contrast mechanisms along with the magnetization transfer (MT) imaging technique to improve image contrast between ventricular structures of differing macromolecular content. METHODS: Three fixed porcine ventricular samples were used with free-running PFs on the endocardium. T1, T2*, T2, and M0 were evaluated on 2D slices for each sample at 9.4 T. MT parameters were optimized using hard pulses with different amplitudes, offset frequencies and durations. The cardiac structure was assessed through 2D and 3D T1w images with isotropic resolutions of 150 µm. Histology, immunofluorescence, and qPCR were performed to analyze collagen contents of cardiac tissue and PF. RESULTS: An MT preparation module of 350 ms duration inserted into the sequence with a B1 = 10 µT and frequency offset = 3000 Hz showed the best contrast, approximately 0.4 between PFs and myocardium. Magnetization transfer ratio (MTR) appeared higher in the cardiac tissue (MTR = 44.7 ± 3.5%) than in the PFs (MTR = 25.2 ± 6.3%). DISCUSSION: MT significantly improves contrast between PFs and ventricular myocardium and appears promising for imaging the 3D architecture of the Purkinje network.
OBJECTIVES: We investigate the possibility to exploit high-field MRI to acquire 3D images of Purkinje network which plays a crucial role in cardiac function. Since Purkinje fibers (PF) have a distinct cellular structure and are surrounded by connective tissue, we investigated conventional contrast mechanisms along with the magnetization transfer (MT) imaging technique to improve image contrast between ventricular structures of differing macromolecular content. METHODS: Three fixed porcine ventricular samples were used with free-running PFs on the endocardium. T1, T2*, T2, and M0 were evaluated on 2D slices for each sample at 9.4 T. MT parameters were optimized using hard pulses with different amplitudes, offset frequencies and durations. The cardiac structure was assessed through 2D and 3D T1w images with isotropic resolutions of 150 µm. Histology, immunofluorescence, and qPCR were performed to analyze collagen contents of cardiac tissue and PF. RESULTS: An MT preparation module of 350 ms duration inserted into the sequence with a B1 = 10 µT and frequency offset = 3000 Hz showed the best contrast, approximately 0.4 between PFs and myocardium. Magnetization transfer ratio (MTR) appeared higher in the cardiac tissue (MTR = 44.7 ± 3.5%) than in the PFs (MTR = 25.2 ± 6.3%). DISCUSSION: MT significantly improves contrast between PFs and ventricular myocardium and appears promising for imaging the 3D architecture of the Purkinje network.
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