[Studies of free breathing three-dimensional heart delayed enhancement MRI under resting respiration using KING]

Heart delayed enhancement magnetic resonance imaging(MRI)is an attempt to obtain intense image contrast using the null-point of normal myocardium, which changes with time. Imaging is generally conducted under breath-hold, but, if the retrospective gating method is used, it is necessary to shorten the imaging time and to fill the center of the k-space with the data in the early phase of imaging. In the present study, we examined free breathing three-dimensional heart delayed enhancement MRI(3D/KING method)using k-space inspired navigator gating(KING). In the 3D/KING, since respiratory artifact decreases by combining with the fat suppression technique and the gating window can be set widely, the imaging time was shortened in comparison with the conventional 3D method. In 3D/KING/isotropic(iso), on the other hand, the respiratory artifact was decreased by transverse imaging. The mean end time of imaging by the 3D/KING method(n=10)and the 3D/KING/iso(n=5)was 3.05+/-0.69 and 4.59+/-0.74 minutes, respectively. Moreover, the signal intensity ratio(SIR)of abnormal myocardium versus normal myocardium in the 3D/KING method was low in comparison with that in the breath-hold method. However, the capability to detect lesions was similar, and good images were obtained from the patients showing poor breath-hold. In the 3D/KING/iso, heart delayed enhancement MRI from multiple directions could be conducted in a single imaging by using the image reconstitution method.