MRI of the coronary arteries: flip angle train optimization for 3D sequences

Application of contrast agents in MRI of coronary arteries improves contrast-to-noise ratio (CNR), but widens the range of T1 relaxation times of the tissues to be imaged. The flip angle train, generated for the measurement of all phase-encoding steps in the 3rd spatial dimension of the navigator echo FLASH sequence used, is optimal only for one T1. Computer simulations show that it is not advisable to optimize the sequence on the basis of an extremely short T1 relaxation time (such as in the case of contrast-enhanced vessels) because the imaging of the surrounding tissue would be negatively influenced. A sequence optimization to a T1 of approximately 200 ms seems to allow a CNR improvement of > or = 50%.