Abstract: Realtime magnetic resonance imaging (MRI) uses cardiac and respiratory monitoring tools to avoid or minimize motion-induced image artifacts. A series of initial MR images are associated with the physiological data from the cardiac, respiratory, or other monitoring tools. The tools provide physiological data in conjunction with anatomic or spatial information such that the optimal gating times (i.e., for acquiring MR image data) in the cardiac and respiratory cycles can be identified and the optimal acquisition durations are identified relative to the physiological data. The process then uses MRI with the identified optimal gating times and acquisition durations to produce a high quality output image of the anatomy of interest. The high quality image can be one or more of the following: a two-dimensional (2D) with a higher signal-to-noise ratio (i.e.

Abstract: An MRI system is employed to acquire a 3D image which is enhanced by injection of a contrast agent into the subject's vasculature. A 3D mask image is also acquired and 2D projection images are produced from both 3D images. The resulting 2D projection mask image is subtracted from the 2D enhanced projection image to produce the contrast enhanced MRA image.

Abstract: An MRI method is provided for determining the arrival of selected contrast material at a target artery or other fluid-carrying vessel after injection of contrast material at a remote vascular site. By precisely knowing the arrival time, an additional MR angiography scan of the artery may be readily coordinated with the onset of artery enhancement. Initiation of this MR angiography scan may be immediate. Alternatively, determination of the arrival time of a test bolus of contrast to the imaging site can be used to calculate the transit time of a test bolus from the injection site to the imaging site. This information may then be used as an estimate of a subsequent MR angiography scan using a full bolus of contrast. The method for determining contrast arrival includes injecting the contrast material at an injection site, and simultaneously commencing acquisition of a succession of MR images of a section taken through the target vessel, proximate to the imaging site.

Abstract: An MR oximetry measurement of % O.sub.2 employs a pulse sequence comprised of a T.sub.2 preparatory segment and an image data acquisition segment. The pulse sequence is used in methods for measuring coronary flow reserve and for measuring myocardial oxygen consumption.

Abstract: An MRI system measures the movements of a subject during the acquisition of a series of NMR images and automatically updates the scan parameters such that the image plane or volume tracks the movement of the anatomy of interest. An array of tracking coils fasten to the subject and an NMR measurement pulse sequence is interleaved with the image acquisitions to measure the location of the tracking cols.

Abstract: The oxygen saturation of blood is determined by obtaining spin-spin relaxation time (T2.sub.b) of the fluid using magnetic resonance imaging techniques. A simplified model relates oxygen saturation of blood to measured spin-spin relaxation time. A pulse sequence is given for in vivo estimation of T2.sub.b including a plurality of 180.degree. refocusing RF signals which are equally spaced in time. The last refocusing pulse is slice selective. Fat signal is suppressed by initially using a short inversion recovery sequence followed by a frequency selective 90.degree. pulse that excites only water protons.

Abstract: The performance of current, flow-based sequences for imaging vasculature using MR is severely restricted in regions with inherently slow flow. We address this problem with a flow-independent imaging method. Specifically, we generate projection images of blood in the limbs while suppressing signals from all other tissues (primarily skeletal muscle, bone marrow, and subcutaneous fat) using a flow-compensated, water-selective, short TI inversion recovery sequence with a long echo time. We experimentally evaluate the effectiveness of this sequence and present in vivo results clearly demonstrating the method's potential.