Abstract: A magnetic resonance (MR) active invasive device system employs a small, high-field polarizing magnet, and a large, possibly low-field magnetic resonance (MR) imaging magnet for the purpose of generating MR angiograms of selected blood vessels. A subject is positioned in a large MR imaging magnet. A catheter is inserted into the patient at or near the root of a vessel tree to be imaged. A fluid, intended to be used as a contrast agent is first cooled and frozen, and then passed through the small high-field polarizing magnet where it becomes highly polarized. The frozen fluid is then heated and melted to physiologic temperatures and introduced into the subject through the catheter. Radiofrequency (RF) pulses and magnetic field gradients are then applied to the patient as in conventional MR imaging.

Abstract: A magnetic resonance (MR) active invasive device system employs a small, high-field polarizing magnet, and a large magnetic resonance (MR) imaging magnet for the purpose of generating MR images of selected body cavities. A subject is positioned in a large low-field MR imaging magnet. A substance, intended to be used as a contrast agent is first cooled, and then passed through the small high-field polarizing magnet where it becomes highly polarized. The substance is then heated to physiologic temperatures, vaporized, and introduced into the subject through a transfer conduit as a vapor. Radiofrequency (RF) pulses and magnetic field gradients are then applied to the patient as in conventional MR imaging. Since the vapor is highly polarized, it can be imaged even though it has a much lower density than the surrounding tissue.

Abstract: A magnetic resonance (MR) active invasive device system employs a small, high-field polarizing magnet, and a large low-field magnetic resonance (MR) imaging magnet for the purpose of generating MR angiograms of selected blood vessels. A subject is positioned in a large low-field MR imaging magnet. A catheter is inserted into the patient at or near the root of a vessel tree desired to be imaged. A hydrogen gas is first cooled and condensed into a liquid state, and then passed through the small high-field polarizing magnet where it becomes highly polarized. A contrast fluid is then made by chemically combining the polarized hydrogen with oxygen to obtain highly polarized water. The water is then heated to physiologic temperatures and, if desired, made more physiologically compatible with the addition of substances such as salts. The physiologically conditioned polarized fluid is then introduced into the subject through the catheter.

Abstract: A magnetic resonance (MR) active invasive device system for imaging blood vessels employs an integrated polarizing and imaging magnet which is comprised of a small, high-field polarizing magnet whose flux return path is routed through pole structures to produce a large substantially uniform low-field magnetic region suitable for low-field magnetic resonance imaging. A subject is positioned in the uniform low-field region. A catheter is inserted into the patient at or near the root of a vessel tree to be imaged. A fluid, intended to be used as a contrast agent is first passed through the small high-field polarizing magnet, creating a large net longitudinal magnetization in the fluid. The fluid is then introduced into the subject is through the catheter. Radiofrequency (RF) pulses and magnetic field gradients are then applied to the patient as in conventional MR imaging.

Abstract: A tracking system monitors the position of a device within a subject and superimposes a graphic symbol on a diagnostic image of the subject. Registration of the tracked location with the diagnostic image is maintained in the presence of subject motion by monitoring subject motion and adjusting the display to compensate for subject motion. Motion monitoring can be performed with ultrasonic, optical or mechanical methods. The display can be adjusted by modifying the displayed location of the device or it can be adjusted by translating, rotating or distorting the diagnostic image.

Abstract: An MRI system includes a noise filter which receives each acquired NMR signal during a scan and detects short-duration noise pulses by sensing the signal level in a band of frequencies outside the imaging bandwidth. A blanking circuit suppresses the NMR signal during the time interval each noise pulse is detected to remove the noise pulse prior to image reconstruction.

Abstract: A magnetic resonance (MR) active invasive device system employs a radio-frequency (RF) coil embedded in an invasive device for the purpose of generating MR angiograms of a selected blood vessels. A subject is first placed in a polarizing magnetic field. The invasive device is then placed into a selected blood vessel of the subject such that the RF coil of the invasive device is located at or near the root of a vessel tree desired to be imaged. The RF coil is then used to alter the nuclear spin magnetization of blood flowing within the vessel. This is done by employing an RF excitation signal to the coil at the Larmor frequency of the blood. The nutation of spin magnetization can change the amount of longitudinal spin magnetization or the Amount of magnetization in the transverse plane. Because the size of the radio-frequency coil in the invasive device is small, the change in spin magnetization is limited to blood flowing by the invasive device.

Abstract: A magnetic resonance (MR) angiography system employs a Faraday catheter for generating MR angiograms of selected blood vessels. A subject is first placed in a polarizing magnetic field. The Faraday catheter is then inserted into a selected blood vessel of the subject at or near the root of a vessel tree desired to be imaged. An MR imaging pulse sequence is then applied to the subject to obtain image information from the region containing the desired vessel tree. Fluid inside the Faraday catheter is shielded from the RF pulses of the MR imaging sequence allowing the fluid to be in a relaxed state, while tissue outside the Faraday catheter is on a steady-state. As the fluid exits the catheter, and before it reaches steady-state, it produces an increased MR response signal causing the desired vessel tree to be imaged.

Abstract: A tracking system employs magnetic resonance signals to monitor the position of a device such as a catheter within a subject. The device has a receiver coil which is sensitive to magnetic resonance signals generated in the subject. These signals are detected in the presence of magnetic field gradients and thus have frequencies which are substantially proportional to the location of the coil along the direction of the applied gradient. Signals are detected responsive to applied magnetic gradients to determine the position of the device in several dimensions. Sensitivity of the measured position to resonance offset conditions such as transmitter frequency misadjustment, chemical shift and the like is minimized by repeating the process a plurality of times with selected amplitudes and polarities for the applied magnetic field gradient.

Abstract: A tracking system employs magnetic resonance signals to monitor the position and orientation of at least one device such as a catheter within a subject. The device has a plurality of receiver coils which are sensitive to magnetic resonance signals generated in the subject. These signals are detected in the presence of magnetic field gradients and thus have frequencies which are substantially proportional to the location of the coil along the direction of the applied gradient. Signals are detected responsive to sequentially applied mutually orthogonal magnetic gradients to determine the device's position and orientation in several dimensions. The position and orientation of the device as determined by the tracking system is superimposed upon independently acquired medical diagnostic images. One or more devices can be simultaneously tracked.

Abstract: A tracking system employs magnetic resonance signals to monitor the position of a device such as a catheter within a subject. The device has a receiver coil which is sensitive to magnetic resonance signals generated in the subject. These signals are detected in the presence of magnetic field gradients and thus have frequencies which are substantially proportional to the location of the coil along the direction of the applied gradient. Signals are detected responsive to sequentially applied mutually orthogonal magnetic gradients to determine the position of the device in several dimensions. The position of the device as determined by the tracking system is superimposed upon independently acquired medical diagnostic images.

Abstract: A tracking system employs magnetic resonance signals to monitor the position and orientation of a device, such as a catheter, within a subject. The device has an MR active sample and a receiver coil which is sensitive to magnetic resonance signals generated by the MR active sample. These signals are detected in the presence of magnetic field gradients and thus have frequencies which are substantially proportional to the location of the coil along the direction of the applied gradient. Signals are detected responsive to sequentially applied mutually orthogonal magnetic gradients to determine the device's position in several dimensions. The position of the device as determined by the tracking system is superimposed upon independently acquired medical diagnostic images. One or more devices can be simultaneously tracked.

Abstract: A method of collecting three-dimensional magnetic resonance (MR) fluid flow images from a volume of a subject and constructing a high contrast low noise two-dimensional image therefrom is accomplished by statistical calculation of voxel values along projection lines cast through a three-dimensional data volume obtained from three-dimensional MR angiography techniques, and converting the data to projection images by summing the weighted differences from the projection average of data for each voxel along a projection ray. The data are then normalized and repeated for all projection rays to obtain a set of projection values which are displayed on a two-dimensional display device.

Abstract: A method for providing a volumetrically-rendered projection image using reverse ray casting, uses the steps of: acquiring, from an object volume of interest, a set of data sampled from each volume element (voxel) therein responsive to a selected characteristic of that object volume; storing the data for each object voxel in a corresponding data volume element; scanning sequentially through each data voxel within the data volume corresponding to the object volume of interest; projecting each scanned data voxel to an image plane, at a solid angle determined from the solid angle at which the object volume is viewed; storing a value for each image plane pixel, responsive to a selected criteria, from the values of all projected data voxel values impingent upon that image plane pixel; and then scaling the dimensions of each image plane pixel responsive to the dimensions of the corresponding object volume shape, and the involved projection solid angle, to correct for anisotropy.

Abstract: A tracking system in which radiofrequency signals emitted by an invasive device such as a catheter are detected and used to measure the position and orientation of the invasive device within a subject. Detection of the radiofrequency signals is accomplished with coils having sensitivity profiles which vary approximately linearly with position. The invasive device has a transmit coil attached near its end and is driven by a low power RF source to produce a dipole electromagnetic field that can be detected by an array of receive coils distributed around a region of interest of the subject. The position and orientation of the device as determined by the tracking system are superimposed upon independently acquired Medical Diagnostic images, thereby minimizing the diagnostic exposure times. One or more invasive devices can be simultaneously tracked.

Abstract: A three dimensional image of a human brain or other body structure is constructed using a single flow sensitive data array and a flow insensitive data array to generate the contrasts necessary to differentiate among stationary tissues and also between stationary tissues and flowing blood. A plurality of data points from this combined image data are identified to tissue types and used to segregate the remaining data by using a nearest neighbor process in which each data value takes the tissue type of its nearest neighbor data point.

Abstract: An antenna for NMR imaging of the eye of a patient includes a small circular or oval surface coil which is locatable immediately adjacent to the eye of the patient and supported by a member having a shape contoured to fit in the region between the zygomatic and supra-orbital arches of the face. The supporting member may be a disc supporting a whole-eye surface coil anterior of the eye, or may be a contact-lens-like member supporting a fine wire surface coil substantially in contact with the anterior orbital aspect.

Abstract: Apparatus for detecting movement of an anatomical sample undergoing NMR imaging uses at least one optical sensor, each having an output responsive to the intensity of received illumination and each directed to view a selected portion of sample; and apparatus for monitoring the output of each sensor to detect a change therein responsive to movement of the sample.

Abstract: A method for simultaneously obtaining a three-dimensional nuclear magnetic resonance (NMR) angiographic image of moving spins associated with fluid flow in a region of a living organism sample, and a three-dimensional NMR image of stationary tissue in the same sample region, by immersing the sample in a main static magnetic field; nutating, in an excitation subsequence of each of a plurality of NMR sequences, the nuclear spins and the generating a flow-encoding magnetic field gradient selected to cause a resulting NMR response echo signal from the spin of a moving nucleus to be different from the NMR response echo signal from the spin of a substantially stationary nucleus.

Abstract: A method for providing a nuclear magnetic resonance (NMR) angiographic image substantially only of moving spins associated with fluid flow in a living organism sample having a cardiac cycle at a cardiac rate, and immersed in a main static magnetic field, commences by nutating the spins by a preselected amount .alpha. less than 90.degree., in the initial part of each of a pair of imaging sequences. The repetition time interval T.sub.R between sequential nutations occurs at a rate greater than the cardiac rate. After each nutation, a pair of alternating-polarity flow-encoding signal pulses are generated in a first magnetic field gradient impressed upon the sample, with each of the flow-encoding pulses in the first sequence of each pair having a polarity opposite to the polarity of the like-positioned flow-encoding pulse in the second sequence of each pair.