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: A novel RF coil attached to an invasive device, such as a catheter, is used to detect magnetic resonance (MR) signals for monitoring the position of the device within a subject and for the acquisition of high-resolution magnetic resonance images of the tissue surrounding the device. The novel coil is sensitive to a small volume of MR active tissue during tracking procedures, but is sensitive to a larger volume during imaging procedures. During tracking, the MR 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 coil in several dimensions. The position of the novel coil, and hence the device, as determined by the tracking system is superimposed upon independently acquired medical diagnostic images.

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 images of blood perfusion in tissue. 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 supplying blood to a portion of tissue to be imaged. A fluid, intended to be used as a contrast agent is first passed through the small high-field polarizing magnet, causing a high degree of net longitudinal magnetization to be produced in the fluid. The fluid is then introduced into the subject through the catheter. Radiofrequency (RF) pulses and magnetic field is gradients are then applied to the patient as in conventional MR imaging. Since the fluid has a larger longitudinal magnetization, before the MR imaging sequence, the fluid produces a much larger MR response signal than other tissue.

Abstract: An interactive three-dimensional (3D) pointing device for selecting points within a subject employs a tracking device which determines the position of the operator, a semi-transparent screen positioned by the operator and the subject and provides this information to a model workstation. The model workstation superimposes computer graphic images of internal structures of the subject on a the semi-transparent screen through which the operator is viewing the subject. The superimposed image is derived from image data either previously generated and stored or obtained with an imaging system. The images of the internal structures are registered with the operator's view of the external structures of the operator. The operator interactively views internal and external structures and the relation between them simultaneously, while moving the screen to select 3D target points at an image depth within the subject. Optionally other input devices may be used to identify current `target points` as selected points.

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: Radiofrequency (RF) and magnetic field gradient pulse sequences employ Time-of-Flight (TOF) strategy to selectively create transverse spin magnetization which is then maintained for a selected period of time and then imaged in order to generate a vessel selective magnetic resonance angiogram. The pulse sequence employs a spatially selective excitation pulse which is used to create transverse spin magnetization in a selected region of a subject. This region typically is made to include the root of the vessel to be imaged. After excitation, transverse magnetization is maintained with a series of refocusing RF pulses while the blood moves along the vessel. The transverse magnetization is then sampled at one or more selected times after excitation with conventional imaging strategies.