Abstract: An implantable fiducial marker having a sealed cavity for the introduction of an imaging agent that provides imaging capability in several modes, including Computed Tomographic imaging (CT) and Magnetic Resonance Imaging (MRI) is disclosed. The marker may be permanent, or it may be temporary and readily detachable from its anchor site. Combinations or agents imageable under CT scanning are combined with agents imageable under MRI scanning.

Abstract: An implantable fiducial marker having a sealed cavity for the introduction of an imaging agent that provides imaging capability in several modes, including Computed Tomographic imaging (CT) and Magnetic Resonance Imaging (MRI) is disclosed. The marker may be permanent, or it may be temporary and readily detachable from its anchor site. Combinations or agents imageable under CT scanning are combined with agents imageable under MRI scanning.

Abstract: A method is disclosed for superimposing field strength gradients on the image produced by an NMR imager by using a preparation step of tipping the spins of the volume elements with a 90.degree. wait 90.degree. RF pulse sequence for each data collection pass and performing the image encoding and data collection required to obtain the desired data set and transforming the data set into a planar image. A method is also disclosed for superimposing gradients on such an image indicative of the accuracy of the tipping process of an NMR imager.

Abstract: A phantom for an NMR machine is disclosed that includes a plurality of containers each filled with a material having a known spin density, T1, or T2 characteristic that differs a preselected amount from the spin density, T1, or T2 characteristics of the material in at least a portion of the other containers.

Abstract: A method of tuning an NMR spectrometer is disclosed that includes the step of locating a specimen in a stationary magnetic field, generating a 90.degree. alternating magnetic field excitation pulse at the Larmor frequency of the selected nuclei of the specimen followed by one or more 180.degree. alternating magnetic field refocusing pulses of preselected duration at fixed time intervals having the same phase relationships using a free-running oscillator that is turned off between pulses, measuring the primary echo train of a selected nuclear magnetic resonance signal, changing the strength of the stationary magnetic field to change the Larmor frequency of the selected nuclei, repeating the pulsing step and the measuring step until the maximum primary echo is obtained, and while holding the stationary field at that strength, measuring the desired nuclear magnetic resonance characteristic using the spin-echo method and the free-running oscillator to supply the pulses.

Abstract: A method is disclosed for measuring the NMR spin-spin relaxation time (T.sub.2) of nuclei using spin-echos comprising the steps of locating the nuclei in a static magnetic field, applying an RF pulse to the nuclei at the Larmor frequency of the nuclei of sufficient duration to rotate the net magnetic moment of the nuclei 90.degree., waiting a time period tau that is at least the time required for the free induction decay signal to go to zero, applying an RF pulse at the same Larmor frequency to the nuclei of sufficient duration to rotate the net magnetic moment of the nuclei 180.degree., recording the primary echo induced, waiting a time period equal to at least 3 tau, to cause the stimulated echos produced by the inhomogeneities in the RF magnetic field to fall into separate time zones from each other and the primary echo, applying an RF pulse at the same Larmor frequency to the nuclei of sufficient duration to rotate the net magnetic moment of the nuclei another 180.degree.