PatentsALERT VII

5497773

NUCLEAR MAGNETIC RESONANCE IMAGING WITH PATIENT

PROTECTION AGAINST NERVE

of the two logs are subtracted and the remainder divided by the hydrogen index of the gas at reservoir conditions to determine the pore volume occupied by gas.

5498962 STIMULATION AND IMAGE QUALITY PROTECTION AGAINST ARTIFACTS IMAGING METHOD

Kuhara Shigehid; Sato Kozo; Kanayama Shoich Kanagawa, JAPAN assigned to Kabushiki Kaisha Toshiba

Sepponen Raimo Helsinki, FINLAND assigned to Picker Nordstar Inc

A nuclear magnetic resonance imaging scheme capable of reducing the eddy currents induced within the living body outside of the imaging region, so as to protect the patient against the nerve stimulation due to the eddy currents, and obtaining the MR images at high image quality by protecting the image quality against the N/2 and chemical artifacts. The nerve stimulation is prevented by providing a shield member for shielding a nerve stimulation sensitive portion of the patient located outside of the imaging region from a change of the gradient magnetic fields. The artifacts are prevented by applying a reading gradient magnetic field which is repeatedly switching its polarity along a phase encoding gradient magnetic field applied at a rate of once in every two switchings of the reading gradient magnetic field, separating the acquired NMR signals resulting from odd and even turns of switchings of the reading gradient magnetic field as separate data sets, and re-constructing MR images from the separate data set for odd turns and even turns separately.

An SLP pulse is applied to an object to be imaged preceding one or more excitation pulses (ao or a) of a known magnetic resonance imaging technique. The SLP pulse tilts the nuclear magnetization away from the direction of Bo, locks the magnetization with the rotating magnetic component and returns the magnetization back to the direction of Bo. The known magnetic resonance imaging technique used with the SLP pulse includes applying at least one excitation pulse to generate transverse magnetization in the object. The excitation pulse causes the angle between the nuclear magnetization and Bo to be less than 90 degrees.

5498963

CORRECTION OF GEOMETRIC DISTORTION IN MRI PHASE AND

PHASE DIFFERENCE IMAGES

5498960

NMR LOGGING OF NATURAL GAS IN RESERVOIRS

Schneider Erika; Zang Xiguang; Hartley Michael R Brookfield, WI, UNITED STATES assigned to General Electric Company

Vinegar Harold J; Akkurt Ridva; Tutunjian Pierre N Houston, TX, UNITED STATES assigned to Shell Oil Company

A lithology-independent method of well logging the gas saturation in a reservoir containing natural gas. The method makes use of a pulsed NMR logging tool utilizing a recovery time that is greater than the relaxation time of hydrocarbon gas within the formation. In a preferred embodiment, two different NMR logs are obtained: one with a recovery time significantly shorter than the longitudinal relaxation time, Tl, of the gas and one with a recovery time equal to or longer than Tl . The amplitudes

In an MRI system NMR data is acquired and an image is reconstructed based on the net phase or phase difference of spins at locations in the imaged object. The phase or phase difference image is corrected for errors caused by non-linearities in one or more of the gradient fields. The phase or phase difference image values are weighted with spin signal magnitude image values and their locations warped to reflect gradient field non-linearity. The warped values are remapped to the image pixel locations and converted back to phase values by dividing by an average spin signal magnitude. In this manner geometric distortion caused by non-uniform magnetic field gradients are corrected without loss of quantitative phase or phase difference information.