New Patents III

noise ratio, for NMR use, has a reduced length Lc, which is between about 0.3rs and about 1.5rs, where rs is the radius of a sample-to-be- investigated, contained within the cylindrical volume coil, with the volume coil radius rc being between about l.Ors and about 1.6rs. the short volume coil has an improved SNR for a voxel located substantially on the central plane of the coil, relative to the SNR of a normal -1enth volume coil with Lc) or =4rs.

4885541

APPARATUS AND METHOD FOR ENHANCED MULTIPLE COIL

NUCLEAR MAGNETIC RESONANCE (NMR) IMAGING

Cecil Hayes assigned to General Electric Com- pany

A nuclear magnetic resonance (NMR) signal ac- quisition apparatus includes a cylindrical array of overlapping coils. Coupling of currents bet- ween coils due to re-radiation of received signals, in particular noise currents, is reduced by pre- senting a high impedance to each coil, thereby reducing the current circulating in each coil. A PREDAMP circuit is disclosed which utilizes the input impedance of a preamplifier, transformed through a quarter-wavelength transmission line segment, to achieve the high input impedance for the coil. As a result, multiple images, each with a high signal-to-noise ratio (SNR), can be simul- taneously obtained. A method is disclosed for combining the multiple images into a composite image with optimum SNR, taking into account the phase shifts between the images resulting from the spatial orientation of the coils.

4885542

MRI COMPENSATED FOR SPURIOUS NMR

FREQUENCY/PHASE SHIFTS CAUSED BY SPURIOUS

CHANGES IN MAGNETIC FIELDS DURING NMR DATA

MEASUREMENT PROCESSES

Ching Yao, James Hale, Lawrence E Crooks, Leon Kaufman assigned to The Regents of the University of California

At .least one extra NMR measurement cycle is performed without any imposed magnetic grad- ients during readout and recordation of the

NMR RF response. Calibration data derived from this extra measurement cycle or cycles can be used for resetting the RF transmitter fre- quency and/or for phase shifting other conventionally acquired NMR RF response data to compensate for spurious changes in magnetic fields experienced during the NMR data measuring processes. Some such spurious fields may be due to drifting of the nominally static magnetic field. Another source of spurious fields are due to remnant eddy currents induced in surrounding conductive structures by magnetic gradient pulses employed prior to the occurrence of the NMR RF response signal. Special procedures can be employed to permit the compensation data itself to be substantially unaffected by relatively static inhomogeneities in the magnetic field and/or by differences in NMR spectra of fat and water types of nuclei in imaged volumes containing both.

4885549

METHOD OF PHASE AND AMPLITUDE CORRECTION OF

NMR SIGNALS USING A REFERENCE MARKER

Robert L Thrift, Paul Morris assigned to Gene- ral Electric Company

A marker substance is introduced into the sam- ple volume undergoing NMR analysis. The fre- quency spectrum of the NMR signal is analyzed to isolate the marker substance frequency peaks. Comparison of marker substance frequency peak phase and amplitude between NMR ex- periments provides information from which a correction for phase and amplitude variations due to system instability can be made.

4887034

METHODS AND APPARATUS FOR DETECTING CERTAIN

COMPOUNDS

John A Smith, London, United Kingdom as- signed to National Research Development Cor- poration

The detection of compounds containing both nuclei of a kind which exhibit nuclear magnetic resonance (nmr) and nuclei of a kind which ex- hibit nuclear qyadrupole resonance (nqr), for ex- ample compounds containing both 1 H and 14N nuclei, is carried out by subjecting a substance

IV New Patents

suspected of containing such a compound to a magnetic field and repetitively to three parallel activities A,H and B. Activity A comprises two similar rf pulse sequences PA and PB at the nmr frequency. Activity H is a temporary change in the value of the magnetic field, which may be a reduction to zero. Activity B is the application of additional rf signals. Activity H and/or activity B are different during each of the respective pulse sequences PA and PB. The activity B rf signals are at one or more frequencies selected so that in combination with the activity H in at least one of the pulse sequences the subsequent nmr signal is modified if such a compound is present. The dif- ference in magnitude of the nmr signals obtained following the two types of rf pulse sequence is then measured.

4887035

MAGNETIC RESONANCE SPECTROSCOPY SYSTEM

Masatosh Hanawa, Ootawara, Japan assigned to Kabushiki Kaisha Toshiba

A magnetic resonance spectroscopy system repeatedly performs operations of selectively ex- citing, using a 90 degrees pulse, first two regions which sandwich a local region therebetween in the direction of one of the X axis and y axis for a slice portion, subsequently erasing transverse magnetization components in the first two re- gions, selectively exciting, using a 90 degrees pulse, second two regions which sandwich the local region therebetween in the direction of the other of the x axis and y axis, subsequently erasing transverse magnetization components in the second two regions, exciting a region having one local region in the z-axis direction to acquire magnetic resonance data therefor, and exciting a region including another local region in the z- axis direction to acquire magnetic resonance data therefor within a repetition time.

4887038

SOLENOIDAL SURFACE COILS FOR MAGNETIC RESONANCE

IMAGING

Jan Votruba, George Morris assigned to Fonar Corporation

Receiver coil for use with a Nuclear Magnetic Resonance Imaging (NMRI) instrument in- cludes a flexible electrical conductor formed

from a multiplicity of conductor strips con- nected in parallel and carried by a flexible insulator. The insulator is configured to be wrap- ped around an object to be imaged to form the conductor into a coil whose interior is substan- tially occupied by the object. Air vents may also be provided to improve the ventilation of air through the receiver coil in its wrapped con- figuration and to reduce any claustrophobic dis- comfort of a patient.

4887609

APPARATUS AND METHOD FOR FILTERING

ELECTROCARDIOGRAPH SIGNALS

Malcolm P Cole assigned to The Methodist Hospital System

Apparatus and method for filtering the elec- trocardiograph (ECG) signal of a patient of un- wanted signals, such as contamination signals produced by the use of nuclear magnetic resonance imaging system or muscle artifact signals. In a preferred embodiment, variable fil- ter (2) is used to filter an input ECG signal (1). The filtering characteristics applied to the ECG signal by variable filter (2) vary in response to the logical state of a synchronization signal in- dicating a patient’s biophysical state which is in- put to variable filter (2) via line (3). In alternative embodiments, a QRS detector (22), a delay cir- cuit (20), and a pulse stretcher (21) may be used to provide a synchronization signal. In another alternative embodiment, a microprocessor (24) with an input ECG signal and with input data is used to control the filtering of the ECG signal in synchronization with a patient’s ECG signal.

4888552

MAGNETIC RESONANCE IMAGING

Avihai Egozi, Saul Stokar, Netanya, Israel as- signed to Elscint Ltd

A method of acquiring data for use in providing magnetic resonance images (MRI) wherein prior to stabilization of the system, data is acquired using phase encoding gradient pulses far removed from zero. Immediately after system stabilization data proximate and equal to the zero value phase encoding gradient pulse is ac- quired.