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4966149 Reducing the effects of coherence in magnetic resonance imaging
II
New Patents
A method and apparatus for the compensation of an eddy current magnetic field in the magnetic field of a pulsed gradient coil in an MR scanning apparatus, wherein: an MR-active sample is positioned along a given coordinate axis within a magnetic field of the gradient coil and away from its isocenter; a plurality of time-sequential gradient coil pulses are applied to the gradient coil for generating a corresponding plurality of gradient magnetic field pulses; the sample is irradiated with an RF excitation pulse a given time delay which is increased following application of each of the gradient coil pulses, so as to generate a plurality of time-sequential MR signals; each of the MR signals are measured, Fourier transformed and stored as data, the data representative of the eddy current magnetic field; correction coefficients are calculated for compensating the magnetic field of the gradient coil with respect to the eddy current magnetic field using peak frequency shift data determined from the stored data; and the calculated correction coefficients are applied so as to generate a predistorted gradient coil pulse which will compensate for the affect of said eddy current magnetic field upon said gradient coil magnetic field.
4966149 REDUCING THE EFFECTS OF COHERENCE IN MAGNETIC RESONANCE IMAGING Saul Stokar, Ltd
Raanana,
Israel assigned
to Elscint
An unique external averaging system for reducing the coherence of acquired data used for magnetic resonance imaging. The averaging is done after the acquisition of substantially complete matrices of data.
4967764 PRESSURE SENSOR ELEMENT TO MEASURE CONTACT STRESS
solution comprising an agent having at least a first and a second NMR-detectable form, the proportion of the first to the second form of the agent in the gel volume being determined by their electrolytic interaction with the gel, whereby when an external pressure is applied to the sensor element a d(chemica1 shift)/d( sigma/K) greater than 0.0001 ppm is attained, wherein sigma is the external pressure and K is the modulus of the gel. A kit contains sterile, individually wrapped sensor elements. A method of measuring in vivo contact stress applied to an implanted pressure sensor element, comprises implanting the pressure sensor of the invention into a situs of a subject in need of such measurement, non-invasively subjecting the subject situs to a nuclear magnetic resonance source effective to detect said NMRdetectible agent, obtaining the NMR spectrum of said agent, obtaining the chemical shifts from the spectrum, repeating steps (b) to (d) at least once at a desired time interval, comparing the chemical shifts obtaining in step (d) at different time intervals, and calculating the contact stress applied to said sensor element at a desired time from a correlation of observed chemical shifts for normalized stresses ( sigma/K) for the sensor element. A method of measuring in vitro contact stress applied to a pressure sensor element, comprises placing the stress sensor element of the invention in contact with a biological tissue in culture, non-invasively subjecting the biological tissue to a nuclear magnetic resonance source effective to detect said NMR-detectible agent, obtaining the NMR spectrum of said agent, obtaining the chemical shifts from the spectrum, repeating steps (b) to (d) at least once at a desired time interval, comparing the chemical shifts obtained in step (d) at different time intervals, and calculating the contact stress applied to said sensor element at a desired time from a correlation of observed chemical shifts to normalized stresses ( sigma/K) for the sensor element.
4968935 SELECTIVE REPHASING OF NMR SIGNALS TO SUPPRESS MOTION ARTIFACTS
Peter J Basser assigned to The United States of America as represented by the Department of Health and Human Services
Richard L Ehman, Mayo Foundation Research
A biological inplantable pressure sensor element comprises a fixed volume pouch formed by a sealed, flexible, impermeable membrane comprising therewithin a gel mass contained in a gel volume, said gel being hydrated with an aqueous
Motion image central rected duced
Joel P Felmlee assigned to for Medical Education and
artifacts are selectively suppressed in an by correcting only the NMR data in the views. The peripheral views are not corwith the result that motion artifacts proby large objects in the image are
New Patents
A method and apparatus for the compensation of an eddy current magnetic field in the magnetic field of a pulsed gradient coil in an MR scanning apparatus, wherein: an MR-active sample is positioned along a given coordinate axis within a magnetic field of the gradient coil and away from its isocenter; a plurality of time-sequential gradient coil pulses are applied to the gradient coil for generating a corresponding plurality of gradient magnetic field pulses; the sample is irradiated with an RF excitation pulse a given time delay which is increased following application of each of the gradient coil pulses, so as to generate a plurality of time-sequential MR signals; each of the MR signals are measured, Fourier transformed and stored as data, the data representative of the eddy current magnetic field; correction coefficients are calculated for compensating the magnetic field of the gradient coil with respect to the eddy current magnetic field using peak frequency shift data determined from the stored data; and the calculated correction coefficients are applied so as to generate a predistorted gradient coil pulse which will compensate for the affect of said eddy current magnetic field upon said gradient coil magnetic field.
4966149 REDUCING THE EFFECTS OF COHERENCE IN MAGNETIC RESONANCE IMAGING Saul Stokar, Ltd
Raanana,
Israel assigned
to Elscint
An unique external averaging system for reducing the coherence of acquired data used for magnetic resonance imaging. The averaging is done after the acquisition of substantially complete matrices of data.
4967764 PRESSURE SENSOR ELEMENT TO MEASURE CONTACT STRESS
solution comprising an agent having at least a first and a second NMR-detectable form, the proportion of the first to the second form of the agent in the gel volume being determined by their electrolytic interaction with the gel, whereby when an external pressure is applied to the sensor element a d(chemica1 shift)/d( sigma/K) greater than 0.0001 ppm is attained, wherein sigma is the external pressure and K is the modulus of the gel. A kit contains sterile, individually wrapped sensor elements. A method of measuring in vivo contact stress applied to an implanted pressure sensor element, comprises implanting the pressure sensor of the invention into a situs of a subject in need of such measurement, non-invasively subjecting the subject situs to a nuclear magnetic resonance source effective to detect said NMRdetectible agent, obtaining the NMR spectrum of said agent, obtaining the chemical shifts from the spectrum, repeating steps (b) to (d) at least once at a desired time interval, comparing the chemical shifts obtaining in step (d) at different time intervals, and calculating the contact stress applied to said sensor element at a desired time from a correlation of observed chemical shifts for normalized stresses ( sigma/K) for the sensor element. A method of measuring in vitro contact stress applied to a pressure sensor element, comprises placing the stress sensor element of the invention in contact with a biological tissue in culture, non-invasively subjecting the biological tissue to a nuclear magnetic resonance source effective to detect said NMR-detectible agent, obtaining the NMR spectrum of said agent, obtaining the chemical shifts from the spectrum, repeating steps (b) to (d) at least once at a desired time interval, comparing the chemical shifts obtained in step (d) at different time intervals, and calculating the contact stress applied to said sensor element at a desired time from a correlation of observed chemical shifts to normalized stresses ( sigma/K) for the sensor element.
4968935 SELECTIVE REPHASING OF NMR SIGNALS TO SUPPRESS MOTION ARTIFACTS
Peter J Basser assigned to The United States of America as represented by the Department of Health and Human Services
Richard L Ehman, Mayo Foundation Research
A biological inplantable pressure sensor element comprises a fixed volume pouch formed by a sealed, flexible, impermeable membrane comprising therewithin a gel mass contained in a gel volume, said gel being hydrated with an aqueous
Motion image central rected duced
Joel P Felmlee assigned to for Medical Education and
artifacts are selectively suppressed in an by correcting only the NMR data in the views. The peripheral views are not corwith the result that motion artifacts proby large objects in the image are