Apparatus and method for nuclear magnetic resonance scanning and mapping

Abstract

An improved apparatus and method for analyzing the chemical and structural composition of a specimen including whole-body specimens which may include, for example, living mammals, utilizing nuclear magnetic resonance (NMR) techniques. A magnetic field space necessary to obtain an NMR signal characteristic of the chemical structure of the specimen is focused to provide a resonance domain of selectable size, which may then be moved in a pattern with respect to the specimen to scan the specimen.

I claim: 
     
       1. A method of detecting selected nuclei within a specimen utilizing nuclear magnetic resonance phenomenon comprising: (a) providing a .[.nonuniform.]. primary .[.static.]. magnetic field .[.space.]. .Iadd.oriented in a direction H o  .Iaddend.;   (b) focusing the primary .[.static.]. magnetic field .[.space by a time-independent shaping of the primary static magnetic field space.]. to provide a .Iadd.resultant magnetic field oriented in the Ho direction and having .Iaddend.a three dimensional resonance domain of selectable size .[.wherein.]. .Iadd.within which .Iaddend.the field strength .Iadd.in the direction Ho .Iaddend.is substantially uniform .Iadd.and wherein there are points in the resultant magnetic field not in the resonance domain but having the same field strength in the Ho direction, all said points being in regions of non-uniform field intensity having sufficiently large gradients so as not to generate substantial resonance signals;   (c) maintaining the configuration of the resultant field within the resonance domain during generation of a nuclear magnetic resonance signal; .Iaddend.   .[.(c).]. .Iadd.(d) .Iaddend.positioning the specimen such that the resonance domain impinges on the specimen;   .[.(d).]. .Iadd.(e) .Iaddend.directing oscillating magnetic radiation to the resonance domain such that the magnetic field orientation of the oscillating magnetic radiation is orthogonal to the magnetic field orientation of the primary .[.static.]. magnetic field to cause a nuclear magnetic resonance signal to be generated by selected nuclei within the resonance domain;   .[.(e).]. (.Iadd.f) .Iaddend.receiving the nuclear magnetic resonance signal generated; and   .[.(f).]. .Iadd.(g) .Iaddend.processing the nuclear magnetic resonance signal to determine a nuclear magnetic resonance value directly which nuclear magnetic resonance valve represents the selected nuclei extant in the resonance domain .[.impringing.]. .Iadd.impinging .Iaddend.on the specimen.   
     
     
       2. A method of detecting selected nuclei within a specimen utilizing nuclear magnetic resonance phenomenon comprising: (a) providing a .[.nonuniform.]. primary .[.static.]. magnetic field .Iadd.oriented in a direction Ho and .Iaddend.having a known field configuration with a region of uniformity where the field strength is substantially uniform;   (b) providing a .[.time-independent.]. focusing .[.static.]. magnetic field having a selectable field configuration with a region of uniformity where the field strength is substantially uniform;   (c) superimposing the .[.time-independent.]. focusing .[.static.]. magnetic field on the primary .[.static.]. magnetic field such that the respective regions of uniformity coincide to produce a resulting .[.static.]. magnetic field having a three-dimensional resonance domain located within a region where the regions of uniformity coincide, the field strength of the resulting .[.static.]. magnetic field within the resonance domain being substantially uniform .Iadd.and wherein all points in the resulting magnetic field not in the resonance domain but having the same field strength are in regions of non-uniform field intensity having sufficiently large gradients so as not to generate a nuclear resonance signal; .Iaddend.   (d) maintaining the configuration of the resulting magnetic field within the resonance domain during generation of a nuclear resonance signal;   .[.(d) selecting.]. .Iadd.(e) adjusting .Iaddend.the field configuration of the .[.time-independent.]. focusing .[.static.]. magnetic field to .[.adjust.]. .Iadd.select .Iaddend.the size of the resonance domain;   .[.(e).]. .Iadd.(f) .Iaddend.positioning the specimen such that the resonance domain impinges on the specimen;   .[.(f).]. .Iadd.(g) .Iaddend.directing oscillating magnetic radiation to the resonance domain such that the magnetic field orientation of the oscillating magnetic radiation is orthogonal to the magnetic field orientation of the resulting .[.static.]. magnetic field to cause a nuclear magnetic resonance signal to be generated;   .[.(g).]. .Iadd.(h) .Iaddend.receiving the nuclear magnetic resonance signal generated; and   .[.(h).]. .Iadd.(i) .Iaddend.processing the signal to determine a nuclear magnetic resonance value directly which nuclear magnetic resonance valve represents the selected nuclei extant in the resonance domain within the specimen.   
     
     
       3. The method according to claim 2 wherein the field configuration of the primary static magnetic field has a saddle shaped gradient with the region of uniformity at the saddle point and the focusing static magnetic field has an adjustable saddle shaped gradient with the region of uniformity at the saddle point and wherein the size of the resonance domain is adjusted by changing the gradient of the focusing static magnetic field as it approaches its saddle point. 
     
     
       4. The method according to claim 2 wherein the oscillating magnetic radiation is directed to the resonance domain on a periodic basis and further including the step of repositioning the specimen after a nuclear magnetic resonance signal has been received such that a different portion of the specimen coincides with the resonance domain whereby scanning of the specimen may be accomplished. 
     
     
       5. The method according to claim 4 wherein the specimen is moved in a planar grid pattern across a cross section of the specimen such that a grid of nuclear magnetic resonance values is obtained for the cross section of the specimen. 
     
     
       6. The method according to claim 5 further including the step of displaying the grid of nuclear resonance values to provide a visual image of the grid. 
     
     
       7. The method according to claim 2 wherein a doughnut shaped superconducting magnet is utilized for providing the primary static magnetic field space and wherein the specimen is positioned within the interior space of the doughnut shaped superconducting magnet. 
     
     
       8. The method according to claim 7 wherein field focusing coils are used to provide the focusing static magnetic field. 
     
     
       9. The method according to claim 2 wherein the specimen includes a live mammal and the nuclear magnetic values may include intensities of nuclear magnetic resonance signals received, spin-spin relaxation time, spin-lattice relaxation times, spin-mapping values, and amplitude versus frequency spectra. 
     
     
       10. The method according to claim 2 wherein the selected nuclei may be selected from P 31 , K 39 , Na 23 , H 1 , C 13 , N 15 , N 14  or O 17 . 
     
     
       11. Nuclear magnetic induction apparatus for detecting selected nuclei within a specimen comprising: (a) means for providing a .[.nonuniform.]. primary .[.static.]. magnetic field .[.space.]. .Iadd.oriented in a direction Ho; .Iaddend.   (b) means for focusing the primary .[.static.]. magnetic field .[.space by a time-independent shaping of the primary magnetic field space.]. to provide a .Iadd.resultant magnetic field oriented in the Ho direction and having a .Iaddend.three dimensional resonance domain of selectable size wherein the field strength .Iadd.in the direction Ho .Iaddend.is substantially uniform .Iadd.and wherein there are points in the resultant magnetic field is not in the resonance domain but having the same field strength in the Ho direction, all said points being in regions of non-uniform field intensity having sufficiently large gradients so as not to generate substantial resonance signals.Iaddend.;   i (.Iadd.c) means for maintaining the configuration of the resultant field within the resonance domain during generation of a nuclear magnetic resonance signal.Iaddend.;   .[.(c).]. .Iadd.(d) .Iaddend.means for positioning the specimen such that the resonance domain impinges on the specimen;   .[.(d).]. .Iadd.(e) .Iaddend.means for directing oscillating magnetic radiation to the resonance domain such that the magnetic field orientation of the oscillating magnetic radiation is orthogonal to the magnetic field orientation of the primary .[.static.]. magnetic field to cause a nuclear magnetic .Iadd.resonance .Iaddend.signal to be generated by selected nuclei within the resonance domain;   .[.(e).]. .Iadd.(f) .Iaddend.means for receiving the nuclear magnetic resonance signal generated; and   .[.(f).]. .Iadd.(g) .Iaddend.means for processing the nuclear magnetic resonance signal to determine a nuclear magnetic resonance value directly which nuclear magnetic resonance value represents the selected nuclei extant in the resonance domain impinging on the specimen.   
     
     
       12. Nuclear magnetic induction apparatus for detecting the selected nuclei within a specimen comprising: (a) means for providing a .[.nonuniform.]. primary .[.static.]. magnetic field .Iadd.oriented in a direction Ho and .Iaddend.having a known field configuration with a region of uniformity where the field strength is substantially uniform;   (b) means for providing a .[.time-independent.]. focusing .[.static.]. magnetic field .Iadd.oriented in the Ho direction .Iaddend.having a selectable field configuration with a region of uniformity where the field strength is substantially uniform;   (c) .Iadd.means for .Iaddend.superimposing the .[.time-independent.]. focusing .[.static.]. magnetic field upon the primary .[.static.]. magnetic field such that the respective regions of uniformity coincide to produce a resulting .[.static.]. magnetic field having a three dimensional resonance domain located within a region where the regions of uniformity coincide, the field strength of the resulting .[.static.]. magnetic field within the resonance domain being substantially uniform .Iadd.and wherein all points in the resulting magnetic field not in the resonance domain but having the same field strength are in regions of non-uniform field intensity having sufficiently large gradients so as not to generate resonance signals.Iaddend.;   (d) means for maintaining the configuration of the resultant field within the resonance domain during generation of a nuclear magnetic resonance signal;   .[.(d).]. .Iadd.(e) .Iaddend.means for .[.selecting.]. .Iadd.adjusting .Iaddend.the field configuration of the .[.time-independent.]. focusing .Iadd.static .Iaddend.magnetic field to .[.adjust.]. .Iadd.select .Iaddend.the size of the resonance domain;   .[.(e).]. .Iadd.(f) .Iaddend.means for positioning the specimen such that the resonance domain impinges on the specimen;   .[.(f).]. .Iadd.(g) .Iaddend.means for directing oscillating magnetic radiation to the resonance domain such that the magnetic field orientation of the oscillating magnetic radiation is orthogonal to the magnetic field orientation of the resulting magnetic field to cause a nuclear magnetic resonance signal to be generated;   .[.(g).]. .Iadd.(h) means for .Iaddend.receiving the nuclear magnetic signal generated; and   .[.(h).]. .Iadd.(i) means for .Iaddend.processing the signal to determine a nuclear magnetic resonance value directly which nuclear magnetic resonance value represents the selected nuclei extant in the resonance domain within the specimen.   
     
     
       13. The apparatus according to claim 12 wherein the means for providing oscillating magnetic radiation is actuated on a periodic basis and further includes means for repositioning the specimen with respect to the resonance domain after a nuclear magnetic resonance signal has been received such that a different portion of the specimen coincides with the resonance domain whereby scanning of the specimen may be accomplished. 
     
     
       14. The apparatus according to claim 12 wherein the means for providing a primary static magnetic field comprises a doughnut shaped superconducting magnet. 
     
     
       15. The apparatus according to claim 12 wherein the means for providing a focusing static magnetic field comprises field focusing coils.