Subslicing for remotely positioned MRI

A method for constructing an image of a slice of in situ biological tissue using spin echo signals from nuclei in each of a plurality of subslices of the tissue, the method comprising the steps of:

• determining a value for n, n being an integer having a value on the order of T.sub.1 /T.sub.2, where T.sub.1 is the spin lattice relaxation time of the nuclei being imaged and T.sub.2 is the spin-spin relaxation time of the nuclei being imaged;
• defining a measurement region in a nonhomogeneous magnetic field generated by a remotely positionable MRI device;
• positioning said measurement region over said slice of tissue to be imaged with said measurement surface,
• dividing said slice of tissue to be imaged into n subslices;
• establishing a particular Larmor frequency for each said subslice of tissue;
• selectively irradiating each said subslice of tissue with its respective said particular Larmor frequency to obtain spin echo signals from nuclei in each said subslice to create n subslice images;
• and
• combining said n subslice images to construct an image of said slice of tissue.

A device for constructing an image of a slice of in situ biological tissue using spin echo signals from nuclei in each of a plurality of subslices of the tissue which comprises:

• a magnet for generating a nonhomogeneous magnetic field, said nonhomogeneous magnetic field having a defined measurement region therein, and said magnet being remotely moveable to position said measurement region over the slice of tissue to be imaged;
• means for dividing said slice into n sequentially layered subslices with each said subslice having a particular Larmor frequency, n being an integer having a value less than T.sub.1 /T.sub.2, where T.sub.1 is the spin lattice relaxation time of the nuclei being imaged and T.sub.2 is the spin-spin relaxation time of the nuclei being imaged;
• means for selectively irradiating each of said n subslices of the tissue with its respective particular Larmor frequency to obtain spin echo signals from nuclei in each said subslice to create n subslice images;
• and
• means for combining said n subslice images to construct an image of said slice of tissue.

A method for imaging a slice of in situ biological tissue which comprises the steps of:

• defining a measurement region in a nonhomogeneous magnetic field generated by a remotely positionable MRI device;
• positioning said measurement region over the slice of tissue to be imaged;
• dividing said slice into n sequentially layered subslices, n being approximately equal to T.sub.1 /T.sub.2 where T.sub.1 is the spin lattice relaxation time of nuclei in said tissue in said subslice and T.sub.2 is the spin-spin relaxation time of said nuclei;
• irradiating one said subslice with an excitation pulse, said pulse having a different particular frequency for each said subslice, to tilt said nuclei of said tissue in said subslice;
• refocussing said tilted nuclei with a train of 180.degree. pulses, each said 180.degree. pulse having a particular frequency for said subslice, to generate recordable spin echoes;
• recording said spin echoes from said tilted nuclei to create a subslice image;
• repeating said irradiating step, said refocussing step and said recording step to create a subslice image for each said subslice;
• and
• reconstructing said plurality of subslice images to create a composite image for said slice of tissue.

A method for imaging a slice of in situ biological tissue which comprises the steps of:

• defining a measurement region in a nonhomogeneous magnetic field generated by a remotely positionable MRI device;
• positioning said measurement region over the slice of tissue to be imaged;
• dividing said slice into n sequentially layered subslices, n being no greater than T.sub.1 /T.sub.2 where T.sub.1 is the spin lattice relaxation time of nuclei of said tissue in said subslice and T.sub.2 is the spin-spin relaxation time of said nuclei;
• irradiating one said subslice with an excitation pulse, said pulse having a particular frequency for said subslice, to tilt nuclei of tissue in said subslice;
• refocussing said tilted nuclei with a train of 180.degree. pulses, each said 180.degree. pulse having a particular frequency for said subslice, to generate recordable spin echoes;
• and
• recording said spin echoes from said tilted nuclei to create a subslice image.