MR-tracking based on magnetic signature selective excitation
The present invention relates to a MR tracking method and device. More specifically, the present invention relates to a magnetic resonance tracking method and device, using a magnetic-susceptible object. A magnetic iso-surface induced by the object is selectively excited with a corresponding frequency offset; the magnetic iso-surface is then projected on three axes of a k-space, from which projections the spatial position of the object is calculated.
1. A method for magnetic resonance tracking comprising:
providing a magnetic-susceptible object in an MRI system, wherein said object is magnetically saturated and forms a magnetic dipole;
selecting a predetermined frequency offset corresponding to a desired magnetic iso-surface about the object;
generating the predetermined frequency in the MRI system to selectively excite an induced magnetic iso-surface about the object having a shape corresponding to the magnetic dipole and a size larger than the object;
applying a readout gradient in the MRI system and projecting the excited induced magnetic iso-surface on three axes G1, G2 and G3 in k-space to obtain three projection lines representing the position of the excited induced magnetic iso-surface on the three axes; and
calculating the position of the object from the three projections.
2. A method for magnetic resonance tracking as defined in claim 1 , wherein the three axes G1, G2 and G3 are orthogonal.
3. A method for magnetic resonance tracking as defined in claim 1 , further comprising mounting the magnetic-susceptible object on a medical instrument.
4. A method for magnetic resonance tracking as defined in claim 1 , wherein the magnetic-susceptible object includes a coil, and the method further comprises installing the coil on a medical instrument.
5. A method for magnetic resonance tracking as defined in claim 1 , wherein the object includes an untethered microdevice, the method further comprising propelling the untethered microdevice using magnetic resonance propulsion.
6. A method for magnetic resonance tracking as defined in claim 1 , further comprising obtaining positions of the object at different times by repeating said selectively exciting, projecting and calculating at a given tracking frequency.
7. A method for magnetic resonance tracking as defined in claim 6 , wherein obtaining the positions of the object is performed in real time.
8. A method for magnetic resonance tracking as defined in claim 1 , wherein calculating the position of the object comprises applying a correlation function on the three projections on the three axes G1, G2 and G3 of a line in k-space.
9. A method for magnetic resonance tracking as defined in claim 1 , wherein calculating the position of the object further includes locating the absolute position of the object on a 3D system of reference.
10. A method for magnetic resonance tracking as defined in claim 1 , further comprising storing the position of the object calculated.
11. A method for magnetic resonance tracking as defined in claim 1 , further comprising displaying the calculated position of the object.