WO1994029741B1

WO1994029741B1 - Focal neurographic magnetic resonance imaging system

Info

Publication number: WO1994029741B1
Application number: PCT/US1994/006337
Authority: WO
Filing date: 1994-06-06
Publication date: 1995-02-02
Anticipated expiration: 1995-12-04

Abstract

A focal magnetic resonance imaging system (20) for generating images of neural structures such as nerves. The system (20) includes a control and analysis system (22), a polarizing system (24), and splint-coil assembly (26). The splint-coil assembly (26) includes a splint (28) and various magnetic and electromagnetic coils (32, 40, 42) incorporated within the splint (28). The splint (28) conforms snugly to a patient's body part, e.g., limb, so that the coils (32, 40, 42) are fixed with respect to the patient's body part. The splint-coil assembly (26) can be positioned independently of a main field generated by the polarizing system (24), and a stabilization apparatus (156) is included for adjustably securing the position of the splint-coil assembly (26) during imaging. A focal magnet assembly (60) that can serve as the polarizing system (24) is also provided. Further provided is a method of operating the control and analysis system (22) to consistently generate images depicting the fascicular structure of nerves (100) by ensuring that image gradients (108) are oriented orthogonal to the nerves (100).

Claims

AMENDED CLAIMS

[received by the International Bureau on 5 December 1994 (05.12.94); original claims unchanged; new claims 19-32 added (3 pages)]

(d) processing said resonant response to create an image of said nerve.

16. The method of Claim 15, further including the steps of:

(a) exposing the nerve to an initial magnetic resonance imaging sequence of magnetic and electromagnetic fields;

(b) sensing an initial resonant response of said nerve to said initial magnetic resonance imaging sequence;

(c) analyzing said initial resonant response to determine an orientation of said nerve; and (d) using said determined nerve orientation in said step of creating an alignment between the nerve and an image plane.

17. The method of Claim 16, wherein said initial magnetic resonance imaging sequence is a nerve enhancing sequence.

18. A stabilization apparatus for stabilizing a splint-coil assembly used in a magnetic resonance imaging system, said stabilization apparatus including:

(a) a support frame; and

(b) a plurality of extendible rods each coupled at one end to said support frame and at another end to a splint-coil assembly.

19. A method of using magnetic resonance imaging to generate an image of a nerve, including the steps of:

(a) exposing a region of a subject including a nerve to imaging magnetic field gradients;

(b) exposing the region additionally to a double-lobed magnetic gradient pulse having a strength not greater than 1 Gauss per centimeter; (c) exposing the region to a rf excitation field;

(d) sensing a resonant response of the region, wherein said sensing is performed at a time sufficiently spaced after said step of exposing the region to a rf excitation field so as to provide a long effective echo time TE; and

(e) processing said resonant response to create an image of said nerve in the region.

20. The method of Claim 19, wherein said imaging magnetic field gradients generates an image plane, and wherein said method further comprises the step of establishing a spatial relationship between said image plane and said nerve in which said image plane is substantially orthogonal to the longitudinal axis of said nerve.

21. The method of Claim 19, further including the step of exposing the region to a sequence of electromagnetic fields that suppresses, from said image, the contribution of fat in the region.

22. The method of Claim 19, wherein said steps of exposing the region to an rf excitation field and sensing said resonant response are timed to provide an effective echo time TE of at least 80 milliseconds.

23. The method of Claim 19, wherein said steps of exposing the region to an rf excitation field and sensing said resonant response are timed to provide an effective echo time TE of at least 100 milliseconds.

24. The method of Claim 19, wherein said double-lobed magnetic gradient pulse has a strength within the range of O.l tθ 1 Gauss per centimeter.

25. The method of Claim 19, wherein said rf excitation field includes a series of 180° pulses forming an echo train after said double-lobed magnetic gradient pulse, and further wherein said rf excitation field includes an additional 180° pulse timed to occur between the lobes of said double-lobed magnetic gradient pulse.

26. The method of Claim 19, wherein said double-lobed magnetic gradient pulse is applied along a first axis oriented substantially orthogonal to the longitudinal axis of said nerve, and wherein said method further comprises the step of exposing the region to a second double-lobed magnetic gradient pulse that is oriented substantially orthogonal to said first axis and the longitudinal axis of said nerve.

27. The method of Claim 19, wherein said double-lobed magnetic gradient pulse suppresses, from said image, flowing blood in the region and artifacts due to the flowing blood.

28. The method of Claim 19, wherein said steps (a) - (d) are executed in a manner to form a Fast Spin Echo (FSE) pulse sequence. 29. The method of Claim 20, further including the step of exposing the region to a sequence of electromagnetic fields that suppresses, from said image, the contribution of fat in the region.

30. The method of Claim 29, wherein said double-lobed magnetic gradient pulse has a strength within the range of 0.1 to 1 Gauss per centimeter.

31. The method of Claim 30, wherein said steps of exposing the region to an rf excitation field and sensing said resonant response are timed to provide an effective echo time TE of at least 80 milliseconds.

32. The method of Claim 31, wherein said steps (a) - (d) are executed in a manner to form a Fast Spin Echo (FSE) pulse sequence.

D SHEET (ARTICLE)