Small Magnet and RF Coil for Magnetic Resonance Relaxometry

• US 20100308822A1
• Filed: 11/06/2008
• Published: 12/09/2010
• Est. Priority Date: 11/06/2007
• Status: Active Grant

• Current Assignee: T2 Biosystems, Inc
• Original Assignee: T2 Biosystems, Inc
• Inventors: Lowery, Thomas J., Prado, Pablo J.
• Granted Patent: US 8,519,708 B2
• Time in Patent Office: Days
• US Class Current: 324/309
• CPC Class Codes: G01N 24/08 by using nuclear magnetic resonance G01N24/12 takes precedence
• CPC Class Codes: G01R 33/243 Spatial mapping of the polarizing magnetic field
• CPC Class Codes: G01R 33/302 Miniaturized sample handling arrangements for sampling small quantities, e.g. flow-through microfluidic NMR chips
• CPC Class Codes: G01R 33/307 specially adapted for moving the sample relative to the MR system, e.g. spinning mechanisms, flow cells or means for positioning the sample inside a spectrometer
• CPC Class Codes: G01R 33/34053 Solenoid coils; Toroidal coils
• CPC Class Codes: G01R 33/3806 Open magnet assemblies for improved access to the sample, e.g. C-type or U-type magnets
• CPC Class Codes: G01R 33/383 using permanent magnets
• CPC Class Codes: G01R 33/44 using nuclear magnetic resonance [NMR] G01R33/24, G01R33/62 take precedence
• CPC Class Codes: G01R 33/448 Relaxometry, i.e. quantification of relaxation times or spin density G01R33/50 takes precedence
• CPC Class Codes: G01R 33/465 applied to biological material, e.g. in vitro testing

Abstract

Small and inexpensive probeheads for use in nuclear magnetic resonance systems, in particular, magnetic resonance relaxometry systems are provided. The design of the magnet-radiofrequency coil configurations within the probeheads is guided by an excitation bandwidth associated with radiofrequency pulses to be applied to a sample.

Claims

1. A small probehead for use in a portable magnetic resonance relaxometer, comprising:

(a) at least one magnet or magnetic field generator providing a magnetic field;

(b) a space capable of accommodating a sample volume having an associated excitable volume; and

(c) a radiofrequency coil having an associated detection volume, the radiofrequency coil being adapted and positioned such that its detection volume overlaps at least partly with the excitable volume;

wherein the magnetic field provided is inhomogeneous and the space accommodating the sample volume and the radiofrequency coil are adapted and positioned according to a radiofrequency pulse bandwidth optimized for a magnetic field distribution corresponding to the position of the sample volume; and

wherein the probehead is optimized to obtain relaxometry parameters from a sample contained in the detection volume.

2. The probehead of claim 1, wherein the magnetic resonance relaxometer comprises a further radiofrequency coil, a radiofrequency pulse being provided by the further radiofrequency coil.

3. The probehead of claim 1, a radiofrequency pulse being provided by the radiofrequency coil.

4. The probehead of claim 1, further comprising a housing, wherein the at least one magnet or magnetic field generator and the radiofrequency coil is attached to the housing.

5. The probehead of claim 1, wherein the detection volume includes between about 10 percent and about 100 percent of the excitable volume.

13. The probehead of claim 1, wherein the probehead further comprises a sample volume and the sample volume includes between about 10 percent and about 100 percent of the excitable volume.

20. The probehead of claim 1, comprising two permanent magnets providing the magnetic field.

21. The probehead of claim 1, wherein (i) the radiofrequency coil is part of a radiofrequency circuit, the radiofrequency circuit comprising a capacitor;

(ii) the radiofrequency coil is wound to enclose a coil volume having the shape of about cylindrical shape and the associated detection volume is effectively the volume of the cylindrical shape; and

(iii) the radiofrequency coil is positioned to have the coil volume include between about 80 percent and about 100% of the excitable volume.

26. The probehead of claim 2, wherein the further radiofrequency coil is positioned outside of the probehead.

27. The probehead of claim 1, wherein the radiofrequency pulse length is between about 0.4 microseconds and about 10 microseconds.

29. The probehead of claim 1, wherein the at least one magnet or magnetic field generator are shaped and/or configured to provide the magnetic field in a gap, and wherein the radiofrequency coil is positioned partly or completely within the gap.

31. The probehead of claim 1, wherein the magnetic field is provided by two permanent magnets, the south pole surface of one of the permanent magnets opposing the north pole surface of the other permanent magnet to form a gap and to provide the magnetic field in the gap, the radiofrequency coil being positioned partly or completely within the gap and wherein the magnetic field has magnetic field strengths within the gap of less than about 2 Tesla.

37. The probehead of claim 1, wherein the magnetic field has magnetic field strengths of less than about 2 Tesla.

40. The probehead of claim 1, further comprising at least one capacitor, the at least one capacitor and the radiofrequency coil being part of a radiofrequency circuit.

41. The probehead of claim 1, wherein each of the at least one magnet or magnetic field generator is in any dimension less than about one two inches.

43. The probehead of claim 1, wherein the radiofrequency coil is wound to enclose a volume of less than about 500 μ

l.

51. The probehead of claim 1, wherein the detection volume is about 1.6 μ

l and the sample volume is about 0.4 μ

l.

6-12. -12. (canceled)

14-19. -19. (canceled)

22-25. -25. (canceled)

28. (canceled)

30. (canceled)

32-36. -36. (canceled)

38-39. -39. (canceled)

42. (canceled)

44-50. -50. (canceled)

52. A small probehead for use in a portable magnetic resonance relaxometer, comprising:

(a) two magnets or two magnetic field generators attached to a yoke, the south pole surface of one of the magnets or magnetic field generators opposing the north pole surface of the other magnet or magnetic field generator to form a gap between the magnets or magnetic field generators and to provide a magnetic field in the gap;

(b) a space capable of accommodating a sample volume having an associated excitable volume; and

(c) a radiofrequency coil within the gap, the radiofrequency coil having an associated detection volume, and being adapted to emit a radiofrequency pulse with a pulse length, and being positioned such that its detection volume overlaps at least partly with the excitable volume within the gap;

wherein the magnetic field provided is inhomogeneous and the space accommodating the sample volume and the radiofrequency coil are adapted and positioned according to a radiofrequency pulse bandwidth optimized for the magnetic field distribution corresponding to the position of the sample volume; and

wherein the probehead is optimized to obtain relaxometry parameters from a sample contained in the sample volume.

53. A method for preparing a small probehead for use in a portable magnetic resonance relaxometer, the method comprising the steps of:

(a) providing at least one magnet or magnetic field generator providing a magnetic field;

(b) providing a radiofrequency coil;

(c) positioning the radiofrequency coil to have its associated detection volume overlap at least partly with an excitable volume associated with a sample volume;

(d) positioning a space capable of accommodating a sample volume having an associated excitable volume; and

(e) adapting the space for the sample volume and the radiofrequency coil according to a radiofrequency pulse bandwidth optimized for the magnetic field distribution corresponding to the position of the sample volume;

wherein the probehead is optimized to obtain relaxometry parameters from a sample contained in the sample volume.

54-93. -93. (canceled)

94. A method of preparing a small probehead for use in a portable magnetic resonance relaxometer, the method comprising the steps of:

(a) attaching two magnets or two magnetic field generators to a yoke such that the south pole surface of one of the magnets or magnetic field generators opposes the north pole surface of the other magnet or magnetic field generator to form a gap between the magnets or magnetic field generators and to provide a magnetic field in the gap;

(b) positioning a space capable of accommodating a sample volume having an associated excitable volume; and

(c) positioning a radiofrequency coil within the gap, the radiofrequency coil having an associated detection volume and being adapted to emit a radiofrequency pulse with a pulse length, the radiofrequency coil being positioned and designed to have the detection volume at least partly overlap with an excitable volume within the gap;

wherein the probehead is optimized to obtain relaxometry parameters from a sample contained in the sample volume.