PROCESS OF ENHANCING NITROGEN VACANCY (NV) CENTER SPIN EXCITATION IN HYPERPOLARIZATION APPLICATION

Abstract

A process for enhancing polarization of .sup.13C for subsequence MRI imaging, the process comprising providing a suspension consisting of a first plurality of particulates having NV centers and a second plurality of particulates for providing internal reflection of light with wavelength for the excitement of NV centers and .sup.13C; and applying light, magnetic field and microwave to said suspension, such that the NV centers are polarized and such that the electron spins of the VN centres are transferred to .sup.13C atoms upon the Rabi frequency of the NV centres matching the Larmor frequency of .sup.13C; wherein the particulates of the second plurality reflect and transmit the light through the suspension such that said light is distributed through said suspension.

Claims

1.-19. (canceled)

20. A suspension for enhanced polarization of .sup.13C and MRI imaging, said suspension comprising of a first plurality of particulates having NV centers and a second plurality of particulates for providing internal reflection of light with wavelength for the excitement of NV centers and .sup.13C.

21. The suspension according to claim 20, wherein first plurality of particulates is comprised of nanodiamonds, and wherein the nanodiamonds are sized in the range from 30 nm to 999 nm.

22. (canceled)

23. The suspension according to claim 2, wherein the second plurality of particulates is comprised of minidiamonds or the second plurality of particulates is comprised of microdiamonds or the second plurality of particulates is comprised of quartz or the second plurality of particulates is comprised of glass.

24.-27. (canceled)

28. The suspension according to claim 20, wherein the second plurality of particulates is comprised of two or more of minidiamonds, microdiamonds, quartz or glass.

29.-31. (canceled)

32. A process using refractive material as optical repeaters for dispersing light into and throughout an opaque powder, for enhancing spin excitation of the powder in a hyperpolarization application.

33. The process according to claim 32, wherein the opaque powder is nanodiamonds or microdiamonds, and wherein the nanodiamonds or microdiamonds is blended with other chemicals.

34. (canceled)

35. The process according to claim 32, wherein the optical repeaters are provided by microdiamonds, minidiamonds or crushed quartz, glass or the like, or combinations thereof.

36. A process for enhancing polarization of .sup.13C for subsequence MRI imaging, the process comprising: providing a suspension according to claim 20; and applying light, magnetic field and microwave field to said suspension, such that the NV centers are polarized and such that the electron spins of the NV centres are transferred to .sup.13C atoms upon the Rabi frequency of the NV centres matching the Larmor frequency of .sup.13C; wherein the particulates of the second plurality reflect and transmit the light through the suspension such that said light is distributed through said suspension.

37. The process according to claim 36, wherein said light is applied by an optical laser.

38. The process according to claim 36, wherein .sup.13C for subsequence MRI imaging is derived from the first plurality of particulates.

39. The process according to claim 36, wherein .sup.13C for subsequence MRI imaging is provided by way of a further chemical composition which is present within said suspension. and wherein the further chemical composition which is present within said suspension is a pyruvate.

40. The process according to claim 39, wherein after the enhancing polarization of .sup.13C the first plurality of particulates and the second plurality of particulates are filtered out of the suspension, leaving the hyperpolarized further chemical composition for injection into the human body for MRI imaging.

41. The process according to claim 40, wherein after the enhancing polarization of .sup.13C the first plurality of particulates and the second plurality of particulates are filtered out of the suspension, leaving hyperpolarized pyruvate for injection into the human body for MRI imaging.

42. The process according to claim 36, wherein the microwave is a pulsed microwave field.

43. The process according to claim 36, wherein the light is provided by a pulse laser.

44. The process according to claim 36, wherein the light is pulsed light.

45. The process according to claim 36, wherein the light is monochromatic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order that a more precise understanding of the above-recited invention can be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. The drawings presented herein may not be drawn to scale and any reference to dimensions in the drawings or the following description is specific to the embodiments disclosed.

[0048] FIG. 1 shows a schematic representation of a system for use in the present invention, for the for stimulation of the electron spins of NV centres in nanodiamonds;

[0049] FIG. 2 shows a schematic representation of an enlarged view of the specimen or sample tube of FIG. 1;

[0050] FIG. 3a shows an enlarged view of the feature around 291 mT in the process of the present invention; and

[0051] FIG. 3b shows the enhancement of polarisation (signal) in which the full spectrum of FIG. 3a is shown.

DETAILED DESCRIPTION OF THE DRAWINGS

[0052] The present inventors have identified shortcomings of the problems with the prior art, and have provided a system and process which is more consistent and reliable, and overcomes the problems of the prior art.

Problems of Prior Art Identified by Present Inventors

[0053] The present invention relates to hyperpolarization of .sup.13C by the hyperpolarization of the electron spins of nitrogen-vacancy (NV) centres in nanodiamonds (NDs), and transfer to electron spin to .sup.13C atoms.

[0054] The present inventors have identified that as nanodiamonds are optically opaque, optical pumping for providing excitation to the electron spins of NV centres in nanodiamonds is not efficient.

[0055] In view of this observation and phenomena, the present inventors have sought improve the efficiency of optical hyperpolarization of nanodiamonds for .sup.13C.

[0056] The present inventors have thus provided a method to increase the efficiency of optical hyperpolarization of nanodiamonds for .sup.13C.

[0057] Such a method of the present invention enhances dispersion of laser light into opaque nanodiamond powder.

Invention Background Theory

[0058] Diamonds contain Nitrogen Vacancy (NV) centres with one negative charge captured from the surroundings. The diamond NV-centres are paramagnetic with spin S=1 with a large zero field splitting, with D=2.87 GHz wherein D is the energy difference between electron spin state of zero-field splitting of NV center, the energy range is in microwave band.

[0059] Laser can be used for optical pumping, providing excitation, to the electron spins of NV centres in nanodiamonds.

[0060] The electron spins of the NC centres can then be transferred to .sup.13C atoms when the Rabi frequency of the NV centres match the Larmor frequency of .sup.13C.

[0061] However, the present inventors have noted and identified that nanodiamonds typically contain a lot of different impurities other than NV centres. For example, different kinds of nitrogen centres, surface attached amorphized carbon for example exist.

[0062] Therefore, nanodiamonds are essentially opaque, and the present inventors have noted that only the NV centres on surface of a powder of nanodiamonds can be efficiently excited by the laser.

Present Invention

[0063] In accordance with the present invention, a method has been proposed and developed to enhance the efficiency of optical pumping for stimulation of the electron spins of NV centres in nanodiamonds.

[0064] The present invention achieves such enhanced efficiency of optical pumping by introducing “optical repeaters” within a nanodiamond powder, by providing a plurality of such “optical repeaters” dispersed throughout the nanodiamond powder.

[0065] The present inventors have provided such “optical repeaters” by introducing particulates for providing internal reflection of light with wavelength for the excitement of NV centers and .sup.13C.

[0066] Such particulates can be cut and polished minidiamonds for example, which have sizes around 1 mm, which are introduced into the powder of nanodiamonds. It has been found that the high refractive index (n=2.4) of diamonds causes a lot of total internal reflection inside the minidiamonds.

[0067] Alternatively, quartz or glass for example can be used as such optical repeaters to internally reflect light in the invention.

[0068] Further, a mixture of two or more different materials can be used as the optical repeaters, such as two or more of a plurality of minidiamonds, quartz or glass could be used to provide optical repeaters in accordance with the present invention.

[0069] Therefore, in accordance with the present invention, each “optical repeater” suspended within the nanodiamond powder can disperse laser light into different directions and reach another “optical repeater”, thus allowing the added minidiamonds, for example, to act as optical repeaters to advantageously transmit laser light deep into the nanodiamond powder.

[0070] Referring to FIG. 1, there is shown a system 100 for use in the present invention, for the stimulation of the electron spins of NV centres in nanodiamonds. As is shown, the system 100 includes a magnet 110 for providing a magnetic field, a resonator 120 for applying a microwave field, a laser light source 130 for providing optical pumping which may introduce light via an optical fibre, and a specimen tube 140 for containing a suspension of nanodiamonds and “optical repeaters”.

[0071] Any kinds of resonator may be used, such as pulsed or continuous microwave resonators.

[0072] Light can be provided by a laser for example. The light may be pulsed light. Preferably monochromatic light is used. Although the light source is preferably a laser light source, other light sources may be utilised in alternate configurations and embodiments.

[0073] Referring now to FIG. 2, there is shown an enlarged view of the specimen or sample tube 200 which is depicted as item 140 of FIG. 1.

[0074] Within the sample tube 200 is an embodiment of a suspension consisting of a first plurality of particulates 210 having NV centers, whereby the first plurality of particulates is typically a plurality of nanodiamonds.

[0075] The suspension further comprises and a second plurality of particulates 220 for providing internal reflection of light with wavelength for the excitement of NV centers and .sup.13C, which are to function as “optical repeaters” as described in accordance with the invention.

[0076] As shown, in the present embodiment, the second plurality of particulates 220 are “minidiamonds”. However alternatively in other embodiments, quartz or glass for example can be used to internally reflect light and be used as “optical repeaters”. In alternate embodiments, the “optical repeaters” may be a mixture of two or more different types of particulates.

[0077] Light is applied by optical fibre 230, and a magnetic field and microwave field are also applied to the suspension in the sample tube 200, such that the NV centers of the first plurality of particulates, which are nanodiamonds in the present embodiment, are polarized and the electron spins of the NV centres of the nanodiamonds will then be transferred to .sup.13C atoms when the Rabi frequency of the NV centres match the Larmor frequency of .sup.13C.

[0078] In accordance with invention and as described above, the particulates of the second plurality reflect and transmit the light through the suspension such that said light is distributed through the suspension, thus acting as optical repeaters.

[0079] Hence, in accordance with the present invention more nanodiamonds can absorb laser light, and thus the present invention provides for more efficient optical pumping.

[0080] The .sup.13C for subsequence MRI imaging, as is described further below, may be derived from the first plurality of particulates. Alternatively, the suspension in tube 200 may further comprising a further chemical composition as a source of .sup.13C. The further chemical, for example, may be a pyruvate as a source of .sup.13C.

[0081] Referring to FIGS. 3a and 3b, as is shown, enhancement of NV centre by optical pumping utilizing light at a wavelength of 532 nm, using a 220 mW fibre optic positioned 4 mm above sample and the microwave signal being a pulsed microwave field, in an arrangement of FIG. 2, is now shown.

[0082] The suspension used was 5 milligram (mg) ND sample with diamond ‘rocks’ to help scatter laser light into the opaque ND powder.

[0083] Now referring to FIG. 3a, there is shown an enlarged view of the feature around 291 mT, with line 1 indicating “laser on”, and line 2 indicating “laser off”, with signal intensity shown on the vertical axis in arbitrary units (au).

[0084] As is shown in FIG. 3b, the enhancement of polarisation (signal) is x 14.7 in which the full spectrum is shown.

[0085] Thus, optical pumping with 532 nm laser and fibre optic with 220 mW output at the tip was shown to be effective. The polarisation of the triplet state (S=1) of diamond NV center was enhanced up to a factor of 15 with optical pumping in this arrangement in accordance with the present invention.

[0086] In accordance with the invention, as discussed above, other materials with high refractive indices and transparent to light will also work as “optical repeaters” such as quartz or glass.

[0087] One important requirement of the optical repeaters is those materials cannot have electron paramagnetic resonance (EPR) signal in the detection range of nanodiamonds. Otherwise, the EPR signal of the nanodiamonds will be overlapped and interfered with. Quartz crushed from an EPR tube for example, which doesn't have any signal to EPR, can also serve in this process of the present invention.

[0088] The size of nanodiamonds, when used as the first plurality of particulates, is preferably in the range of 30 nm-999 nm. Microdiamonds, when used as the second plurality of particulates with sizes of 1 μm-100 μm can also be used as the “optical repeaters”.

[0089] In an embodiment of the present invention, within the specimen tube preferably, .sup.13C enriched pyruvate, nanodiamonds and minidiamonds are put and mixed together, for subsequent hyperpolarisation during the hyperpolarization process.

[0090] Then, after the hyperpolarization process, the nanodiamonds and minidiamonds are filtered out of the mixture, leaving behind hyperpolarized pyruvate which can be subsequently injected to the human body for the purpose of MRI imaging.

[0091] Within the present specification, the term “suspension” is used and understood to mean that the second plurality of particulates is mixed within and suspended or distributed within the first plurality of particulates. As such, the first plurality may be considered dispersion medium through which the particles of the second plurality of particulates is dispersed throughout and are essentially considered suspended within the first plurality of particulates.