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In re NeuroGrafix ('360) Patent Litigation

United States District Court, D. Massachusetts

August 19, 2016

In re NEUROGRAFIX ('360) PATENT LITIGATION

          MEMORANDUM AND ORDER ON CLAIM CONSTRUCTION

          RICHARD G. STEARNS UNITED STATES DISTRICT JUDGE

         This is the second wave in a Multidistrict Litigation (MDL) involving U.S. Patent No. 5, 560, 360 (the ’360 patent), directed to “[a] neurography system [] for generating diagnostically useful images of neural tissue [] employing a modified magnetic resonance imaging [(MRI)] system.” ’360 patent, Abstract. In 2012, plaintiffs NeuroGrafix, Neurography Institute Medical Associates, Inc., Image-Based Surgicenter Corporation, and Dr. Aaron G. Filler, launched an armada of lawsuits against MRI equipment manufacturers and university and hospital end-users, accusing them of infringing the ’360 patent. With one exception, the nine cases originally consolidated by the MDL Panel in this district for pretrial proceedings resolved before reaching claim construction.[1] In 2015, plaintiffs filed six new lawsuits. These too were consolidated with this MDL proceeding.[2] Before the court are the parties’ competing briefs on claim construction. Pursuant to Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996), the court received tutorials in the underlying technology and heard argument on August 18, 2016.

         THE ’360 PATENT

         The ’360 patent, entitled “Image Neurography and Diffusion Anisotropy Imaging, ” was issued on October 1, 1996. It lists as its inventors Aaron G. Filler, [3] Jay S. Tsuruda, Todd L. Richards, and Franklyn A. Howe. The ’360 patent sets out 66 claims.

         The ’360 patent discloses methods and apparatus for generating “diagnostically useful” images of peripheral nerves (the term includes peripheral, autonomic, and cranial nerves) using MRI technology. ’360 patent, Abstract. These nerves

commonly travel through and along bone, muscle, lymphatics, tendons, ligaments, intermuscular septa, collections of fatty tissues, air and fluid spaces, veins, arteries, joints, skin, mucous membranes and other tissues. The relatively small size of peripheral nerves, as well as their close proximity to other tissue of comparable size and shape, makes them difficult to locate and identify.

Id. col. 1, ll. 32-38. The complex structure of neural plexus (where bundles of nerve fibers “may join together, separate, rejoin, intermix, and resegregate, forming intricate three dimensional patterns”) also complicates the examination of peripheral nerves. Id. col. 1, ll. 39-51.

         Prior to the invention of the ’360 patent, MRI technology had been used to image peripheral nerves with only limited success. By way of a brief background,

MRI involves the exposure of tissue to a variety of different magnetic and radio-frequency ([RF]) electromagnetic fields. The response of the specimen’s atomic nuclei to the fields is then processed to produce an image of the specimen.

Id. col. 2, ll. 5-9. The patient is first exposed to a polarizing magnetic field that causes hydrogen protons’ axes to align themselves with the field. When additional energy in the form of an RF electromagnetic wave pulse is applied, the protons change the alignment of their axes. When the RF pulse is switched off, the protons reorient their alignment with the magnetic field, causing them to emit detectable resonance (also in the form of radio waves). Receiver coils detect the radio signal, which is converted by a computer using Fourier analysis into a visual image. Various RF pulse sequences can be used to emphasize or suppress different types of tissues within the body.

         Prior to the ’360 patent, MRI was used in conjunction with injectable contrast agents to image peripheral nerves. This technique requires two-part contrast agents - one part to promote neural uptake of the dye, and the other to enhance the imageability of the nerve. The technique has several limitations. In addition to being invasive, only a single nerve or nerve group can be imaged at one time, and the contrast agent typically reduces the intensity of the imaged nerve.

         MRI had also been used to successfully image non-peripheral white matter nerve tracts in the brain without the use of contrast agents. White matter nerve tracts, in comparison to the surrounding gray matter, exhibit a relatively high diffusion anisotropy, that is, water mobility in the direction along the white matter tracts is relatively high, while water mobility perpendicular to the tracts is l0w.

[T]his process involves the use of a pair of field gradient pulses (hereinafter referred to as diffusion gradients), oriented perpendicular and parallel to the white matter tracts to be imaged. . . . [G]iven the anisotropic nature of the tracts, water will diffuse freely along a tract, but is restricted in it[s] motion perpendicular to the tract. When the diffusion gradient is aligned with the tract there is thus a greater reduction in signal than when the diffusion gradient is aligned perpendicular to the tract. Because this phenomenon is not exhibited by the surrounding gray matter tissue, the white matter tracts can be identified.

Id. col. 5, ll. 19-39.

         This technique, however, does not transfer easily to the imaging of peripheral nerves even though these nerves are also diffusionally anisotropic. Peripheral nerves are considerably smaller than white matter tracts and their return signals are too weak for effective imaging. In addition to fat (which is isotropic and distinguishable from the nerves when imaged), peripheral nerves are also surrounded by muscle, which is also diffusionally anisotropic and not easily distinguished.

         To solve the problem of effectively imaging peripheral nerves without the use of contrast agents, the inventors discovered

novel ways of assembling complex pulse sequences, wherein even though the simple components of the sequence decrease the signal-to-noise ratio of nerve or decrease the signal strength of nerve relative to other tissues, the fully assembled complex sequence actually results in the nerve signal being more intense than any other tissue.

Id. col. 6, ll. 39-45. More specifically, “[t]he combined use of fat suppression [pulses] and diffusional weighting has [] been found to be extremely effective in providing the desired nerve image enhancement” and has the “synergistic benefit . . . [of] an actual increase in neural signal anisotropy . . . with the conspicuity of the neural component of the image increasing by roughly 250 percent when the fat component is removed.” Id. col. 22, ll. 32-35; 58-64.

         The patent describes two nerve imaging approaches depending on the diffusion-weighted gradients used. Subtraction neurography is appropriate where the diffusion-weighted gradients match the nerve axes.

[I]n one currently preferred embodiment, the analysis involves the application of pulsed magnetic field gradients to the polarizing field in two or more directions to produce images in which the peripheral nerve is enhanced or suppressed, depending upon the “diffusion weighting” resulting from the particular pulsed gradient axis chosen. Discrimination of water diffusion anisotropy is then achieved by subtracting the suppressed image from the enhanced image, in the manner described in greater detail below, producing an image depicting only the peripheral nerve.
Most preferably, the magnetic field gradients are applied in mutually substantially orthogonal directions. For example, with gradients approximately perpendicular and parallel to the axis of the peripheral nerve at the particular point being imaged, the parallel gradient image can be subtracted from the perpendicular gradient image to produce the desired “nerve only” image.

Id. col. 15, ll. 40-57. However, where the gradients do not align with the nerve(s) to be imaged, vector processing is used to obtain the image.

[I]f the axis of the peripheral nerve is not known, or if many nerves having different axes are being imaged, the neurography system must employ a system of gradient orientations suitable for imaging nerve having substantially any axial alignment. For example . . . a full three-dimensional vector analysis can be used to characterize the diffusion coefficient and provide a nerve image by construction based upon a fixed arrangement of diffusion weighting gradients.

Id. col. 15, l. 63 - col. 16, l. 4.

         Claim 36 is a representative method claim.

         36. A method of utilizing magnetic resonance to determine the shape and position of a structure, said method including the steps of:

(a) exposing a region to a magnetic polarizing field including a predetermined arrangement of diffusionweighted gradients, the region including a selected structure that exhibits diffusion anisotropy and other structures that do not exhibit diffusion anisotropy;
(b) exposing the region to an electromagnetic excitation field;
(c) for each of said diffusion-weighted gradients, sensing a resonant response of the region to the excitation field and the polarizing field including the diffusionweighted gradient and producing an output indicative of the resonant response; and
(d) vector processing said outputs to generate data representative of anisotropic diffusion exhibited by said selected structure in the region, regardless of the alignment of said diffusion-weighted gradients with respect to the orientation of said selected structure; and
(e) processing said data representative of anisotropic diffusion to generate a data set describing the shape and position of said selected structure in the region, said data set distinguishing said selected structure from other structures in the region that do not exhibit diffusion anisotropy.

         Claim 54 is a representative apparatus claim.

         54. A magnetic resonance apparatus for determining data representative of the diffusion anisotropy exhibited by a structure, said apparatus including:

(a) excitation and output arrangement means for exposing a region to a suppression sequence of electromagnetic fields that suppresses the electromagnetic responsiveness of structures in the region that do not exhibit diffusion anisotropy, so as to increase the apparent diffusion anisotropy of structures in the region that exhibit diffusion anisotropy, said suppression sequence of electromagnetic fields not including diffusionweighted magnetic gradients;
(b) polarizing field source means positioned near said excitation and output arrangement means for exposing the region to a predetermined arrangement of diffusionweighted magnetic gradients chosen to:
i) emphasize a selected structure in the region exhibiting diffusion anisotropy in a particular direction; and
ii) suppress other structures in the region exhibiting diffusion anisotropy in directions different from said particular direction, said excitation and output arrangement means further for sensing a resonant response of the region to the diffusion-weighted gradient and producing an output indicative of the resonant response, for each of said diffusionweighted gradients; and
(c) processor means coupled to said excitation and output arrangement means for processing said outputs to generate data representative of the diffusion anisotropy of the selected structure.
The parties dispute the construction of 9 claims terms. [4]
• “processing said data representative of anisotropic diffusion to generate a data set describing the shape and position of said selected structure in the region, said data set distinguishing said selected structure from other structures in the region that do not exhibit diffusion anisotropy” (claim 36)
• “processing said outputs to generate data representative of the diffusion anisotropy of the selected ...

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