Non-invasive imaging of biological tissue

Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation

Reexamination Certificate

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C600S323000, C600S328000, C600S431000, C600S476000

Reexamination Certificate

active

06397099

ABSTRACT:

The invention provides proof in principle of the practicality for medical purposes of imaging body tissue, and in particular, neural tissue, especially the brain, using spectrophotometric techniques.
Certain prior work has produced low resolution shadowgrams of the exterior of the cortex, lacking edges or defined contours.
We have shown that by employing an array of ports for a set of single source, single detector pairs, and by implementing the system to acquire a sequence of data sets, distinct difference image data sets can be realized that are useful in diagnosis and treatment, e.g. on a real time basis, with relatively low expense. Blood volume and oxygenation, for instance, can be directly imaged.
We have demonstrated in brain models and human brains, that an optical imaging device can localize the activated area of the human brain. We have produced defined images that show that single functions of the brain such as observing an object (visual), moving a small part of the body (sensory motor) and thinking (cognition) appear to activate only an area as small as 0.5 to 1 cm of the brain cortex. The place of activation observed from the produced image was where it was expected. In the case of side-by-side source and detector pair, between which the probability pattern of photons takes a banana shape, the theoretical resolution and sensitive depth depends on the source-detector distance (half of the distance). By selection of the source-detector distance, a resolution of the image as good as 1.25 cm has been obtained. Imaging of white brain matter to selected depths is realized by increasing the spacing up to 7 cm.
By acquiring the images quickly (2 to 8 seconds for a data set, within about 20 seconds for a distinct difference image data set) we have demonstrated the practicability of optical imaging as a tool for the fields of psychiatry, psychology, neurology, patho-physiology, surgery, etc. Direct contact of the input and output ports with the subject lead to favorable signal-to-noise ratio that leads to good image resolution. In particular, direct contact of an array of miniature sources (lamps or diodes) and detectors has provided ample signal.
By the ability to obtain images in a short span of time (within a few minutes, typically within less than a minute), the field of real-time noninvasive and nonharmful optical monitoring of tissue at a depth from the surface is shown to be within practical grasp.
Using optical techniques avoids tissue damage, can be done inexpensively, and can provide other advantages compared to MRI, FMRI, P.E.T., E.G.G. mapping and the like.
For instance, the source and detector module are readily affixed to the head or other body part, as by a helmet, and alleviate a serious problem of artifacts related to movement of the subject relative to the detector during the time of taking an image that occurs with other imaging techniques.
The work reported here leads to diagnosis of impairment due to trauma, stroke, Alzheimer's disease, and various patho-physiological manifestations. Furthermore the invention, together with current knowledge in the field, shows practicality of the technique in wide fields of utility, encompassing the detection and imaging of local perturbation or change related broadly to mental function, physiological function and biochemical function.
It is shown that light sources that provide no safety hazard, at relatively low cost can be usefully employed in true imaging. By employing difference measurements, the uncertainties normally limiting continuous wave spectroscopy (CWS) to trend indications are avoided. The greater information content of phase modulation and time resolved spectroscopy leads to even more informative images.
According to one important aspect of the invention, an optical system is provided for in vivo, non-invasive imaging of tissue change comprising an optical module including an array of input ports and detection ports located in a selected geometrical pattern to provide a multiplicity of arrayed single source, single detector pairs engaged directly with the subject, a spectrophotometer including a light source means constructed to introduce electromagnetic radiation of visible or infra-red wavelength into the examined tissue successively at the input ports, the wavelength being sensitive to a constituent of the imaged tissue, detector means constructed to detect, at the detection ports, radiation of the selected wavelength that has migrated in the tissue from respective input ports, and a processor receiving signals of the detected radiation from the detector means, and constructed and arranged to create a defined spatial image of the tissue by effectively producing from signals from the multiplicity of arrayed single source, single detector pairs, a succession of data sets representing, from a selected view, a succession of spatial images of the tissue, and an image data set related to differences between data of the successive data sets.
In another important aspect of the invention, an optical system is provided for in vivo, non-invasive functional neuroimaging of tissue comprising a stimulator constructed to stimulate a selected functional activity of neural tissue of interest, an optical module including an array of input ports and detection ports located in a selected geometrical pattern to provide a multiplicity of arrayed single source, single detector pairs engaged directly with the subject, a spectrophotometer including light source means constructed to introduce electromagnetic radiation of visible or infra-red wavelength into the examined neural tissue successively at the input ports, the wavelength being sensitive to a tissue constituent associated with a physiological response of the imaged functional activity, detector means constructed to detect, at the detection ports, radiation of the selected wavelength that has migrated in the stimulated neural tissue from respective input ports, and a processor receiving signals of the detected radiation from the detector means, and constructed and arranged to create a defined spatial image of the functional activity of neural tissue by effectively producing from the signals from the multiplicity of arrayed single source, single detector pairs, a first data set representing, from a selected view, a spatial image of the neural tissue at rest, a second data set representing, from the same selected view, a spatial image of the neural tissue during stimulation, and a functional image data set that is related to the differences between the first and second data sets, over the sets.
Preferred embodiments of these aspects of the inventions have one or more of the following features.
The optical module is constructed to maintain a selected distance between the input and detection ports for the respective source-detector pairs during the production of the first and second data sets, the distance being selected according to the tissue depth desired to be imaged.
The optical module or an associated set of the modules is constructed to take readings at different depths to produce 3D data sets from which an image date set may be produced.
The processor is adapted to produce the image data set by implementing an optical tomography algorithm.
The optical tomography algorithm preferably employs factors related to determined probability distribution of photons attributable to the scattering character of the tissue being imaged.
The optical system is constructed to form the image data set from a part of the head. In particular embodiments the optical system is constructed to form the functional image data set from below the surface region of the cortex.
The stimulator is constructed to stimulate the visual cortex, the cognitive cortex, the sensory motor cortex, or spinal tissue.
In various embodiments the stimulator is constructed to deliver electrical signals to selected tissue, apply an electrical field to selected tissue, or deliver magnetic signals to selected tissue.
In various embodiments the image set is related to at least one of the group consisting of b

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