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Broadband solid-state spectroscopy illuminator and method

Broadband solid-state spectroscopy illuminator and method description/claims

This application is a continuation-in-part of U.S. patent application Ser. No. 11/451,681 filed on Jun. 12, 2006, relating to the detection of local tissue ischemia, which is a continuation-in-part of U.S. patent application Ser. No. 10/651,541 filed on Aug. 29, 2003, now U.S. Pat. No. 7,062,306; which is a continuation of U.S. patent application Ser. No. 10/119,998 filed on Apr. 9, 2002, now U.S. Pat. No. 6,711,426, the disclosures of all of which are incorporated in full by reference.

The present invention relates to devices and methods for providing, simultaneously or near-simultaneously, spectroscopic analysis from more than one somatic site, and more particularly relates to the determination of a difference-weighted analysis wherein the near-simultaneous determination of two (or more) spectroscopically-determined somatic oxygenation saturation values is performed in a manner allowing for the direct and near-simultaneous comparison of these two (or more) somatic saturation values, by direct mutual inspection or computational means, in order to provide synergistic and added medical value above that provided by each individual value considered separately. In another aspect, the present invention provides real-time spectroscopic analysis of in-vivo tissue perfusion from more than one somatic site that is sensitive to local tissue ischemia and insensitive to regional arterial and venous oxygenation.

Ischemia, defined as a reduction in blood flow, can be due to local causes (e.g., due to vascular occlusion or increased metabolism such as a tumor), global causes (e.g., due to body-wide reduced blood flow from reduced cardiac output), or both. However, discriminating the source of changes in tissue oxygenation can be difficult, considering values at each site individually.

Collecting spectroscopic values from two different sites (e.g., organ versus organ, or two sites within the same organ), and considering or analyzing these together as a difference-weighted measure, can add medical value. For example, a growing difference between a stable and normal cheek tissue oximetry, and a falling colon tissue oximetry, points to a colon-centered pathology rather than to a global cause such as impending cardiac failure. Similarly, a widening difference-weighted measurement between a pulse and tissue oximeter (estimates of arterial and venous saturation, respectively), helps pinpoint the source of the change as cardiovascular pathology, rather than increasing pulmonary failure. Last, a widening spatial gradient, such as a difference-weighted value between a pair of sensors that is scanned over a single breast, reduces the noise from organ-wide regional gradients and highlights local inhomogeneities associated with tumors such as breast cancer. Each of these three exemplary difference-weighted values add medical value above what the absolute values, considered alone and separately, would merit.

The noninvasive spectroscopic monitoring of hemoglobin saturation in vivo is known in the art. The great majority of such known devices and methods monitor only at one site (U.S. Pat. No. 6,662,033, WO/2003/003914); such devices do not allow for mutual or computational determination of a difference-weighted value. A few devices and methods in the art teach monitoring at more than one sites. For example, U.S. Pat. No. 6,615,065 describes dual monitoring of the brain, wherein the two sensors are applied to a head of the test subject, taking advantage of the unique hemispheric and non-somatic structure of the brain, to monitor two mutually separate regions within a brain of the test subject, with the two values being simultaneously displayed to allow a user to observationally and mutually compare the two. No computational comparison is taught. Further, the '065 patent teaches that it is the unique, hemispheric structure of the brain that allows the device of '065 to operate, and thus the device would not be suitable for somatic monitoring. In contrast, clinicians recognize that the non-brain (the “somatic”) regional of the body constitute an advantageous early warning system not present in the brain, and are some of the first key tissues to be shut down by the body during impending failure of oxygen delivery to tissue. Similarly, U.S. Patent Application Publication no. 2006/0105319 describes the measuring of two values, arterial and venous. However, again no computational comparison is taught, and one of these values is determined through invasive blood sample, not from spectrophotometric measurement of tissue itself.

All of the above devices are limited to being single measures of oxygenation, are limited or optimized by design or omission to non-somatic tissue, and/or do not allow direct and near-simultaneous mutual comparison or computational processing of at least two somatic values obtained by spectrophotometric measures.

None of the prior devices or methods allow for a difference-weighted spectroscopy that facilitates simultaneous or near-simultaneous comparison of spectroscopic values from two somatic regions or sites by inspection or computation. Such a system has hot been previously described, nor successfully commercialized. Thus, further developments are needed.

The inventors have discovered that certain diseases (vascular ischemia, cancer) are frequently localized, and by comparing at least two somatic values—either multiple sites or times—within the body, resulting in a more sensitive detection of such local conditions.

A salient feature of the present invention is that the detection and treatment of diseases such as somatic ischemia or cancer is aided by use of at least two measurements—either by multiple somatic sensors monitoring at least two nearby or distant regions or by dual measurements made by a single sensor over space or time—allowing a direct comparison of these different spectroscopic values by mutual inspection or computation.

In one aspect, the present invention provides a somatic monitoring apparatus comprising: a first and second sensor, each configured to generate, based upon light produced and/or detected by each sensor, first and second somatic output signals that are a function of each somatic target site, and a difference unit for comparing said first and second signals, and for generating a difference-weighted output signal based upon this comparison.

In other embodiments, this dual-sensor somatic tissue ischemia monitoring apparatus generates an output signal that is a function of the presence or degree of local tissue ischemia or cancer at a first and second target site, with a display unit configured to display or allow near or substantially simultaneous comparison of said signals at the two target sites. This can be expanded to N sensors, with comparisons of a first through Nth output signals via a difference unit configured to compare at least two of said first through Nth somatic signals, and to generate a difference-weighted output signal based upon said comparison.

In yet another aspect, the difference measurement can be generated using a single sensor moved through space (allowing comparison of two sites with one detector), or used over time (such as reporting changes with time), or even measuring both arterial and tissue oximetry measurements using one probe (allow arteriovenous differences to be detected).

In embodiments of the present invention, we provide both apparatus and methods for the dual, N, and signal sensor approaches. In one embodiment of the invention there is provided a device with dual somatic spectroscopic monitoring sites, including two solid state broadband light sources and sensors for generating, delivering, and detecting light from at least two target sites, for the purpose of allowing a direct comparison of the spectroscopic values by mutual inspection or computation, thereby adding medical value. In another example, the system uses dual phosphor-coated white LED's to produce continuous, broadband, visible light from 400 nm to 700 nm at two somatic sites. Scattered light returning from each target is detected by a wavelength-sensitive detector, and two signals, one from each site, is generated using this wavelength-sensitive information via spectroscopic analysis. The values are displayed or computed in a manner to allow direct comparison of the spectroscopic values by mutual inspection or computation. Systems incorporating the difference-weighted somatic spectroscopic system arid medical methods of use are described.

Some embodiments the present invention further provide a device for detecting local ischemia in a tissue at one or more tissue sites, characterized in that the device is configured such that wavelengths of light are selectively emitted, and the selective wavelengths are substantially transmitted through capillaries in tissue while being substantially absorbed by arterial and venous vessels in the tissue.

As will be understood by the detailed description below, the somatic monitoring apparatus provides one or more advantages. For example, by way of illustration and in no way limiting the invention, one advantage is that the system and method may be constructed to detect ischemia, cancer, or changes in perfusion.

Another exemplary advantage is that a physician or surgeon can obtain improved real-time feedback regarding local tissue ischemia, cancer, or perfusion in high-risk patients, and to respond accordingly.

Another exemplary advantage is that ischemia (low delivery of oxygen to tissues) can be differentiated from pulmonary-induced hypoxemia (low arterial saturation).

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