Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-11-16
2003-02-25
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S476000, C600S310000, C600S323000, C600S334000, C356S041000
Reexamination Certificate
active
06526309
ABSTRACT:
BACKGROUND OF THE INVENTION
Continuous wave (CW) spectrophotometers have been widely used to determine in vivo concentration of an optically absorbing pigment (e.g., hemoglobin, oxyhemoglobin) in biological tissue. The CW spectrophotometers, for example, in pulse oximetry introduce light into a finger or the ear lobe to measure the light attenuation and then evaluate the concentration based on the Beer Lambert equation or modified Beer Lambert absorbance equation. The Beer Lambert equation (1) describes the relationship between the concentration of an absorbent constituent (C), the extinction coefficient (&egr;), the photon migration pathlength <L>, and the attenuated light intensity (I/I
o
).
log
[
I
/
I
0
]
⟨
L
⟩
=
∑
ε
i
C
i
(
1
)
However, direct application of the Beer Lambert equation poses several problems. Since the tissue structure and physiology vary significantly, the optical pathlength of migrating photons also varies significantly and can not be simply determined from geometrical position of a source and detector. In addition, the photon migration pathlength itself is a function of the relative concentration of absorbing constituents. As a result, the pathlength through an organ with high blood hemoglobin concentration, for example, will be different from the same with a low blood hemoglobin concentration. Furthermore, the pathlength is frequently dependent upon the wavelength of the light since the absorption coefficient of many tissue constituents is wavelength dependent. One solution to this problem is to determine &egr;, C, and <L> at the same time, but this is not possible with the pulse oximeters known previously.
Furthermore, for quantitative measurement of tissue of a small volume (e.g., a finger) photon escape introduces a significant error since the photons escaped from the tissue are counted as absorbed. Other errors may occur due to irregular coupling of light to the examined tissue or varying relative geometry of the input and detection ports.
The time resolved (TRS-pulse) and phase modulation (PMS) spectrophotometers can measure the average pathlength of migrating photons directly, but the proper quantitation of the time resolved or frequency resolved spectra can be performed only when the spectra are collected at a relatively large source-detector separation. This separation is difficult to achieve for a small volume of tissue such as the earlobe, a finger or a biopsy tissue.
Therefore, there is a need for a optical coupler used with a spectrophotometric system and method that quantitatively examines a relatively small volume of biological tissue.
SUMMARY OF THE INVENTION
The invention features a spectrophotometric system for examination of a relatively small volume of biological tissue of interest using visible or infra-red radiation.
According to one aspect of the invention, a spectrophotometric system for examination of a relatively small object of interest (e.g., biological tissue, organic or inorganic substance in a solid, liquid or gaseous state) using visible or infra-red radiation introduced to a path passing through the object. The. system includes a spectrophotometer with an optical input port adapted to introduce radiation into the object and an optical detection port adapted to detect radiation that has migrated through a path in the object, photon escape preventing means arranged around the relatively small object of interest and adapted to limit escape of the introduced photons outside the object, and processing means adapted to determine an optical property of the object based on the changes between the introduced and the detected radiation.
According to another aspect of the invention, a system for examination of a relatively small volume of biological tissue of interest using visible or infra-red radiation includes a spectrophotometer with a light source adapted to introduce radiation at an optical input port, a detector adapted to detect radiation that has migrated through a path from the input port to an optical detection port, and a processor adapted to evaluate changes between the introduced and the detected radiation. The system also includes an optical medium of a relatively large volume, forming photon preventing means, having selectable scattering and absorptive properties, positioning means adapted to locate the biological tissue of interest into the migration path to create a tissue-medium optical path, the optical medium substantially limiting escape of photons from the tissue-medium optical path, and processing means adapted to determine a physiological property of the tissue based on the detected optical property of the tissue-medium optical path and the scattering or absorptive properties of the optical medium.
Preferred embodiments of these aspects of the invention include one or more of the following features.
The photon escape preventing means include an optical medium of a selectable optical property surrounding the object. The selectable optical property is an absorption or scattering coefficient.
The photon escape preventing means include an optical medium surrounding the object; the medium has at least one optical property substantially matched to the optical property of the object.
The spectrophotometer is a continuous wave spectrophotometer (CWS) as described in PCT applications WO 92/20273 and PCT/US95/15666, a phase modulation spectroscopic unit (PMS) as described in U.S. Pat. Nos. 4,972,331, 5,187,672, or a PCT application WO 94/21173, time resolved spectroscopic (TRS) unit as described in U.S. Pat. Nos. 5,119,815 or 5,386,827 or a PCT application WO 94/22361, or a phased array system as described in WO 93/25145, all of which are incorporated by reference as if set forth in their entireties herein.
The determined physiological property is the hemoglobin saturation, the concentration of an enzyme or the concentration of a tissue substance such as glucose.
The system performs a single measurement or a continuous, time-dependent monitoring of the selected physiological property.
The above-described system operates by introducing into the object, surrounded by the photon escape preventing means, electromagnetic radiation of a selected wavelength and detecting radiation that has migrated in the object from the input port to the optical detection port. The system determines an optical property of the object based on the changes between the introduced and the detected radiation. In addition, different photon escape preventing means having a surrounding optical medium with the optical property comparable to the optical property of the object may be selected. Then, the system measures again the optical property of the object. The measurements may be repeated iteratively until the optical property of the surrounding medium is substantially matched to the optical property of the object.
According to another important aspect, the invention is an optical coupling system for non-invasively monitoring a region of living tissue. The coupling system includes an excitation (input) port positionable at the tissue and adapted to introduce optical radiation into the monitored tissue, a first light guide defining an excitation channel for conveying the radiation from a source to the excitation port, and a detection port, positionable at the tissue, adapted to receive radiation that has migrated in the monitored tissue from the excitation port to the detection port. The detection port has a detection area larger than a input area of the excitation port. Connected to the detection port is a detecting light guide, for conveying the radiation from the detection port to an optical detector. The coupling system also includes optical matching fluid contained within a flexible optically transparent bag and disposed partially around the monitored tissue and the excitation and detection ports.
Preferred embodiments of this aspect of the invention includes one or more of the following features.
The optical coupling system may include multiple excitation (input) ports positio
Fish & Richardson P.C.
Lateef Marvin M.
Non-Invasive Technology Inc.
Pass Barry
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