Apparatus and method for non-invasive and minimally-invasive sensing of venous oxygen saturation and pH levels
First Claim
1. An apparatus, comprising:
- an ultrasound transducer configured to provide an ultrasound radiation pressure field to modulate a target area within a body at a modulation frequency;
an optical source configured to generate one or more pulses of radiation containing temporally correlated groups of photons, wherein the photons in each group are characterized by two or more different wavelengths, the two or more different wavelengths being selected to have specific interaction with a target chromophore, and wherein the two or more different wavelengths being selected to have substantially similar scattering cross-sections and anisotropy parameters in the target and its surroundings;
launch optics configured to transmit the pulses of radiation from the optical source to the target area being modulated by the radiation pressure field and to inject the pulses of radiation into the body in proximity to the target area;
an optical detector configured to detect in temporal coincidence photon groups at each of the different wavelengths that are backscattered from the target area, the optical detector using time-gated amplification or time-gated background-free amplification of the return signal so as to exclude photons which could not by virtue of their arrival time have interacted with the radiation-pressure-modulated target; and
a filter coupled to the optical detector, the filter being configured to select those detected photon groups with a modulation component at the same frequency as the modulation frequency of the radiation pressure modulation field, or at a harmonic of the modulation frequency.
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Abstract
Medical diagnostic apparatus and methods are disclosed. Ultrasound radiation pressure selectively modulates a target area within a body. One or more pulses of radiation containing temporally correlated groups of photons are generated. The photons are characterized by two or more different wavelengths that are selected to have specific interaction with a target chromophore. The two or more different wavelengths are also selected to have substantially similar scattering cross-sections and anisotropy parameters in the target and its surroundings. The pulses of radiation are injected into the body proximate the target area being modulated by the radiation pressure field. Photon groups at each of the different wavelengths that are backscattered from the target area are detected in temporal coincidence. Time-gated background-free amplification of the return signal is used to exclude photons which could not by virtue of their arrival time have interacted with the radiation-pressure-modulated target. Photon groups are selected with a modulation component at the modulation frequency of the radiation pressure modulation field, or at a harmonic of the modulation frequency. From the arrival rate of the detected temporally correlated photon pairs or multiplets, chemical information about the target area, such as an oxygenation or pH level can be inferred. Cardiac output may be computed from measurements of venous and/or arterial oxygenation using this technique.
269 Citations
40 Claims
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1. An apparatus, comprising:
an ultrasound transducer configured to provide an ultrasound radiation pressure field to modulate a target area within a body at a modulation frequency;
an optical source configured to generate one or more pulses of radiation containing temporally correlated groups of photons, wherein the photons in each group are characterized by two or more different wavelengths, the two or more different wavelengths being selected to have specific interaction with a target chromophore, and wherein the two or more different wavelengths being selected to have substantially similar scattering cross-sections and anisotropy parameters in the target and its surroundings;
launch optics configured to transmit the pulses of radiation from the optical source to the target area being modulated by the radiation pressure field and to inject the pulses of radiation into the body in proximity to the target area;
an optical detector configured to detect in temporal coincidence photon groups at each of the different wavelengths that are backscattered from the target area, the optical detector using time-gated amplification or time-gated background-free amplification of the return signal so as to exclude photons which could not by virtue of their arrival time have interacted with the radiation-pressure-modulated target; and
a filter coupled to the optical detector, the filter being configured to select those detected photon groups with a modulation component at the same frequency as the modulation frequency of the radiation pressure modulation field, or at a harmonic of the modulation frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
Specification