Ultrasound-Optical Doppler Hemometer and Technique for Using the Same
According to embodiments, a sensor assembly and/or systems for ultrasound-optical measurements may provide information related to hemodynamic parameters. An ultrasound beam may be used to generate a Doppler field for optical elements of a sensor assembly. By combining information received from ultrasound and optical elements of the sensor assembly, more accurate values for hemodynamic parameters may be determined.
1 . A monitoring system comprising:
a storage device storing routines for:
receiving a signal from a photodetector;
receiving a signal from an ultrasound transducer;
determining at least one of a blood flow velocity or a red blood cell level based at least in part on the photodetector signal;
determining a blood vessel size based at least on part on the ultrasound transducer signal;
determining a physiological parameter based at least in part on the blood vessel size and one or more of the flow velocity or the red blood cell level; and
a processor capable of executing the stored routines.
2 . The system as set forth in claim 1 , wherein the physiological parameter comprises a hemoglobin value, a hematocrit value, or a blood pressure value.
3 . The system as set forth in claim 1 , comprising an emitter capable of emitting light into a tissue and generating the signal at the photodetector.
4 . The system as set forth in claim 3 , wherein the emitter and the photodetector are spaced about 2 mm to about 3 mm apart from one another.
5 . The system as set forth in claim 3 , comprising the ultrasound transducer.
6 . The system as set forth in claim 5 , wherein the ultrasound transducer is capable of being focused at a depth of less than 5 mm from a surface of the tissue.
7 . The system as set forth in claim 5 , wherein the ultrasound transducer is capable of transmitting a frequency-modulated ultrasound wave.
8 . The system as set forth in claim 5 , wherein the ultrasound transducer is spaced apart less than 2 mm from either the emitter or the photodetector.
9 . The system as set forth in claim 5 , wherein the ultrasound transducer is capable of transmitting ultrasound waves into the tissue at the same time the emitter transmits light into the tissue.
10 . A method, comprising:
receiving a signal from a photodetector;
receiving a signal from an ultrasound transducer;
determining at least one of a blood flow velocity or a red blood cell level based at least in part on the photodetector signal;
determining a blood vessel size based at least on part on the ultrasound transducer signal;
determining a physiological parameter based at least in part on the blood vessel size and one or more of the flow velocity or the red blood cell level.
11 . The method as set forth in claim 10 , wherein determining the physiological parameter comprises determining a hematocrit value.
12 . The method as set forth in claim 10 , wherein determining the physiological parameter comprises determining a blood pressure value.
13 . A method comprising:
emitting photons into a blood vessel of a patient's tissue;
focusing an ultrasonic beam into the blood vessel so that a portion of the photons in the blood vessel experience a Doppler shift;
generating a signal related to detected photons at a detector; and
processing the signal to isolate a signal component representative of photons that have undergone a Doppler shift of a magnitude greater than a predetermined threshold; and
analyzing the isolated signal component to determine one or more properties of the blood vessel.
14 . The method as set forth in claim 13 , comparing the isolated component to a reference signal comprising a different isolated signal component representative of photons that do not traverse the blood vessel.
15 . The method as set forth in claim 14 , comprising emitting photons into the tissue away from the direction of flow of the blood vessel to generate the reference signal.
16 . The method as set forth in claim 13 , wherein focusing an ultrasonic beam comprises focusing a frequency-modulated ultrasonic beam.
17 . The method as set forth in claim 13 , comprising analyzing a speckle pattern of the photons detected at the detector to determine information about the blood vessel.
18 . The method as set forth in claim 15 , comprising determining a vessel diameter based at least in part on the speckle pattern.
19 . The method as set forth in claim 13 , comprising determining a concentration of red blood cells based at least in part on the detected photons.
20 . The method as set forth in claim 13 , comprising determining a concentration of velocity of red blood cells based at least in part on the detected photons.