# US 12,004,843 B2 · Frequency domain diffuse optical spectroscopy device and optical detector calibration method

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- Number: US 12,004,843 B2
- Document ID: US12004843B2
- Status: Granted
- Kind: B2
- Application number: 17/045,070
- Filed: 2019-04-05
- Published: 2021-06-03
- Granted: 2024-06-11
- Earliest claimed: 2018-04-05
- Assignees: University of Notre Dame du Lac
- Applicants: University of Notre Dame Du Lac
- Inventors: Roy A. Stillwell; Vincent James Kitsmiller; Thomas D. O'Sullivan
- Web page: https://patentgrep.com/patent/US12004843B2

## CPC

- A61B 5/0075: {by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy (A61B5/0071 takes precedence)}
- A61B 5/0013: {Medical image data (A61B1/00011, A61B6/56, A61B8/56 take precedence)}
- A61B 5/7228: {Signal modulation applied to the input signal sent to patient or subject; Demodulation to recover the physiological signal}
- A61B 5/742: {using visual displays (displays for heart-related electrical signals, e.g. ECG, A61B5/339)}
- G01N 21/255: {Details, e.g. use of specially adapted sources, lighting or optical systems}
- G01N 21/359: using near infrared light
- G01N 21/474: {Details of optical heads therefor, e.g. using optical fibres}
- A61B 2560/0214: of power generation or supply
- A61B 2560/0223: of calibration, e.g. protocols for calibrating sensors
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A frequency domain diffuse optical spectroscopy (FD-DOS) device and calibration method. The FD-DOS device includes a radio frequency signal generator, a driver, a light source, a silicon photomultiplier, an analog to digital conversion circuit, and an electronic processing circuit. The light source is configured to generate modulated light at a plurality of different wavelengths and modulation frequencies. The silicon photomultiplier is configured to generate analog detection signals indicative of detected optical signals. The analog to digital conversion circuit is configured to generate digital sample values from the analog detection signals. The electronic processing circuit is configured to determine absorption values and scattering values based on the digital sample values. The electronic processing circuit is also configured to determine concentration values based on the absorption values and the scattering values. The electronic processing circuit is further configured to determine an image stream based on the concentration values.

## Claims

### Claim 1

A frequency domain diffuse optical spectroscopy device, comprising:
a housing sized to be handheld, wherein a light source is positioned at a first end of the housing;
a radio frequency signal generator;
a driver coupled to the radio frequency signal generator;
the light source coupled to the driver and configured to generate modulated light at a plurality of different wavelengths and a plurality of different modulation frequencies, the light source for emitting the modulated light at a sample;
a silicon photomultiplier configured to generate analog detection signals indicative of amplitude and phase of radio frequency modulation components of detected optical signals emanating from the sample in response to the modulated light;
an analog to digital conversion circuit (ADC) coupled to the radio frequency signal generator and coupled to the silicon photomultiplier, wherein the ADC is configured to generate digital sample values from the analog detection signals; and
an electronic processing circuit (EPC) coupled to the analog to digital conversion circuit and configured to
determine absorption values and scattering values based on the digital sample values,
determine concentration values based on the absorption values and the scattering values, and
determine an image stream based on the concentration values.

### Claim 2 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, wherein the EPC is further configured to
determine first amplitude data and phase data from the digital sample values, adjust the first amplitude data based on an inverse response of the silicon photomultiplier to determine second amplitude data, and
determine the absorption values and the scattering values based on the second amplitude data and the phase data.

### Claim 3 (depends on 2)

The frequency domain diffuse optical spectroscopy device of claim 2, wherein the EPC is further configured to determine the first amplitude data and the phase data from the digital sample values using a Goertzel algorithm.

### Claim 4 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, further comprising one or more orientation sensors configured to generate orientation signals, wherein the EPC is further configured to correlate the orientation signals to the image stream.

### Claim 5 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, further comprising a communication module coupled to the EPC and configured to transmit the image stream.

### Claim 6 (depends on 1)

A frequency domain diffuse optical spectroscopy system, comprising:
the frequency domain diffuse optical spectroscopy device of claim 1; and
a display device configured to receive and display the image stream.

### Claim 7 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, wherein the EPC is further configured such that a frame rate of the image stream is greater than thirty hertz.

### Claim 8 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, wherein the EPC includes a field programmable gate array.

### Claim 9 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, wherein the analog to digital conversion circuit is configured to undersample the analog detection signals.

### Claim 10 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, further comprising a battery module for power generation.

### Claim 11 (depends on 10)

The frequency domain diffuse optical spectroscopy device of claim 10, wherein the radio frequency signal generator, the driver, the silicon photomultiplier, the analog to digital conversion circuit, the EPC, and the battery module are mounted in the housing.

### Claim 12 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, wherein the radio frequency signal generator is configured to generate radio frequency modulation signals, and wherein the radio frequency signal generator is further configured to increase power of the radio frequency modulation signals as a function of frequency.

### Claim 13 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, wherein signals from the silicon photomultiplier to the ADC are not amplified, and wherein the ADC generates digital reference values from radio frequency modulation signals.

### Claim 14 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, wherein the driver comprises a plurality of DC bias drivers which drives the light source and modulates light at a plurality of different wavelengths and a plurality of different modulation frequencies.

### Claim 15 (depends on 14)

The frequency domain diffuse optical spectroscopy device of claim 14, wherein the light source comprises multiple laser diodes each configured to emit at a different wavelength, wherein each of the multiple laser diodes are coupled to a separate DC bias driver of the plurality of DC bias drivers.

### Claim 16 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, wherein the EPC comprises a field programmable gate array and a memory, and wherein the EPC is configured to receive digital sample values and digital references values from the ADC.

### Claim 17 (depends on 1)

The frequency domain diffuse optical spectroscopy device of claim 1, wherein the EPC is further configured to:
process digital sample values into a frequency domain representation using a Fourier transform.

### Claim 18 (depends on 17)

The frequency domain diffuse optical spectroscopy device of claim 17, wherein the EPC uses a full fast Fourier transform (FFT) to determine the amplitude and phase responses from the digital sample values.

### Claim 19 (depends on 17)

The frequency domain diffuse optical spectroscopy device of claim 17, wherein the EPC uses a Goertzel algorithm to determine the amplitude and phase responses from the digital sample values faster than with a full FFT.