Systems and methods for dynamic imaging of tissue using digital optical tomography

Abstract

A methods for imaging tissue using diffuse optical tomography with digital detection includes directing at the tissue a plurality of amplitude modulated optical signals from a plurality of optical signal sources illuminating the tissue at a plurality of locations; detecting a resulting plurality of attenuated optical signals exiting the tissue to obtain a plurality of analog signals containing diffuse optical tomographic information; converting the analog signals into digital signals; recovering the tomographic information from the digital signals using a digital signal processor-based detection module that performs digital detection, wherein the detection module includes a master digital signal processing subsystem and at least one slave digital signal processing subsystem that processes at least a portion of the digital signals and the master digital signal processing subsystem controls the at least one slave digital signal processing subsystem; and transmitting the recovered tomographic information in digital form to a host computer.

1 - 51 . (canceled) 
     
     
         52 . A method for imaging tissue using diffuse optical tomography with digital detection, the method comprising:
 directing at the tissue a plurality of amplitude modulated optical signals from a plurality of optical signal sources illuminating the tissue at a plurality of locations;   detecting a resulting plurality of attenuated optical signals exiting the tissue to obtain a plurality of analog signals containing diffuse optical tomographic information;   at the time of the directing and detecting, applying a stimulus to the tissue;   converting the analog signals into digital signals using an analog-to-digital converter;   recovering the tomographic information from the digital signals using a digital signal processor-based detection module that performs digital detection by multiplying the digital signals by corresponding in-phase reference signals to obtain in-phase signal components, the corresponding in-phase reference signals having the corresponding frequencies;   multiplying the digital signals by corresponding quadrature reference signals to obtain quadrature signal components, the quadrature reference signal having the corresponding frequencies;   passing the in-phase signal components through an averaging filter;   passing the quadrature signal components through the averaging filter;   computing signal amplitudes based on the filtered in-phase signal components and the filtered quadrature signal components, the signal amplitudes being representative of the tomographic information; and   outputting the demodulated signal amplitudes.   
     
     
         53 . The method of  claim 52 , wherein the amplitude modulated optical signals comprise optical signals at a plurality of wavelengths. 
     
     
         54 . The method of  claim 53 , wherein the optical signals are time and frequency multiplexed. 
     
     
         55 . The method of  claim 54 , wherein an optical signal of a first wavelength and an optical signal of a second wavelength are amplitude-modulated at a first frequency and a second frequency, respectively, at a first time, and an optical signal of a third wavelength and an optical signal of a fourth wavelength are amplitude-modulated at the first frequency and the second frequency, respectively, at a second time. 
     
     
         56 . The method of  claim 55 , wherein the analog signals are amplified by programmable gain amplifiers controlled by the programmable logic devices. 
     
     
         57 . The method of  claim 52 , wherein the tissue comprises breast tissue. 
     
     
         58 . The method of  claim 57 , wherein a plurality of amplitude modulated optical signals is directed at both breasts simultaneously. 
     
     
         59 . The method of  claim 52 , wherein the tissue comprises brain tissue. 
     
     
         60 . The method of  claim 59 , wherein a plurality of amplitude modulated optical signals is directed at both brain hemispheres simultaneously. 
     
     
         61 . The method of  claim 52 , wherein the tissue comprises extremity tissues. 
     
     
         62 . The method of  claim 61 , wherein the extremity tissues include two legs and the plurality of amplitude modulated optical signals is directed at both legs simultaneously. 
     
     
         63 . The method of  claim 52 , wherein the stimulus is applied by having the patient perform the Valsalva maneuver. 
     
     
         64 . The method of  claim 52 , wherein the stimulus is applied by applying a mechanical pressure to the tissue. 
     
     
         65 . The method of  claim 52 , wherein the stimulus is applied by having the patient breathe a determined concentration of oxygen. 
     
     
         66 . A system for imaging tissue using diffuse optical tomography with digital detection, the method comprising:
 a light delivery subsystem configured to direct at the tissue a plurality of amplitude modulated optical signals from a plurality of optical signal sources illuminating the tissue at a plurality of locations;   a light detection subsystem configured to detect a resulting plurality of attenuated optical signals exiting the tissue to obtain a plurality of analog signals containing diffuse optical tomographic information;   a tissue stimulation element adapted to, at the time of the directing and detecting, apply a stimulus to the tissue;   an analog-to-digital converter connected to receive analog signals from the light detection subsystem and convert the analog signals into digital signals;   a processor that receives the digital signals and recovers tomographic information from the digital signals using a digital signal processor-based detection module that performs digital detection by:
 multiplying the digital signals by corresponding in-phase reference signals to obtain in-phase signal components, the corresponding in-phase reference signals having the corresponding frequencies; 
 multiplying the digital signals by corresponding quadrature reference signals to obtain quadrature signal components, the quadrature reference signal having the corresponding frequencies; 
 passing the in-phase signal components through an averaging filter; 
 passing the quadrature signal components through the averaging filter; 
 computing signal amplitudes based on the filtered in-phase signal components and the filtered quadrature signal components, the signal amplitudes being representative of the tomographic information; and 
 outputting the demodulated signal amplitudes. 
   
     
     
         67 . The system of  claim 66 , wherein the amplitude modulated optical signals comprise optical signals at a plurality of wavelengths. 
     
     
         68 . The system of  claim 67 , wherein the optical signals are time and frequency multiplexed. 
     
     
         69 . The system of  claim 68 , wherein an optical signal of a first wavelength and an optical signal of a second wavelength are amplitude-modulated at a first frequency and a second frequency, respectively, at a first time, and an optical signal of a third wavelength and an optical signal of a fourth wavelength are amplitude-modulated at the first frequency and the second frequency, respectively, at a second time. 
     
     
         70 . The system of  claim 69 , wherein the analog signals are amplified by programmable gain amplifiers controlled by the programmable logic devices. 
     
     
         71 . The system of  claim 66 , wherein the tissue comprises breast tissue. 
     
     
         72 . The system of  claim 71 , wherein a plurality of amplitude modulated optical signals is directed at both breasts simultaneously. 
     
     
         73 . The system of  claim 66 , wherein the tissue comprises brain tissue. 
     
     
         74 . The system of  claim 73 , wherein a plurality of amplitude modulated optical signals is directed at both brain hemispheres simultaneously. 
     
     
         75 . The system of  claim 66 , wherein the tissue comprises extremity tissues. 
     
     
         76 . The system of  claim 75 , wherein the extremity tissues include two legs and the plurality of amplitude modulated optical signals is directed at both legs simultaneously. 
     
     
         77 . The system of  claim 75 , wherein the extremity tissues include two arms and the plurality of amplitude modulated optical signals is directed at both legs simultaneously. 
     
     
         78 . The system of  claim 66 , wherein the stimulus is applied by having the patient perform the Valsalva maneuver. 
     
     
         79 . The system of  claim 66 , wherein the stimulus is applied by applying a mechanical pressure to the tissue. 
     
     
         80 . The system of  claim 66 , wherein the stimulus is applied by having the patient breathe a determined concentration of oxygen.