Frequency-Domain Inverse Monte Carlo Simulation And Data Aquisition For The Frequency-Domain Measurement

Measurement of near infrared diffuse light on frequency domain is a new technology for the diagnosis of early cervical cancer. Concerning the structure of the cervix, Monte-Carlo simulation (MC) has to be adopted for describing the photon migration in tissue. This article deals with the optical property reconstruction based on MC, especially with the extraction of frequency domain information from the time-domain MC and the retrenchment of the reconstruction time. In extracting the frequency domain information, in addition to the traditional discrete Fourier Transform method, an improved method is developed for reducing the reconstruction error. In order to shorten the computation time, MC simulation databases under a range of scattering coefficients were pre-built and combined with Lagrange interpolation and Lambert-Beer's Law for rapidly obtaining the MC simulation in any optical properties. The simulated and phantom experiment has also been done. Reconstruction results from simulated data showed that the improved method has the advantages over the traditional one in both the reconstruction accuracy and computation time. The relative error in reconstruction of scattering coefficient and absorption coefficient is mainly less than±10% in range of 30<μs<100 cm-1, 0.2<μa<0.50 cm-1, particularly, the error can be less than±8% in the optical properties range of the cervix. With the rapid reconstruction strategy developed in this article the computation time for reconstructing one set of the optical properties is less than 1min. Besides, the phatom experiment prove the preciseness of this method.In the study of data acquiring and proceesing of the frequency domain measurement, PCI-1202H data acquisition card was discuss. LabVIEW based code were developed for getting the amplitude attenuation and phase delay from the signal. Correlation method, discrete Fourier transform method were induced, wave-average method for restraining the noise were also adoptded in the code. Experiment were taken to validate the precision and the anti-noise capacity of code by using the virtual and true signal generated by computer and function generator, respectively. Results of the repetitious experiments showed that Fourier transform method provides better performance in both the accuracy and noise restraining than the correlation precision.