|
To acquire the optical diffuse tomographic image of the cervix, a novel endoscopic rotary probe is designed and the
frequency domain measurement system is developed. The finite element method and Gauss-Newton method are
proposed to reconstruct the image of the phantom.
In the optical diffuse tomographic imaging of the cervix, an endoscopic probe is needed and the detection of light at
different separation to the irradiation spot is necessary. To simplify the system, only two optical fibers are adopted for
light irradiation and collection, respectively. Two small stepper motors are employed to control the rotation of the
incident fiber and the detection fiber, respectively. For one position of source fiber, the position of the detection fiber is
changed from -61.875° to -50.625° and 50.625° to 61.875° to the source fiber, respectively. Then, the position of the source fiber is changed to another preconcerted position, which deviates the precious source position in an angle of
11.25°, and the detection fiber rotates within the above angles. To acquire the efficient irradiation and collection of the
light, a gradient-index (GRIN) lens is connected at the head of the optical fiber. The other end of the GRIN lens is cut to
45°. With this design, light from optical fiber is reflected to the cervix wall, which is perpendicular to the optical fiber or
vice versa. Considering the cervical size, the external diameter of the endoscopic probe is made to 20mm.
A frequency domain (FD) near-infrared diffuse system is developed aiming at the detection of early cervical cancer,
which modulates the light intensity in radio frequency and measures the amplitude attenuation and the phase delay of the
diffused light using heterodyne detection.
Phantom experiment results demonstrate that the endoscopic rotary scan probe and the system perform well in the
endoscopic measurement.
|
