In this paper, we presents a newly developed near-infrared optical tissue imaging system with single channel detection based on the principles of frequency-domain spectroscopy, which uses diffusive photons to detect the breast cancer. The patient’s breast is slightly compressed between two parallel glass plates, which are located between the source fiber and the detector fiber. The laser beam travels in the source fiber to the breast, and the transmitted light is detected by a photomultiplier tube and then demodulated. The ac amplitude of the signal is sampled to the computer by an A/D board. The source fiber and the detector fiber are driven by stepper motors and move synchronously in two dimensions, which enable the fibers to scan the entire breast. The scanning process is automatically controlled by computer. And the optical mammograms are displayed on the computer screen after the scanning process. In comparison with our former instrument that uses multichannel and scans only in one dimension to shorten the time of scanning, the new prototype has only one transmitter and one detector. This structure not only reduces the costs of the apparatus but also leads to a
much more simplified system. Unfortunately, it makes the scanning time much longer. However, a new sampling mode is developed for the system to sample the data continuously, which compensates the disadvantage of the single-channel structure and reduces the scanning time. The results of intralipid experiments and pre-clinical experiments prove the potential of this approach to distinguish between tumors and healthy tissues.
Characterization of human tissue using near-IR (NIR) light is becoming increasingly popular. The light signal transmitted from the tissue contains information concerning inhomogeneities in tissue, such as size, position, and pathological states (benign or malignant). We discuss the most probable diffuse path (MPDP) related to frequency-domain diffuse photon density waves (DPDWs) propagating inside turbid media. We find that for a medium of finite size, the existence of boundaries between tissue and nonscattering media would have considerable impact on the path shape. It is also demonstrated that such paths can be used to obtain higher accuracy in localizing absorbers embedded in a homogeneous background. Based on the proposed MPDP, a new method for 3-D localization of heterogeneities in turbid media is proposed, which is validated by experiments using Intralipid and pork fat. The experiments are performed with an NIR breast cancer detection system designed and assembled in our lab, using 780-nm NIR light. In Intralipid, when the size of a single absorber is less than 1 cm, the localization error is about 2 mm. The results from pork fat are also acceptable.