On The Development Of Hand Breast Tumor Detector

The study of using near-infrared light to non-invasively detect breast cancer has been a worldwide hot issue in the field of biomedical engineering.From 1995 to 2001, the"Runman"instrument developed by University of Pennsylvania in USA and the"TBO Breast Tumor Detector"developed by College of Life Science and Technology in Huazhong University of Science and Technology and University of Naval Engineering was used to detect the relative blood concentration and the relative oxygenation level of 336 breast tumors in China. High relative blood concentration and low relative blood oxygenation level are used to diagnose breast cancer. Because their sensitivities are more than 83.3%, these two instruments have caught the notice of the medicine circle. These two instruments use a broadband light source to illuminate breast, and two light filters to choose wavelength. They have the disadvantages of large size, needing recorder, lacking storing function, fast aging of light filter, and low accuracy of diagnosing the lesions smaller than 1cm.The"Hand Breast Tumor Detector"presented in this thesis is developed after analyzing the circuits and the modeling principles of the"Runman"instrument and the"TBO Breast Tumor Detector". Its probe uses two LEDs with the wavelength of 660nm and 880nm to illuminate breast, and a single PIN photon diode to receive light signal. The two LEDs light alternatively at an adjustable frequency. By choosing precise operational amplifier OPA364, the noise induced by the preamplifier is reduced to only 1% of the shot noise of photon diode. PCB layout techniques such as placement, shield, grounding and decoupling is used to avoid the coupling of noise and signal. Data sampled is averaged and then subtracted to reduce random noise and background light noise. To overcome the shortcomings of the"Runman"instrument and the"TBO Breast Tumor Detector", a clear user interface and the functions of storage and query are programmed. On the premise of ensuring patients'safety, integration and portability are realized in the"Hand Breast-tumor Detector"through applying lithium cells and appropriate peripheral parts.Blood model experiments and clinical experiments are conducted to validate the detector. The results of blood experiments indicate that the detector can accurately detect the relative blood concentration and relative oxygenation level of the models. The value K deduced from mathematical modeling can decrease the error of relative blood concentration caused by different light absorptions coefficient of Hb and HbO2. The medical statistical analysis of clinical detection of 55 patients with breast tumors shows: the sensitivity of malignant tumor is 93.3%, the specificity of benign tumors is 82.5%, the accuracy is 85.5%. The detector has the advantages of light portability, low cost and high accuracy.