High Frequency Ultrasonic Imaging for the Development of Breast Biopsy Needle with Miniature Ultrasonic Transducer Array

摘要

High frequency ultrasonic transducers integrated in a breast biopsy needle have been researched at the University of Southern California. It can obtain information in the vicinity of the needle and resolve microcalcifications that are indicative of precancerous changes or early breast carcinomas such as ductal carcinoma in situ. X-ray mammography is the best diagnostic modality to detect microcalcifications currently, but patients are exposed to ionizing radiation. More recently, a new ultrasound-guided breast biopsy technique was proposed. This technique utilizes conventional ultrasound guidance coupled with high frequency ultrasound from the biopsy needle. Current ultrasound-guided breast biopsy can often result in false negative diagnosis that causes serious consequences because of the inaccuracy of the position of the biopsy needle. This proposed technology can improve localization of lesions and the accuracy of the diagnosis of breast pathology.;In this study, for the purpose of demonstrating the proof of the concept with respect to the miniature high frequency ultrasonic transducer embedded within a biopsy needle, backscattering analysis for the characterization of breast biopsy tissues was conducted by using a single element high frequency ultrasonic transducer with a center frequency of 74 MHz. The effective bandwidth was from 41 MHz to 88 MHz and was defined on - 8 dB relative to the maximum value of the pulse echo spectrum on the transducer. The slope and the 0 Hz y-intercept of the spectral backscattering features were calculated with linear approximation as well as the integrated backscattering coefficient. Four breast biopsy tissue specimens in each agar block used for embedding were measured utilizing a standard ultrasonic bio-microscopy (UBM) scanning methodology. All of the backscattering coefficients were two-dimensionally mapped and co-registered with each histopathological image for the identification of tissue types.;The results of the analysis indicate that the integrated backscattering coefficient successfully differentiated microcalcifications from other tissues around them. And adenocarcinoma is also differentiated from adipose tissues by observing the integrated backscattering and the slope of the spectral backscattering feature. These results indicate that backscattering analysis is able to quantitatively distinguish tissues into normal and abnormal, which should help radiologists locate abnormal areas during the proposed ultrasound-guided breast biopsy with high frequency ultrasound.;Current imaging systems for conventional ultrasound are available for less than 20 MHz. To evaluate the miniature high frequency ultrasonic transducer, a test system with synthetic aperture technique was built, and used to process the data to produce ultrasound images without any large scale electronics. The GUI controlling the data acquisition and the image processing program are beneficial for those who research high frequency ultrasonic transducer arrays. It takes a few minutes to reconstruct a synthetic B-mode image after the acquisition of the RF echo signals.;In conclusion, the backscattering analysis shows that high frequency ultrasound is significantly useful for the proposed ultrasound-guided breast biopsy, and the testing system based on a GUI should be flexibly available for the evaluation of every high frequency transducer array. Therefore, the development of the miniature high frequency ultrasonic transducer integrated in a breast biopsy needle can be easily advanced to the next stage.