Whaley, Dana H.

Vibro-acoustography has gained interest in the recent years as a new modality for medical imaging. This method is based on low-frequency vibrations induced in the object by the radiation force of ultrasound. This paper focuses on potential applications of vibro-acoustography in breast imaging, including detection of microcalcifications, detection of arterial calcifications, and soft tissue imaging. In addition, we will briefly discuss our recent results of in vivo breast vibro-acoustography. Future developments and potential impact of vibro-acoustography in breast imaging are also discussed.

Vibro-acoustography image is a function of the dynamic characteristics of the object at the vibration (difference) frequency (df). The dynamic characteristic of tissue is closely related to pathology. Therefore, it is important to evaluate image features versus df. Here, the influence of df on breast vibro-acoustography images is studied by scanning human breast at various df values ranging from 20 to 90 kHz. The subjects were chosen from a group of volunteers with different breast abnormalities. Images were compared subjectively to study image features and the appearances of breast lesions versus df. It is demonstrated that having a collection of images of the same tissue at different df values generally provides a better perception of the tissue structure and improves lesion identification. In most cases, higher df resulted in a higher signal-to-noise ratio and thus a higher image quality. Finally, a frequency-compounded images was obtained by calculating the weighted sum of images at different df values. It is demonstrated that image compounding normally improves visualization of breast tissue and abnormalities. [Work supported by NIH Grant EB-00535 and Grant BCTR0504550 from the Susan G. Komen Breast Cancer Foundation. Disclosure: Parts of the techniques used here are patented by MF and JFG.]

Vibro-acoustography is an imaging method based on the sound emitted due to the harmonic motion of tissue induced by the radiation force of focused ultrasound. This paper presents recent progress in vibro-acoustography of human breast. Matching vibro-acoustography and mammography images are acquired using a combined mammography/vibro-acoustography machine. Images of various types of breast masses are investigated and their characteristics features are compared. The study includes malignant masses, benign masses such as fibroadenomas, cysts, calcified lesions, and surgical scars. Image features, such as lesion borders, interior texture, and speculation pattern, are studied. Vibro-acoustography images demonstrate that calcified masses normally show sharp borders, benign noncalcified masses have smooth texture, and, in some cases, malignant masses are characterized with spiculation. These results, which are based on the data collected from an ongoing study, indicate that the above-mentioned image features may be used for differentiation of breast masses. It is noted that more data from a larger population are needed to establish the results in a statistical sense. [Work supported by NIH Grant EB-00535 and Grant BCTR0504550 from the Susan G. Komen Breast Cancer Foundation. Disclosure: Parts of the techniques used here are patented by MF and JFG.]

Vibro-acoustography is based on audio-frequency harmonic vibrations induced in the object by the radiation force of focused ultrasound. The resulting object vibration produces a hydrophone detectable acoustic emission that is a function of regional dynamic properties of the object at the vibration frequency. The amplitude of the hydrophone signal is mapped into an image that represents the object’s vibro-acoustic response to the radiation force by scanning the focused ultrasound across the object. Contrast in Vibro-acoustography images represent several properties of the object, including the dynamic characteristics at the audio frequency and scattering and absorption properties at the ultrasound frequency. A Vibro-acoustography system has been combined with a stereo-tactic x-ray mammography system for in vivo breast imaging and has been tested on a number of volunteers. Resulting images show soft tissue structures and microcalcifications within breast with high contrast, high resolution, and no speckles. The results have been verified using x-ray mammograms of the breast. The encouraging results from in vitro and in vivo experiments suggest further development of vibro-acoustography may lead to a new clinical breast imaging modality. [Work supported in part by a grant from the Susan G. Komen Breast Cancer Foundation. Vibro-acoustography is patented by MF and JFG.]

Abstract Objective: This paper introduces an alternative non-invasive and non-ionizing breast imaging tool called vibro-acoustography (VA). This method is based on low-frequency harmonic vibrations induced in the object by the radiation force of ultrasound. Contrast in Vibro-acoustography images represent several properties of the object, including the dynamic characteristics at the audio frequency and scattering and absorption properties at the ultrasound frequency. X-ray mammography and ultrasound are the main imaging modality used today for detection of breast lesions. X-ray mammography, however, is ionizing and its sensitivity is greatly reduced in dense breasts. Ultrasound images suffer from speckles or other or artifact that prevents the physician from delineating the mass lesion from the background tissue. Hence, VA may be used as a stand-alone imaging device or as a tool to provide supplementary information to other existing imaging modalities. Materials & Methods: Matching vibro-acoustography and mammography images of human breast are acquired using a combined mammography/vibro-acoustography machine. Images of various types of breast masses are investigated and their characteristics features are compared. Image features, such as lesion borders, interior texture, and speculation pattern, are studied. Results: Resulting images show soft tissue structures, breast lesions and microcalcifications within breast with high contrast, high resolution, and no speckles. The results have been verified using x-ray mammograms of the breast. Vibro-acoustography images demonstrate that calcified masses normally show sharp borders, benign non-calcified masses have smooth texture, and, in some cases, malignant masses are characterized with spiculation. Conclusion: The encouraging results which are based on the data collected from an ongoing study indicate that the above mentioned image features may be used for differentiation of breast masses and suggest that further development of vibro-acoustography technology may lead to a new clinical tool for various imaging applications. Work supported in part by Grant CA121579-01A1from NIH and Grant BCTR#0504550 from Susan G. Komen Breast Cancer Foundation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4047. doi:1538-7445.AM2012-4047