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Shear Strain Imaging for Breast Cancer Diagnosis
Detection, Diagnosis and Prognosis
Background: Early diagnosis of breast cancer, critical for favorable clinical outcomes, is difficult since cancerous tumors, benign masses and healthy tissue respond similarly in many diagnostic imaging modalities. One physical property that clearly distinguishes healthy from cancerous tissue is their relative stiffness, and this feature has been utilized by clinicians for centuries using manual palpation. This property also is utilized in the newly developing field of elastographic imaging, where elastic properties of tissue are imaged using ultrasound, providing images of strain and Young's modulus. However, in the current practice of elastography, only one of three components of the tissue displacement vector and one of nine components of the strain tensor are accurately estimated and imaged. Other another important elastic parameter, the shear strain is not currently imaged. However, research suggests that shear strain imaging may enable differentiation of malignant from benign masses. Objective/Hypothesis: We have developed a new method for estimating all tissue displacement vector components and strain tensor components following a quasi-static compression. The method uses displacements estimated from radiofrequency echo-signals along multiple ultrasound beam directions. Following displacement estimation in orthogonal directions, components of corresponding normal and shear strain tensors are estimated. Specific Aims: 1. Implement the shear strain estimation algorithm on a clinical ultrasound breast scanner. 2. Perform initial assessments in-vivo in patients with malignant and benign breast masses. Study Design: The research plan develops and implements this method on a state–of-the-art Siemens Antares scanner, capitalizing on a newly developed ultrasound research interface to facilitate angular beam data acquisition and control. Potential Outcomes/Benefits: Our method will be evaluated for differentiating malignant from benign masses in the breast. Lateral slippage is believed to occur in many benign masses when the tissue is compressed, while slippage appears to be absent with malignant masses. Since cancers infiltrate into surrounding normal tissue and include calcifications and spiculations, they are far less mobile and not slip during compression as do fibroadenomas. The proposed shear strain images are particularly sensitive to such phenomena and clearly depict the sliding or slippage that occurs during compression.
Breast cancer remains the second-leading cause of cancer deaths in women, and over 200,000 new cases of invasive breast cancer are expected in the United States this year alone. As suggested by The American Cancer Society, breast self examination and clinical breast examination (palpation) are the most frequently used diagnostic tools for detecting breast abnormalities. In our research, we propose to utilize a new imaging technique termed elastography, to determine the elastic properties of tissue. The practice of elastography can be considered to be a ‘high-tech’ form of palpation, Imaging of tissue elastic parameters for diagnosis and treatment is rapidly gaining attention because of the ability to provide noninvasive and new diagnostic information. In elastography, we typically estimate the axial strain (along the direction of insonification/compression) by analyzing ultrasonic signals obtained from standard medical ultrasound diagnostic equipment. Elastography has been used for imaging and characterizing tumors in breast, and other biological tissue. Since ultrasonic visualization is widely used in practically all-medical specialties. The proposed technique could therefore have a large impact on medical practice in the United States . We have developed a new technique of producing shear strain images in elastography using angular ultrasound data. Shear strain elastograms enable the differentiation of infiltrating carcinomas from benign fibroadenomas. Since cancers infiltrate into surrounding normal tissue and include calcifications and spiculations, they may be far less mobile and not slip during compression as do fibroadenomas. Shear strain elastograms estimated from the normal strain tensors derived here have the potential for clearly depicting sliding or slippage of such masses that may occur during compression thereby differentiating fibroadenomas from cancers.