Breast Ultrasound Tomography

Both mammography and standard ultrasound (US) rely upon subjective criteria within the breast imaging reporting and data system (BI-RADS) to provide more uniform interpretation outcomes, as well as differentiation and risk stratification of associated abnormalities. In addition, the technical performance and professional interpretation of both tests suffer from machine and operator dependence. We have been developing a new technique for breast imaging that is based on ultrasound tomography which quantifies tissue characteristics while also producing 3-D images of breast anatomy. Results are presented from clinical studies that utilize this method. In the first phase of the study, ultrasound tomography (UST) images were compared to multi-modal imaging to determine the appearance of lesions and breast parenchyma. In the second phase, correlative comparisons with MR breast imaging were used to establish basic operational capabilities of the UST system. The third phase of the study focused on lesion characterization. Region of interest (ROI) analysis was used to characterize masses. Our study demonstrated a high degree of correlation of breast tissue structures relative to fat subtracted contrast-enhanced MRI and the ability to scan ~90% of the volume of the breast at a resolution of 0.7 mm in the coronal plane

Temperature Monitoring During Tissue Freezing Using Ultrasound Speed Measurements

A major limitation of thermal therapies is the lack of detailed thermal information needed to monitor the therapy. Temperatures are routinely measured invasively with thermocouples, but only sparse measurements can be made. Ultrasound tomography is an attractive modality for temperature monitoring because it is non- invasive, non-ionizing, convenient and inexpensive. It capitalizes on the fact that the changes in temperature cause the changes in sound speed. In this work we investigate the possibility of monitoring large temperature changes, in the interval from body temperature to −40◦C. The ability to estimate temperature in this interval is of a great importance in cryosurgery, where freezing is used to destroy abnormal tissue. In our experiment, we freeze locally a tissue-mimicking phantom using a combination of one, two or three cryoprobes. The estimation of sound speed is a difficult task because, first, the sound is highly attenuated when traversing the frozen tissue; and second, the sound speed to be reconstructed has a high spatial bandwidth, due to the dramatic change in speed between the frozen and unfrozen tissue. We show that the first problem can be overcome using a beamforming technique. As the classical reconstruction algorithms inherently smooth the reconstruction, we propose to solve the second problem by applying reconstruction techniques based on sparsity

Computerized Ultrasound Risk Evaluation (CURE) System: Development of Combined Transmission and Reflection Ultrasound with New Reconstruction Algorithms for Breast Imaging

Our Computerized Ultrasound Risk Evaluation (CURE) system has been developed to the engineering prototype stage and generated unique data sets of both transmission and reflection ultrasound (US). This paper will help define the clinical underpinnings of the developmental process and interpret the imaging results from a similar perspective. The CURE project was designed to incorporate numerous diagnostic parameters to improve upon two major areas of early breast cancer detection. CURE may provide improved tissue characterization of breast masses and reliable detection of abnormal microcalcifications found in some breast cancers and ductal carcinoma in situ (DCIS). Current breast US is limited to mass evaluation, whereas mammography also detects and guides biopsy of malignant calcifications. Screening with CURE remains a distant goal, but improved follow-up of mammographic abnormalities may represent a feasible breakthrough. Improved tissue characterization could result in reduction of the estimated one million benign biopsies each year in the United States, costing up to several billion dollars. Most breast calcifications are benign and comprise-80% of stereotactic biopsies guided by mammography. Ultrasound has the capability of finding some groups of calcifications, but further improvements in resolution should also address tissue characterization to define the soft tissue filling of ducts by DCIS. In this manner, CURE may be able to more accurately identify the malignant calcifications associated with progression of DCIS or early cancers. Currently, high-resolution US images of the breast are performed in the reflection mode at higher frequencies, which also limits depth of penetration. Reconstruction of reflection ultrasound images relies upon acoustic impedance differences in the tissue and includes only direct backscatter of the ultrasound signal. Resolution and tissue contrast of current US continues to improve with denser transducer arrays and image processing, but the operator dependent nature of using a moveable transducer head remains a significant problem for thorough coverage of the entire breast. We have therefore undertaken the development of a whole breast (i.e., including auxiliary tail) system, with improved resolution and tissue characterization abilities. The extensive ultrasound physics considerations, engineering, materials process development and subsequent algorithm reconstruction are beyond the scope of this initial paper. The proprietary nature of these processes will be forthcoming as the intellectual property is fully secured. We will focus here on the imaging outcomes as they apply to eventual expansion into clinical use

Magnetic resonance imaging of femoral head development in roentgenographically normal patients

Magnetic resonance images (MRI) of 22 patients with roentgenographically normal hips were reviewed retrospectively and the findings categorized according to age. With increasing maturity, the MR intensity of the femoral heads on spin echo images increased, as marrow fat became a dominant tissue in the head. The femoral head pattern was relatively inhomogeneous, with a broad band of diminished intensity extending in a posteromedial to anterolateral direction, corresponding to the pattern of trabecular bone. The femoral capital epiphyses were visible in younger patients as structures of bright intensity which remained evident through early adulthood. The articular cartilage of the hip joint was noted as a distinctive “halo” around the femoral head. An understanding of the MR pattern of the normal hip will aid in the early recognition of pathologic conditions, such as osteonecrosis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46778/1/256_2004_Article_BF00355555.pd

Short-term changes in ultrasound tomography measures of breast density and treatment-associated endocrine symptoms after tamoxifen therapy

Although breast density decline with tamoxifen therapy is associated with greater therapeutic benefit, limited data suggest that endocrine symptoms may also be associated with improved breast cancer outcomes. However, it is unknown whether endocrine symptoms are associated with reductions in breast density after tamoxifen initiation. We evaluated treatment-associated endocrine symptoms and breast density change among 74 women prescribed tamoxifen in a 12-month longitudinal study. Treatment-associated endocrine symptoms and sound speed measures of breast density, assessed via novel whole breast ultrasound tomography (m/s), were ascertained before tamoxifen (T0) and at 1-3 (T1), 4-6 (T2), and 12 months (T3) after initiation. CYP2D6 status was genotyped, and tamoxifen metabolites were measured at T3. Using multivariable linear regression, we estimated mean change in breast density by treatment-associated endocrine symptoms adjusting for age, race, menopausal status, body mass index, and baseline density. Significant breast density declines were observed in women with treatment-associated endocrine symptoms (mean change (95% confidence interval) at T1:-0.26 m/s (-2.17,1.65); T2:-2.12 m/s (-4.02,-0.22); T3:-3.73 m/s (-5.82,-1.63); p-trend = 0.004), but not among women without symptoms (p-trend = 0.18) (p-interaction = 0.02). Similar declines were observed with increasing symptom frequency (p-trends for no symptoms = 0.91; low/moderate symptoms = 0.03; high symptoms = 0.004). Density declines remained among women with detectable tamoxifen metabolites or intermediate/efficient CYP2D6 metabolizer status. Emergent/worsening endocrine symptoms are associated with significant, early declines in breast density after tamoxifen initiation. Further studies are needed to assess whether these observations predict clinical outcomes. If confirmed, endocrine symptoms may be a proxy for tamoxifen response and useful for patients and providers to encourage adherence

Breast density measurements with ultrasound tomography: A comparison with film and digital mammography

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134902/1/mp2057.pd

The Potential Role of the Fat–Glandular Interface (FGI) in Breast Carcinogenesis: Results from an Ultrasound Tomography (UST) Study

This study explored the relationship between the extent of the fat–glandular interface (FGI) and the presence of malignant vs. benign lesions. Two hundred and eight patients were scanned with ultrasound tomography (UST) as part of a Health Insurance Portability and Accountability Act (HIPAA)-compliant study. Segmentation of the sound speed images, employing the k-means clustering method, was used to help define the extent of the FGI for each patient. The metric, α, was defined as the surface area to volume ratio of the segmented fibroglandular volume and its mean value across patients was determined for cancers, fibroadenomas and cysts. ANOVA tests were used to assess significance. The means and standard deviations of α for cancers, fibroadenomas and cysts were found to be 4.0 ± 2.0 cm−1, 3.1 ± 1.7 cm−1 and 2.3 ± 0.9 cm−1, respectively. The differences were statistically significant (p < 0.001). The separation between the groups increased when α was measured on only the image slice where the finding was most prominent, with values for cancers, fibroadenomas and cysts of 5.4 ± 3.6 cm−1, 3.6 ± 2.3 cm−1 and 2.4 ± 1.5 cm−1, respectively. Of the three types of masses studied, cancer was associated with the most extensive FGIs, suggesting a potential role for the FGI in carcinogenesis, a subject for future studies

Whole Breast Sound Speed Measurement from US Tomography Correlates Strongly with Volumetric Breast Density from Mammography.

OBJECTIVE: To assess the feasibility of using tissue sound speed as a quantitative marker of breast density. METHODS: This study was carried out under an Institutional Review Board–approved protocol (written consent required). Imaging data were selected retrospectively based on the availability of US tomography (UST) exams, screening mammograms with volumetric breast density data, patient age of 18 to 80 years, and weight less than 300 lbs. Sound speed images from the UST exams were used to measure the volume of dense tissue, the volume averaged sound speed (VASS), and the percent of high sound speed tissue (PHSST). The mammographic breast density and volume of dense tissue were estimated with three-dimensional (3D) software. Differences in volumes were assessed with paired t-tests. Spearman correlation coefficients were calculated to determine the strength of the correlations between the mammographic and UST assessments of breast density. RESULTS: A total of 100 UST and 3D mammographic data sets met the selection criteria. The resulting measurements showed that UST measured a more than 2-fold larger volume of dense tissue compared to mammography. The differences were statistically significant (P < 0.001). A strong correlation of r(S) = 0.85 (95% CI: 0.79–0.90) between 3D mammographic breast density (BD) and the VASS was noted. This correlation is significantly stronger than those reported in previous two-dimensional studies (r(S) = 0.85 vs r(S) = 0.71). A similar correlation was found for PHSST and mammographic BD with r(S) = 0.86 (95% CI: 0.80–0.90). CONCLUSION: The strong correlations between UST parameters and 3D mammographic BD suggest that breast sound speed should be further studied as a potential new marker for inclusion in clinical risk models