Guided By Research

The science behind SoftVue™ is based on several years of ultrasound research conducted within technical and clinical domains. These data have demonstrated the potential benefits this technology can bring to the challenges of finding breast disease at an early stage, particularly in dense breast tissue. 




                    
  • Determinants of the Reliability of Ultrasound Tomography
    Sound Speed Estimates as a Surrogate for Volumetric Breast Density

    Med Phys. 2015 Oct; 42(10): 5671–5678.

    Published online 2015 Sep 8. doi:  10.1118/1.4929985

     

    Selection of starting breast tissue image slice from the first four tomograms, which borders the chest wall. In this example, slice three was chosen to be the first slice without any chest wall present. Slices three and four were included in the final.
    Selection of starting breast tissue image slice from the first four tomograms, which borders the chest wall. In this example, slice three was chosen to be the first slice without any chest wall present. Slices three and four were included in the final.

    PURPOSE:

    High breast density, as measured by mammography, is associated with increased breast cancer risk, but standard methods of assessment have limitations including 2D representation of breast tissue, distortion due to breast compression, and use of ionizing radiation. Ultrasound tomography (UST) is a novel imaging method that averts these limitations and uses sound speed measures rather than x-ray imaging to estimate breast density. The authors evaluated the reproducibility of measures of speed of sound and changes in this parameter using UST.

     


    Depiction of the segmentation algorithm that was utilized to remove sections of each image associated with the water bath: (left) in this example using a midsection slice, the breast/water bath.
    Depiction of the segmentation algorithm that was utilized to remove sections of each image associated with the water bath: (left) in this example using a midsection slice, the breast/water bath.

    METHODS:

    One experienced and five newly trained raters measured sound speed in serial UST scans for 22 women (two scans per person) to assess inter-rater reliability. Intrarater reliability was assessed for four raters. A random effects model was used to calculate the percent variation in sound speed and change in sound speed attributable to subject, scan, rater, and repeat reads. The authors estimated the intraclass correlation coefficients (ICCs) for these measures based on data from the authors’ experienced rater.

     

     

    RESULTS: 
    Median (range) time between baseline and follow-up UST scans was five (1-13) months. Contributions of factors to sound speed variance were differences between subjects (86.0%), baseline versus follow-up scans (7.5%), inter-rater evaluations (1.1%), and intrarater reproducibility (∼0%). When evaluating change in sound speed between scans, 2.7% and ∼0% of variation were attributed to inter- and intrarater variation, respectively. For the experienced rater’s repeat reads, agreement for sound speed was excellent (ICC = 93.4%) and for change in sound speed substantial (ICC = 70.4%), indicating very good reproducibility of these measures.

     


    Scatterplot of baseline and follow-up sound speed measures for each participant as measured by the experienced rater (N = 22).
    Scatterplot of baseline and follow-up sound speed measures for each participant as measured by the experienced rater (N = 22).

    CONCLUSIONS:

    UST provided highly reproducible sound speed measurements, which reflect breast density, suggesting that UST has utility in sensitively assessing change in density.

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  • Breast Density Measurements
    Using Ultrasound Tomography For Patients Undergoing Tamoxifen Treatment

    Published online 2013 Feb 9. doi:  10.1117/12.2007146
    PMCID: PMC4241344
    NIHMSID: NIHMS618425

     

    Plots of the average change in sound speed measured using all separate measures of sound speed for patients that showed at least a 1 m/s decrease who had two UST scans (Left, n = 8) and three UST scans (Right, n = 7).
    Plots of the average change in sound speed measured using all separate measures of sound speed for patients that showed at least a 1 m/s decrease who had two UST scans (Left, n = 8) and three UST scans (Right, n = 7).

    Women with high breast density have an increased risk of developing breast cancer. Women treated with the selective estrogen receptor modulator tamoxifen for estrogen receptor positive breast cancer experience a 50% reduction in risk of contralateral breast cancer and overall reduction of similar magnitude has been identified among high-risk women receiving the drug for prevention. Tamoxifen has been shown to reduce mammographic density, and in the IBIS-1 chemoprevention trial, risk reduction and decline in density were significantly associated. Ultrasound tomography (UST) is an imaging modality that can create tomographic sound speed images of the breast.

     

    article_02_img_01These sound speed images are useful because breast density is proportional to sound speed. The aim of this work is to examine the relationship between UST-measured breast density and the use of tamoxifen. So far, preliminary results for a small number of patients have been observed and are promising. Correlations between the UST-measured density and mammographic density are strong and positive, while relationships between UST density with some patient specific risk factors behave as expected. Initial results of UST examinations of tamoxifen treated patients show that approximately 45% of the patients have a decrease in density in the contralateral breast after only several months of treatment.

     

     

    Average Sound Speed of Patients Showing a Decrease in Sound Speed. WVSS – whole volume sound speed; CVSS – common volume sound speed; DRWVSS – donut removed whole volume sound speed; DRCVSS – donut removed common volume sound speed
    Average Sound Speed of Patients Showing a Decrease in Sound Speed. WVSS – whole volume sound speed; CVSS – common volume sound speed; DRWVSS – donut removed whole volume sound speed; DRCVSS – donut removed common volume sound speed

    The true effect of tamoxifen on UST-measured density cannot yet be fully determined until more data are collected. However, these promising results suggest that UST can be used to reliably assess quantitative changes in breast density over short intervals and therefore suggest that UST may enable rapid assessment of density changes associated with therapeutic and preventative interventions.

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  • Using Speed of Sound Imaging
    To Characterize Breast Density

    Published online Ultrasound Med Biol. 2016 Sep 29. doi: 10.1016/j.ultrasmedbio.2016.08.021.

    A population of 165 women with negative mammographic screens also received an ultrasound tomography (UST) examination at the Karmanos Cancer Institute in Detroit, MI. Standard statistical techniques were employed to measure the associations between the various mammographic- and UST-related density measures and various participant characteristics such as age, weight and height. The mammographic percent density (MPD) was found to have similar strength associations with UST mean sound speed (Spearman coefficient, rs = 0.722, p < 0.001) and UST median sound speed (rs = 0.737, p < 0.001). Both were stronger than the associations between MPD with two separate measures of UST percent density, a k-means (rs = 0.568, p < 0.001) or a threshold (rs = 0.715, p < 0.001) measure. Segmentation of the UST sound speed images into dense and non-dense volumes showed weak to moderate associations with the mammographically equivalent measures. Relationships were found to be inversely and weakly associated between age and the UST mean sound speed (rs = -0.239, p = 0.002), UST median sound speed (rs = -0.226, p = 0.004) and MPD (rs = -0.204, p = 0.008). Relationships were found to be inversely and moderately associated between body mass index (BMI) and the UST mean sound speed (rs = -0.429, p < 0.001), UST median sound speed (rs = -0.447, p < 0.001) and MPD (rs = -0.489, p < 0.001). The results confirm and strengthen findings presented in previous work indicating that UST sound speed imaging yields viable markers of breast density in a manner consistent with mammography, the current clinical standard. These results lay the groundwork for further studies to assess the role of sound speed imaging in risk prediction.

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