Quantitative Ultrasonic Parameters Research Articles

Quantitative ultrasound parameters from scattering and propagation may reduce the biopsy rate for breast tumor

Breast cancer has become the most common cancer worldwide, and early screening improves the patient’s survival rate significantly. Although pathology with needle-based biopsy is the gold standard for breast cancer diagnosis, it is invasive, painful, and expensive. Meanwhile it makes patients suffer from misplacement of the needle, resulting in misdiagnosis and further assessment. Ultrasound imaging is non-invasive and real-time, however, benign and malignant tumors are hard to differentiate in grayscale B-mode images. We hypothesis that breast tumors exhibit characteristic properties, which generates distinctive spectral patterns not only in scattering, but also during propagation. In this paper, we propose a breast tumor classification method that evaluates the spectral pattern of the tissues both inside the tumor and beneath it. First, quantitative ultrasonic parameters of these spectral patterns were calculated as the representation of the corresponding tissues. Second, parameters were classified by the K-Nearest Neighbor machine learning model. This method was verified with an open access dataset as a reference, and applied to our own dataset to evaluate the potential for tumors assessment. With both datasets, the proposed method demonstrates accurate classification of the tumors, which potentially makes it unnecessary for certain patients to take the biopsy, reducing the rate of the painful and expensive procedure.

Quantitative ultrasound techniques for assessing thermal ablation: Measurement of the backscatter coefficient from ex vivo human liver.

Understanding the changes occurring in biological tissue during thermal ablation is at the heart of many current challenges in both therapy and medical imagingresearch. The objective of this work is to quantitatively interpret the scattering response of human liver samples, before and after thermal ablation. We report acoustic measurements performed involving n = 21 human liver samples. Thermal ablation is achieved at temperatures between 45 and 80°C and quantification of the irreversible changes in acoustic attenuation and Backscattering Coefficient (BSC) is reported, with a particular attention to thelatter. Both attenuation coefficient and BSCs were measured in the frequency range from 10 to 52 MHz. Scans were performed before heating and after cooling down. Attenuation coefficients were calculated using spectral difference method and BSC estimated using the reference phantommethod. Strong increases of attenuation coefficients and BSCs with heating temperature were observed. Quantitative ultrasonic parameters obtained with the polydisperse structure factor model (poly-SFM)are compared to histological observations and seen to be close to hepatocyte mean diameter (HMD). The results presented in this study provide a description of the impact of thermal ablation in human liver tissue on acoustic attenuation and the BSC. For the first time, quantitative agreement between the Effective Scatterer Diameter (ESD) estimated from BSC and HMD was shown, highlighting the important role of cellular network in the scattering response of the medium. This core result is an important step toward the determination of the nature of scattering sources in biologicaltissues.

Quantitative Assessment of First Annular Pulley and Adjacent Tissues Using High-Frequency Ultrasound.

Due to a lack of appropriate image resolution, most ultrasound scanners are unable to sensitively discern the pulley tissues. To extensively investigate the properties of the A1 pulley system and the surrounding tissues for assessing trigger finger, a 30 MHz ultrasound system was implemented to perform in vitro experiments using the hypodermis, A1 pulley, and superficial digital flexor tendon (SDFT) dissected from cadavers. Ultrasound signals were acquired from both the transverse and sagittal planes of each tissue sample. The quantitative ultrasonic parameters, including sound speed, attenuation coefficient, integrated backscatter (IB) and Nakagami parameter (m), were subsequently estimated to characterize the tissue properties. The results demonstrated that the acquired ultrasound images have high resolution and are able to sufficiently differentiate the variations of tissue textures. Moreover, the attenuation slope of the hypodermis is larger than those of the A1 pulley and SDFT. The IB of A1 pulley is about the same as that of the hypodermis, and is very different from SDFT. The m parameter of the A1 pulley is also very different from those of hypodermis and SDFT. This study demonstrated that high-frequency ultrasound images in conjunction with ultrasonic parameters are capable of characterizing the A1 pulley system and surrounding tissues.

Hepatitis fibrosis characterization by a multiparametric study

The ultrasonic tissue characterization (UTC) is primarily based on radio-frequency (RF) signals’ analysis. The processing of these signals allowed the estimation of different quantitative ultrasonic parameters (backscattered coefficients—ICB-, velocity—SoS, etc). It is known that the RF contains information that can be used to noninvasively characterize the structural and mechanical properties of tissue. Scatterer diameter (or size) from ICB measurements have been already used to discriminate fibrosis from normal tissue. From these findings, our goal was to evaluate the scatterer diameter to test its potential in the discrimination of fibrosis groups (F0, F1, F2, F3, and F4, METAVIR scale) from 20 in-vitro human liver samples, explored at 20 MHz. The mean scatterer diameters (µm) measured were: 42.14–4.90 (F0), 40.18–10.51 (F1), 38.82–6.05 (F3), and 40.30–2.22 (F4). The Kolmogorov-Smirnov test has shown a non-significant level (p > 0.05) indicating that the scatterer size estimation alone cannot differentiate between all fibrosis groups; an obvious overlap between groups appears. However, for the two different combinations (ICB, Size) and (ICB, Size, SoS), the discriminant analysis has correctly classified 75% and 85%, respectively, of liver samples at a significant level (p < 0.00005). The multiparametric study could play an important role to aid in the diagnostic of liver fibrosis.

Quantitative Ultrasound Characterization of Cancer Radiotherapy Effects In Vitro

Currently, no routinely used imaging modality is available to assess tumor responses to cancer treatment within hours to days after radiotherapy. In this study, we demonstrate the preclinical application of quantitative ultrasound methods to characterize the cellular responses to cancer radiotherapy in vitro. Three different cell lines were exposed to radiation doses of 2-8 Gy. Data were collected with an ultrasound scanner using frequencies of 10-30 MHz. As indicators of response, ultrasound integrated backscatter and spectral slope were determined from the cell samples. These parameters were corrected for ultrasonic attenuation by measuring the attenuation coefficient. A significant increase in the ultrasound integrated backscatter of 4-7 dB (p < 0.001) was found for radiation-treated cells compared with viable cells at all radiation doses. The spectral slopes decreased in the cell samples that predominantly underwent mitotic arrest/catastrophe after radiotherapy, consistent with an increase in cell size. In contrast, the spectral slopes did not change significantly in the cell samples that underwent a mix of cell death (apoptosis and mitotic arrest), with no significant change in average cell size. The changes in ultrasound integrated backscatter and spectral slope were direct consequences of cell and nuclear morphologic changes associated with cell death. The results indicate that this combination of quantitative ultrasonic parameters has the potential to assess the cell responses to radiation, differentiate between different types of cell death, and provide a preclinical framework to monitor tumor responses in vivo.

Robust diffraction correction method for high-frequency ultrasonic tissue characterization

The computation of quantitative ultrasonic parameters such as the attenuation or backscatter coefficient requires compensation for diffraction effects. In this work a simple and accurate diffraction correction method for skin characterization requiring only a single focal zone is developed. The advantage of this method is that the transducer need not be mechanically repositioned to collect data from several focal zones, thereby reducing the time of imaging and preventing motion artifacts. Data were first collected under controlled conditions from skin of volunteers using a high-frequency system (center frequency=33 MHz, BW=28 MHz) at 19 focal zones through axial translation. Using these data, mean backscatter power spectra were computed as a function of the distance between the transducer and the tissue, which then served as empirical diffraction correction curves for subsequent data. The method was demonstrated on patients patch-tested for contact dermatitis. The computed attenuation coefficient slope was significantly (p&amp;lt;0.05) lower at the affected site (0.13±0.02 dB/mm/MHz) compared to nearby normal skin (0.2±0.05 dB/mm/MHz). The mean backscatter level was also significantly lower at the affected site (6.7±2.1 in arbitrary units) compared to normal skin (11.3±3.2). These results show diffraction corrected ultrasonic parameters can differentiate normal from affected skin tissues.

Quantitative ultrasonic methods for characterization of skin lesions in vivo

Quantitative ultrasonic methods were studied for characterizing skin lesions in vivo using contact dermatitis as an example. The parameters studied include skin thickness, echogenicity, attenuation coefficient slope and parameters related to echo statistics (signal-to-noise ratio and shape parameters of Weibull, K and generalized gamma distributions). Data were collected using a high-frequency ultrasound (US) system (center frequency = 33 MHz). To compensate for depth-dependent diffraction effects, correction curves as a function of the distance between the transducer and the tissue were first empirically obtained. Diffraction-corrected quantitative parameters were then compared between healthy and affected skin of volunteers, who underwent patch testing for allergic and irritant contact dermatitis. A significant increase in skin thickness, decrease in echogenicity of the upper dermis and decrease in attenuation coefficient slope were found at the affected sites compared to those of healthy skin. However, no differences in parameters related to the echo statistics of the mid-dermis were found. These results indicate that a combination of quantitative ultrasonic parameters have the potential for extracting information for characterizing skin conditions.

Evaluation of a gel‐coupled quantitative ultrasound device for bone status assessment.

To evaluate a new gel-coupled calcaneal quantitative ultrasound system, Osteospace (Medilink, Montpellier, France), which was designed to assess the status of bone in the calcaneus. The study group consisted of 215 healthy white women aged 20 to 85 years and 51 white women aged 60 to 86 years with osteoporotic fractures. Fifty-two healthy women aged 50 to 85 years were randomly selected from the healthy cohort as the control group. All the women had calcaneal quantitative ultrasonic measurements. The women with osteoporotic fractures and the control group also had proximal femur and lumbar anteroposterior spine bone mineral density measurements using dual X-ray absorptiometry. Bone mineral density was also measured in a subgroup of 54 women at the calcaneus. There was a significant inverse correlation of broadband ultrasound attenuation and speed of sound with age (P < .001). Short-term measurement precision values expressed as coefficients of variation were 1.72% for broadband ultrasound attenuation and 0.64% for speed of sound, and standardized short-term precision values were 6.09% for broadband ultrasound attenuation and 3.87% for speed of sound. The correlations between the quantitative ultrasonic parameters and calcaneal bone mineral density were 0.69 (P = .0001) for broadband ultrasound attenuation and 0.45 (P = .0008) for speed of sound. Both quantitative ultrasonic parameters and all bone mineral density measurements of the hip and spine differed significantly between the control and osteoporotic fracture groups (P < .01). Age-, weight-, and height-adjusted odds ratios per SD decrease were as follows: broadband ultrasound attenuation, 1.79; speed of sound, 1.83; spine bone mineral density, 2.34; femoral neck bone mineral density, 1.69; and total hip bone mineral density, 1.85. The areas under the receiver operating characteristic curve for quantitative ultrasound parameters and bone mineral density measurements were close, ranging from 0.75 to 0.80. This new quantitative ultrasound system can detect age- and menopause-related influences on skeletal status and can discriminate healthy women from those with osteoporotic fractures in a manner comparable with that of bone mineral density measurement by dual X-ray absorptiometry.

Parametric (integrated backscatter and attenuation) images constructed using backscattered radio frequency signals (25–56 MHz) from human aortae in vitro

Quantitative ultrasonic tissue characterization using backscattered high-frequency intravascular ultrasound could provide a basis for the objective identification of lesions in vivo. Representation of local measurements of quantitative ultrasonic parameters in a conventional image format should facilitate their interpretation and thus increase their clinical utility. Toward this goal, the apparent integrated backscatter, the slope of attenuation (25–56 MHz) and the value of the attenuation on the linear fit at 37.5 MHz were measured using the backscattered radio frequency signals from in vitro human aortae. Local estimations of these ultrasonic parameters from both normal and atherosclerotic aortic segments were displayed in a B-scan format. The morphological features of these parametric images corresponded well to features of histological images of the same regions. The attenuation from 25–56 MHz of seven segments of the medial layer (both with and without overlying atheroma) were measured using the multinarrow-band backscatter method. The average attenuation in the media at 24°C ± 3°C was 45 ± 16 dB/cm at 25 MHz and 102 ± 13 dB/cm at 50 MHz. This work represents progress toward the development of quantitative imaging methods for intravascular applications.