Zhou, Boran

Many lung diseases including interstitial lung disease (ILD) are associated with changes in the lung’s biomechanical properties. ILD comprises a number of serious diseases in which fibrosis stiffens and damages lung tissue. Most ILDs are typically distributed in the lung’s peripheral and subpleural regions. Pulmonary function test (PFT) and high-resolution computed tomography (HRCT) are used to assess ILD. Ultrasonography is not widely used for lung assessment because ultrasound cannot image deep lung tissue. We have developed lung ultrasound surface wave elastography (LUSWE) for measuring superficial lung wave speed. In LUSWE, a 0.1-s harmonic vibration is generated on the chest wall of a subject using a handheld vibrator. An ultrasound probe is aligned with the vibration excitation in the same intercostal space to measure the generated surface wave propagation on the lung. A human subject is examined in a sitting position. The lung is tested at the total lung volume and through six intercostal spaces. Significant differences of surface wave speed between patients and controls were found in 6 lung regions and for 3 excitation frequencies. A positive correlation between LUSWE and clinical tests including HRCT and PTF was found. LUSWE may complement the clinical standard HRCT for assessing ILD.

Lung ultrasound (LUS) detects the presence of extravascular lung water (EVLW) through the visualization of B-Line artifacts. However, the qualitative nature of LUS limits its effectiveness in serial or longitudinal studies such as evaluating changes in EVLW at different time points in patients undergoing diuretic therapy for congestive heart failure. Lung ultrasound surface wave elastography (LUSWE) is a novel technique using a small handheld device that can measure superficial lung tissue elastic properties. We aimed to evaluate the use of LUSWE to measure quantitative changes in lung elasticity caused by acute changes in EVLW. We performed LUSWE on consecutive days in 14 patients hospitalized for acute congestive heart failure with evidence of pulmonary edema (clinical EVLW). From day#1 to day#2, the patients had an average diuresis of net negative 2.1 l associated with an average decrease in 13 B-Lines by lung ultrasound, signifying a reduction in EVLW. LUSWE analysis demonstrated a significant reduction (p < 0.05) in surface wave velocity in all interrogated intercostal spaces from day#1 to day#2. In summary, LUSWE performed at the bedside was able to demonstrate improvement in lung compliance (decreased elasticity) correlating with a reduction in EVLW in hospitalized patients being treated for congestive heart failure.

Biomechanical properties of the eye are important in understanding glaucoma. However, specific tissues that may be affected are unclear. In this study, we compared glaucomatous and normal eyes for differences in corneal tissue elasticity (as indicated by wave speed) and global ocular rigidity. Both eyes of 10 glaucoma patients and 10 normal controls, matched for age and intraocular pressure (IOP), were included. The ocular rigidity coefficient was calculated from supine IOP measured with and without a 10 g weight added to the tonometer. The wave speed in the cornea was measured by ultrasound surface wave elastography. With this technique, a spherical-tipped probe (4 mm diameter) was placed on the closed eyelid and vibrated at 100 Hz for 0.1 s. The wave speed was calculated using the phase gradient method. Measurements for normal and glaucoma eyes were compared using generalized estimating equation models. The corneal wave speed was similar between normal and glaucomatous eyes (P = 0.4). However, ocular rigidity was significantly lower in glaucomatous eyes (P < 0.001) compared with normal eyes. There was no difference in age or IOP (P > 0.3). Lower ocular rigidity in glaucomatous eyes suggests that a more compliant ocular shell may predispose to glaucoma. However, the lack of difference in the corneal wave speed suggests that corneal tissue is not significantly affected, and changes likely involve the sclera.

Hypertrophic scars and keloids are characterized by excessive fibrosis and can be functionally problematic. Indeed, hypertrophic scarring is characterized by wide, raised scars that remain within the original borders of injury and have a rapid growth phase. There is a need for quantitative scar measurement modalities to effectively evaluate and monitor treatments. We aim to assess the role of the non-invasive scar-measuring device, ultrasound surface wave elastography (USWE), in accurately evaluating scar metrics. Two sites of breast tissue were tested control and scar portions. In USWE, a small, local, and 0.1-s harmonic vibration at three excitation frequencies (100, 150, and 200 Hz) was generated on these sites, and the resulting surface wave speed was measured via an ultrasound probe with a central frequency of 6.4 MHz. There was a statistically significant difference in the wave speed at three frequencies of the scar portion between prior and after treatment, suggesting that the scar portion was softener after treatment. USWE provides an objective assessment of the reaction of the scar to injury and treatment response.

Purpose: Optimal strategies to detect early interstitial lung disease (ILD) are unknown. ILD is frequently subpleural in distribution and affects lung elasticity. Lung ultrasound surface wave elastography (LUSWE) is a noninvasive method of quantifying superficial lung tissue elastic properties. In LUWSE a handheld device applied at the intercostal space vibrates the chest at a set frequency, and the lung surface wave velocity is measured by an ultrasound probe 5 mm away in the same intercostal space. We explored LUWSE’s ability to detect ILD and correlated LUSWE velocity with physiological, quantitative, and visual radiologic features of subjects with known ILD and of healthy controls. Materials and Methods: Seventy-seven subjects with ILD, mostly caused by connective tissue disease, and 19 healthy controls were recruited. LUSWE was performed on all subjects in 3 intercostal lung regions bilaterally. Comparison of LUSWE velocities pulmonary function testing, visual assessment, and quantitative analysis of recent computed tomographic imaging with Computer-Aided Lung Informatics for Pathology Evaluation and Rating (CALIPER) software. Results: Sonographic velocities were higher in all lung regions for cases, with the greatest difference in the lateral lower lung. Median velocity in m/s was 5.84 versus 4.11 and 5.96 versus 4.27 (P<0.00001) for cases versus controls, left and right lateral lower lung zones, respectively. LUSWE velocity correlated negatively with vital capacity and positively with radiologist and CALIPER-detected interstitial abnormalities. Conclusions: LUSWE is a safe and noninvasive technique that shows high sensitivity to detect ILD and correlated with clinical, physiological, radiologic, and quantitative assessments of ILD. Prospective study in detecting ILD is indicated.

Interstitial lung disease manifested as fibrotic and stiffened lung tissue, resulting in symptoms such as dyspnea and may lead to respiratory failure. We recently developed a lung ultrasound surface wave elastography for evaluating the elastic properties of superficial lung tissue. In this abstract, we present a finite element analysis to investigate the effects of pleural effusion on the shear wave propagation of superficial lung tissue. The muscle, pleural effusion, and lung tissue were simulated by a 2D planar model of an infinite elastic medium with densities for different materials. A nearly incompressible, linear elastic model was used to model muscle, pleural effusion and lung. The model was excited using a line source on the muscle surface. Harmonic excitations were performed at 100, 150 and 200 Hz with duration of 0.1 s. The boundaries of lung and muscle were attached to an infinite. The mesh of muscle, pleural effusion, and lung were constructed using linear quadrilateral elements. The infinite region was meshed by infinite elements (type CINPE4). The dynamic responses of the tissue model to the excitations were solved by the ABAQUS explicit dynamic solver with automatic step size control. Insignificant difference in shear wave speeds of lung tissue at different excitation frequencies was found in both simulations with and without taking into account the pleural effusion, indicating that pleural effusion does not affect the measurements of shear wave speeds in ultrasound elastography.

Color flow imaging is an ultrasound imaging technique widely used to image the blood movement through arteries and veins. Quantification of velocity is urgently demanding. The objective of this study is to use ultrafast plane wave imaging to measure the flow in speed in vitro. For the flow phantom, the diagonal vessel (2-mm inner diameter at 40° angle) was studied with injection of blood mimic fluid via syringe pump at various volume rates (15, 20, 25, and 30 ml/min). Verasonics Vantage system (Verasonics Inc., Kirkland, WA, USA) and a linear array transducer L11-4v (Verasonics Inc., Kirkland, WA, USA) were used for ultrasound acquisition, a 8-angle (−7° to 7°) plane wave compounding with effective pulse-repetition frequency (PRF) of 1000 Hz was used (central frequency = 6.42 MHz, number of transmit cycles = 4). A total of 600 ensembles were acquired. The frame rate was 1000/s.[XZ1] [BZ2] The ultrasound in-phase quadrature data size was 195 × 156 × 600 (axial x lateral x temporal) with data type of complex double. Singular value decomposition (SVD)-based ultrasound blood flow clutter filters was used for ultrafast plane wave imaging.[XZ3] [BZ4] Randomized SVD was utilized to filter noise and tissue motion. Power Doppler image was generated. The color flow images were generated by using the 2-D autocorrelation method. Results showed that color flow measurement can quantitatively evaluate the flow speed in the tube of the flow phantom.

A lung ultrasound surface wave elastography (LUSWE) technique is developed for assessing interstitial lung disease (ILD). In LUSWE, a 0.1 second harmonic vibration is generated on the chest wall of a subject using a handheld vibrator. An ultrasound probe is aligned with the vibration indenter in the same intercostal region to measure the generated surface wave speed of the lung. A human subject is examined in a sitting position. The lung is tested at the total lung volume. The upper anterior lungs are tested through the second intercostal space in the mid-clavicular line. The lower lateral lungs are tested in the mid-axillary line and the lower posterior lungs are tested in the mid-scapular line. In a prospective clinical study, we measure both lungs through the six intercostal regions for patients and healthy controls. The surface wave speed is measured at 100 Hz, 150 Hz, and 200 Hz. Significant differences of wave speed between patients and controls were found in all lung regions at all frequencies. We also found positive correlation between LUSWE and CT analyses. LUSWE is a safe and noninvasive technique for generating and measuring surface wave propagation on the lung. LUSWE may be useful for assessing ILD.

Lung density is directly associated with lung pathology. Computed Tomography (CT) evaluates lung pathology using the Hounsfield unit (HU) but not directly the lung density. We recently developed a lung ultrasound surface wave elastography (LUSWE) technique for measuring the surface wave speed of superficial lung tissue. The objective of this study is to analyze lung density of superficial lung tissue using deep neural network (DNN) and wave speed measurements obtained from LUSWE. The synthetic training dataset (7,88,000 in total) in terms of wave speeds of superficial lung tissue at different excitation frequencies from LUSWE, viscoelasticity and density of lung tissue was used to train the DNN. DNN is composed of 3 hidden layers of 1024 neurons and trained for 10 epochs with a batch size of 4096 and a learning rate of 0.001 with Adam optimizer. Test dataset in terms of wave speeds at different excitation frequencies (100, 150, and 200 Hz) as well as elasticity was used to predict the lung density and evaluate its accuracy. The obtained results showed that predictions matched well with test dataset (validation accuracy is 0.997). This method may be useful to analyze lung density based on the LUSWE measurements.