Zhang, Xiaoming

Abstract Objective . Penile vibro-elastography (PVE) is complicated by reverberant shear wavefields from the cylindrical geometry of the corpus cavernosum (CC), which bias shear wave speed (SWS) estimates. This study evaluated local phase velocity imaging with wavefield-based filtering (LPVI-WBF) for CC stiffness assessment in post-prostatectomy erectile dysfunction (ED), compared against phase gradient (PG) and time-of-flight (TOF) methods. Approach . Six patients with post-prostatectomy ED underwent PVE at four longitudinal visits (902 acquisitions). SWS was estimated in flaccid and erect states at 100, 150, and 200 Hz using LPVI-WBF, PG, and TOF. Wavefield composition was quantified via the standing wave index. Simulations evaluated accuracy and frequency stability under clean and reverberant conditions. Main results . Reverberant components dominated penile acquisitions, with traveling wave energy absent in 59% of acquisitions and mean standing wave fraction of 57 ± 17%. LPVI-WBF was the only method producing physiologically consistent estimates, with erect SWS exceeding flaccid (3.59 ± 0.48 vs 3.25 ± 0.58 m s −1 , p < 0.0001). PG and TOF yielded reversed results ( E < F, p < 0.0001). The dispersion exponent was near-zero for LPVI-WBF ( α = 0.048, p = 0.21), consistent with weakly viscoelastic tissue, while PG ( α = 0.184) and TOF ( α = 0.321) showed significant frequency dependence from reverberant contamination. Simulations confirm PG accuracy in clean wavefields but collapse under reverberant ones. Significance . LPVI-WBF produced SWS estimates consistent with expected CC biomechanics across all patients and frequencies, a criterion PG and TOF failed to satisfy. Phantom validation and multi-directional wavefield simulation are needed to establish accuracy.

ObjectivesThe aim of this study was to assess bleomycin‐induced pulmonary fibrosis on ex vivo mouse lungs using ultrasound image grading and texture analysis.MethodsExcised mouse lungs were divided into 3 groups: control, mild fibrosis, and severe fibrosis based on the monitored indicators of health. B‐mode ultrasound images were obtained via scanning the mouse lungs ex vivo. The surface smoothness, echo density, and angle of lesions or the lung margin were graded, and the imaging contrast, correlation, homogeneity, and entropy were assessed via texture analysis.ResultsThe grades of surface smoothness, echo density, and angle were statistically higher for the severe fibrosis group compared with those of the control and mild fibrosis groups (P < .05). In addition, statistically significant differences in the contrast, correlation, and homogeneity between mild and severe fibrosis groups were observed (P < .05).ConclusionsThe results obtained in this study suggest that ultrasound image grading and texture analysis are valuable and meaningful methods for assessing pulmonary fibrosis in a bleomycin mouse model.

Background Lymphedema treatment is an ongoing challenge. It impacts quality of life due to pain, loss of range of motion of the extremity, and repeated episodes of cellulitis. Different modalities have been used to evaluate lymphedema; some are more error-prone and some are more invasive. However, these measurements are poorly standardized, and intrarater and interrater reliabilities are difficult to achieve. This pilot study aims to assess the feasibility of ultrasound vibroelastography for assessing patients with extremity lymphedema via measuring shear wave speeds of subcutaneous tissues. Methods Patients with clinical and lymphoscintigraphic diagnosis of secondary lymphedema in the extremities without prior surgical treatment were included. A 0.1-s harmonic vibration was generated at three frequencies (100, 150, and 200 Hz) by the indenter of a handheld shaker on the skin. An ultrasound probe was used for noninvasively capturing of wave propagation in the subcutaneous tissue. Wave speeds were measured in the subcutaneous tissues of both the control and affected extremities. Results A total of 11 female patients with secondary lymphedema in the extremities were enrolled in this study. The magnitudes of the wave speeds of the region of interest in the subcutaneous tissue at lymphedema sites in the upper extremity (3.9 ± 0.17 m/s, 5.96 ± 0.67 m/s, and 7.41 ± 1.09 m/s) were statistically higher than those of the control sites (2.1 ± 0.27 m/s, 2.93 ± 0.57 m/s, and 3.56 ± 0.76 m/s) at 100, 150, and 200 Hz (P < 0.05), and at 100 and 200 Hz (P < 0.05) between lymphedema (4.33 ± 0.35 m/s, 4.17 ± 1.00 m/s, and 4.56 ± 0.37 m/s) and controls sites (2.48 ± 0.43 m/s, 2.77 ± 0.55 m/s, and 3.06 ± 0.29 m/s) in the lower extremity. Conclusions These preliminary data suggest that ultrasound vibroelastography may be useful in the evaluation of secondary lymphedema and can be a valuable tool to noninvasively track treatment progress.

Lung ultrasound (US) surface wave elastography (SWE) is a novel technique that measures superficial lung tissue elastic properties. A thin pleural fluid layer covers a lung, but its effect on lung measurements in SWE is unknown. We modeled a lung and pleural fluid with sponges and a thin layer of US transmission gel. Sponge surface wave speeds measured from SWE were compared for sponges without and with the thin US gel layer at 3 wave excitation frequencies. The comparison showed that the sponge surface wave speed measurements were not affected by the thin gel layer.

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.

Purpose: Abnormal ocular biomechanical properties may be important for understanding the risk of glaucoma. However, there are no clinical methods for measuring standard material properties in patients. In this feasibility study we demonstrated proof-of-principle for a novel method, ultrasound surface wave elastography (USWE), to determine the in vivo Young’s modulus of elasticity of corneas in normal human eyes. Methods: In total, 20 eyes of 10 healthy subjects (mean age, 51.4±7.2; ±SD; range, 43 to 64 y) were studied. A spherical-tipped probe (3-mm diameter) was placed on closed eyelids and generated a gentle harmonic vibration at 100 Hz for 0.1 second. Wave speed propagation in the cornea was measured by USWE, and Young’s modulus was calculated from the wave speed. Associations between Young’s modulus and intraocular pressure (IOP), age, central corneal thickness, and axial length were explored by the Pearson correlation. Statistical significance was determined by using generalized estimating equation models to account for possible correlation between fellow eyes. Results: Mean IOP was 12.8±2.7 mm Hg. Mean wave speed in the cornea was 1.82±0.10 m/s. Young’s modulus of elasticity was 696±113 kPa and was correlated with IOP (r=0.57; P=0.004), but none of the other variables (P>0.1). Conclusions: USWE is a novel noninvasive technique for measuring ocular biomechanical properties. Corneal Young’s modulus in normal eyes is associated with IOP, consistent with measurements in cadaver eyes. Further work is needed to determine elasticity in other ocular tissues, particularly the sclera, and if elasticity is altered in glaucoma patients.

ABSTRACT Carpal tunnel pressure is a key factor in the etiology of carpal tunnel syndrome. Numerous approaches have been conducted to measure carpal tunnel pressure. However, most techniques are invasive and take time and effort. We have developed an innovative approach to noninvasively assess the tunnel pressure by using the ultrasound surface wave elastography (USWE) technique. In a previous study it was shown that the shear wave speed in a tendon increased linearly with increasing tunnel pressure enclosed the tendon in a simple tendon model. This study aimed to examine the relationship between the carpal tunnel pressure and the shear wave speeds inside and outside the carpal tunnel in a human cadaveric model. The result showed that the shear wave speed inside the carpal tunnel increased linearly with created carpal tunnel pressure, while the shear wave speed outside the carpal tunnel remained constant. These findings suggest that noninvasive measurement of carpal tunnel pressure is possible by measuring the shear wave speed in the tendon. After fully establishing this technology and being applicable in clinic, it would be useful in the diagnosis of carpal tunnel syndrome. For that reason, further validation with this technique in both healthy controls and patients with carpal tunnel syndrome is required. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:477–483, 2018.

The purpose of this Letter to the Editor is to demonstrate an effective method for estimating viscoelasticity based on measurements of the Rayleigh surface wave speed. It is important to identify the surface wave mode for measuring surface wave speed. A concept of start frequency of surface waves is proposed. The surface wave speeds above the start frequency should be used to estimate the viscoelasticity of tissue. The motivation was to develop a noninvasive surface wave elastography (SWE) technique for assessing skin disease by measuring skin viscoelastic properties. Using an optical based SWE system, the author generated a local harmonic vibration on the surface of phantom using an electromechanical shaker and measured the resulting surface waves on the phantom using an optical vibrometer system. The surface wave speed was measured using a phase gradient method. It was shown that different standing wave modes were generated below the start frequency because of wave reflection. However, the pure symmetric surface waves were generated from the excitation above the start frequency. Using the wave speed dispersion above the start frequency, the viscoelasticity of the phantom can be correctly estimated.

Characterization of the viscoelastic mechanical properties of skin is important for improving accurate medical examination and diagnosis of disorders involving cutaneous and subcutaneous tissues; more thoroughly understanding skin biophysical and physiological properties; identifying normal and abnormal skin aging and disease processes; developing and applying improved pharmacologic and other therapeutic interventions; as well as cosmetic applications. Several noninvasive methods have been developed for measurement of mechanical properties of skin [1]. However, most methods measure a stiffness parameter but not the material properties of skin. For example, the suction method measures the displacement of skin in response to suction. The measurement is dependent on the aperture and fixation of probes and also difficult to interpret.