Jun-Feng He

Dynamic changes of elasticity, cross-sectional area, and fat infiltration of multifidus at different postures in men with chronic low back pain.

BACKGROUND CONTEXT Multifidus cross-sectional area was often measured in chronic low back pain (LBP) patients to estimate the muscle activity for spinal stability. However, such estimation may be inadequate as the contribution of muscle elasticity in muscle activity is ignored. In vivo quantitative data on multifidus elasticity is therefore important for the study of muscle contractile function in response to motor control for spinal stability in chronic LBP patients. PURPOSE The purpose of this study was to quantify the elasticity, cross-sectional area, and fat area of the multifidus for the contractile function and the distribution of deformable muscle tissue and nondeformable fat tissue at different postures in patients with and without chronic LBP. STUDY DESIGN/SETTING This is a prospective study. Force-deformation data of the multifidus were acquired using ultrasound elastography. The anatomical changes of the multifidus were measured on the cross-sectional images of the multifidus acquired using B-mode ultrasound imaging. PATIENT SAMPLE The sample comprised 12 adult male patients with chronic LBP and 12 asymptomatic male controls. OUTCOME MEASURES The outcome measure was the elasticity of the multifidus at the L4 level for the assessment of muscle contractile function when patients were in the prone, upright, and 25° and 45° forward stooping positions. The cross-sectional area and fat area were also measured on the B-mode ultrasound images of the multifidus acquired at the same vertebral level and the postures. METHODS With the patients in each of the prone, upright, and 25° and 45° forward stooping positions, ultrasound elastography and B-mode ultrasound imaging were performed on the left and right multifidus at the L4 level. The elasticity of multifidus indicated by the effective Youngs modulus was derived from the force-deformation data acquired using ultrasound elastography. The cross-sectional area and fat area were assessed on the B-mode ultrasound images. The effective Youngs modulus, cross-sectional area, and fat area were analyzed with multivariate general linear model analysis to investigate the possible effects of LBP and posture. RESULTS There was an increasing stiffness of multifidus demonstrated by increasing effective Youngs modulus from the prone to upright position and 25° and 45° forward stooping positions. Differences in multifidus stiffness between chronic LBP patients and asymptomatic controls were shown in the upright and 25° and 45° forward stooping positions but not in the prone position. The cross-sectional area of the multifidus increased from the prone position to the greatest value in the upright position and decreased in 25° and 45° forward stooping positions. Smaller multifidus cross-sectional area was demonstrated in chronic LBP patients than that in controls at all postures. No effect of posture on fat area within the multifidus was shown although the fat area within the multifidus was larger in chronic LBP patients. CONCLUSIONS Different, changing patterns of elasticity and cross-sectional area were identified in the multifidus in relation to posture. Increased stiffness of multifidus in response to the physiologic range of static loads and smaller cross-sectional area was characterized in the chronic LBP condition for spinal stability. Ultrasound elastography offers in vivo assessment of muscle contractile function of deep trunk muscles, which benefits the future investigation of the neuromuscular regulating mechanism in LBP. It can also be applied to refine the palpatory skill for the physical assessment in sports training and physical therapy.

A System for the Synchronized Recording of Sonomyography, Electromyography and Joint Angle

Ultrasound and electromyography (EMG) are two of the most commonly used diagnostic tools for the assessment of muscles. Recently, many studies reported the simultaneous collection of EMG signals and ultrasound images, which were normally amplified and digitized by different devices. However, there is lack of a systematic method to synchronize them and no study has reported the effects of ultrasound gel to the EMG signal collection during the simultaneous data collection. In this paper, we introduced a new method to synchronize ultrasound B-scan images, EMG signals, joint angles and other related signals (e.g. force and velocity signals) in real-time. The B-mode ultrasound images were simultaneously captured by the PC together with the surface EMG (SEMG) and the joint angle signal. The deformations of the forearm muscles induced by wrist motions were extracted from a sequence of ultrasound images, named as Sonomyography (SMG). Preliminary experiments demonstrated that the proposed method could reliably collect the synchronized ultrasound images, SEMG signals and joint angle signals in real-time. In addition, the effect of ultrasound gel on the SEMG signals when the EMG electrodes were close to the ultrasound probe was studied. It was found that the SEMG signals were not significantly affected by the amount of the ultrasound gel. The system is being used for the study of contractions of various muscles as well as the muscle fatigue.

Performances of One-Dimensional Sonomyography and Surface Electromyography in Tracking Guided Patterns of Wrist Extension

Electromyography (EMG) and ultrasonography have been widely used for skeletal muscle assessment. Recently, it has been demonstrated that the muscle thickness change collected by ultrasound during contraction, namely sonomyography (SMG), can also be used for assessment of muscles and has the potential for prosthetic control. In this study, the performances of one-dimensional sonomyography (1D SMG) and surface EMG (SEMG) signal in tracking the guided patterns of wrist extension were evaluated and compared, and the potential of 1D SMG for skeletal muscle assessment and prosthetic control was investigated. Sixteen adult normal subjects including eight males and eight females participated in the experiment. The subject was instructed to perform the wrist extension under the guidance of displayed sinusoidal, square and triangular waveforms at movement rates of 20, 30, 50 cycles per min. SMG and SEMG root mean squares (RMS) were collected from the extensor carpi radialis, respectively, and their RMS errors in relation to the guiding signals were calculated and compared. It was found that the mean RMS tracking errors of SMG under different movement rates were 18.9% +/- 2.6% (mean+/-SD), 18.3% +/- 4.5%, and 17.0% +/- 3.4% for sinusoidal, square and triangular guiding waveforms, while the corresponding values for SEMG were 30.3% +/- 0.4%, 29.0% +/- 2.7% and 24.7% +/- 0.7%, respectively. Paired t test showed that the RMS errors of SMG tracking were significantly smaller than those of SEMG. Significant differences in RMS tracking errors of SMG among the three movement rates (p<0.01) for all the guiding waveforms were also observed using one-way analysis of variance (ANOVA). The results suggest that SMG signal, based on further improvement, has great potential to be an alternative method to SEMG to evaluate muscle function and control prostheses.

Development of a foot scanner for assessing the mechanical properties of plantar soft tissues under different bodyweight loading in standing

Mechanical properties of plantar soft tissues are important characteristics of the foot and are prone to being affected by foot pathologies such as diabetes. Therefore, it is of great importance to measure the mechanical properties of plantar soft tissues in vivo. However, such measurement in previous studies is mostly conducted in foot without loading and there is a paucity of instrument available which can assess the foot mechanical properties under a weight-loading status. In this study, a foot scanner incorporating a tissue ultrasound palpation (indentation) system (TUPS) which could assess the mechanical properties of plantar soft tissues under different body-weight loading was developed. The movement of the foot could also be monitored in real time during the indentation test to improve the test reliability. Preliminary tests were conducted on ten normal subjects at the heel region under various loading of the bodyweight. The results showed that the thickness decreased by 12.0% (from 13.83±2.52 mm to 12.10±1.95 mm) while the stiffness increased by 83.4% (from 40.0±20.7 kPa to 69.0±26.0 kPa) when the loading increased from 0% to 80% of the bodyweight (both p<0.001, repeated measure one-way ANOVA). Therefore, our system has been demonstrated to be useful in studying the loading dependence of mechanical properties of plantar soft tissues. Potential applications of the system in clinical studies for characterization and monitoring of foot pathologies such as ageing and diabetes are discussed at the end of this note.

In-vitro Strain and Modulus Measurements in Porcine Cervical Lymph Nodes

Cervical lymph nodes are common sites of metastatic involvement in head and neck cancers. These lymph nodes are superficially located and palpation is a common practice for assessing nodal hardness and staging cancer which is, however, too subjective and with limited accuracy. In this study, the mechanical properties of pig lymph node tissues were investigated using ultrasound elastography and indentation test. Lymph nodes were excised from fresh pork pieces and embedded in an agar-gelatin phantom for strain imaging by elastography. A strain ratio reflecting the strain contrast of lymph node over agar-gelatin phantom was used to assess the elasticity of the lymph node. A cutting device was then custom-designed to slice the phantom into uniform slices for indentation test. The measurements revealed that there were significant differences in both the strain ratio and Young’s modulus between the peripheral and middle regions of the lymph nodes (both p < 0.05); however, the results appeared contradictory. Correlation between the results of the two measurements (modulus ratio vs. inversed strain ratio) showed their association was moderate for both the peripheral and middle regions (R2 = 0.437 and 0.424 respectively). As the tests were only performed on normal lymph nodes, comparison in stiffness between healthy and abnormal lymph nodes could not be made. Future studies should be conducted to quantify the stiffness change in abnormal lymph nodes.

Comparison of sonomyography and electromyography of forearm muscles in the guided wrist extension

Electromyography (EMG) and ultrasonography have been widely used for skeletal muscle assessment. The muscle thickness change detected using ultrasound has been recently defined as sonomyography. In this study, the performances of one dimensional sonomyography (1-D SMG) and surface EMG signal in tracking the guided patterns of wrist extension were compared, and the potential of 1-D SMG for skeletal muscle assessment and prosthesis control was investigated. Sixteen normal subjects were instructed to perform the wrist extension under the guidance of displayed sinusoidal, square and triangular waveforms at movement rates of 20, 30, 50 cycles per minute. SMG and EMG root mean squares (RMS) were collected from the extensor carpi radialis respectively and their RMS errors in relation to the guiding signals were compared. Paired t-test showed that the RMS errors of SMG tracking were significantly smaller than those of EMG. The results suggest that SMG signal has great potential to be an alternative method of EMG to evaluate muscle function and control prosthesis.

Liver Fibrosis Assessment Using Transient Elastography Guided with Real-Time B-Mode Ultrasound Imaging

Liver fibrosis is a kind of chronic damage of the liver. The progression of liver fibrosis will result cirrhosis which is one of the top 10 causes of death in the western world. Recently, a device developed based on transient ultrasound elastography, named as Fibroscan, shows promising results with high accuracy and good reproducibility. However, this device does not provide visual guidance for the liver being tested during measurement. We aim to design and validate a transient elastography system with real-time B-mode imaging for liver fibrosis assessment. Our development is based on a conventional B-mode ultrasound scanner, which consists of a B-mode ultrasound probe fixed along the axis of a mechanical vibrator. The induced shear wave propagates through the liver tissue. During measurement, B-mode ultrasound imaging with a frame rate of 30 f/s is generated in real-time to view the morphological information of the tissue, and an A-mode ultrasound with a frame rate of 6000 f/s is generated to track the propagation of shear wave at a selected location. The propagation speed of the shear wave is related to the tissue stiffness and Young’s modulus is calculated. The system was tested using a series of custom-made phantoms with different stiffness and the results were compared with those measured by Fibroscan. For phantom A1, the Young’s modulus is 32.4 kPa and 35.4 kPa obtained by Fibroscan and our system, respectively. For phantom A2, the modulus is 15.9 kPa and 19.8 kPa, respectively. For the preliminary in vivo assessment, the Young’s modulus of a normal male subject is 5.8 kPa and 7.5 kPa obtained by Fibroscan and our system, respectively. In summary, we have successfully developed a transient ultrasound elastography system with real-time B-mode imaging for the assessment of liver fibrosis.