Yuexiang Wang

Evaluation of Elastic Stiffness in Healing Achilles Tendon After Surgical Repair of a Tendon Rupture Using In Vivo Ultrasound Shear Wave Elastography.

Background There has been no published report assessing the mechanical properties of a repaired Achilles tendon after surgery using shear wave elastography (SWE). The aim of this study was to investigate the changes in mechanical properties of the healing Achilles tendon after surgical repair of a tendon rupture using ultrasound SWE and how these changes correlate with tendon function. Material/Methods Twenty-six patients who underwent surgical repair for Achilles tendon rupture were examined with ultrasound SWE coupled with a linear array transducer (4–15 MHz). The elasticity values of the repaired Achilles tendon in a longitudinal view were measured at 12, 24, and 48 weeks postoperatively. Functional outcomes were assessed with the American Orthopedic Foot and Ankle Society (AOFAS) rating system at 12, 24, and 48 weeks postoperatively. General linear regression analysis and correlation coefficients were used to analyze the relationship between elasticity and the AOFAS score. Results There were significant differences with respect to the mean elasticity values and functional scores of the repaired Achilles tendon at 12, 24, and 48 weeks postoperatively (all P<0.05). Tendon function was positively correlated with the elasticity of the repaired Achilles tendon (P=0.0003). Conclusions Our findings suggest that SWE can provide biomechanical information for evaluating the mechanical properties of healing Achilles tendon and predict Achilles tendon function.

Effects of Local Vibration on Bone Loss in ­Tail-Suspended Rats

We investigated the effects of vibration (35 Hz, 45 Hz and 55 Hz) as countermeasure locally applied to unloading hind limbs on bone, muscle and Achilles tendon. 40 female Sprague Dawley rats were divided into 5 groups (n=8, each): tail-suspension (TS), TS plus 35 Hz/0.3 g vibration (TSV35), TS plus 45 Hz/0.3 g vibration (TSV45), TS plus 55 Hz/0.3 g vibration (TSV55) and control (CON). After 21 days, bone mineral density (BMD) and the microstructure of the femur and tibia were evaluated by μCT in vivo. The biomechanical properties of the femur and Achilles tendon were determined by a materials testing system. Ash weight of bone, isotonic contraction and wet weight of soleus were also investigated. 35 Hz and 45 Hz localized vibration were able to significantly ameliorate the decrease in trabecular BMD (expressed as the percentage change from TS, TSV35: 48.11%, TSV45: 31.09%), microstructure and ash weight of the femur and tibia induced by TS. Meanwhile, 35 Hz vibration significantly improved the biomechanical properties of the femur (57.24% bending rigidity and 41.66% Youngs modulus vs. TS) and Achilles tendon (45.46% maximum load and 66.67% Youngs modulus vs. TS). Additionally, Youngs modulus of the femur was highly correlated with microstructural parameters. Localized vibration was useful for counteracting microgravity-induced musculoskeletal loss. In general, the efficacy of 35 Hz was better than 45 Hz or 55 Hz in tail-suspended rats.

Quantitative Evaluation of the Peripheral Nerve Blood Perfusion with High Frequency Contrast-Enhanced Ultrasound

RATIONALE AND OBJECTIVES The blood perfusion of peripheral nerves plays an important role in regeneration after nerve injury. Previous studies have shown that it is possible to quantitatively assess the blood perfusion of the tissue using contrast-enhanced ultrasound (CEUS). The aim of this study was to evaluate the feasibility of CEUS for quantitative assessment of the blood perfusion of the sciatic nerve in normal New Zealand white rabbits and to compare these parameters to those of surrounding skeletal muscle and the main artery in the thigh. MATERIALS AND METHODS CEUS of the bilateral sciatic nerves was performed in 12 normal New Zealand white rabbits after a bolus injection of SonoVue (0.13 mL/kg). Pulse-inversion harmonic imaging was used for real-time CEUS. The blood perfusion of the left sciatic nerve was compared to that of its surrounding muscle, the arterial branch in the thigh, and the contralateral side. RESULTS The supplying arteries in the sciatic nerve could be demonstrated during the early phase of CEUS, followed by the homogeneous enhancement of the whole nerve. The area under the curve and the perfusion index of the sciatic nerve were higher than those of the surrounding muscle and lower than those of the arterial branch in the thigh (both P values = .000). The maximum intensity of the sciatic nerve was similar to that of skeletal muscle and lower than that of the arterial branch. The time to peak was not significantly different among the sciatic nerve, skeletal muscle, and arterial branch (P = .551). There were no differences in area under the curve, mean transit time, perfusion index, maximum intensity, and time to peak between the left and right sciatic nerves (P > .05). CONCLUSIONS CEUS may be a feasible method for the quantitative assessment of blood perfusion of the peripheral nerves.

Sonographic evaluation of peripheral nerve injuries following the Wenchuan earthquake

To analyze retrospectively the sonographic characteristics of the peripheral nerve injuries (PNIs) resulted from Wunchuan earthquake.

Ultrasonic reflection coefficient and surface roughness index of OA articular cartilage: relation to pathological assessment

BackgroundEarly diagnosis of Osteoarthritis (OA) is essential for preventing further cartilage destruction and decreasing severe complications. The aims of this study are to explore the relationship between OA pathological grades and quantitative acoustic parameters and to provide more objective criteria for ultrasonic microscopic evaluation of the OA cartilage.MethodsArticular cartilage samples were prepared from rabbit knees and scanned using ultrasound biomicroscopy (UBM). Three quantitative parameters, including the roughness index of the cartilage surface (URI), the reflection coefficients from the cartilage surface (R) and from the cartilage-bone interface (Rbone) were extracted. The osteoarthritis grades of these cartilage samples were qualitatively assessed by histology according to the grading standards of International Osteoarthritis Institute (OARSI). The relationship between these quantitative parameters and the osteoarthritis grades was explored.ResultsThe results showed that URI increased with the OA grade. URI of the normal cartilage samples was significantly lower than the one of the OA cartilage samples. There was no significant difference in URI between the grade 1 cartilage samples and the grade 2 cartilage samples. The reflection coefficient of the cartilage surface reduced significantly with the development of OA (p < 0.05), while the reflection coefficient of the cartilage-bone interface increased with the increase of grade.ConclusionHigh frequency ultrasound measurements can reflect the changes in the surface roughness index and the ultrasound reflection coefficients of the cartilage samples with different OA grades. This study may provide useful information for the quantitative ultrasonic diagnosis of early OA.

Ultrasound speed and attenuation in progressive trypsin digested articular cartilage.

Subtle changes of articular cartilage (AC) can lead to tissue degeneration and even osteoarthritis (OA). The early degeneration of AC is closely related to a change in proteoglycans (PG) content. The observation of PG is therefore an appropriate way of studying OA and evaluating the degree of AC degeneration. In this study, 20 cartilage-bone samples were prepared from normal porcine femoral condyle cartilage and 10 samples were digested over 2 h using 0.25% trypsin solution. The dynamic process of PG-digestion was explored using a conventional A-mode ultrasound (US) experimental system with a 10 MHz center frequency. Quantitative acoustic parameters were calculated from ultrasonic radio-frequency echo signals and included US speed (USS), US amplitude attenuation coefficient (UAA) and broadband US attenuation coefficient (BUA). The experimental results showed that the conventional A-mode ultrasound is valuable for tracking the degree of PG-digestion. Histology also confirmed the validity of the ultrasound observations. For every AC sample, the degree of PG-digestion within a given time was different and was affected by individual differences. After two hours of degeneration, USS showed a mean decrease of 0.4% (P<0.05). UAA was significantly lower after a two-hour PG depletion period (from (2.45±0.23) to (2.28±0.41) dB mm−1). BUA showed no significant differences during this process. In conclusion, conventional ultrasound can provide useful information about trypsin-induced progressive PG depletion in AC and can reflect variations of PG content via the quantitative acoustic parameters USS and UAA. The results of this study may be used to identify an indirect indicator of cartilage matrix integrity and OA disease progression.

The Characteristics of Ultrasound Speed and Attenuation in Progressive Trypsin Digested Articular Cartilage

Articular cartilage is a biological weight-bearing tissue covering the bony ends of articulating joints. Subtle changes in tissue composition can lead to degeneration of articular cartilage. Some studies indicated that ultrasound acoustic parameters are related with the degeneration of articular cartilage. The aim of this study is to investigate the changes of ultrasound speed and attenuation in progressive trypsin digested articular cartilage using high frequency ultrasound. Fresh intact cartilage specimens were monitored with a 25 MHz ultrasound transducer during progressive trypsin digestion for 1 hour. The result showed that ultrasound speed increased and ultrasound amplitude attenuation decreased in articular cartilage with PG digestion. However, broadband ultrasound attenuation was non-sensitive to PG degeneration. The results maybe provide some information for diagnosing of early AC diseases.

Ultrasound Biomicroscopy for the Detection of Early Osteoarthritis in an Animal Model

RATIONALE AND OBJECTIVES Osteoarthritis (OA) is a common disease, and early diagnosis is essential for preventing further cartilage destruction and decreasing severe complications. Ultrasound biomicroscopy (UBM) is sensitive for detecting minute lesions in tissue because of its higher resolution, but its B-mode characterization of the early stage of OA has not been widely studied. The aim of this study was to determine the usefulness of UBM for detecting the early stage of OA using a rabbit model of early OA. MATERIALS AND METHODS Eighteen adult New Zealand White female rabbits were used in this study, which included 12 rabbits that underwent transections of the left anterior cruciate ligament and six control rabbits. At 2, 4, and 6 weeks after surgery, four experimental rabbits and two control rabbits were euthanized. UBM was performed to evaluate the articular cartilage surfaces of the left knee, using a 55-MHz transducer. All the articular cartilage surfaces were independently assessed in blinded fashion by two radiologists for the severity of OA. The value of UBM, interobserver reliability, and the concordance between UBM and pathologic grades were determined. RESULTS For the first radiologist, the sensitivity, specificity, positive predictive value, and negative predictive value of UBM for the diagnosis of OA were 91%, 83%, 89%, and 86%, respectively. For the second radiologist, the sensitivity, specificity, positive predictive value, and negative predictive value of UBM were 93%, 86%, 91%, and 89%, respectively. The concordance between UBM and pathologic grades for both radiologists was high (κ = 0.72 and 0.76), and the interobserver agreement was high (κ = 0.80). CONCLUSIONS UBM can be used to evaluate cartilage defects in an animal model, and further study is needed to determine whether this technique can be valuable for detecting early OA in humans.

Gray-scale Contrast-enhanced Ultrasonography for Quantitative Evaluation of the Blood Perfusion of the Sciatic Nerves with Crush Injury

RATIONALE AND OBJECTIVES Blood perfusion of peripheral nerves plays an important role in regeneration after nerve injury. Functional recovery after a peripheral nerve injury depends not only on the survival of the affected neurons but also on the recovered blood perfusion. Previous studies have shown that it is possible to quantitatively assess blood perfusion of tissue using contrast-enhanced ultrasound (CEUS). The aim of this study was to evaluate the usefulness of CEUS for the quantitative evaluation of blood perfusion of the sciatic nerves with crush injury. MATERIALS AND METHODS Crush injuries were created in the left sciatic nerve of 30 New Zealand white rabbits. CEUS of the bilateral sciatic nerves was performed in six experimental rabbits at 3 days, 1 week, 2 weeks, 4 weeks, and 8 weeks after injury. Pulse-inversion harmonic imaging was used for real-time CEUS. The other six rabbits were used as a control group. Serial laser Doppler measurements of blood flow and quantitative histologic evaluation were performed parallel to CEUS on all animals. RESULTS Quantitative analysis of CEUS showed that the perfusion index of the crushed sciatic nerves was increased at 3 days after injury, with a peak at 1 week after injury (P = .000). The area under the curve for the crushed sites was increased at 3 days after injury, with a peak at 2 weeks after injury (P = .000). The mean transit time and maximum intensity of the crushed site of the left sciatic nerves were not significantly changed during the 2 months after injury (P = .335 and P = .157 respectively). The perfusion indices measured by CEUS correlated well with those measured by laser Doppler (r = 0.791, P = .000). Marked Wallerian degeneration was found at the crushed site of sciatic nerves at 3 days after injury. The percentage of degenerated myelinated axons was increased during the first 2 weeks after injury and then decreased during the following period. Regenerated axons with small diameter and thin myelin sheaths were found at 2 weeks after injury and during the following period. CONCLUSIONS CEUS may provide a new imaging method to quantitatively analyze blood perfusion of injured peripheral nerves.

Virtual ultrasonic waveform acquisition and analysis system based on LabVIEW and PCI-12400 A/D card

A-mode medical ultrasound device is important tool for clinical examinations in many clinical departments, especially ophthalmology. However, many complex or obscure features can not be identified well using these existing instruments, the reason is that ultrasonic echo waveforms from body contain more plentiful information than is utilized in conventional A-model medical ultrasound instrument, so more sophisticated procedures and algorithms maybe required to process the acquired waveform. In this study, a flexible PC-based virtual instrument system for acquisition and analysis of ultrasonic echo signal was developed based on LabVIEW graphical programming language (National Instruments, USA) and a high digitization-rate A/D sample card PCI-12400 (CompuScope, Gage, Canada). Ultrasound speed and ultrasound attenuation coefficients were computed in this virtual instrument system. In addition, this system can provide an adaptable tool that may be modified to suit a given application, with scope for future implementation in the field.