Quantification of Nerve Viscosity Using Shear Wave Dispersion Imaging in Diabetic Rats: A Novel Technique for Evaluating Diabetic Neuropathy

Systematic quantification of differences in shear wave elastography estimates between linear-elastic and viscoelastic material assumptionsa)

Quantitative, accurate, and standardized metrics are important for reliable shear wave elastography (SWE)-based biomarkers. For over two decades, the linear-elastic material assumption has been employed in SWE modes. In recent years, viscoelasticity estimation methods have been adopted in a few clinical systems. The current study aims to systematically quantify differences in SWE estimates obtained using linear-elastic and viscoelastic material assumptions. An acousto-mechanical simulation framework of acoustic radiation force impulse-based SWE was created to elucidate the effect of material viscosity and shear modulus on SWE estimates. Shear modulus estimates exhibited errors up to 72% when a numerical viscoelastic phantom was assessed as linearly elastic. Shear modulus estimates of polyvinyl alcohol phantoms between rheometry and SWE following the Kelvin-Voigt viscoelastic model assumptions were not significantly different. However, the percentage difference in shear modulus estimates between rheometry and SWE using the linear-elastic assumption was 50.1%-62.1%. In ex vivo liver, the percentage difference in shear modulus estimates between linear-elastic and viscoelastic methods was 76.1%. These findings provide a direct and systematic quantification of the potential error introduced when viscoelastic tissues are imaged with SWE following the linear-elastic assumption. This work emphasizes the need to utilize viscoelasticity estimation methods for developing robust quantitative imaging biomarkers.

Quantitative analysis of contrast-enhanced ultrasonography in rat models of hepatic acute graft-versus-host disease

Background

Hepatic acute graft-versus-host disease (aGVHD) is a major life-threatening complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). We hypothesized that contrast-enhanced ultrasound (CEUS) could serve as a new imaging biomarker in early diagnosis of hepatic aGVHD by detecting liver microcirculation.

Methods

Thirty Wistar rats received allo-HSCT were finally included after excluding 9 rats, and they were randomly divided into 5 groups (1- to 5-week groups, 6 per group). Six rats were used for the control group without any intervention. We observed the clinical scores, serum liver enzyme levels and liver CEUS parameters of rats in each group. Hepatic aGVHD was finally confirmed by histopathologic analysis. The diagnostic performance of CEUS parameters in detecting GVHD was evaluated by comparing the area under the receiver operating curve (AUC) values.

Results

After HSCT, the rats developed ruffling of fur, maculopapular rash, weight loss, accompanied by increased clinical scores. Serum liver enzymes were significantly higher than those in the control group from the third week, especially alkaline phosphatase, while CEUS parameters, peak intensity (PI) and mean transit time (MTT), changed in the second week (P<0.001). Compared with non-aGVHD group, the PI was significantly decreased while time to peak and MTT were prolonged in aGVHD group. CEUS parameters were more strongly correlated with pathological grade than serology. PI was an independent predictor for hepatic aGVHD. The AUC of CEUS parameters for diagnosing hepatic aGVHD was 0.933 (95% CI: 0.779-0.992), which was higher than that of clinical scores (AUC =0.748, 95% CI: 0.557-0.888, P=0.032) and serological markers (AUC =0.902, 95% CI: 0.737-0.980, P=0.694).

Conclusions

CEUS exhibits promising applications as a quantitative method to detect hepatic aGVHD and early liver damage.

Ultrasonic visualization technique for anatomical and functional analyses of the sciatic nerve in rats

Background and objective

Ultrasound has been widely used in the diagnosis and minimally invasive treatment of peripheral nerve diseases in the clinic, but there is still a lack of feasibility analysis in rodent models of neurological disease. The purpose of this study was to investigate the changes in the cross-sectional area of the sciatic nerve of different genders and body weights and to explore the effectiveness and reliability of an ultrasound-guided block around the sciatic nerve in living rats.

Methods

Using ultrasound imaging anatomy of the sciatic nerve of rats, the cross-sectional area of the sciatic nerve in rats of different genders from 6 to 10 weeks old was calculated, and then analyzed its correlation with body weight. Further analyses were conducted through behavioral and cadaveric studies to evaluate the feasibility of ultrasound-guided perineural injection of the sciatic nerve in rats.

Results

We first reported that the sciatic nerve cross-sectional area of rats was increased with age (F = 89.169, P < 0.001), males had a higher sciatic nerve cross-sectional area than females (F = 60.770, P < 0.001), and there was a positive correlation with body weight (r_Male = 0.8976, P < 0.001; r_Female = 0.7733, P < 0.001). Behavioral observation of rats showed that the lower extremity complete block rate was 80% following the administration of drugs around the sciatic nerve under ultrasound guidance and staining with methylene blue occurred in all sciatic nerves and surrounding muscles and fascia using 20 ultrasound-guided injections.

Conclusions

Ultrasound visualization technology can be used as a new auxiliary evaluation and intervention therapy for animal models of peripheral nerve injury, and will provide overwhelming new references for the basic research of neurological diseases.

Electrodiagnostic Testing and Nerve Ultrasound of the Carpal Tunnel in Patients with Type 2 Diabetes

In diabetic patients, controversies still exist about the validity of electrodiagnostic and nerve ultrasound diagnosis for carpal tunnel syndrome (CTS). We analyzed 69 patients with type 2 diabetes. Nerve conduction studies and peripheral nerve ultrasound of the median nerve over the carpal tunnel were performed. CTS symptoms were assessed using the Boston Carpal Tunnel Questionnaire. Polyneuropathy was assessed using the Neuropathy Symptom Score and the Neuropathy Disability Score. Although 19 patients reported predominantly mild CTS symptoms, 37 patients met the electrophysiological diagnosis criteria for CTS, and six patients were classified as severe or extremely severe. The sonographic cross-sectional area (CSA) of the median nerve at the wrist was larger than 12 mm² in 45 patients (65.2%), and the wrist-to-forearm-ratio was larger than 1.4 in 61 patients (88.4%). Receiver operating characteristic analysis showed that neither the distal motor latency, the median nerve CSA, nor the wrist-to-forearm-ratio could distinguish between patients with and without CTS symptoms. Diagnosis of CTS in diabetic patients should primarily be based upon typical clinical symptoms and signs. Results of electrodiagnostic testing and nerve ultrasound have to be interpreted with caution and additional factors have to be considered especially polyneuropathy, but also body mass index and hyperglycemia.