What is the role of measuring shear wave dispersion using shear wave elastography in pancreatic parenchyma?

Value of Two-Dimensional Shear-Wave Elastography in Differentiating Pancreatic Steatosis From Pancreatic Fibrosis

OBJECTIVES

Pancreatic steatosis (PS) and pancreatic fibrosis (PF) both show increased pancreatic echogenicity on conventional B-mode ultrasound. In this study, we assessed the applicability of two-dimensional shear-wave elastography (2D-SWE) for their discrimination.

METHODS

We gathered data from 120 adults with valid 2D-SWE measurements, comprising 40 healthy individuals, 55 individuals diagnosed with PS via non-enhanced computed tomography (CT), and 25 patients clinically diagnosed with non-calcific chronic pancreatitis. The participants were divided into three groups: normal pancreas (NP), PS, and PF. pancreatic echogenicity, pancreatic stiffness, and CT values between groups were analyzed.

RESULTS

The 2D-SWE and CT values among the NP, PS, and PF groups all showed significant differences (P < .001). For the diagnosis of PS and PF using 2D-SWE, the area under the curve (AUC) values were 0.9100 and 0.9940, respectively, with optimal cut-off values of 5.7 kPa for predicting PS and 8.2 kPa for predicting PF.

CONCLUSIONS

The 2D-SWE technique enabled rapid and quantitative assessment of the hardness of hyperechoic pancreas visualized on conventional B-mode ultrasound, which holds certain value in distinguishing PS from PF.

Efficacy of shear wave elastography for the diagnosis of chronic pancreatitis

BACKGROUND/PURPOSE

Shear wave elastography (SWE) is a clinical method used to evaluate liver hardness. In this study, we assessed its applicability in assessing the pancreas and its potential for diagnosing chronic pancreatitis.

METHODS

We performed SWE on 59 patients who underwent abdominal ultrasound, and measured the computed tomography (CT) values of the pancreas. Patients were classified as having a normal pancreas (NP), early chronic pancreatitis (ECP), or chronic pancreatitis (CP). SW elasticity (SWe), SW dispersion (SWd), and CT values between groups were analyzed.

RESULTS

SWe significantly differed between the CP and NP/ECP groups (NP vs CP; P = 0.001, ECP vs CP; P = 0.026,), while SWd showed a significant difference only between the NP and CP group (NP vs CP; P = 0.001). The CT values were significantly different between the CP and NP/ECP groups (NP vs CP; P = 0.0006, ECP vs CP; P = 0.0027).

CONCLUSION

Pancreatic SWE and CT values were helpful in the diagnosis of chronic pancreatitis. SWd may reveal status changes in ECP.

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

Objective

Viscoelasticity is an essential feature of nerves, although little is known about their viscous properties. The discovery of shear wave dispersion (SWD) imaging has presented a new approach for the non-invasive evaluation of tissue viscosity. The present study investigated the feasibility of using SWD imaging to evaluate diabetic neuropathy using the sciatic nerve in a diabetic rat model.

Materials and Methods

This study included 11 diabetic rats in the diabetic group and 12 healthy rats in the control group. Bilateral sciatic nerves were evaluated 3 months after treatment with streptozotocin. We measured the nerve cross-sectional area (CSA), nerve stiffness using shear wave elastography (SWE), and nerve viscosity using SWD imaging. The motor nerve conduction velocity (MNCV) was also measured. These four indicators and the histology of the sciatic nerves were then compared between the two groups. The performance of CSA, SWE, and SWD imaging in distinguishing the two groups was assessed using receiver operating characteristic (ROC) analysis.

Results

Nerve CSA, stiffness, and viscosity in the diabetic group was significantly higher than those in the control group (all p < 0.05). The results also revealed a significantly lower MNCV in the diabetic group (p = 0.005). Additionally, the density of myelinated fibers was significantly lower in the diabetic group (p = 0.004). The average thickness of the myelin sheath was also lower in the diabetic group (p = 0.012). The area under the ROC curve for distinguishing the diabetic neuropathy group from the control group was 0.876 for SWD imaging, which was significantly greater than 0.677 for CSA (p = 0.030) and 0.705 for SWE (p = 0.035).

Conclusion

Sciatic nerve viscosity measured using SWD imaging was significantly higher in diabetic rats. The viscosity measured using SWD imaging performed well in distinguishing the diabetic neuropathy group from the control group. Therefore, SWD imaging may be a promising method for the evaluation of diabetic neuropathy.

Evaluation of ulcerative colitis activity using transabdominal ultrasound shear wave elastography

BACKGROUND

Transabdominal ultrasound (US) has been reported to be effective in the evaluation of ulcerative colitis (UC). US can measure shear wave elastography (SWE) and shear wave dispersion (SWD), which may be correlated with inflammation and necrosis. We aimed to investigate the relationship between UC activity and SWE and SWD.

METHODS

Patients with UC who underwent US within 2 days before or after a colonoscopy between April 2019 and March 2020 were included. SWE and SWD were measured in the sigmoid colon; the correlations of SWE and SWD with the Lichtiger index and the Ulcerative Colitis Endoscopic Index of Severity (UCEIS) were investigated. We also compared SWE and SWD between patients with mucosal healing and those in the active phase according to the UCEIS.

RESULTS

Twenty-six UC patients were enrolled. The median Lichtiger index, UCEIS, SWE values, and SWD values were 8 [interquartile range (IQR), 5.3-10.8], 4 (IQR, 3.3-5), 1.69 (IQR, 1.49-2.16) m/s, and 11.9 (IQR, 10.9-13.3) (m/s)/kHz, respectively. The Lichtiger index and UCEIS were negatively correlated with the SWE values (rs=-0.404 and rs=-0.506) but not with the SWD values (rs=0.004 and rs=0.002). The SWE values differed significantly between the mucosal healing and active phase groups [2.40 (IQR, 2.18-3.38) vs. 1.62 (IQR, 1.44-1.95) m/s, P=0.007], whereas the SWD values did not [13.1 (IQR, 7.05-21.6) vs. 11.9 (IQR, 11.1-13.2) (m/s)/kHz, P=0.918].

CONCLUSIONS

SWE may be useful for the evaluation of UC activity and could be a noninvasive method of assessing disease severity.

An initial trial of quantitative evaluation of autoimmune pancreatitis using shear wave elastography and shear wave dispersion in transabdominal ultrasound

BACKGROUND/OBJECTIVES

We aimed to examine therapeutic efficacy and prognosis prediction of autoimmune pancreatitis (AIP) using shear wave elastography (SWE) and shear wave dispersion (SWD) in transabdominal ultrasound (US).

METHODS

The subjects were 23 patients with diffuse type 1 AIP who underwent SWE and SWD, and 34 controls with a normal pancreas. Elasticity and dispersion were defined as the pancreatic elastic modulus (PEM) and dispersion slope, respectively. PEM and dispersion slope were compared between AIP and control cases, and the short-term therapeutic effect and long-term prognosis were examined.

RESULTS

PEM (30.9 vs. 6.6 kPa, P < 0.001) and dispersion slope (15.3 vs. 13.0 (m/sec)/kHz, P = 0.011) were significantly higher in AIP cases than in controls. Among the 17 AIP patients followed-up in two weeks after treatment, these parameters were 12.7 kPa and 10.5 (m/sec)/kHz with median decrease rate of 37.2% and 32.8%, respectively, which were significantly higher than the change in the size of pancreatic parenchyma (14.4%, P = 0.026). Fourteen of these subjects were followed up for >12 months, during which 2 had relapse; diabetes improved in 5 and worsened in 2; in 60% of cases, the pancreatic parenchyma was atrophied. The % change in PEM after two weeks was tended to be higher in non-atrophy cases.

CONCLUSION

SWE and SWD measurement in US may be useful for quantitative assessment of AIP and evaluation of short-term treatment efficacy.

Imaging diagnosis of autoimmune pancreatitis: computed tomography and magnetic resonance imaging

Autoimmune pancreatitis (AIP) is a pancreatic phenotype of IgG4-related systemic disease. Since its first description in the literature, characteristic imaging features have gradually become known to many clinicians encompassing various specialties in the past quarter century. CT and MRI have been the workhorses for imaging diagnosis of AIP. Typical features include sausage-like swelling of the focal or entire pancreas, duct-penetrating sign, a capsule-like rim of the affected lesions, and homogeneous delayed enhancement or enhanced duct sign after contrast administration, as well as characteristic combined findings reflecting coexisting pathologies in the other organs as a systemic disease. In this review, recent and future developments in CT and MRI that may help diagnose AIP are discussed, including restricted diffusion and perfusion and increased elasticity measured using MR.