[The clinical utility of elastography, a new ultrasound technique]. / La elastografía: una nueva aplicación de la ecografía. ¿Cuál es su utilidad clínica?

Sonoelastography combines elastography and B mode ultrasonography to show parameters related to the structural organization of tissues in real time. Thus, this noninvasive technique shows us the mechanical characteristics of each tissue. The different elastography techniques (qualitative and quantitative, in ultrasonography or magnetic resonance imaging) are based on the hypothesis that soft tissues are more deformable than stiff tissues and that these differences can be captured in images. Elastography adds a new perspective to conventional ultrasonography: it reflects the stiffness of the tissues, and this information, together with the anatomic information from B mode imaging and the vascular information from Doppler, is key for the diagnosis. This article aims to provide a brief summary of what elastography is, the different types of elastography, and the range of possible applications of this technique.

Detection of non-alcoholic steatohepatitis in patients with morbid obesity before bariatric surgery: preliminary evaluation with acoustic radiation force impulse imaging.

OBJECTIVE: To investigate the utility of acoustic radiation force impulse (ARFI) imaging, with the determination of shear wave velocity (SWV), to differentiate non-alcoholic fatty liver disease (NAFLD) from non-alcoholic steatohepatitis (NASH) in patients with morbid obesity before bariatric surgery. METHODS: Thirty-two patients with morbid obesity were evaluated with ARFI and conventional ultrasound before bariatric surgery. The ARFI and ultrasound results were compared with liver biopsy findings, which is the reference standard. The patients were classed according to their histological findings into three groups: group A, simple steatosis; group B, inflammation; and group C, fibrosis. RESULTS: The median SWV was 1.57 ± 0.79 m/s. Hepatic alterations were observed in the histopathological findings for all the patients in the study (100 %), with the results of the laboratory tests proving normal. Differences in SWV were also observed between groups A, B and C: 1.34 ± 0.90 m/s, 1.55 ± 0.79 m/s and 1.86 ± 0.75 m/s (P < 0.001), respectively. The Az for differentiating NAFLD from NASH or fibrosis was 0.899 (optimal cut-off value 1.3 m/s; sensitivity 85 %; specificity 83.3 %). CONCLUSION: The ARFI technique is a useful diagnostic tool for differentiating NAFLD from NASH in asymptomatic patients with morbid obesity. KEY POINTS : • Acoustic radiation force impulse imaging provides ultrasonic shear wave velocity measurements. • SWV measurements were higher in patients with inflammation or fibrosis than NAFLD. • ARFI differentiates NAFLD from NASH in patients with morbid obesity. • Results suggest that ARFI can detect NASH in asymptomatic morbidly obese patients.