Fibroscan ® practice improvement with a real-time assistance ultrasound tool: a premiminary study. Stéphane Audière 1,2 , Yassine Mofid 1 , Maurice Charbit 2 , Elsa Angelini 2 , Veronique Miette 1 , Laurent Sandrin 1 1 Echosens, Research and Development Department, Paris, FRANCE. 2 Institut Telecom, Telecom ParisTech, CNRS LTCI, Paris, FRANCE stephane.audiere@echosens.com Abstract— Vibration-controlled transient elastography (VCTE™) based on the Fibroscan ® device (Echosens, Paris, France) is used to assess non invasively liver stiffness which is correlated to hepatic fibrosis. Currently, operators need to be trained to conduct successful examinations with the Fibroscan ® . The liver is visually localized via TM and Ascan modes. Furthermore, the use of an ultrasound scanner is recommended to localize the liver on obese patients, and to identify the optimal measurement window. To facilitate the examination, we propose in this paper new indicators derived from the ultrasound signal to enable automated liver localization. Assistance tool, Elastography, Fibroscan device, Liver, Stiffness, Texture analysis, Ultrasound, VCTE™ I. INTRODUCTION A. Background The Fibroscan ® is a vibration-controlled transient elastography (VCTE™) based device used to quantify liver stiffness by measuring the velocity of a low frequency shear wave that travels through the liver. The Fibroscan ® can measure the Young’s modulus (E) of the liver at depths between 25 and 65 mm. It has been demonstrated that E is highly correlated to the fibrosis stage assessed by liver biopsy. The shear wave is induced mechanically by means of an electrodynamic transducer. An ultrasound transducer is mounted on the axis of the electrodynamic transducer to measure the evolution of the displacements induced by the shear wave as a function of depth and time. Figure 1. Fibroscan ® probe. The Fibroscan ® is non-invasive, easy to use, has a good reproducibility of the examination and provides a good alternative to hepatic biopsy. Clinical interests of liver stiffness measurements using the Fibroscan ® has been largely validated for adult patients with chronic liver diseases [1]. Elastography is a technique that measures the elasticity (specifically the Young's modulus) of biological tissues. This is a quantitative approach mimicing the widespread medical palpation procedure. It enables the detection of tumors that are often stiffer than normal tissues. There exist several types of elastography measurement devices, that can be classified with respect to the kind of tissue solicitation being used and the kind of tissue displacement measures being performed. Static elastography [2] uses the ultrasound to measure displacements (speckle distortion), before and after a small compression. In dynamic elastography, the shear wave is induced mechanically and monochromatically in the case of magnetic resonance elastography (MRE) [3] and sonoelastography [4]. In our case, transient elastography uses a shear wave generated by a mechanical pulse and followed with ultrasound echoes [1], [5], [6]. B. Purpose Our aim is to develop a new tool for real-time assistance of Fibroscan ® acquisition in order to ease the localization of the liver, especially in obese patients. II. METHODS AND MATERIALS A. Mode A & TM Ultrasound A-mode imaging provides only one- dimensional information. However, the temporal motion of a boundary surface can be investigated by encoding the echo amplitude as the brightness of the display. TM mode is obtained by writing successive echo lines next to each other instead of superimposing them. A-mode ultrasound systems employ single element transducers using a single channel pulser and receiver. This means that a single RF line is acquired, and that no information in 2D is obtained. This is the most common scanning method used for medical applications in the pulse-echo technique. Short ultrasound pulses are sent