Probe for transient elastography

Abstract

A probe ( 1 ) for transient elastography comprising a probe casing (PC), at least one ultrasound transducer (US) having a symmetry axis (A), at least a vibrator (VIB), said vibrator (VIB) being located inside the probe casing (PC), a position sensor (POS) coupled to the probe casing (PC), the position sensor (POS) being arranged to measure the displacement of the probe ( 1 ), wherein the vibrator (VIB) is arranged to induce a movement of the probe casing (PC) along a predefined axis, the predefined axis being the symmetry axis (A) of the ultrasound transducer (US), the ultrasound transducer is bound to the probe casing (PC) with no motion of the ultrasound transducer (US) with respect to the probe casing (PC), and the probe comprises comprises a feedback circuit comprising the position sensor and a control loop and configured to use the displacement of the probe as a feedback signal and to control the movement of the vibrator inside the probe casing and the shape of a low frequency pulse applied by the probe.

1 . A probe ( 1 ) for transient elastography comprising:
 a probe casing (PC);   at least one ultrasound transducer (US) having a symmetry axis (A);   at least a vibrator (VIB), said vibrator (VIB) being located inside the probe casing (PC);   
       the probe ( 1 ) being characterized in that:
 the vibrator (VIB) is arranged to induce a movement of the probe casing (PC) along a predefined axis, the predefined axis being the symmetry axis (A) of the ultrasound transducer (US); 
 the ultrasound transducer is bound to the probe casing (PC) with no motion of the ultrasound transducer (US) with respect to the probe casing (PC); 
 the probe ( 1 ) comprises a position sensor (POS) coupled to the probe casing (PC), the position sensor (POS) being arranged to measure the displacement of the probe ( 1 ); 
 the displacement of the probe ( 1 ) is used as a feedback signal in order to control the movement of the vibrator inside the probe casing and the shape of a low frequency pulse applied by the probe ( 1 ). 
 
     
     
         2 . The probe ( 1 ) for transient elastography according to  claim 1  characterized in that the ultrasound transducer (US) is bound to the probe casing (PC) by means of a probe tip (PT), said probe tip (PT) having a first extremity (PTE 1 ) fixed to the probe casing (PC) and a second extremity (PTE 2 ) fixed to the ultrasound transducer (US). 
     
     
         3 . The probe ( 1 ) according to one of the previous claims characterized in that it comprises at least a force sensor (FS) which is fixed to the probe casing (PC), the force sensor (FS) being arranged to measure the deformation of the probe casing PC due to the contact with the tissue to be analyzed. 
     
     
         4 . The probe ( 1 ) according to  claim 3  characterized in that the force sensor (FS) comprises a housing (HOU) adapted to receive and secure the ultrasound transducer (US). 
     
     
         5 . The probe ( 1 ) according to  claim 2  and  claim 3  characterized in that the force sensor (FS) comprises a housing (HOU) adapted to receive and secure the first extremity (PTE 1 ) of the probe tip (PT). 
     
     
         6 . The probe ( 1 ) according to one of the previous claims characterized in that the position sensor (POS) is coupled to the probe casing (PC). 
     
     
         7 . The probe ( 1 ) according to  claim 3  and one of the previous claims characterized in that the force sensor (FS) comprises at least a strain gauge (SG) and/or at least a strain sensing resistor. 
     
     
         8 . The probe ( 1 ) according to one of the previous claims characterized in that the at least one ultrasound transducer (US) is interchangeable. 
     
     
         9 . The probe ( 1 ) according to one of the previous claims characterized in that at least one ultrasound transducer (US) is a disk shape ultrasound transducer. 
     
     
         10 . The inertial probe ( 1 ) according to one of the previous claims characterized in that the vibrator (VIB) comprises at least an electrodynamic actuator comprising a part fixed (FIX) to the probe casing (PC) and a mobile part (MOV). 
     
     
         11 . The inertial probe ( 1 ) according to the previous claim characterized in that the mass of the mobile part (MOV) of the vibrator is equal or greater than one fourth of the total mass M of the inertial probe ( 1 ). 
     
     
         12 . A transient elastography method ( 100 ) to measure the stiffness of a viscoelastic medium comprising at least the following steps:
 placing (PLACE) the probe ( 1 ) according to one of the  claims 1  to  11  in order to keep the ultrasound transducer (US) in contact with viscoelastic medium to analyze and/or with the patient's body;   triggering (START) the application of the low frequency pulse for generating a shear wave inside the viscoelastic medium to analyze;   emitting (EM-US) ultrasound shots inside the medium and recording the backscattered ultrasound signals;   
     
     
         13 . The transient elastography ( 100 ) method according to the previous claim further comprising at least the following steps:
 analyzing (CALCUL) the recorded backscattered ultrasound signals in order to determine the displacement of the viscoelastic medium subjected to the propagation of the shear wave;   based on the calculated displacement determine (DET) at least one viscoelastic parameter of the medium to analyze.   
     
     
         14 . The transient elastography ( 100 ) method according to  claim 12  or  claim 13  characterized in that the step (START) of triggering the application of the low frequency pulse is initiated manually by the operator or is conditioned on the verification of a verticality condition between the symmetry axis (A) of the ultrasound transducer (US) and the surface of the viscoelastic medium or other surface of the patient's body.