Method for obtaining a functional parameter of a muscle

1. Method for obtaining at least one functional parameter of a muscle having at least one part, the method comprising the steps of:

a) applying ultrasound waves to the muscle,

b) collecting the ultrasound waves retrodiffused by the muscle at a plurality of times, to obtain collected ultrasound waves,

c) determining a first plurality of values representative of stiffness values of at least one part of the parts of the muscle at a first plurality of times by using the collected ultrasound waves, the first plurality of times being included in the plurality of times, each value representative of stiffness is selected from the group consisting of a shear modulus of the muscle, a Young's modulus of the muscle, and a propagation speed of shear waves in the muscle,

d) determining a second plurality of values representative of deformation values of said part at a second plurality of times by using the collected ultrasound waves, the second plurality of times being included in the plurality of times and being associated with the first plurality of times in a one-to-one relationship, each value representative of deformation is selected from the group consisting of a cumulative deformation, a length of the muscle, a normalized length of the muscle and a volume of the muscle, and

e) deducing at least one functional parameter based on the first plurality of values and the second plurality of values, wherein the first plurality of values and the second plurality of values form a stiffness-deformation loop.

2. Method for obtaining at least one functional parameter according to claim 1 , wherein steps a) and b) are carried out in vivo.

3. Method for obtaining at least one functional parameter according to claim 1 , wherein the muscle has a cycle having a temporal duration, the absolute value of the difference between a time of the first plurality of times and the associated time of the second plurality of times below or equal to 200 milliseconds.

4. Method for obtaining at least one functional parameter according to claim 1 , wherein the functional parameter is representative of the mechanical work of the part, and wherein at step f), the functional parameter is the area of the stiffness-deformation loop.

5. Method for obtaining at least one functional parameter according to claim 1 , wherein the first plurality of values and the second plurality of values form a stiffness-deformation loop with four inflexion points and wherein step f) comprises determining, for at least one of the inflexion points, a first value representative of stiffness value and a second value representative of deformation value.

6. Method for obtaining at least one functional parameter according to claim 1 , wherein the first plurality of values and the second plurality of values form a stiffness-deformation loop with four inflexion points linked by four parts and wherein step f) comprises curve fitting at least one of the parts by an exponential function whose coefficient is the functional parameter.

7. Method for obtaining at least one functional parameter according to claim 1 , wherein the muscle has reflecting particles, wherein at step a), at least one focused ultrasound wave is applied to generate an elastic shear wave in the muscle and a succession of ultrasound waves are applied so that at least some of said ultrasound waves penetrate into an area of the muscle while the shear wave is propagating in the same area and wherein at step b), the collected ultrasound waves are echoes generated by ultrasound compression waves interacting with reflecting particles in the muscle.

8. Method for obtaining at least one functional parameter according to claim 1 , wherein the method further comprises a step of storing the at least one deduced functional parameter in a memory unit.

9. Method for obtaining at least one functional parameter according to claim 1 , wherein the method further comprises a step of displaying the at least one deduced functional parameter on a displaying unit.

10. Method for obtaining at least one functional parameter according to claim 1 , wherein the muscle is the myocardium, the part is at least a segment of the myocardium and the functional parameter is at least one of end-diastolic passive myocardial stiffness, myocardium work, the passive myocardial stiffness variation with deformation and the end-systolic myocardial stiffness.

11. Method for obtaining at least one functional parameter according to claim 1 , wherein steps a) to f) are iterated to obtain a plurality of values for the functional parameter.

12. Method for obtaining at least one functional parameter according to claim 1 , wherein several iterations of steps a) to f) are carried out and each iteration corresponds to different operating conditions for the muscle.

13. Method for monitoring a state of a muscle comprising the steps of:

carrying out the method for obtaining at least one functional parameter of said muscle according to claim 11 , to obtain a plurality of values for at least one functional parameter of said muscle,

comparing the plurality of values for the functional parameter with a plurality of expected values for the functional parameter according to a comparison criteria, and

emitting a warning in case the comparison criteria is not met.

14. Method according to claim 13 , wherein the muscle is the myocardium and the state is chosen in the group consisting of in good health, in stunning state, in ischemia and in infarction.

15. Device for obtaining at least one functional parameter of a muscle having at least one part, the device comprising:

an applying unit adapted to apply ultrasound waves to the muscle,

a collecting unit adapted to collect the ultrasound waves retrodiffused by the muscle at a plurality of times, to obtain collected ultrasound waves,

a calculator being adapted to carry out the steps of:

determining a first plurality of values representative of stiffness values of at least one part of the parts of the muscle at a first plurality of times by using the collected ultrasound waves, the first plurality of times being included in the plurality of times, each value representative of stiffness is selected from the group consisting of a shear modulus of the muscle, a Young's modulus of the muscle, and a propagation speed of shear waves in the muscle,

determining a second plurality of values representative of deformation values of said part at a second plurality of times by using the collected ultrasound waves, the second plurality of times being included in the plurality of times and being associated with the first plurality of times in a one-to-one relationship, each value representative of deformation is selected from the group consisting of a cumulative deformation, a length of the muscle, a normalized length of the muscle and a volume of the muscle, and

deducing at least one functional parameter based on the first plurality of values and the second plurality of values, wherein the first plurality of values and the second plurality of values form a stiffness-deformation loop.

16. System for monitoring the state of a muscle comprising:

a device for obtaining at least one functional parameter of a muscle according to claim 15 , the device being adapted to obtain a plurality of values for at least one functional parameter of said muscle,

a comparator adapted to compare the plurality of values for the functional parameter with a plurality of expected values for the functional parameter according to a comparison criterion, and

a warning unit adapted to emit a warning in case the comparison criterion is not met.