1. An apparatus configured to detect lumen-intima and media-adventitia interfaces in a blood vessel comprising: a means for aquiring a two-dimensional cross-sectional representation of said blood vessel, said two-dimensional representation being obtained as a grey level image, said acquisition means arranged to define in said image a region of interest (ROI) which includes said lumen-intima interface and said media-adventitia interface of said vessel, said region of interest consisting of a grey level map f(n, m) of said representation, being n and m coordinates of each pixel of said two-dimensional representation, a means for executing, along a search path (i) (with i=1. .. N) in said region of interest that is substantially orthogonal to a wall of said vessel where the following operations are executed: detection of any discontinuity points by means of filtering said values f(n, m) along said path (i) and localization of said points, definition along said path of a first discontinuity point P 1 (i) having contrast greater or equal to a first reference value S 1 , and definition of a second discontinuity point P 2 (i) having contrast greater or equal to a second reference value S 2 , repeating the acquisition, filtering and definition operations for a number N of rectilinear search paths (i) in the above described region of interest (ROI): detection of said lumen-intima interface by means of interpolation of a set α of said points P 1 (i) of the different search paths (i), detection of said media-adventitia interface by means of interpolation of a set β of said points P 2 (i) of the different search paths (i), wherein said step of detection of said discontinuity points P 1 (i) and P 2 (i) provides an operation selected from the group consisting of: defining local peaks of a first order absolute central moment operator calculated as: e ⁡ ( n , m ) = ∑ ⁢ ⁢ ∑ ( k 2 , l 2 ) ∈ Θ 2 ⁢ ⁢  [ ∑ ⁢ ⁢ ∑ ( k 1 , l 1 ) ∈ Θ 1 ⁢ f ⁡ ( n - k 1 , m - l 1 ) ⁢ w ⁡ ( k 1 , l 1 , r 1 ) ] - f ⁡ ( n - k 2 , m - l 2 )  ⁢ w ⁡ ( k 2 , l 2 , r 2 ) being Θ 1 and Θ 2 two circular domains having radius r 1 and r 2 respectively, defined as: 
 Θ i ={( k i ,l i )ε Z 2 :√{square root over ( k i 2 +l i 2 )}≦ r i }, where Z represents a set of whole numbers and (k i ,l i ) are coordinates of a generic point with respect to a Cartesian plane with origin at (n, m), and wherein w(k 1 , l 1 , r 1 ) is a weight function with unitary summation on a domain Θ 1 and w(k 2 , l 2 , r 2 ) is a weight function with unitary summation on a domain Θ 2 , defining local peaks of a gradient of Gaussian operator calculated as: G ⁡ ( n , m ) = ( ∑ ∑ ( k , l ) ∈ Θ ⁢ f ⁡ ( n - k , m - l ) · g x ⁡ ( k , l ) ) 2 + ( ∑ ∑ ( k , l ) ∈ Θ ⁢ f ⁡ ( n - k , m - l ) · g y ⁡ ( k , l ) ) 2 where g x (k, l) and g y (k, l) are derivatives of a Gaussian function with respect to directions x and y, defining zero crossings of a Laplacian of Gaussian operator calculated as: L ⁡ ( n , m ) = ∑ ⁢ ⁢ ∑ ( k , l ) ∈ Θ ⁢ f ⁡ ( n - k , m - l ) · ( g xx ⁡ ( k , l ) + g yy ⁡ ( k , l ) ) where g xx (k, l) and g yy (k, l) are second derivatives of a Gaussian function with respect to directions x and y.