Contrast Agent
(C. Cachard - in collaboration with the Dynamic imaging theme)
To highlight the presence of the contrast agent (which reflects the vascularization of the tissues) and to minimize the ultrasound information obtained from non vascularized tissue, we proposed 2 complementary approaches. These 2 approaches are on the one hand temporal variance imaging (TVI) in a multi-shot mode [thesis N. Rognin ROGN-02] and, on the other, imaging from order 2 autoregressive modeling of the second harmonic, of the ultrasound signal in a single-shot mode. The advantage of the latter approach lies in the fact that it makes it possible to detect the contrast product with low concentrations and mechanical indexes. The following figure illustrates the results obtained with this approach [DYDE-05, Ultrasound imaging].
Results for detection of a contrast product obtained by order 2 autoregressive modeling regularized for the second harmonic (parameter SM2). The results were obtained on a phantom for 3 different concentration conditions (c) and mechanical index (MI): column (a) c = 2.10-6, MI = 0.10; column (b) c = 5.10-6, MI = 0.29 and column (c) c = 5.10-5, MI = 0.36. The images presented correspond to the following processings: (1st line) image envelopes; (2nd line) Amplitude of the SM2 parameter before regularization (scale in dB); (3rd line) Amplitude of the SM2 parameter after non quadratic regularization (scale in dB).