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5×128-Element array transducer for elevational motion consideration in strain imaging
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Edité par CCSD -
International audience. Background, Motivation and ObjectiveUltrasound is a widely used imaging modality, both for diagnosis and guidance of interventional procedures such as biopsies. Ultrasound imaging commonly provides 2D data, which can be a limitation for further data processing, since information like out-of-plane motion is inaccessible. In this study, a specific multi-row array transducer – developed for the elastography application – is presented. This prototype acquires series of three adjacent imaging planes over time and makes therefore possible to compute 2D strain images of the central plane, with consideration of out-of-plane motion.Statement of Contribution/MethodsThe developed transducer is a 7-MHz central frequency probe, composed of 640 elements organized in five rows of 128 elements. Their dimensions vary with the row. The elements from the rows #1, 2, 4 and 5 all measure 0.725 mm x 0.275 mm (height x width), while those from the central row are larger, measuring 3.125 mm x 0.275 mm. The horizontal andvertical spacing between elements (kerf) is 25 μm. This probe allows the acquisition of three adjacent imaging planes by electronically switching between element rows. The first plane is obtained by the simultaneous activation of rows #1, 2 and 3, the second one (or central plane) of the rows #2, 3 and 4 and the third imaging plane by activation of the rows #3, 4 and 5. This strategy permits to vary the position of the emitting surface in 0.75-mm step in elevation, without mechanical translation of the array.This probe was connected to an Ultrasonix ultrasound scanner and initial tests were conducted with phantoms and bovine tissue samples. Data were acquired at 40 MHz and 2D axial strain images of the central plane were computed using a 3D motion estimation method, based on correlation coefficient maximization.Results/DiscussionFig. 1 provides an example of results, obtained with a CIRS phantom (model 049), along with the axial strain images from the same technique but restricted to in-plane motion analysis. Elastograms are given for increasing steps of probe displacement in elevation (a,b,c). Results show the interest of the proposed approach – compared to a 2D technique –for larger elevational motion, with an increase in the mean correlation coefficient values achieved during elastogram computation: 0.95, 0.91, and 0.82 versus 0.96, 0.94, and 0.89 for the 2D vs 3D estimation technique and increasing probe displacements.
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