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5C-3 3D Electrode Displacement Elastography Using the Siemens C7F2 fourSight 4D Ultrasound Transducer

Because ablation therapy alters the elastic modulus of tissues, emerging strain imaging methods may enable clinicians for the first time to have readily available, cost effective, real-time guidance to identify the location and boundaries of thermal lesions. Electrode displacement elastography is a method of strain imaging tailored specifically to ultrasound-guided electrode-based ablative therapies (eg. radiofrequency or microwave ablation). Here tissue deformation is achieved by applying minute perturbations to the unconstrained end of the treatment electrode, resulting in localized motion around the end of the electrode embedded in tissue. In this paper, we present a method for 3D elastographic reconstruction from volumetric data acquired using the C7F2 fourSight 4D ultrasound transducer, provided by Siemens Medical Solutions. Lesion reconstruction is demonstrated for a spherical inclusion centered in a tissue-mimicking phantom, which simulates a thermal lesion embedded in a normal tissue background. Elastographic reconstruction is also performed for a thermal lesion created in vitro in canine liver using radiofrequency ablation. Post-processing is done on the 2D strain images to form surface-rendered 3D elastograms of the inclusion. Elastographic volume estimates of the inclusion compare reasonably well with the actual known inclusion volume, with 3D electrode displacement elastography slightly underestimating the true inclusion volume.