Characterization of VHR using SWE

Joseph S Fernandez-Moure, MD, MS1, Anuj Chaudhry, PhD2, Jeffrey L Van Eps, MD1, P. S Shajudeen2, Fernando Cabrera, MD3, Rafaella Righetti, PhD2, Brian J Dunkin, MD, FACS1. 1Houston Methodist Hospital, Department of Surgery, 2Texas A&M, Department of Electrical and Computer Engineering, 3Houston Methodist Research Institute, Depart of Regenerative and Biomimetic Medicine

Introduction: In the United States, over 300,000 hernia repairs are performed annually. To assess the integrity of repair, imaging modalities like computed tomography (CT) or ultrasound (US) are used. However, either modality properly characterizes the hernia prior to repair or is capable of reliably identifying the mesh after repair. Shear Wave Elastography (SWE) is an evolving US technique capable of simultaneous real-time imaging and mechanical property analysis. This modality can be utilized in 3D to visually reconstruct a defect or repair. In this study, we sought to demonstrate the utility of 2D and 3D SWE to characterize ventral hernias prior to and after repair using Parietex™ or Strattice™ mesh in a rat model of chronic hernia repair. We hypothesize that, using SWE, one can obtain a preoperative reconstruction of a hernia and, after repair, identify the mesh and characterize its stiffness based on Young’s Modulus.

Methods: Tissue mimicking gelatin-agar phantoms were embedded with Parietex™ or Strattice™ and assessed by SWE. Following this, twenty Lewis rats underwent hernia creation. At 30 days, 16 rats underwent underlay repair with Parietex™ or Strattice™. After 4 weeks, animals were euthanized, underwent SWE, and stiffness measured. Stiffness measurements were made from a center point in the hernia. 3D reconstructions of the hernia pre- and post-repair were performed using in-house image processing algorithms via Image-vis 3D software.

Results: Parietex™ and Strattice™ mesh demonstrated clearly identifiable elastograms in phantoms gels that corresponded to US B-mode imaging with Young’s modulus of 98 ± 6.7KPa and 46 ± 4.4 KPa, respectively. In vivo, SWE was capable of accurate and real time assessment and diagnosis of the hernia defect. Young’s modulus of Parietex™ and Strattice™ mesh in vivo were respectively 92±3.6 KPa and 42±3.1 KPa. SWE was capable of accurate 3D reconstruction of the hernia defect pre- and post-repair.

Discussion: In this study we show the feasibility of using ultrasound SWE to detect ventral hernias and evaluate mesh repair in-vivo.  Our results indicate that the presence of a hernia and repair can be reliably visualized by 2D SWE and reconstructed in 3D to provide more spatial information regarding the hernia itself, the contour of the mesh, and the position of the mesh. SWE can be done at the bedside and eliminates exposure to radiation with no loss of diagnostic accuracy. This represents a new modality for the “in office” characterization of incisional hernias or mesh repair for the practicing herniologist.

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