Advancements in Double-Profile Intersection (DoPIo) and Viscoelastic Response (VisR) Imaging for On-Axis Surveillance of Renal Allograft Dysfunction

The long-term survival of renal allografts strongly depends on the early detection and management of transplant rejection, especially in the identification of parenchymal inflammation and fibrosis. However, current diagnostic techniques are either nonspecific and insensitive or invasive and subjective. Ultrasound elastography has emerged as a promising noninvasive imaging modality for assessing tissue mechanical properties associated with allograft pathology, but existing methods have limitations in accuracy and clinical utility. I demonstrate two different acoustic radiation force (ARF)-based ultrasound elastography techniques to assess renal allograft pathology. First, I evaluate the ability of Viscoelastic Response (VisR) ultrasound, where tissue displacement responses from two successive ARF excitations are tracked on-axis to separately estimate surrogate metrics for shear elasticity and viscosity, to estimate biopsy findings in in vivo clinically acquired images of the renal allograft parenchyma. Then, I develop and assess a novel technique, Double Profile Intersection (DoPIo), where ARF-induced displacements are tracked on-axis using a novel combination of two different beamforming approaches to quantitatively estimate shear elasticity. Finally, I compare DoPIo and VisR’s abilities to distinguish in in vivo images of porcine renal parenchyma with inflammation and/or fibrosis from healthy controls. I demonstrate herein the ability to relate VisR-based metrics to biopsy-based findings of interstitial fibrosis and tubular atrophy in renal allografts, DoPIo’s ability to estimate shear elasticity without tracking shear wave propagation, and both techniques’ abilities to distinguish pathological from healthy renal parenchyma in a porcine model. These results suggest that ARF-based ultrasound elastography techniques, particularly VisR and DoPIo, have potential as noninvasive tools for assessing renal allograft pathology and guiding clinical management.