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Double-Profile Intersection (DoPIo) Imaging

Background

Double Profile Intersection (DoPIo) ultrasound is a quantitative Acoustic Radiation Force (ARF)-based technique designed to estimate the shear elasticity of soft tissues without requiring observation of shear wave propagation. Instead, DoPIo analyzes on-axis displacement measurements following a single ARF excitation. Two ultrasonic tracking beams with distinct focal configurations—a tightly focused narrow track and a more broadly focused wide track—are used to monitor the induced motion field.

The narrow and wide tracking beams sample motion over different lateral regions of the tissue. The narrow beam, being more localized, records larger scatterer motion near the center of the ARF excitation, while the wide beam averages motion over a broader lateral extent. The key DoPIo parameter, known as the intersection time (t_int), is defined as the time point where the displacement-time profiles from the two tracking beams intersect. This intersection time reflects the rate at which scatterer motion propagates across the tracking point spread functions (PSFs). In stiffer materials, scatterer motion spreads more rapidly across the PSFs, causing t_int to occur earlier, whereas in softer tissues, slower motion results in a later t_int.

Through an empirically derived regression model, t_int can be correlated with the shear elastic modulus, providing a direct and localized measure of relative tissue stiffness. DoPIo therefore enables quantitative elasticity assessment using a simple, single-push acquisition, eliminating the need for shear wave velocity tracking or complex inverse modeling.

The following figure shows the DoPIo workflow, followed by DoPIo-based shear elasticity estimates in a calibrated phantom with a soft inclusion embedded in a stiffer background, and in an excised porcine kidney containing a gelatin–graphite inclusion that is stiffer than its surroundings. These examples highlight DoPIo’s ability to produce localized stiffness maps that clearly delineate inclusions from background tissue.

 

 

Application

DoPIo imaging has been used in conjunction with Viscoelastic Response (VisR) ultrasound to characterize renal tissue mechanics in both healthy and diseased states. In experimental and preclinical studies, DoPIo successfully distinguished between healthy, inflamed, and fibrotic kidneys, capturing stiffness variations associated with fibrosis progression. The method’s simplicity—requiring only a single ARF excitation and standard motion tracking—makes it attractive for translational applications where rapid and robust elasticity assessment is needed.

Beyond renal imaging, DoPIo’s noninvasive and propagation-free approach holds promise for other organ systems where localized mechanical heterogeneity plays a key diagnostic role, such as the liver, breast, and musculoskeletal tissues.

Select Publications

  • K. A. Yokoyama, M. Murad Hossain and C. M. Gallippi, “Double-profile intersection (DoPIo) elastography: a new approach to quantifying tissue elasticity,” 2019 IEEE International Ultrasonics Symposium (IUS), Glasgow, UK, 2019, pp. 431-434, doi: 10.1109/ULTSYM.2019.8925667.
  • K. A. Yokoyama, K. S. Anand and C. M. Gallippi, “Assessing the Impact of ARF Excitation Beam Width and Tracking Beam Concurrency on DoPIo Imaging Performance in a Calibrated Phantom,” 2021 IEEE International Ultrasonics Symposium (IUS), Xi’an, China, 2021, pp. 1-4, doi: 10.1109/IUS52206.2021.9593658.