Shear imaging is a term denoting the hardness of the tissue which has many indications of pathology. We have implemented several modes of shear for specific applications or the OEMs to pursue.
Static shear is where the transducer is pressed very lightly into the patient. In this case, we take a small kernel of 32 RF digitizations of the focused sum of the aperture and sum the multiplication of each element in the kernel by a previously sampled 32 RF digitizations from the same point and create a correlation value. We compare the correlation value to the local correlation values in two dimensions and estimate where the tissue has moved to in real-time for every RF digitization (4096) in the image. We then track these movements to estimate the relative hardness of the tissue. Hard tissue will move and soft tissue will compress. This mode is available from the UltraVision Company.
Shear wave imaging is where an Acoustic Radiation Force Push (ARFI) is applied to part of the tissue and the tissue moves away from the transducer. This movement induced in the tissue causes a shear wave to propagate at ninety degrees to the movement. Shear waves move much slower than compressional waves and their progression across the tissue is proportional to the tissues Young’s Modulus. This propagation speed can be measured by B-mode imaging along the expected track of the shear wave. This mode is also available from The UltraVision Corporation.