3d Sonoelastography for Prostate Tumor Imaging

Sonoelastography is a new imaging technique to detect hard tumors in soft tissue. In sonoelastography imaging low frequency (200-500 Hz) shear waves are propagated through a tissue sample while real time Doppler techniques are used to image the resulting vibration pattern on an ultrasound scanner. A sonoelastography image is therefore a mapping of the relative vibration amplitude of the tissue sample. Hard tumors are visualized as a deficit or local perturbation of the low-frequency vibration pattern in tissue. A prostate phantom containing an isoechoic tumor was imaged using sonoelastography. The phantom was manufactured so that the phantom material mimicked both the acoustical and elastic properties of human tissue with the tumor having an elasticity 7 times that of the surrounding normal tissue. This value is in the range of reported values for hard tumors in soft tissue. Two-dimensional images of the phantom were obtained and captured using a special research package supplied with the GE scanner. Three-dimensional renderings were obtained by acquiring sequential tomographic slices and applying segmentation algorithms to delineate the tumor. Although the tumor was isoechoic on the b-scan image, it was detectable using sonoelastography. Three-dimensional renderings of the hard tissue in the phantom were made using the phantom gland surface as a reference. We conclude that the presence of hard tumors in soft surrounding tissue can be rendered in 3D using sonoelastography even when the stiff tissue is not visible when scanned using conventional ultrasound b-scan imaging.