| Sonoelastography is an ultrasound imaging technique first proposed by Parker and Lerner at the University of Rochester in the 1980's. In this modality low amplitude, low frequency shear waves (less than 0.1 mm displacement and less than 1 KHz frequency) are propagated deep into tissue, while real time Doppler techniques are used to image the resulting vibration pattern. When a discrete hard inhomogeneity, such as a tumor, is present within a region of soft tissue, a decrease in the vibration amplitude will occur at its location. This forms the basis for tumor detection using sonoelastography. The acquisition of a commercial scanner modified to do vibration Doppler imaging provided the opportunity to implement sonoelastography as a real-time imaging system. Sonoelastography is applied to the imaging of hard lesions in ultrasound phantoms, thermal necrosis lesions induced in liver tissue and in-vitro prostate cancer detection. A lesion model using the injection of formaldehyde in liver tissue is developed and explored. Sonoelastography and magnetic resonance images of a tissue phantom containing a hard isoechoic inclusion are compared to evaluate the accuracy of this method. The principles behind this imaging modality are explained and the practical aspects of acquiring sonoelastography images are described. Results are shown from three-dimensional sonoelastography reconstruction of ex-vivo whole prostate specimens containing prostate cancer. |
