Realtime Ultrasound Prostate Young’s Modulus Reconstruction Technique Using a Full Inversion Approach

In this work, we present a real-time prostate elastography reconstruction technique which incorporates an accelerated method of tissue stress calculation in its algorithms. The accelerated FE method uses a database of prostate-tumor configurations obtained from imaging. These configurations undergoing specific mechanical loading, e.g. US probe, are modeled and analyzed using conventional FEM to obtain the corresponding stress fields. Principal component analysis (PCA) is used to obtain the main modes of shape and stress fields. As such, the shape and stress fields can be described by these main modes weighted by a small number of weight factors. Next, an efficient mapping technique is developed to relate the weight factors of shape to those of the stress fields. We used Artificial Neural Network (ANN) and PCA based regression for this mapping. Once the mapping function is obtained it can be used for analyzing prostate shapes not included in the database. For a typical prostate, our results indicate that analysis using our technique takes less than 0.1 seconds on a desktop computer irrespective of the model size, while the maximum stress error is less than 5% per element. This mapping is then used for our novel real-time Young’s modulus reconstruction technique in which prostate and tumor moduli are updated iteratively using strain images acquired from an ultrasound imaging system and stress field estimated with the proposed method. Results of elastography show that relative Young’s moduli can be reconstructed fairly accurately.