Filter-based speckle tracking for freehand prostate biopsy: Theory, ex vivo and in vivo Results

Abstract

In conventional prostate biopsy for cancer diagnosis, the 2D nature of ultrasound (US) guidance limits targeting accuracy and does not allow a 3D record of core locations. Several research groups are investigating the use of an electromagnetically tracked US transducer to reconstruct a volumetric scan. Unfortunately, the tracking measurements contain significant errors that affect spatial accuracy. We propose a new filter-based framework of speckle tracking for enchantment of prostate volume reconstruction based on speckle/noise extraction and provide its theoretical basis. A gamma multiplicative noise model is considered and a probability patch-based non-local means (PPB-NLM) filter is used for the task of speckle extraction. The spatial variation of the beam profile is also incorporated using a linear regression model of the beam. Validation tests are first performed on tissue samples obtained ex vivo using a linear motor stage and an optical tracker as gold standards. Further validation is performed on the gastrocnemius muscle in vivo. We then demonstrate the performance of the tracking system on prostate scans obtained in vivo. The results show that the proposed approach produces visually continuous anatomical boundaries in reconstructed 3D US volumes of the prostate. © 2014 Springer International Publishing Switzerland.