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Large core needle biopsy is a common procedure used to obtain histological samples when cancer is suspected in diagnostic breast images. The procedure is typically performed under image guidance, with freehand ultrasound and stereotactic mammography (SM) being the most common modalities used. To utilize the advantages of both modalities, a biopsy device combining three-dimensional ultrasound (3DUS) and digital SM imaging with computer-aided needle guidance was developed. An implementation of a stereo camera method was applied to SM calibration, providing a target localization error of 0.35 mm. The 3-D transformation between the two imaging modalities was then derived, with a target registration error of 0.52 mm. Finally, the needle guidance error of the device was evaluated using tissue-mimicking phantoms, showing a sample mean and standard deviation of 0.44 [+ or -] 0.22 and 0.49 [+ or -] 0.27 mm for targets planned from 3DUS and SM images, respectively. These results suggest that a biopsy procedure guided using this device would successfully sample breast lesions at a size greater than or equal to the smallest typically detected in mammographic screening (~ 2 mm). Index Terms--Breast biopsy, digital stereotactic mammography, interventional radiology, three-dimensional ultrasound.

Successful cryotherapy of the prostate for neoplasms relies on imaging to achieve good oncological outcomes with minimal complications. Traditional prostatic cryotherapy relies on 2-dimensional ultrasonography (2DUS) guidance, which often makes it difficult to track the passage of needles in an oblique plane. We describe our initial 3-dimensional ultrasonography (3DUS) system, and the subsequent improvements that have been made during the last 10 years. Our imaging system uses a Philips HDI 5000 ultrasonography unit, a standard PC, a Matrox Meteor II video frame grabber and 3DUS developed at Robarts Research Institute. For the cryotherapy we use ultrathin (17-gauge) IceRod needles. After image acquisition, preplanning is performed using the 3-dimensional (3D) software, and then the IceRod needles are inserted into the prostate. As the freezing process commences, continuous 3DUS images are taken and analyzed during the double freeze-thaw cycles to monitor the progress of the ice ball formation. Real-time intraoperative 3D imaging of the prostate during cryotherapy has allowed us to accurately preplan and then monitor the progression of ice ball formation, which represents a significant advantage over conventional 2DUS.