Prostate biopsy tracking with deformation estimation.

Transrectal biopsies under 2D ultrasound (US) control are the current clinical standard for prostate cancer diagnosis. The isoechogenic nature of prostate carcinoma makes it necessary to sample the gland systematically, resulting in a low sensitivity. Also, it is difficult for the clinician to follow the sampling protocol accurately under 2D US control and the exact anatomical location of the biopsy cores is unknown after the intervention.

Prostate biopsy assistance system with gland deformation estimation for enhanced precision.

Computer-assisted prostate biopsies became a very active research area during the last years. Prostate tracking makes it possible to overcome several drawbacks of the current standard transrectal ultrasound (TRUS) biopsy procedure, namely the insufficient targeting accuracy which may lead to a biopsy distribution of poor quality, the very approximate knowledge about the actual location of the sampled tissues which makes it difficult to implement focal therapy strategies based on biopsy results, and finally the difficulty to precisely reach non-ultrasound (US) targets stemming from different modalities, statistical atlases or previous biopsy series. The prostate tracking systems presented so far are limited to rigid transformation tracking.

[Real-time three-dimensional (4D) ultrasound-guided prostatic biopsies on a phantom. Comparative study versus 2D guidance].

Objective: The objective of this study was to determine the added value of real-time three-dimensional (4D) ultrasound guidance of prostatic biopsies on a prostate phantom in terms of the precision of guidance and distribution.

Methods: A prostate phantom was constructed. A real-time 3D ultrasonograph connected to a transrectal 5.

Towards 3D ultrasound image based soft tissue tracking: a transrectal ultrasound prostate image alignment system.

The emergence of real-time 3D ultrasound (US) makes it possible to consider image-based tracking of subcutaneous soft tissue targets for computer guided diagnosis and therapy. We propose a 3D transrectal US based tracking system for precise prostate biopsy sample localisation. The aim is to improve sample distribution, to enable targeting of unsampled regions for repeated biopsies, and to make post-interventional quality controls possible.

MRI/TRUS data fusion for brachytherapy.

Background: Prostate brachytherapy consists in placing radioactive seeds for tumour destruction under transrectal ultrasound imaging (TRUS) control. It requires prostate delineation from the images for dose planning. Because ultrasound imaging is patient- and operator-dependent, we have proposed to fuse MRI data to TRUS data to make image processing more reliable.

Prostate biopsies guided by three-dimensional real-time (4-D) transrectal ultrasonography on a phantom: comparative study versus two-dimensional transrectal ultrasound-guided biopsies.

Objective: This study evaluated the accuracy in localisation and distribution of real-time three-dimensional (4-D) ultrasound-guided biopsies on a prostate phantom.

Methods: A prostate phantom was created. A three-dimensional real-time ultrasound system with a 5.

Accurate localization of needle entry point in interventional MRI.

In interventional magnetic resonance imaging (MRI), the systems designed to help the surgeon during biopsy must provide accurate knowledge of the positions of the target and also the entry point of the needle on the skin of the patient. In some cases, this needle entry point can be outside the B(0) homogeneity area, where the distortions may be larger than a few millimeters. In that case, major correction for geometric deformation must be performed.

MR-guided balloon angioplasty of stenosed aorta: in vivo evaluation using near-standard instruments and a passive tracking technique.

The purpose of this study was to assess the feasibility of magnetic resonance (MR)-guided balloon angioplasty of a stenosed aorta on an open low-field magnet using a passive tracking technique. Visualization of vessels and position of instruments were realized by using a fast low-angle shot (FLASH) sequence. Catheters and guidewire were prepared for susceptibility-based MR visualization.

Automatic quality assessment protocol for MRI equipment.

The authors have developed a protocol and software for the quality assessment of MRI equipment with a commercial test object. Automatic image analysis consists of detecting surfaces and objects, defining regions of interest, acquiring reference point coordinates and establishing gray level profiles. Signal-to-noise ratio, image uniformity, geometrical distortion, slice thickness, slice profile, and spatial resolution are checked.

[Interventional MRI. Analysis of data and prospects].

In spite of its many advantages: 3D imaging, improved tissue characterization, and lack of ionizing radiation, interventional MRI remains seldom used. Several factors are involved. The purpose of this paper is to analyze the factors preventing or slowing the development of this technique based on a review of data from the literature, work presented at the second symposium on interventional MRI (Düsseldorf, 1997), and our own experimental data.