1,650 research outputs found
Biopsym : a learning environment for transrectal ultrasound guided prostate biopsies
This paper describes a learning environment for image-guided prostate
biopsies in cancer diagnosis; it is based on an ultrasound probe simulator
virtually exploring real datasets obtained from patients. The aim is to make
the training of young physicians easier and faster with a tool that combines
lectures, biopsy simulations and recommended exercises to master this medical
gesture. It will particularly help acquiring the three-dimensional
representation of the prostate needed for practicing biopsy sequences. The
simulator uses a haptic feedback to compute the position of the virtual probe
from three-dimensional (3D) ultrasound recorded data. This paper presents the
current version of this learning environment
BiopSym: a simulator for enhanced learning of ultrasound-guided prostate biopsy
This paper describes a simulator of ultrasound-guided prostate biopsies for
cancer diagnosis. When performing biopsy series, the clinician has to move the
ultrasound probe and to mentally integrate the real-time bi-dimensional images
into a three-dimensional (3D) representation of the anatomical environment.
Such a 3D representation is necessary to sample regularly the prostate in order
to maximize the probability of detecting a cancer if any. To make the training
of young physicians easier and faster we developed a simulator that combines
images computed from three-dimensional ultrasound recorded data to haptic
feedback. The paper presents the first version of this simulator
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.
Tracking systems for prostate biopsies make it possible to generate biopsy
distribution maps for intra- and post-interventional quality control and 3D
visualisation of histological results for diagnosis and treatment planning.
They can also guide the clinician toward non-ultrasound targets. In this paper,
a volume-swept 3D US based tracking system for fast and accurate estimation of
prostate tissue motion is proposed. The entirely image-based system solves the
patient motion problem with an a priori model of rectal probe kinematics.
Prostate deformations are estimated with elastic registration to maximize
accuracy. The system is robust with only 17 registration failures out of 786
(2%) biopsy volumes acquired from 47 patients during biopsy sessions. Accuracy
was evaluated to 0.760.52mm using manually segmented fiducials on 687
registered volumes stemming from 40 patients. A clinical protocol for assisted
biopsy acquisition was designed and implemented as a biopsy assistance system,
which allows to overcome the draw-backs of the standard biopsy procedure.Comment: Medical Image Analysis (2011) epub ahead of prin
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. Since the patient is
not immobilized, since the prostate is mobile and due to the fact that probe
movements are only constrained by the rectum during biopsy acquisition, the
tracking system must be able to estimate rigid transformations that are beyond
the capture range of common image similarity measures. We propose a fast and
robust multi-resolution attribute-vector registration approach that combines
global and local optimization methods to solve this problem. Global
optimization is performed on a probe movement model that reduces the
dimensionality of the search space and thus renders optimization efficient. The
method was tested on 237 prostate volumes acquired from 14 different patients
for 3D to 3D and 3D to orthogonal 2D slices registration. The 3D-3D version of
the algorithm converged correctly in 96.7% of all cases in 6.5s with an
accuracy of 1.41mm (r.m.s.) and 3.84mm (max). The 3D to slices method yielded a
success rate of 88.9% in 2.3s with an accuracy of 1.37mm (r.m.s.) and 4.3mm
(max)
Influence of statin use on clinicopathological characteristics of localized prostate cancer and outcomes obtained after radical prostatectomy: a single center study
To assess the impact of statin use on biochemical recurrence (BCR) of prostate cancer after radical prostatectomy (RP)
Intensity-Based Registration of Freehand 3D Ultrasound and CT-scan Images of the Kidney
This paper presents a method to register a pre-operative Computed-Tomography
(CT) volume to a sparse set of intra-operative Ultra-Sound (US) slices. In the
context of percutaneous renal puncture, the aim is to transfer planning
information to an intra-operative coordinate system. The spatial position of
the US slices is measured by optically localizing a calibrated probe. Assuming
the reproducibility of kidney motion during breathing, and no deformation of
the organ, the method consists in optimizing a rigid 6 Degree Of Freedom (DOF)
transform by evaluating at each step the similarity between the set of US
images and the CT volume. The correlation between CT and US images being
naturally rather poor, the images have been preprocessed in order to increase
their similarity. Among the similarity measures formerly studied in the context
of medical image registration, Correlation Ratio (CR) turned out to be one of
the most accurate and appropriate, particularly with the chosen non-derivative
minimization scheme, namely Powell-Brent's. The resulting matching transforms
are compared to a standard rigid surface registration involving segmentation,
regarding both accuracy and repeatability. The obtained results are presented
and discussed
Aid to Percutaneous Renal Access by Virtual Projection of the Ultrasound Puncture Tract onto Fluoroscopic Images
Background and Purpose: Percutaneous renal access in the context of
percutaneous nephrolithotomy (PCNL) is a difficult technique, requiring rapid
and precise access to a particular calix. We present a computerized system
designed to improve percutaneous renal access by projecting the ultrasound
puncture tract onto fluoroscopic images. Materials and Methods: The system
consists of a computer and a localizer allowing spatial localization of the
position of the various instruments. Without any human intervention, the
ultrasound nephrostomy tract is superimposed in real time onto fluoroscopic
images acquired in various views. Results: We tested our approach by laboratory
experiments on a phantom. Also, after approval by our institution's Ethics
Committee, we validated this technique in the operating room during PCNL in one
patient. Conclusion: Our system is reliable, and the absence of
image-processing procedures makes it robust. We have initiated a prospective
study to validate this technique both for PCNL specialists and as a learning
tool
Framework for 3D TransRectal Ultrasound
Prostate biopsies are mainly performed under 2D TransRectal UltraSound (TRUS)
control by sampling the prostate according to a predefined pattern. In case of
first biopsies, this pattern follows a random systematic plan. Sometimes,
repeat biopsies can be needed to target regions unsampled by previous biopsies
or resample critical regions (for example in case of cancer expectant
management or previous prostatic intraepithelial neoplasia findings). From a
clinical point of view, it could be useful to control the 3D spatial
distribution of theses biopsies inside the prostate. Modern 3D-TRUS probes
allow acquiring high-quality volumes of the prostate in few seconds. We
developed a framework to track the prostate in 3D TRUS images. It means that if
one acquires a reference volume at the beginning of the session and another
during each biopsy, it is possible to determine the relationship between the
prostate in the reference and the others volumes by aligning images. We used
this tool to evaluate the ability of a single operator (a young urologist
assistant professor) to perform a pattern of 12 biopsies under 2D TRUS
guidance
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