70 research outputs found
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. The technical
accuracy of this approach has already been evaluated. METHODS: We present work
in progress concerning the evaluation of the approach from the dosimetry
viewpoint. The objective is to determine what impact this system may have on
the treatment of the patient. Dose planning is performed from initial TRUS
prostate contours and evaluated on contours modified by data fusion. RESULTS:
For the eight patients included, we demonstrate that TRUS prostate volume is
most often underestimated and that dose is overestimated in a correlated way.
However, dose constraints are still verified for those eight patients.
CONCLUSIONS: This confirms our initial hypothesis
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
Assessment of a percutaneous iliosacral screw insertion simulator.
International audienceBACKGROUND: Navigational simulator use for specialized training purposes is rather uncommon in orthopaedic and trauma surgery. However, it reveals providing a valuable tool to train orthopaedic surgeons and help them to plan complex surgical procedures. PURPOSE: This work's objective was to assess educational efficiency of a path simulator under fluoroscopic guidance applied to sacroiliac joint percutaneous screw fixation. MATERIALS AND METHODS: We evaluated 23 surgeons' accuracy inserting a guide-wire in a human cadaver experiment, following a pre-established procedure. These medical trainees were defined in three prospective respects: novice or skilled; with or without theoretical knowledge; with or without surgical procedure familiarity. Analysed criteria for each tested surgeon included the number of intraoperative X-rays taken in order to achieve the surgical procedure as well as an iatrogenic index reflecting the surgeon's ability to detect any hazardous trajectory at the time of performing said procedure. RESULTS: An average number of 13 X-rays was required for wire implantation by the G1 group. G2 group, assisted by the simulator use, required an average of 10 X-rays. A substantial difference was especially observed within the novice sub-group (N), with an average of 12.75 X-rays for the G1 category and an average of 8.5 X-rays for the G2 category. As far as the iatrogenic index is concerned, we were unable to observe any significant difference between the groups
Decontamination of 16S rRNA gene amplicon sequence datasets based on bacterial load assessment by qPCR
Identification of unexpected taxa in 16S rRNA surveys of low-density microbiota, diluted mock communities and cultures demonstrated that a variable fraction of sequence reads originated from exogenous DNA. The sources of these contaminants are reagents used in DNA extraction, PCR, and next-generation sequencing library preparation, and human (skin, oral and respiratory) microbiota from the investigators
Anniversary Paper: A sampling of novel technologies and the role of medical physicists in radiation oncology
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135037/1/mp1006.pd
Matériaux électrostrictifs pour actuateurs
Electrostrictive ceramic materials with a large electrostriction coefficient are intensively investigated for some displacement transducers. In order to obtain materials as good as PMN-PT, a material newly developed but not very easy to prepare, a solid solution of PZT type widely substituted with Sr-Ba ions has been studied. Two methods of preparation were used : a conventional solid one and a coprecipitation one which allows the fabrication of ceramics with a better density and an uniform grain size. In this paper it is shown that the sintering conditions have an influence both on the magnitude and on the hysteresis of the field induced strain. A comparison of the electrostrictive constants of the PZT selected composition with PMN-PT and PLZT ceramics is given.Les matériaux électrostrictifs sous forme de céramique, à fort coefficient d'électrostriction, sont trÚs recherchés pour certains transducteurs de déplacement. La recherche de matériaux aussi performants que le PMN-PT, matériau le plus utilisé actuellement, nous a amenés à étudier une composition du type PZT fortement substituée par des ions Sr-Ba et de préparation plus aisée. Deux méthodes de fabrication sont utilisées : la voie solide classique et la coprécipitation qui permet d'obtenir des céramiques plus denses et de granulométrie plus réguliÚre On montre dans cette étude que les conditions de frittage ont une influence à la fois sur l'amplitude et l'hystérésis de la déformation. Une comparaison des constantes électrostrictives du composé choisi avec des céramiques PMN-PT et PLZT est donnée
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