Grégoire Chevreau

University Joseph Fourier - Grenoble 1, Grenoble, Rhône-Alpes, France

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Publications (12)14.66 Total impact

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    ABSTRACT: Prostate biopsies, most often performed transrectally, are essential for the diagnosis and assessment of prognosis of prostate cancer. Biopsy localization accuracy is questionable. The development of computer systems allow to record their precise location and guide them to improve their distribution. These same devices can merge ultrasound images and MRI images and merge different sets of biopsies. All these data could be transferred inside ultrasound HIFU systems in order to make focal treatment protocols more accurate.
    Progrès en Urologie - FMC 09/2011; 21(3). DOI:10.1016/j.fpurol.2011.04.001 · 0.77 Impact Factor
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    ABSTRACT: This paper describes a learning environment for image-guided prostate biopsies for 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 is designed particularly to help improve the acquisition of the three-dimensional representation of the prostate required for practicing biopsy sequences. The simulator uses 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.
    Studies in health technology and informatics 01/2011; 163:242-6.
  • The Journal of Urology 04/2010; 183(4). DOI:10.1016/j.juro.2010.02.2243 · 3.75 Impact Factor
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    ABSTRACT: The objective of this article was developing an automated tool for routine clinical practice to estimate urinary stone composition from CT images based on the density of all constituent voxels. A total of 118 stones for which the composition had been determined by infrared spectroscopy were placed in a helical CT scanner. A standard acquisition, low-dose and high-dose acquisitions were performed. All voxels constituting each stone were automatically selected. A dissimilarity index evaluating variations of density around each voxel was created in order to minimize partial volume effects: stone composition was established on the basis of voxel density of homogeneous zones. Stone composition was determined in 52% of cases. Sensitivities for each compound were: uric acid: 65%, struvite: 19%, cystine: 78%, carbapatite: 33.5%, calcium oxalate dihydrate: 57%, calcium oxalate monohydrate: 66.5%, brushite: 75%. Low-dose acquisition did not lower the performances (P < 0.05). This entirely automated approach eliminates manual intervention on the images by the radiologist while providing identical performances including for low-dose protocols.
    Urological Research 09/2009; 37(5):241-5. DOI:10.1007/s00240-009-0195-3 · 1.31 Impact Factor
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    ABSTRACT: Mapping of transrectal ultrasonographic (TRUS) prostate biopsies is of fundamental importance for either diagnostic purposes or the management and treatment of prostate cancer, but the localization of the cores seems inaccurate. Our objective was to evaluate the capacities of an operator to plan transrectal prostate biopsies under 2-dimensional TRUS guidance using a registration algorithm to represent the localization of biopsies in a reference 3-dimensional ultrasonographic volume. Thirty-two patients underwent a series of 12 prostate biopsies under local anesthesia performed by 1 operator using a TRUS probe combined with specific third-party software to verify that the biopsies were indeed conducted within the planned targets. The operator reached 71% of the planned targets with substantial variability that depended on their localization (100% success rate for targets in the middle and right parasagittal parts versus 53% for targets in the left lateral base). Feedback from this system after each series of biopsies enabled the operator to significantly improve his dexterity over the course of time (first 16 patients: median score, 7 of 10 and cumulated median biopsy length in targets of 90 mm; last 16 patients, median score, 9 of 10 and a cumulated median length of 121 mm; P = .046). In addition to being a useful tool to improve the distribution of prostate biopsies, the potential of this system is above all the preparation of a detailed "map" of each patient showing biopsy zones without substantial changes in routine clinical practices.
    Journal of ultrasound in medicine: official journal of the American Institute of Ultrasound in Medicine 05/2009; 28(4):455-60. · 1.40 Impact Factor
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    ABSTRACT: 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.
    Studies in health technology and informatics 02/2009; 142:301-6.
  • The Journal of Urology 04/2008; 179(4):589-589. DOI:10.1016/S0022-5347(08)61727-9 · 3.75 Impact Factor
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    ABSTRACT: Prostate biopsies are performed under 2D TransRectal UltraSound (US) guidance by sampling the prostate according to a predefined pattern. Modern image processing tools allow better control of biopsy distribution. We evaluated the accuracy of a single operator performing a pattern of 12 ultrasound-guided biopsies by registering 3D ultrasound control images acquired after each biopsy. For each patient, prostate image alignment was performed automatically with a voxel-based registration algorithm allowing visualization of each biopsy trajectory in a single ultrasound reference volume. On average, the operator reached the target in 60% of all cases. This study shows that it is difficult to accurately reach targets in the prostate using 2D ultrasound. In the near future, real-time fusion of MRI and US images will allow selection of a target in previously acquired MR images and biopsy of this target by US guidance.
    Progrès en Urologie 03/2008; 18(1 Suppl FMC):F15-8. · 0.77 Impact Factor
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    ABSTRACT: This paper is about the application of a 3D ultrasound data fusion technique to the 3D reconstruction of prostate biopies in a reference volume. The method is introduced and its evaluation on a series of data coming from 15 patients is described.
    Progrès en Urologie - FMC 02/2008; DOI:10.1016/S1761-676X(08)71466-4 · 0.77 Impact Factor
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    ABSTRACT: 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.
  • Urology 09/2007; 70(3):8-8. DOI:10.1016/j.urology.2007.06.027 · 2.13 Impact Factor
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    ABSTRACT: Prostate biopsies are in general carried out following a systematic, sector-based acquisition pattern under endorectal 2D ultrasound (US) guidance. The goal of this study is to evaluate the accuracy with which biopsy pattern targets can be reached under 2D US control. We therefore conceived a 3D US based prostate image registration system which makes it possible to project biopsy needle trajectories into a reference prostate volume in order to achieve a biopsy distribution map. The fully automatic system is robust (96% of correct registrations), has a root mean square (r.m.s.) accuracy of 1.41mm and requires about 5s to align two volumes. Analysis of the biopsy distribution showed that the planning target was reached for 63% of all biopsies, and that the average length of the needle trajectories in the sectors was 14mm for a 24mm needle.

Publication Stats

44 Citations
14.66 Total Impact Points

Institutions

  • 2009
    • University Joseph Fourier - Grenoble 1
      Grenoble, Rhône-Alpes, France
  • 2008
    • Hôpital La Pitié Salpêtrière (Groupe Hospitalier "La Pitié Salpêtrière - Charles Foix")
      Lutetia Parisorum, Île-de-France, France