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

Estimation of urinary stone composition by automated processing of CT images

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

Mapping of transrectal ultrasonographic prostate biopsies: quality control and learning curve assessment by image processing

Objective: 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. Methods: 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. RESULTS: 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). Conclusions: 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

Resting Muscle Shear Modulus Measured With Ultrasound Shear-Wave Elastography as an Alternative Tool to Assess Muscle Fatigue in Humans

The aim of this study was to investigate the time course of the resting vastus lateralis (VL) muscle shear elastic modulus (μ) measured with ultrasound shear-wave elastography during repetition of isometric maximal voluntary contractions (MVCs) of the knee extensors (KE). Fifteen well-trained young males repeated 60 5-s isometric MVCs. Evoked electrical stimulations and the VLμ were measured every ten MVCs at rest. The resting VLμ significantly decreased (−34.7 ± 6.7%; P &lt; 0.001) by the end of the fatigue protocol. There was also a 38.4 ± 12.6 % decrease in MVC after exercise (P &lt; 0.001). The potentiated doublet and single twitch torque amplitudes and properties were significantly modified by the end of exercise (P &lt; 0.001). This study shows the time course of the resting VLμ during the repetition of maximal voluntary fatiguing exercise of the KE muscles. The decrease of the resting VLμ could directly affect the force transmission capabilities accounting for peripheral fatigue

Aspects physico-chimiques des biomatériaux utilisés en Urologie

Les solides se distinguent des autres états de la matière (liquides et gaz) par le fait qu'ils possèdent un volume et une forme qui leur sont propres. Les atomes sont en effet fortement maintenus ensemble par des forces interatomiques dont la nature, le nombre, l'intensité et la direction conditionnent les propriétés à la fois physiques et chimiques des solides. La nature de ces liaisons dépend essentiellement de celle des atomes qui les constituent et en particulier si ce sont des métaux, des non-métaux ou des semi-métaux..

Kidney stones and imaging: what can your radiologist do for you?

International audienc

Training in Percutaneous Nephrolithotomy-A Critical Review

Aim: To study factors influencing training and maintaining skills in performing percutaneous nephrolithotomy (PCNL). Methods: We matched key words, throughout Medline, MeSH, and Cochrane databases including: renal stone, percutaneous, nephrostomy, endourology, educational, training, learning curve, expertise, skill, residency,practice, survey, simulator, and robotics. For this topic we defined,if possible, levels of evidence based on International Consultation on Urological Diseases (ICUD) and World Health Organization recommendations. Results: Obtaining renal access is one of the most important factors in training for PCNL. A resident has to perform about 24 PCNL procedures to obtain a good proficiency during the residence period. Competence at performing PCNL is reached after 60 cases and excellence is obtained at >100 cases. Stone centers providing all the endoscopic treatment options seem to provide the best conditions to ensure a sufficient volume of patients recruited. Virtual reality simulators may have a potential in training for PCNL. To maintain one's expertise, participation in continuing educational programs is recommended. Conclusion: PCNL is currently the most complicated stone surgery technique to teach. The steep learning curve is mainly related to obtaining renal access. The traditional method of acquiring surgical skills is by apprenticeship in the absence of validated virtual simulators. Given the complexity of the treatment of renal stones, one may consider a centralized renal stone treatment in dedicated stone centers. (C) 2008 European Association of Urology. Published by Elsevier B.V. All rights reserve