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The aim of this study was to assess polyethylene wear in a total hip prosthesis by digitized radiography of the whole pelvis in the anteroposterior (AP) plane. The three-dimensional (3-D) pose of the nonmetal-backed acetubular cup, materialized by its metal ring and the femoral head made of metal or ceramic, was estimated using iterative algebraic algorithms with inner bias correction and bootstrapping for variance reduction. Points of interest were obtained by maximizing the correlation between sampled density profiles and 3-D geometric models degraded by the modulation transfer function (MTF) of the radiographic system and the film scanner. The error in the maximal correlation estimate were inferred from noise power spectra (NPS) and allowed the calculation of the point covariance matrix. Both NPS and MTF were modeled for each stage and estimated using least-square fitting of the overall NPS model to the autospectral density function calculated in stationary regions. Comparison of the radiographic time series was made possible by the high accuracy level and 3-D matching from the cup orientation. The feasibility of the full 3-D measurement, the assumption of negligible lateral wear and its influence on AP wear are discussed on simulated and real radiographic data.

We evaluated the direct location in the globus pallidus (GP) under stereotactic MRI (sMRI) guidance in five parkinsonians treated with chronic deep brain stimulation (four bilaterally). The sMRI consisted of three orthogonal (horizontal, frontal, sagittal) sets of images obtained with a stereotactic frame and its localiser. The sMRI was coupled with ventriculography to compare the location with the classic indirect method based on commissural landmarks. The target was defined on T2-weighted slices in the anterior part of the medial GP, at the vertex of the nucleus. It was reached via one track with a semi-micro-electrode and step by step high frequency stimulation, then replaced by a quadripolar electrode once we located the site enabling the optimal clinical improvement. Stereotactic x-rays localised the final position of the electrode. A company software matched sMRI, ventriculography, and peroperative (perop) x-rays, with reference to the stereotactic location boxes. We analysed the effects of acute (perop) and chronic (six-month follow-up) stimulation of active plots (acplots), i.e. leading to optimal clinical improvement. Three distances with reference to the acplots were measured both on sMRI and ventriculography: the laterality from the median sagittal plane of the third ventricle; the anterior position from the midpoint of the intercommissural line (Icl), and the vertical position with regard to the Icl. We then compared the differences in measurements (n = 64) with the Bland and Altman method. The mean difference was 0.09 mm with 95% of the values between +/- 1 mm, but only the laterality had a statistically significant agreement (all the differences included between +/- two times the standard deviation of the mean). The acplots distances from the dorsal, ventral, and medial boundaries of GP (defined by manual surrounding on frontal and horizontal planes) were measured on sMRI. With one exception, the acplots were all included in the nucleus. The six-month acplots were located dorsally with reference to the perop ones. Clinical benefit at six-months follow-up showed results comparable to the literature. Direct location of GP target based on sMRI seems a simple and reliable method.

N -Acetic acid derivatives of 4-carboxy-6-arylpyridazin-3-ones were synthesized for the dual purpose of inhibiting aldose reductase and exhibiting antioxidant properties. All the prepared compounds showed a significant in vitro aldose reductase inhibitory effect (10 −5 M ≤ IC 50 ≤ 10 −4 M). The spatial configuration of the most active derivative 4f (4- i -PrC 6 H 4 at C 6 , IC 50 = 0 95 × 10 −5 M) was compared with pharmacophore requirements of the aldose reductase inhibitor site using a molecular modeling system. The antioxidant action of 4a–f was also studied in vitro . Compound 4c (4-ClC 6 H 4 at C 6 , IC 50 = 1.56 × 10 −3 M) was the most effective at scavenging the superoxide anion whereas compound 4a (C 6 H 5 at C 6 , IC 50 = 1.28 × 10 −3 M) was the most active at inhibiting lipid peroxidation. In addition, biological activities (log 1/IC 50 ) for most of the data sets could be correlated directly to lipophilic, electronic and steric parameters.

Slow waves in intracranial pressure (ICP) and related signals seems of interest to evaluate the dynamic autoregulation, i.e. by comparison of the frequency links between an intracranial signal, e.g. ICP, cerebral blood velocity (CBV), and arterial blood pressure (ABP). To clarify the links, we compared two frequency methods based on coherence function to estimate the influence of ICP, ABP and CBV on couples, respectively CBV-ABP, ICP-CBV and ICP-ABP, of slow waves in the B and the UB bands. We found that B and UB waves activity in ICP, CBV and ABP had reciprocal influences, except for the UB activity in ICP-CBV link which seems to be less sensitive to ABP. These data confirmed the interest of to analyse the slow wave activity to evaluate dynamic autoregulation. The interest of taking into account the reciprocal influence of the signals must be evaluated.

We propose in this article to compute White Matter (WM), Gray Matter (GM) and Cerebrospinal Fluid (CF) volumes from MR images of a human brain using possibilistic logic and a fusion scheme. The fusion process is divided into three steps: fuzzy tissue maps are first computed on all images using a possibilistic clustering algorithm. Fusion is then achieved for all tissues with a context based fusion operator. The final segmentation allows for the computation of brain tissue volumes. Applications on a brain model show a great agreement between the results and the true segmentation, thus affording a relevant tissue classification on clinical data.

We measured the modulation depth of an interference pattern after double passage through the eye with different entry positions of the linearly polarized incident beam in the pupil plane. This shifting of the incident beam greatly modifies the mean irradiance and the modulation depth of the aerial image, whatever the direction of the polarizer. These measurements give a better understanding of the respective contributions of the retinal layers to the formation of the aerial image. Consequently, the modulation transfer function of the optics of the eye deduced from measurements with the aerial image must be considered cautiously.

After a light stimulation, the electrical potentials are recorded on the ocular zone (electroretinogram), on the temporal and parietal zones (electroaxogram), and on the occipital zone (electrovisiogram or visual evoked cortical potential). Using mathematical methods (with microcomputer) the morphology and the propagation of electrophysiological signals are studied. Apart from the future possibilities, a clinical application exists now: early detection of demyelinating diseases such as multiple sclerosis.

To study the relationship between peak latencies of visual electrograms and photostimulation parameters, the authors worked on two different stimulation protocols: flash and pattern reversal. The recording gave differents signals, all of them lost in noise. Starting from the study of this kind of signal, the authors carried out processing in five steps: averaging, filtering (digital), modeling, standardizing, and extracting of peak latencies. Next, statistical studies were conducted using an analysis of variance and a Tukey test. The main results are particularly interesting for a visual evoked response with pattern where peak latencies are selectively sensitive to luminance-color or contrast. This could be extended to pathological cases with a view to use as a diagnostic aid. >