Biomedical subjects
Publications and source records attributed to J P Morucci.
The main experimental problems (temperature, electrode, polarisation, non-uniformity of electric field, non-homogeneity of biological material) of impedance measurements of biological tissue are discussed. Minimisation of the inherent sources of experimental error is proposed.
In order to characterise small samples of tissue by complex impedance measurements between 10(-6) and 20 MHz, an experimental set-up is proposed. This paper describes the methodology used and presents some preliminary results.
Optimal control techniques have been combined with Alessandrini's singular perturbation method and Wexler's algorithm to reconstruct images in impedance imaging. We have also considered an integral formulation of the potential problem, which has led us to introduce an array of dipoles whose position, orientation and length can be optimised to model the conductivity discontinuities.
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The concepts of the point spread function (PSF) and its Fourier transform, the modulation transfer function (MTF) are introduced to evaluate an impedance imaging system. The effects of some practical factors which should be taken into account in calculating the MTF are analysed. Experimental results from the groups in Sheffield, Barcelona and Toulouse are presented.
Is there an effect on binocular coordination during reading of oculomotor imbalance (heterophoria, strabismus and inadequate convergence) and of functional lateral characteristics (eye preference and perceptually privileged visual laterality)? Recordings of the binocular eye-movements of ten-year-old children show that oculomotor imbalances occur most often among children whose left visual perceptual channel is privileged, and that these subjects can present optomotor dissociation and manifest lack of motor coordination. Close binocular motor coordination is far from being the norm in reading. The faster reader displays saccades of differing spatial amplitude and the slower reader an oculomotor hyperactivity, especially during fixations. The recording of binocular movements in reading appears to be an excellent means of diagnosing difficulties related to visual laterality and to problems associated with oculomotor imbalance.
The modal analysis of a human tibia consisted of characterizing its dynamic behavior by determining natural frequency, damping ratio and mode shapes. Two methods were used to perform the modal analysis: (1) a finite element method (structural model); (2) an experimental modal analysis (modal model). The experimental modal model was used to optimize the structural model. After optimization, differences in results between the two models were found to be due only to mechanical properties and mass distribution. The influences of boundary conditions and geometric properties (such as inertia and length) were eliminated by the finite element model itself. The percent relative error between the two methods was approximately 3%, corresponding to the standard deviation of the measured frequencies. For the frequency range considered, the mode shapes were bending modes in two different vibration planes (latero-medial and sagittal), with a slight torsion effect due to the twisted geometry of the tibia.
Bone cutting has always been a problem for surgeons because bone is a hard living material, and many osteotomes are still very crude tools. Technical improvement of these surgical tools has first been their motorization. Studies of the bone cutting process have indicated better features for conventional tools. Several non-conventional osteotomes, particularly ultrasonic osteotomes are described. Some studies on the possible use of lasers for bone cutting are also reported. Use of a pressurised water jet is also briefly examined. Despite their advantages, non-conventional tools still require improvement if they are to be used by surgeons.
The anterior displacement of the tibial condyle was proposed as early as 1963 by P. Maquet as a therapeutic solution to treat femoropatellar arthritis. However, the benefits of such a procedure remain controversial. In this work, the effects of a 1. cm anterior displacement of the tibial condyle, with and without section of the patellar wings, have been studied on the knees of fresh corpses without osteoarthritis. The knees were tested in flexion from 10 to 70 degrees. The study dealt with the contact surfaces, pressures, and femoropatellar forces, which were analyzed with an original and efficient measurement system, with the Fuji Prescale Film as a sensor. This study showed that the femoropatellar contact has not been significantly modified by the displacement of the tibial condyle. We have noted only a slight decrease in the pressure after this type of surgery. These results are in contradiction with Marquet's results. In all cases, the anterior displacement of the tibial condyle with resection of both patellar wings produced the best results. These results suggest that displacing the tibial condyle anteriorly does not have the expected effects. The indication of such a surgical procedure must therefore be established only cautiously and after ruling out other therapeutic methods.
Maintenance of a constant level in the oxygenator during surgical extracorporeal circulation (ECC) is of paramount importance. We propose a device able to regulate the pump speed accordingly to the level in the oxygenator, and an automatic clamp to control venous return from the patient. The level regulator permits pump speed control and also stops the pump when a prefixed low level is reached (during ECC). Linearization of the level sensor has been made in order to optimize the PI regulator. Simulation results are presented and the regulator is evaluated in a clinical environment. The automatic clamp provides a good solution for reproducible and easy transitions in venous return. When coupled with the level regulator, the pump speed will increase automatically from zero to the correct equilibrium speed, with variable duration (from 30 seconds to 5 minutes) chosen by the operator. The same technique is used for stopping the ECC. These two devices are, in fact, modules, making up part of an evolutive device for ECC automation. The modules can exchange data with a supervising microcomputer.
In 1963 P. Maquet suggested tibial tuberosity advancement as a therapeutic solution for patellofemoral arthrosis, but the fiability of the operation remains controversial. An advancement of the tibial tuberosity by 1.5 centimeter, with and without bilateral retinacular release, was performed on non arthrosic knees of fresh cadavers and on knees presenting medial, lateral or bipolar patellofemoral arthrosis. The joints were tested with flexion ranging from 10 to 70 degrees. The study concentrated on contact areas, pressures and patellofemoral forces analysis using an original and efficient measuring system. The pressure sensitive film used was the Fuji Prescale Film. The study showed that, on non arthrosic knees, the patellofemoral contact was not modified to any significant extent by advancing the tibial tuberosity. In cases of bipolar patellofemoral arthrosis reduced pressures were noted. On the lateral patellofemoral arthrosis experimental model, the tibial tuberosity advancement was efficient as it allowed a 50 per cent reduction in pressure at 10 to 30 degrees of flexion and a 20 per cent reduction at 40 to 50 degrees of flexion and a 20 per cent reduction at 40 to 50 degrees of flexion. In all cases, the best results were obtained from tibial tuberosity advancement associated with bilateral retinacular release. These results indicate that tibial tuberosity advancement may have beneficial effects in cases of lateral and bipolar patellofemoral arthrosis.
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The efficiency of a light amplifier system for the improvement of night vision has been tested on 30 normal subjects and on subjects suffering from night blindness including 36 patients with pigmentary retinopathy, 18 myopic patients with night blindness and 12 patients with senile cataracts. In all cases, the scotopic vision presented a great improvement and it reached up to half of photopic vision. The use of the light amplifier would certainly provide a considerable improvement for subjects suffering from night blindness and mostly for those suffering from pigmentary retinopathy. But two conditions are necessary for this: miniaturization of the device and absence of major macular lesions in the patient.
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Explore the source record for details and available documents.