Medical progress through technology最新文献

The human body is a medium which consists of various tissues such as skin, fat, muscle and bone. Each of the tissues has their own biomechanical properties. We have measured biomechanical impedances by applying a random vibration (30-1000 Hz) to the layered model of human tissues to study the occurring mechanism of impedances measured at the skin surface. The data showed that the top tissue layer and the underlying layer both contribute to the impedance depending on the thickness of the top layer. The contribution of the underlying layer was clearer over the frequency range from 30 to 400 Hz. Quantitatively we found the following: The impedance measured at the surface was roughly expressed as the model which is connected in series by the impedances of the top and underlying tissues. The contribution of the underlying tissue decreased according to the increase of the thickness of the top tissue, and disappeared over a certain thickness (18 mm in this paper).

The electrically evoked potential in the auditory nerve is measured when the cochlear is stimulated with a high density electrode array whose microcontacts (20 x 160 microns) are placed close to the nerve cells. Threshold range from 8 to 35 microA with the stimulating electrodes near the spiral ganglion cells. A multi-pole technique for restricting the spread of current with electrical stimulation of the cochlea is tested using neural recording in deafened guinea pigs. The ground based quadrupolar electrode driving configuration has thresholds for neural activation only slightly greater than monopolar stimulation when the electrode contacts are placed less than 50 microns from the neurons. During simultaneous stimulation the monopole and the ground based quadrupolar modes tend to generate similar growth functions (magnitude and latency). The electrode interactions are generally factorial, which means that the algebraic sum of the responses (magnitude growth functions) produced by 2 distinct electrodes is less than when the same 2 electrodes are stimulated simultaneously.

The SmartDrive console represents an important advance in small bone surgery because it monitors and coordinates the operation of its handpieces. The SmartDrive console has the following unique features: 1) a handpiece recognition system; 2) an instrument speed display; 3) a handpiece display and monitoring system; 4) a torque instrument control system; 5) a temperature monitoring system; 6) and an irrigation system. Mechanical performance studies have been undertaken that have validated the accuracy of the monitoring systems of the consoles. The consoles provided reliable recordings of the rotational speeds of their hi-speed drills. The MicroAire console automatically shuts off its power as the temperature increased to 110 degrees F (43 degrees C). In contrast, the Stryker Command 2 console has a limited monitoring system that can not alter the operation of the handpieces.

Knowledge about the viscoelastic behaviour of the arterial wall has been proved to have physiological importance and clinical usage. Our purpose was to study the changes of the systemic arterial wall's elastic properties non-invasively, in patients with established essential and with borderline hypertension, and to evaluate its possible determinants. Three groups of normotensive, borderline and established essential hypertensive patients were evaluated. Arterial pulse wave velocity (PWV) was measured and arterial compliance (Cm) was derived in all patients. Pulse wave velocity was obtained from the pressure values of digitized carotid and radial arteries. Arterial compliance (Cm = dD/dP with P pressure and D diameter) was calculated using a formula derived from the Bramwell and Hill equation: Cm = (1,334 x D)/(2 rho x PWV2), where for D humeral diameter was used as measured by high resolution echograph, and rho is the blood density (rho = 1.06). Pulse wave velocity was significantly higher in established essential hypertensive patients with respect to normotensive patients (p < 0.05). Arterial compliance was significantly diminished in established and in borderline hypertensive patients with respect to normotensive patients (p < 0.05), which implies early alterations in hypertensive cardiovascular disease. Multiple regression analysis of the cofactors showed that age and diastolic pressure are independent determinants of Cm. Impairment of the arterial wall's intrinsic elastic properties was demonstrated in established essential hypertension, independent of age and diastolic pressure.

A reasoning method to explicate the conclusions-a posteriori- and to prospect for the next test-a priori-applied to medical expert systems based on fuzzy analog ganglionar lattices is presented. This method is founded on the sensitivity criterion of the consequent respect to the antecedents. It proves to be suited for problems of any complexity, specially when they are formulated on well-established intermediate concepts, such as syndromes, clinical finding, laboratory procedures, etc., as is usually the case in medical procedures. This type of expert system uses the structural properties of the ganglionar lattice to produce explications for its conclusions at different levels of abstraction, and to an arbitrary, but fixed, explicative degree. A measure to evaluate the consequent's achieved preciseness (certainty) is also supplied. A full example of application in the diagnosis of cardiac insufficiency with hypertensive myocardiopathy is shown, and a computational implementation of this analog procedure is described. Finally, the reasoning methods for explicating and prospecting are discussed.

NiTi alloy specimens were plasma cleaned and then coated with a thin film of plasma-polymerized tetrafluoroethylene (TFE) in a Radio-Frequency reactor. The corrosion protection provided by these films was studied by potentiodynamic tests performed in Hank's physiological solution. Surface properties which determine biocompatibility were characterized by X-ray photoelectron spectroscopy (XPS). The results showed that the surface of untreated NiTi was mostly composed by oxygen, carbon, titanium oxide (TiO2) with traces of nickel oxides (NiO and Ni2O3) and metallic Ni. The passivity of untreated NiTi was found to be unstable in the simulated human body media. After plasma treatment, the NiTi surface contained only carbon and fluor. The plasma-polymerized thin film was found to stabilize the NiTi passivity and to increase its pitting potential. This treatment provides a good protection against dissolution of nickel from NiTi alloys.

The purpose of this study was to perform a biomechanical performance study and a clinical trial on a new external condom catheter system. The biomechanical performance study demonstrated that the vented connector failed following exposure to urine for 14 days. In addition, angulation of the inlet adapter of anti-reflux valve of the urinary leg bag to an angle of 35 degrees (+/-5 degrees) caused complete obstruction of urinary flow. A clinical trial of the new condom catheter with its inner flap revealed twisting of the catheter that interrupted urinary flow in four of ten patients. This catheter twisting was not observed in condom catheters without inner flaps. Furthermore, this new system is not easily applied or removed by patients with neurosensory deficits or musculoskeletal weakness. Design modifications of the vent within the connection tubing, the anti-reflux valve in the collection bag, the condom catheter with its inner flap, as well as the leg bag attachments should remarkably improve the performance of this new urinary drainage system.

The accuracy of the radiology vocabulary domain of the IBM VoiceType Dictation for Windows speech recognition system for use in a clinical setting was evaluated. Six men and one woman dictated a case report under several conditions. The impact of vocabulary domain, microphone position, personal enrollment, and background noise were assessed. The dictations were exported to Microsoft Word 6.0, printed, and graded for accuracy. The data were expressed as a percentage correct. The enrollment and training processes took an average of 5 hours to complete. The accuracy of VoiceType Dictation was significantly reduced by speech volume and background noise level so that it could not be used to dictate clinical information accurately in a hospital setting. Although IBM's VoiceType Dictation with the radiology vocabulary domain has improved speech recognition, it is not a reliable dictation system for accurate and efficient clinical dictation in a hospital setting.

The lack of depth perception hampers the surgeon during laparoscopic operation. Laparoscopes usually are monocular, but binocular ones are currently available. Depth perception, however, does not exclusively rely on binocular disparity. An observer, with only one eye, who is able to move that eye, obtains the same information as an observer who has two eyes. This principle of movement parallax can be applied to laparoscopy by coupling the head movements of the surgeon to the motions of the tip of the laparoscope. In an experiment we investigated if this principle is applicable to laparoscopy. Two groups of testees with no background in surgery were used. The first group was assisted by movement parallax, the second group was viewing a static image. Both groups of testees had to perform an exploration and a manipulation task. Since the amount of space for camera motion within the laparoscope is limited, implementation potential depends on the amount of movements that will be made by the observer. Therefore the movements of the observer performing the exploration task were registered and analysed. Results of the experiment indicate the advantage of movement parallax for the exploration task (performance increases by factor 2 while using only 30% more time) but not for the manipulation task. The analysis of the movements indicates that small movements are sufficient for implementation. Based on these results we concluded that movement parallax is applicable to laparoscopy.