Medical progress through technology最新文献

{"title":"The nature of the bone-implant interface. The lessons learned from implant retrieval and analysis in man and experimental animal.","authors":"J H Boss,&nbsp;I Shajrawi,&nbsp;D G Mendes","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>The morphological appearances of the interface between the bone and the components of arthroplasties depend on multiple factors. Present-day biomaterials being biocompatible when in bulk form, a host reaction consequent upon untoward effects of the implants as such is not expected. Thus, osseointegration, i.e., the direct apposition of bone to the surface of a foreign material at the light microscopical level, occurs, under favorable biomechanical circumstances, irrespective of the chemical composition of the implant. Osseointegration is a multifaceted phenomenon. First and foremost, it evolves when an initially rigid fixation of the component is surgically attained. Interfacial motions are associated with resorption of the bony bed, macrophagic activation and production of wear particles, the close bone-implant apposition is lost and the formation of an interfacial membrane (IM) ensues. The histological features of the IM coincide with the context of its formation and evolution. The quiescent IM is composed of a thin layer of fibrous tissue and its occurrence is compatible with the biofunctionality of the implant. The aggressive or lytic IM (LIM) develops when tissue-irritating, small, irregularly shaped and edgy breakdown products are deposited at the interface. The thick LIM consists of an inflamed fibrous tissue, scattered within which are myriad granulomas, and its surface facing the implant displays a synovial-like aspect. The mono- and polykaryonic macrophages, constituting the granulomatous response, ingest and abut on the wear particles. Amongst the intermediary substances of inflammation elaborated by the lymphocytes and macrophages of the LIM, factors which stimulate the osteoclasts play the pivotal role in as much as progressive bone resorption is associated with progressive growth of the IM and, hence, with incremental interfacial motion, interfacial deposition of wear particles and inflammatory-granulomatous response. The ensuing vicious circle culminates in aseptic loosening of the arthroplasty. The morphological features of the LIM, though characterized by a stereotypical reaction pattern, are, in their details, closely linked with the nature of the diverse components of the composite joint replacement. The histological appearances of the bone-implant interface of stable and loose arthroplasties, the tissular reactions to polymethylmethacrylate, polyethylene, polyacetal, metals and hydroxyapatite as well as the characteristics of cemented and cementless porous-coated, press-fit and hydroxyapatite-coated prostheses are described.</p>","PeriodicalId":76136,"journal":{"name":"Medical progress through technology","volume":"20 3-4","pages":"119-42"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18874495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Topographic mapping of the visual evoked potential after source derivation.","authors":"S V Carreño-Rimaudo,&nbsp;A F Catelli-Infantosi","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Visual Evoked Potentials (VEP) have been considered an important complementary diagnostic method for the study of the physiology of the visual pathways and cortex. It is suggested that topographic maps of Visual Evoked Potentials (VEP) generate information related to the anatomy and physiology of the visual cortex. The source derivation technique applied to electroencephalographic signals has been shown to improve the sensitivity and spatial selectivity of the results. Mapping VEP after source derivation was implemented in order to facilitate the interpretation of the VEP signals and as an aid in identifying the distribution of the sources generating them. The signals were obtained from normal individuals stimulated with full-field and half-field pattern reversal checker-boards. The electrode system used (16 channels) was that proposed by Bodis-Wollner; this system concentrates the electrodes in the scalp areas related to the visual cortex. Signals were sampled simultaneously with a 10-bit A/D converter, saved and, thereafter, processed in an IBM/PC compatible microcomputer. After coherently averaging the responses, source derivation considering inter-electrode distances was applied. It was observed that the spatial spreading of the signals was reduced, leading to an improved spatial selectivity, locating the VEP sources in the expected brain regions and suggesting the existence of electrical dipoles.</p>","PeriodicalId":76136,"journal":{"name":"Medical progress through technology","volume":"20 1-2","pages":"5-13"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18964345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Scalp potential and current density mapping with an enhanced spherical spline interpolation.","authors":"F Hassainia,&nbsp;V Medina,&nbsp;A Donadey,&nbsp;F Langevin","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>A method for producing rapid and accurate scalp electroencephalography, evoked potential and current density mapping is described. This method is based on the spherical spline interpolation, which has been validated as the most suitable function for this application. In comparison with the basic algorithm, the proposed technique is accurate and fast: it reduces the computation time by a factor of 10, while preserving the desired precision level. Furthermore, we study the choice of an optimal configuration and number of electrodes in order to produce a good reconstruction of brain electrical activity with this method. The implementation and application of this enhanced method in a three-dimensional brain mapping system is shown.</p>","PeriodicalId":76136,"journal":{"name":"Medical progress through technology","volume":"20 1-2","pages":"23-30"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18964341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improved white noise method in the evaluation of linear hearing-aids characteristics.","authors":"P Granados,&nbsp;T Aljama,&nbsp;M Cadena,&nbsp;J M Cornejo","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>In this paper an alternative method of determining the standardized electroacoustical parameters for hearing aids is discussed. This is done by using white noise as the input stimulus and a high resolution algorithm, Burg's method, to obtain the spectral estimation of the frequency response. Three types of hearing-aid are analyzed according to both the pure tonal and white noise method and their standardized computed electroacoustical characteristics are compared. The results show deep differences at the low frequency range and a close match at high frequencies (HFA-ref. test and SSPL-90 dBSPL).</p>","PeriodicalId":76136,"journal":{"name":"Medical progress through technology","volume":"20 1-2","pages":"37-42"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18964343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pitch perception in patients with a multi-channel cochlear implant using various pulses width.","authors":"L Aronson,&nbsp;J Rosenhouse,&nbsp;L Podoshin,&nbsp;G Rosenhouse,&nbsp;S B Zanutto","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Cochlear implants have been designed to partially restore hearing to those people who are totally deaf. Multi-channel cochlear implants offer the opportunity to evoke acoustic perceptions like loudness and pitch, elicited by a controllable pattern of electric stimulation by means of electrodes placed in different places along the cochlear length. In this study, two psychophysical experiments were conducted with 4 patients, 1 prelingually and 3 postlingually-deafened, implanted with the multi-channel cochlear prosthesis Nucleus 22. Experiments were carried out to study the effect of varying the width of the electric biphasic pulsatile stimuli on the discriminative abilities of the pitch perception. The tests involved place pitch ranking and pulse rate discrimination. Place pitch ranking was studied by determining the just noticeable difference in pitch pairs (jnd-pp), defined as the pair of nearest electrodes which elicit different pitch perception. Pulse rate discrimination was studied by determining the just noticeable difference in pulse rate (jnd-pr) defined as the minimal difference in stimulus repetition rate over a given electrode, which elicits different pitch perceptions. Both experiments were conducted using pulses of 400, 200, 100 and 50 microseconds/phase. The results indicated that in spite of the differences in pathologies and personal histories, both jnd-pp and jnd-pr decrease by diminishing the pulse width. Speech perceptual data, measured for various pulse widths, validates the usefulness of decreased pulse width which yields favorable results in the psychophysical tests.</p>","PeriodicalId":76136,"journal":{"name":"Medical progress through technology","volume":"20 1-2","pages":"43-51"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18964344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Biomaterial-host interactions: consequences, determined by implant retrieval analysis.","authors":"S S Kaplan","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Prosthetic biomaterials have had a profound impact on reconstructive surgery but complete biocompatability remains illusive. This review considers the retrieval analysis of four common prosthetic structures: the hip, the knee, heart valves, and blood vessels. We show that despite a fine record of early success, deterioration due to mechanical failure or deleterious host responses to the implant may compromise long term function. The eventual retrieval and detailed analysis of implanted structures provides an invaluable opportunity to determine the characteristics of implant success or failure and to provoke the development of still better materials.</p>","PeriodicalId":76136,"journal":{"name":"Medical progress through technology","volume":"20 3-4","pages":"209-30"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18878695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Single beat evaluation of circumferential aortic elastin elastic modulus in conscious dogs. Potential application in non-invasive measurements.","authors":"R L Armentano,&nbsp;E I Cabrera Fischer,&nbsp;J G Barra,&nbsp;J A Levenson,&nbsp;A C Simon,&nbsp;R H Pichel","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>A description of the arterial wall elastic properties comprehends both collagen and elastin, clearly shown in a biphasic stress-strain relationship. From chronically instrumented conscious dogs, aortic pressure-diameter curves can be obtained in a single beat, which is impossible to perform in human beings. In control conditions, the collagen fibers are almost not distended and the resistance to stretch is mainly supported by the elastin fibers. Therefore, the mechanical properties of the aorta are almost purely elastic in the basal beat to beat conditions. In this study we propose and test five indexes, which include as variables: systolic, diastolic and mean arterial pressure and diameter; besides, arterial compliance and pressure-strain elastic modulus as suggested to evaluate the elastic behaviour of the elastic fibers. This data can be easily obtained by non-invasive methods, such as Doppler-ultrasound techniques and auscultative esphygmomanometrical measurements, while the indexes evaluated can be retrieved from a single beat evaluation. Of three measurements performed in chronically instrumented conscious dogs on different days, one of these indexes, the ME5 = [formula: see text] x Rdias proved to be an accurate and reliable parameter to evaluate the mechanical behaviour of arteries. This kind of parameter may be useful for research and evaluation of several diseases that markedly alter the arterial wall compliance.</p>","PeriodicalId":76136,"journal":{"name":"Medical progress through technology","volume":"20 1-2","pages":"91-9"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18964275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Basic considerations of acoustic lenses for ultrasonic transducers.","authors":"R M Ichinose,&nbsp;J C Machado","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>This is a theoretical and experimental work that provides an acoustic lenses' computer simulation program for ultrasonic transducers. The program may be used as a tool to aid in the design of acoustic lenses, giving an estimation of the ultrasonic beam characteristics generated by various types of lenses. Spherical, conical and toroidal lenses were designed and manufactured for a 2.7 MHz transducer with 12.7 mm diameter face. Theoretical and experimental results are consistent considering the effective diameter of the transducer, a concept introduced in this work.</p>","PeriodicalId":76136,"journal":{"name":"Medical progress through technology","volume":"20 1-2","pages":"53-8"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18964270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Real-time digital processing of Doppler ultrasound signals and calculation of flow parameters.","authors":"F S Schlindwein,&nbsp;M H Vieira,&nbsp;C F Vasconcelos,&nbsp;D M Simpson","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Vascular diseases and their complications are responsible for around 27% of deaths in Brazil. Doppler ultrasound is a non-invasive technique that has been used to study blood flow in intact blood vessels since Satomura first reported the potential of the technique in 1959. Because it is non-invasive it makes sequential studies and those in normals feasible. Whereas in contrast angiography only vessel anatomy is displayed, Doppler ultrasound produces dynamic information on blood-flow. It may be used to estimate flow-rates, to image regions of blood flow (colour Doppler), and to help in locating sites of arterial disease, thus complementing X-ray examinations. This paper describes a system based on a Digital Signal Processor for real-time spectrum analysis of Doppler ultrasound signals, real-time display of sonograms, and calculation and analysis of three parameters of clinical interest derived from the Doppler signal. The system comprises a TMS320C25 development board, which acquires the signal and performs spectrum analysis, and a microcomputer, which reads the spectral estimates, displays them as a sonogram in real-time and calculates a set of spectral parameters proposed in the literature. The system permits a maximum sampling frequency of 40.96 kHz, and in the sonogram, 80 power spectra per second (each with 128 frequency bins) are displayed. In a preliminary study, the stability of the haemodynamic parameters and their dependence on a user-defined threshold value is investigated.</p>","PeriodicalId":76136,"journal":{"name":"Medical progress through technology","volume":"20 1-2","pages":"81-9"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18964274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Retrieval studies on calcium phosphate-coated implants.","authors":"W J Dhert","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>The search for the improvement of implant fixation in bone resulted several years ago in the introduction of calcium phosphate coatings on orthopaedic (and dental) implants. Since then many animal experiments, especially on hydroxylapatite coatings, have been performed. By now the first promising results from clinical studies are also available. In this review, the plasma-spray process is described and some of the current techniques for the analysis of retrieved implants are discussed. It is now widely understood that the calcium phosphate hydroxylapatite is osteoconductive. Various experimental animal studies revealed the capability of calcium phosphate coatings to enhance implant fixation, especially under specific or less optimal conditions such as a with a porous implant, loose fit, micromotion or experimental arthritis. Clinical studies, including the analysis of retrieved hydroxylapatite coated hip implants, confirmed these promising results and as a consequence, hydroxylapatite coated total joint prostheses are now used on a large scale. Two questions that are closely related with each other are very actual, e.g. the strength of the coating-substrate interface and how stable or crystalline should hydroxylapatite coatings be for a proper clinical function? There does not yet seem to be a consistent answer to these questions.</p>","PeriodicalId":76136,"journal":{"name":"Medical progress through technology","volume":"20 3-4","pages":"143-54"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18874496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}