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Biomedical subjects

P Seitz

Publications and source records attributed to P Seitz.

At least 19 recordsLinked to original sources
PubMed2005

High-density electrode array for imaging in vitro electrophysiological activity.

The development of a high-density active microelectrode array for in vitro electrophysiology is reported. Based on the Active Pixel Sensor (APS) concept, the array integrates 4096 gold microelectrodes (electrode separation 20 microm) on a surface of 2.5 mmx2.5 mm as well as a high-speed random addressing logic allowing the sequential selection of the measuring pixels. Following the electrical characterization in a phosphate solution, the functional evaluation has been carried out by recording the spontaneous electrical activity of neonatal rat cardiomyocytes. Signals with amplitudes from 130 microVp-p to 300 microVp-p could be recorded from different pixels. The results demonstrate the suitability of the APS concept for developing a new generation of high-resolution extracellular recording devices for in vitro electrophysiology.

Animals↗
PubMed1999

Economic outcomes of a targeted intervention program: the costs of treating allergic rhinitis patients.

OBJECTIVES: To determine the annual costs of treating allergic rhinitis patients in a managed care environment and to assess the effect of a treatment intervention program on direct and indirect costs. DESIGN: Two arms of an economics study were designed to calculate annual costs of treating allergic rhinitis in Lovelace Health Systems. Direct and indirect costs were also reviewed for patients participating in an intervention program designed to improve patient outcomes during the 1996 fall allergy season. PATIENTS AND METHODS: Annual medical costs of treating allergic rhinitis within the Lovelace system were reviewed using a patient database. A total of 7936 patients with allergic rhinitis symptoms were identified in the database using a case-finding algorithm. An equal number of patients without allergy conditions were selected for the comparison group. In addition to calculating annual costs of treating allergic rhinitis, direct and indirect costs were reviewed for patients participating in a rhinitis intervention program to determine differences in cost between the treatment and control groups. An intervention group of 247 patients was selected to receive care at clinics randomized to use practice guidelines to improve treatment, while 255 patients were treated in the control group clinics, which did not alter treatment practices. RESULTS: Annual expenditures were nearly $2 million more for the allergic rhinitis group than for the control group. In the intervention study, treatment and control groups expended the same in direct costs, but the intervention group showed a trend toward decreased indirect costs. CONCLUSION: Costs of allergic rhinitis are not trivial to a managed care organization; a specifically designed intervention program shows potential for minimizing the costs associated with the ailment.

Anti-Allergic Agents↗
PubMed1997

The average pressure distribution of the diabetic foot: can it be used as a clinical diagnostic aid?

INTRODUCTION:: The aim of this study was to investigate whether averaged data obtained from pressure distribution measurements could be used to distinguish differences between diabetic feet with normal and no sensation. The calculated parameters most sensitive to any differences were established, and the potential of the averaged maximum pressure picture as a quick recognition pattern of a neuropathic diabetic foot was assessed for clinical use. METHODS:: Dynamic pressure distribution data was collected from 56 diabetics using an emed SF2 platform. The first step method was used, and only one step per subject was recorded for this set of data. Each subject completed a questionnaire which included a grading of the sensitivity to vibration on the plantar surface of the foot evaluated by a clinician. The subjects were subsequently divided into four groups depending on this sensitivity, but only data from the two groups with normal (n=16) and no sensation (n=12) were evaluated in this study. Control data were obtained from two separate sources: for adults (n=40) using an emed SF4 platform and for teenagers (n=73) using a mini-emed platform. The groupmask evaluation program from the novel-win software and the average program from the novel-ortho software were used to evaluate the data. Each dynamic pressure distribution was automatically masked using the foot recognition algorithms of the 'novel' mask, which divided the foot into ten areas: the heel, midfoot, first, second, third, fourth and fifth metatarsal heads (MTH), hallux, second toe, and remaining toes. The parameters analysed for each of these masks included: the mean peak pressure, maximum force, contact time, beginning of contact time, pressure-time integral and force-time integral. RESULTS AND DISCUSSION:: The results showed clearly that both pressure and contact time are important parameters in differentiating a neuropathic from a non-neuropathic diabetic foot. Values of the maximum force in each area of the foot showed no difference between the two groups. Owing to the small sample sizes for the two diabetic groups the 95% confidence limits were relatively large, however, clear differences existed between the two sets of data for the mean peak pressure and the mean pressure-time integral for the total foot and the forefoot. Based upon this data, peak pressure values above 56 N/cm(2) for the 1st MTH, 46 N/cm(2) for the 3rd MTH, 35 N/cm(2) for the 4th MTH and 26 N/cm(2) for the 5th MTH, and pressure-time integrals above 31 Ns/cm(2) for the 1st MTH, 21 Ns/cm(2) for the 2nd MTH, 24 Ns/cm(2) for the 3rd MTH, 19 Ns/cm(2) for the 4th MTH and 12 Ns/cm(2) for the 5th MTH would suggest the possibility of a neuropathic diabetic foot. The averaged maximum pressure distribution picture for each group showed some differences between diabetic feet with normal sensation and those with no sensation. However, owing to the small size of the groups, it was felt that the averaged pressure pictures were, at the moment, limited in their use as a quick recognition pattern for the clinician. Although further data has already been collected and will be added to the databank in the near future. CONCLUSIONS:: These data show that averaged maximum pressure pictures alone do not provide sufficient information to differentiate clearly between a non-neuropathic and a neuropathic diabetic foot. Parameters obtained from the dynamic process, in particular, the pressure-time integral, must also be taken into account. It is anticipated that this work will be continued in order to investigate differences between other dynamic processes of potential importance, such as the location and speed of the gait line. ACKNOWLEDGEMENTS:: The authors would like to thank Dr M Morlock and Dr T Tsvetkova for the control data.

Journal Article↗
PubMed1997

Reproducibility test on a children's insole for measuring the dynamic plantar pressure distribution.

INTRODUCTION:: This study aimed to establish the reproducibility of a insole measuring system specifically designed for use inside children's shoes. It is important to carry out such an investigation before any measurements are taken in order to ensure that any errors associated with the system are known and quantified. The children's insole had 84 pressure sensors, compared to the adult insoles, with 99 pressure sensors. The sensor technology was essentially the same as used in the adult Pedar system, and incorporated capacitance-based pressure transducers. MATERIALS AND METHOD:: An eight year old boy, height 123 cm, weight 29 kg, was used in the study. Dynamic tests were carried out with the Pedar insole measuring system. The subject walked on a treadmill, at a speed comfortable for him (3 km/h), with the insoles placed between the foot and the shoe. No fixation of the insole to the shoe was used. Seven runs were completed, each with four tests recorded of more than twenty steps. In between each run the insoles were completely removed from the shoe and then replaced. A zero measurement was also taken before the continuation of the next run. Before analysis of the data, twenty steps were selected. The first two steps in each sequence were ignored and the following twenty steps were used in the analysis, ten each for the left and the right foot. Any additional steps recorded were also ignored. The average force for the test data file was initially noted, together with the local pressure for each of the forefoot, midfoot, heel and toe regions, for both the left and the right foot, separately. RESULTS:: The within test data and in-between test data when walking on a treadmill at constant speed was found to be reproducible (F(0.01)) for 6 out of 7 tests for the left and the right foot. The standard deviation of the average force for the left and the right foot was 3%. The 95% confidence intervals for the mean of the peak pressure in the total object was within 6% for the treadmill and free walking data. There was no significant difference between these data. The 95% confidence intervals for the mean of the peak pressure under the big toe was 9% for the treadmill data and 16% for the free walking data. CONCLUSIONS:: These results, together with other published data (McPoil et al. 1995) show that the pedar children's insole system provides accurate and reproducible measurements of the dynamic plantar pressure distribution. The clinician can therefore use this system with confidence as a therapeutic or rehabilitative tool.

Journal Article↗
PubMed1997

Transformation and average as handy tools for pressure measurement data analysis.

INTRODUCTION:: Pressure measurement data underneath[Table: see text] the foot represent usually a large number of data files which is equal to double product of the number of the subjects in study and of the number of the trials for each foot. Besides, 'normal' parameters are necessary to compare the results for the controls and for the subjects in study. Statistical parameters (mean values and standard deviations) are not very convenient when it is required to establish cartographical and geometrical parameters or peak pressures, maximum forces, contact areas, contact time and others for foot typing or as a standard. Sometimes it is reasonable to obtain average pressure data as a base for further data analysis. But taking into account that pressure distribution pattern may differ by its length, width and angle of the inclination of the foot axis to the horizontal it was necessary to solve a problem of transformation of any pressure picture to the given length and width (for vertical location of the foot axis). METHODS:: The transformed coordinates X(*) and Y(*) are defined from the following system of equations: X = Y(*) x width/width(*) x sina + X(*) x length/length(*) x cosa + X(o) Y = Y(*) x width/width(*) x cosa - X(*) x length/length(*) x sina + Y(o) where X(o), Y(o) -- the coordinates of the origin; width, length, a -- parameters of the initial pressure picture; width(*), length(*) -- parameters of the transformed pressure picture. X, Y -- are real values but the values of pressure are defined only in the integer coordinates. One of the main parts of average is a reduction of the time process to any number of frames. If N(max) is a maximum number of frames in one of the data files than all other data files must be transformed with accordance to the following formulas: for j-th frame the value of pressure for sensor with coordinates x, y is: P(*1)(xy) (j) = P(1)(xy) (i) x ki + P(1)(xy) (i+1) x k(i+1), where P(1)(xy) (i) -- pressure for sensor with coordinates x, y of the 1-th initial time process; j = 0, ellipsis, N(max) -1; j-th frame corresponds to i-th frame in the initial time process as i = integer(j) x (N -1)/(N(max) -1), N -- a number of frames in initial time process; coefficients k(i) and k(i+1) are equal to k(i) = j x (N -1)/(N(max) -1) -- I, k(i+1) = 1 - ki. Then the values of pressure are averaged: P(*)(xy) (j) = 1 / L x S P(1)(xy) (j), where L is a number of data files. Corresponding software was developed. RESULTS AND DISCUSSION:: 38 files of pressure measurement data of the teenagers from military school were chosen for transformation and average. Statistical errors of transformation and average were calculated for each data file (for peak pressure, force and area) and for all parameters from two software packages: Novel-win v.95.121 and Novel-ortho v.95.121. The maximum errors are for peak pressures (about 7%-10%) and contact areas (about 6%). CONCLUSION:: Transformation and average programs can be successfully used for data analysis additionally to traditional statistical software: groupmask evaluation program.

Journal Article↗
PubMed1994

Innovations in human service technologies. Strengthening health care delivery systems.

The authors report on innovative approaches to the organization of health services and the delivery of patient care in 19 U.S. hospitals and hospital networks. Strengthening patient care is the focus of this initiative. Hospital-wide interdisciplinary planning and the subsequent trial of new human service technologies are explored.

Delivery of Health Care↗
PubMed1991

Partial characterization of rat marrow stromal cells.

Fibroblast-like rat marrow stromal cell (CFU-F) cultures have been characterized in terms of their responsiveness to calciotropic hormones, metal ions, the nonsteroidal antiinflammatory drug, and by their putative paracrine role in the maintenance of active populations of osteoblasts at the marrow-bone interface. These studies indicate that CFU-Fs lack a complete osteoblast signature. Subconfluent CFU-Fs grown in the presence or absence of 10(-7) M dexamethasone lack receptors for PTH and calcitonin, and fail to show enhanced cAMP or cGMP responses to 10(-7) M 1-34 PTH (rat), or any evidence of osteocalcin production [+/- 10(-9) M 1,25-(OH)2D3]. Low concentrations of fluoride [10(-12) and 10(-9) M] stimulated CFU-F grown in vitro in serum-free media, though higher levels (10(-7) and 10(-6) M), inhibited growth in vivo and in vitro. Aluminum (10(-12)-10(-7) M) and ibuprofen (10(-7) M) did not alter normal growth patterns, indicating an action on bone cells more differentiated than CFU-Fs. Serum-free conditioned medium (CM) from control and ovariectomized (OVX)/OVX+ dihydrotachysterol-Rx rat CFU-F cultures was mitogenic for neonatal rat calvarial osteoblasts in vitro, but not for ROS 17/2.8 cells. The studies affirm the mesenchymal-like character of CFU-Fs and project their significant role in sustaining functional endosteal osteogenic cell populations.

Animals↗
PubMed1987

Changes in local bone density after knee arthroplasty. The use of quantitative computed tomography.

Loosening is a serious problem in total arthroplasty and early detection of bone loss in the vicinity of an implant would help in its investigation. We present a method for the objective evaluation of bone adjacent to metallic implants in which a modified technique of quantitative computed tomography (QCT) is used to reconstruct cross-sectional images with few artefacts. We have used this technique in 19 patients with knee arthroplasties to monitor the changes in bone density around the tibial stem of the prosthesis. In the first weeks after operation all patients showed a decrease in bone density ranging from 0.4% to 3.6% per month. One year after arthroplasty bone density had stabilised and only minor changes were observed. Our work indicates that modified QCT is a sensitive method for the long-term monitoring of the anchorage of implants and allows the early detection of osteolytic changes.

Aged↗
PubMed1986

Disuse osteoporosis in patients with total hip prostheses.

Aseptic loosening of total hip arthroplasty is still a serious problem. Bone quality might be one of the major factors influencing loosening. In a previous study, bone loss during the reparation phase was evaluated with modified computed tomography at the site of the implant. The present study documents the degree of disuse osteoporosis prior to and after surgery. Bone density of both tibiae of patients with unilateral artificial hip joints was evaluated longitudinally. Preoperatively a significant right-left difference was found, that has to be attributed to the preoperative unloading of the diseased leg. After surgery a slight but significant bone loss was found in both legs attributable to the immobilization following surgery and the reduced activity in the first 6 months. In successfully operated cases this loss is temporary. In one patient bone loss continued; after 1 year there are now clinical signs of implant loosening. Although the spectrum of physical activity in our group was wide, no correlation between activity and bone loss has been found so far.

Aged↗
PubMed1985

Optimal CT settings for bone evaluations.

In CT densitometry the precision, sensitivity and accuracy of the procedure are limited by photon noise, the degree of tissue differentiation and artefacts caused by the finite size of the x-ray beam, hardening of the x-rays and scattered radiation. These artefacts are highly dependent on the CT settings, such as x-ray spectrum and effective energy, intensity of photon flux and collimation of the beam. To monitor the progression of a disease or the efficacy of a therapy, longitudinal studies are necessary; thus the radiation dose per examination should be kept at a minimum. For bone evaluation of the peripheral skeleton it is shown that there is a narrow optimal energy range of 30-40 keV where a dose below 150 mu Sv is sufficient to detect a change of 1% in trabecular bone density at the 0.1 confidence level. Concomitantly accuracy might be better than 1% if adequate beam collimation is applied.

Absorptiometry, Photon↗
PubMed1985

Reconstruction algorithm for incomplete projections in the framework of linear operators in normed linear spaces.

Based on the linearity of the Radon transform and the convolution-backprojection reconstruction algorithm, a new linear-vector space notation is introduced that is of general use in computed tomography (CT). Using this notation, a consistency condition for the completion of incomplete projection data is described. This consistency condition leads to singular or ill-conditioned systems of linear equations for the unknown projection data. Using regularization methods, an algorithm for the consistent projection completion is presented that can exploit symmetries of the missing data region. The performance of the new algorithm is documented with simulated and actualy measured CT-projection data. The algorithm quantitatively improves CT reconstructions with realistic amounts of data and noise and can be used for the completion of arbitrary regions of missing projections.

Fourier Analysis↗
PubMed1982

Anchorage of femoral implants visualized by modified computed tomography.

Metallic implants produce a great deal of artifacts in standard CT images. These artifacts cover tissue structures and impede visualization of the anchorage of the implant within the bone. Thus a modified CT procedure has been developed to permit reconstructions free from artifacts. It is an iterative procedure using a maximum of measured projection data. Using this modified CT technique, the anchorage of a titanium-alloy femoral prosthesis implanted without cement was examined. Good contact of the implant with the cortical bone has documented. This promises good initial stability. The CT examinations were performed by using a special-purpose CT scanner. It is hoped that the modified CT technique will allow a quantification of bony tissue in the close vicinity of implants and thus provide a non-invasive procedure that will allow the long-term stability of implants to be evaluated.

Aged↗
PubMed1982

Cellular responses to extreme water loss: the water-replacement hypothesis.

The previously advanced hypothesis that desiccation resistance involves the replacement of water adjacent to intracellular surfaces with polyhydroxy compounds has been supported by experiments on cysts of the brine shrimp, Artemia, and in a model system of albumin--glycerol--water, using nuclear magnetic resonance spectroscopy, microwave dielectrics, and density measurements. We have also considered other problems that cells face when large fractions of their total water content are removed. Observations by other investigators have indicated that a variety of mammalian cells can lose roughly 50% of their water and survive; for a given cell type death occurs if its volume is reduced below a certain minimum level. Membrane damage has previously been suggested to be a major cause of dehydration damage. We have proposed some additional plausible mechanisms that might also be involved.

Adaptation, Physiological↗
PubMed1981

Registration of contractions in pregnant women using a microprocessor controlled digital recorder.

As a further development of the two component contraction recorder TOKOPORT, a digital microprocessor controlled contraction memory has been built which registers, analyses and displays contractions in pregnant women. The memorized data can be read out in graphic form. The possibility of conveying the data by telephone is under development. The device is small, simple to operate and portable.

Computers↗
PubMed1980

Mitochondrial water in myocardial ischemia: investigation with nuclear magnetic resonance.

Nuclear magnetic resonance studies of mitochondria isolated from ischemic hearts after coronary vessel occlusion indicated a decrease in water proton relaxation times. This change coincided with a decrease in the hydration of the samples. It is suggested that in ischemia, changes in macromolecular hydration may be one of the first mechanisms to alter function in the mitochondria, which are vital to the energy-transducing process in heart muscle.

Animals↗
PubMed1979

A new tocograph with cassette recording system and separate servo graphic recorder.

In order to register contractional activity, especially in the case of high-risk pregnancies, a tocograph was develop by means of which the contractions are registered by a small cassette recorder, which the patient can carry by about with her. A separate graphic recorder is responsible for the playback and this recorder remains at the doctor's practice. The patient is able to register her contractions herself as the unit is so simple to use. The recording section weighs only 500 grams, including the specially developed pressure transducer with optical distance-meter. The tocograph is produced in series.

Female↗