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PubMed1988

Patch-clamp techniques for time-resolved capacitance measurements in single cells.

Two methods are described for estimation of passive cell parameters such as membrane capacitance, membrane conductance and access resistance in tight-seal whole cell recording. Both methods are restricted in their application to cases where the cell under study can be approximated by a simple three-component network with linear properties over some voltage range. One method, referred to as the time domain technique, requires only standard electrophysiological equipment and a computer. Parameters are derived from an analysis of capacitive transients during square wave stimulation. It is readily adaptable to wide variations in experimental parameters. Particularly, it is equally applicable to the "slow whole-cell" configuration (access resistance in the range 100 M omega to 1 G omega) and to normal whole-cell measurements (access resistance typically 10 M omega). The other method applies a sine wave command signal to the cell and employs a lock-in amplifier to analyse the resulting current signal. Two modes of operating the lock-in amplifier are described. One mode provides an output signal directly proportional to small changes in capacitance at maximum resolution (1-10 fF). The other mode, in conjunction with a digital computer, supplies estimates of all passive cell parameters, as does the time domain technique, but with a large amount of data reduction performed by the lock-in amplifier itself. Due to the special hardware, however, this method is not as flexible as the time domain technique.

Animals↗
PubMedDate not supplied

[Sudden deafness and biometric function analysis of the cervical spine].

Theories concerning the influence of function disturbances of the cervical spine on the development of sudden hearing loss should be re-examined. Forty-eight patients with unilateral sudden hearing loss and 94 controls were examined. X-rays of the cervical spine were made in lateral projection in normal position, and in maximum flexion and extension. The posture and movement of the vertebrae were recorded using a computer digitalization program. Overall mobility of the cervical spine was reduced in the group with sudden hearing loss: reduced movement was found in segments C2/C3, C5/C6, and C6/C7. Segments P0/P1 and C1/C2 were conspicuous by very high standard deviations in the group with sudden hearing loss. The results indicate that sudden hearing loss and function disorders of the cervical spine are related.

Biomechanical Phenomena↗
PubMed1994

[Morphological observations of effects on mouse brain exposed to subteratogenic--dose of methylmercury].

Short-term and long-term changes in mouse brain caused by in utero exposure to subteratogenic-dose of methylmercury were studied with electronic computer digitalized graphic system, electron microscopy and other methods. Results revealed degeneration and loss of mouse brain cells occurred both in short-term and long-term groups, but the lesions were more severe in the latter than in the former groups. The fact that exposed young mice exhibited no obvious abnormality in their outward appearance and behavior indicated subteratogenic-dose of methylmercury had a long-term and latent toxic effects on mouse brain.

Animals↗
PubMed1993

Stability and movement of a one-link neuromusculoskeletal sagittal arm.

This paper's focus is the stability, point-to-point, and rhythmic movements of a one-link sagittal arm. The system is highly nonlinear in all its physical and physiological attributes. The major physiological characteristics of this system are simultaneous activation of a pair of nonlinear muscle-like actuators for control purposes, existence of nonlinear spindle-like sensors, and actions of gravity and loading. Transmission delays are included in the afferent and efferent neural paths to account for a more accurate representation of the reflex loops. An algorithm for computation of the actuator forces and the feedback signals in the system is provided. It automatically renders positive forces and positive neural signals. The positiveness of the forces represents the unidirectional character of muscular forces, i.e., natural muscles can only pull in the direction of shortening. The positiveness of the neural signals implies these signals can correspond to firing rates. The stability of the system is analyzed. The role of the nonlinearities in the dynamics, actuators, and feedback signals, and the delays in the feedback loops in destabilizing the system, and the consequently undesirable oscillations are studied by simulation. The system is designed to perform stable point-to-point movement. The effects of the presetting of the input signals, gain of the feedback loops, and the duration of delays in generating undesirable tremor-like oscillations at the end of the movement are studied and demonstrated by digital computer simulations.

Algorithms↗
PubMed1984

Computerized processing of two-dimensional echocardiograms for the quantification of left ventricular regional contractility.

A new practical method of computer digital image processing of two-dimensional echocardiograms was developed for the quantification of the left ventricular regional contractility. Short axis, cross-sectional images of the left ventricle at the levels of the mitral valve, papillary muscle and apex were recorded by a phased array sector scanner. The echo data recorded on video tape were transfered to a minicomputer through the interface circuits and digitized and processed automatically. Automatic edge detection of the endocardial and epicardial walls was performed by applying sequential steps, including smoothing, dynamic thresholding, region growing and filling small holes. The rationale for edge detection depended upon the assumptions that the abrupt changes of the gray levels occurred at the boundaries and that the points with the maximum gradient values are boundaries of the left ventricular wall. Best-fit contours of endocardial and epicardial edges were drawn by fitting a spline. The short axis cross-sectional left ventricular wall at each level was divided into eight segments, with the center of gravity of enddiastolic left ventricular cavity and the axis connecting this with the posterior end of the right side of the septum being used as the reference point and line. The segmental hemiaxis, area and wall thickness were measured every 33 msec from end-diastole during the cardiac cycle and the systolic percent changes were calculated automatically by a computer. Regional contractility of the left ventricle was evaluated by systolic percent changes of the segmental hemiaxis, area and wall thickness. The measured values in a patient with dilated cardiomyopathy were lower than those of a normal subject, probably reflecting myocardial damage of the left ventricle. Although there are some points to be improved, including a better system for transferring echo data to the computer and the evaluation of the validity of this fixed reference system, it is likely that computer analysis of the short axis cross-sectional echocardiogram of the left ventricle will be useful in a clinical setting.

Cardiomyopathy, Dilated↗
PubMed2000

Sealer distribution in root canals obturated by three techniques.

AIM: The aim of this study was to observe sealer distribution in root canals filled by different root filling techniques. METHODOLOGY: AH26 (0.05 mL) dyed with carbon black powder was placed into the prepared root canals of maxillary central incisors using a lentulo spiral. Thereafter the canals were obturated using three different gutta-percha root-filling techniques. Horizontal sections were cut in the apical and middle portions of the filled canals. Images of the cross sections were scanned and the percentage of sealer coated canal perimeter (PSCP) was measured using a computer digital imaging system. RESULTS: At 3 mm from the apex, the PSCP after lateral condensation was similar to that after vertical condensation (P > 0.05). At 6 mm from the apex, however, the PSCP was significantly higher after lateral condensation than after vertical condensation (P < 0.05). At both levels the PSCP was significantly higher after single cone (no condensation) than after the other two condensation techniques (P < 0.0001). CONCLUSIONS: Sealer may be removed from the canal wall by the condensation procedures.

Bismuth↗
PubMedDate not supplied

In vitro investigation of the wear of resin composite materials and cast direct retainers during removable partial denture placement and removal.

The purpose of this study was to determine whether wear of two resin composite materials and contacting I-bar clasp tips would occur within a simulated RPD placement and removal period of 2 years. The data were compared to enamel with contacting I-bars. Cast I-bar clasps were passed over each specimen in the resin composite and tooth experimental groups (n = 10). Computer digitized image analysis of SEM photomicrographs of the specimens provided data for analysis of wear. Results indicated a statistical difference in the amount of mean wear between the two resin composites and between the I-bar groups. The results from this study suggest that the selection of a resin composite for use as a RPD retentive undercut must be carefully undertaken to avoid excessive wear and loss of retention.

Analysis of Variance↗
PubMed1993

Can pretreatment computed tomography findings predict local control in T3 squamous cell carcinoma of the glottic larynx treated with radiotherapy alone?

PURPOSE: To determine if pretreatment computed tomography findings can predict local control in T3 squamous cell carcinoma of the glottic larynx treated with radiotherapy alone. METHODS AND MATERIALS: Twenty-nine patients with previously untreated T3 squamous cell carcinoma of the glottic larynx were treated for cure with radiotherapy alone; all had a minimum 2-year follow-up. High-quality pretreatment computed tomography scans were retrospectively reviewed by a single head and neck radiologist for tumor involvement of various anatomic subsites within the larynx, and total tumor volumes were calculated for 18 of the most recent patients using a computer digitizer. A tumor score was calculated and assigned to each primary lesion depending on the extent of laryngeal spread. RESULTS: A significant decrease in the local control rate was observed for cancers involving the face of the arytenoid (11 of 20 [55%] vs. 9 of 9 [100%]; p = .02), or the paraglottic space at the false vocal cord level (7 of 16 [44%] vs. 13 of 13 [100%]; p not equal to < .01). Tumors assigned a high tumor score (6, 7, or 8) had a significantly decreased rate of local control with radiation therapy when compared with tumors assigned a low tumor score (< or = 5): 1 of 7 (14%) vs. 19 of 22 (86%) (p = .01). Total tumor volume also significantly correlated with the rate of tumor control. For tumors measuring 3.5 cm3 or less, local control was achieved in 11 of 12 patients (92%), whereas for tumors greater than 3.5 cm3, local control was achieved in 2 of 6 patients (33%) (p = .02). CONCLUSION: Pretreatment computed tomography scans can contribute significantly to the treatment decision for patients with T3 glottic carcinoma and can define a subset of patients with an excellent chance of being cured with preservation of a functional larynx after treatment with radiotherapy alone.

Adult↗
PubMed1984

Relative accuracy of three automated systems for neuropsychological interpretation.

Three computer programs for automated interpretation of variants of the Halstead-Reitan Neuropsychological Test Battery were tested on cases in two data sets. The Key approach of Russell, Neuringer, and Goldstein (1970), Brain I (Finkelstein, 1977), and Adams' (1975) ability-based algorithm were employed in the study. The first data set included 63 well-documented cases with precise criterion data and multiple sources of direct verification. The second data set consisted of 30 equally well-studied cerebrovascular disease patients whose cerebral circulation disorders resulted in clinical manifestations encompassing the entire range of stroke. Results suggested that, while none of the programs do poorly at identifying the presence of brain damage, lateralization and possibly other localization/process predictions are not done well by these programs. The failure described in this particular study does not imply that automated methods are potentially less effective than true actuarial or clinical ones. Rather, we suggest that the translation process from clinical interpretation to the mechanical combinatory logic of the digital computer is at an early stage.

Aged↗
PubMed1979

Coupling interval, exit block, and periodicity of ventricular parasystolic rhythm.

The electrocardiograms in this study of parasystolic rhythm were tape recorded and then analysed with a special purpose hybrid computer. The rate of appearance of specific inter-ectopic intervals was shown to change significantly with small changes in either the sinus or parasystolic pacemaker period. Natural changes in the period of the ectopic pacemakers were observed over several hours. Changes amounting to 14% within 10 min and 18% overall were observed in one patient, and a gradual lengthening of 10% over 3 h in another. A previously undescribed form of exit block has been discovered in one patient where the block remained active for a given time only after propagation from the parasystolic focus. Different interectopic intervals were shown to contribute to specific and restricted coupling interval locations in diastole. Hence this form of exit block, by preventing some inter-ectopic intervals from propagating, limited the locations in diastole in which parasystolic ectopic complexes could appear. In this case later diastolic complexes were inhibited and hence fusion complexes were completely absent. Parasystolic rhythm, with and without the exit block described, was simulated successfully by a digital computer. The simulations aided our understanding of the clinical data.

Aged↗
PubMed1991

A simple radiologic method to estimate the quantity of bowel gas.

Patients with functional bowel disorders frequently complain of bloating and abdominal pain, but no practical method is available to measure intestinal gas objectively. To evaluate a new technique, we evaluated 54 abdominal radiographs from 19 patients. A gastroenterologist and a radiologist independently outlined the intestinal gas bubbles in these films. Areas of gas bubbles were measured with a computer digitizing board. Bowel gas was also measured in 24 healthy controls, and in five emergency room patients, supine and erect radiographs were compared to evaluate the effects of position on bowel gas patterns. The two evaluators agreed well on the measured areas of bowel gas (r = 0.96), showing that this is a reliable method. Bowel gas was significantly greater in patients than in controls but did not correlate with symptoms. Bowel gas was significantly greater in supine than upright films, showing that the position of the patient must be standardized.

Adult↗
PubMed1993

Elastin and fibrillin mRNA and protein levels in the ontogeny of normal human aorta.

Elastin associated microfibrils (EAMF) are ubiquitous connective tissue structures that are believed to provide tensile strength and flexibility to numerous tissues. In this study the ontogeny of EAMF in normal human aorta was examined using immunohistochemical analysis of fibrillin, an EAMF component, and mRNA levels of fibrillin and elastin. Specimens of infra-renal aorta from ages 11 months to 44 years were obtained following organ procurement. Decreasing amounts, as judged by computer digitized image analysis, of immunoreactive fibrillin when compared to elastin auto-fluorescence were observed in aortic sections with increasing age. Elastase treatment would un-mask the anti-fibrillin reactive epitope reinforcing the suggestion that EAMF act as a "scaffold" for elastin deposition. Northern and dot blot hybridizations demonstrated a decrease in relative fibrillin message levels with increasing age. The abundance of fibrillin in relation to elastin may suggest a role for EAMF independent of their association with elastin.

Actin Cytoskeleton↗
PubMed2000

Characterization of acromial concavity. An in vitro computer analysis.

Variations in the shape and orientation of the anterior acromion have been implicated as predisposing factors for the development of rotator cuff problems. We determined and analyzed by computer digitization the anterior and posterior acromial slopes for 141 cadaver shoulders (whose rotator cuff status had been previously assessed). No significant differences in either the anterior or posterior angle were found between the intact and rotator cuff tear groups. Frequency histograms of both angles demonstrated continuous, normal distributions. The individual acromions were consistently asymmetric in that the anterior slope was larger than the posterior slope. However, the anterior slope distribution did not reveal groupings indicative of the specific acromial types previously reported. These results suggest that acromial classification into flat, curved, and hooked types does not accurately describe the actual anatomical findings.

Acromion↗
PubMed2000

The impact of primary tumor volume on local control for oropharyngeal squamous cell carcinoma treated with radiotherapy.

BACKGROUND: A study was needed to determine the effect of primary tumor volume on local control of oropharyngeal carcinoma treated with radiation therapy, with or without induction chemotherapy. METHODS: Between July 1983 and April 1995, 114 patients with T2-T4 squamous cell carcinoma of the oropharynx were treated for cure with radiation therapy, with or without induction chemotherapy, and had a pretreatment CT scan available for retrospective review. All scans were reviewed by a single radiologist (A. A. M.) to determine the tumor volume of the primary lesion. Volume was measured with a computer digitizer for each CT slice showing the primary lesion. RESULTS: A large variation in tumor volume within a given T stage was found. Multivariate analysis demonstrated T stage to be the most significant factor affecting local control. Tumor volume marginally influenced local control (p =.10). CONCLUSIONS: Primary tumor volume varies significantly within a given T stage and has a marginal impact on the likelihood of local control after radiotherapy.

Adult↗
PubMed1983

Electron energy loss chemical mapping of low Z elements in biological sections.

A STEM VG HB 501 equipped with a Gatan spectrometer has been interfaced to a PDP 11-34 computer. Digital energy filtered images have been recorded with several energy windows on both sides of a characteristic level, so that the exact background can be stripped under the core loss signal for each pixel. Results concern the distribution of nitrogen (K-edge at 402 eV), oxygen (K-edge at 532 eV) and iron (L23 edge at 705 eV) in embedded sections of bone marrow. The present performances of the system allow the detection of composition variations of 1 to 2% for these elements, with a lateral accuracy of the order of 5 nm in a section of 50 nm thickness. Individual ferritin molecules distributed within the section are clearly imaged and analyzed with the characteristic iron edge.

Animals↗
PubMed2002

[Development of a computerized automatic identification system for use in cephalometry].

OBJECTIVE: To establish the automatic X-ray cephalometric analysis system to simplify cephalometric steps and to provide a convenient and reliable method for cephalometric analysis. METHODS: The system which was programmed by visual-c language, and graphics and image processing techniques and artificial intelligence were used. The techniques related to computer digital image processing and pattern recognition such as Median filtering, Histogram equalization, Laplacian and Canny edge detection were introduced. It could automatically outline the contour lines of the hard and soft tissues by establishing the templates of the variable anatomical structures. RESULTS: The following functions were established: (1) automatically outlining the contour lines of the soft tissues. (2) automatically recognizing, measuring and analysing the landmarks of soft tissues. (3) automatically recognizing porion, sella and the landmarks of the mandible. (4) automatically building the contour lines of the hard tissues. In brief, the system used the more advanced methods, calculated more precisely and saved more time and energy than other systems. CONCLUSION: The system is a more convenient and precise tool in cephalometry.

Cephalometry↗
PubMed1998

A bronchoscopic, computer-assisted examination of the changes in dimension of the infant tracheal lumen with changes in head position: implications for emergency airway management.

BACKGROUND: Resuscitation guidelines caution against extreme extension or flexion of an infant's head because tracheal obstruction may occur. No data support this recommendation. The authors therefore examined the dimensions of the tracheal lumen in neutral, extended, and flexed head positions in infants undergoing general endotracheal anesthesia for elective surgery. METHODS: Eighteen healthy full-term infants were studied. A flexible fiberoptic bronchoscope was passed through a previously inserted endotracheal tube and positioned above the cricoid cartilage. Video recordings were taken in each of three head positions. Recordings were analyzed by an investigator blinded to head position. A computer-digitized technique was used to measure anterior-posterior and lateral dimensions and cross-sectional area. Data were analyzed using paired t tests and sign tests. RESULTS: No significant differences in mean tracheal dimensions with changes in head position were found. No infant had complete tracheal obstruction. Infants were equally as likely to have a small increase as they were to have a small decrease in tracheal dimension with changes in head position. CONCLUSIONS: Despite the belief that infants and neonates have obstruction at the level of the trachea with extreme positions of the head, the authors were unable to demonstrate this phenomenon.

Airway Obstruction↗
PubMed2004

Cervical spine geometry in the automotive seated posture: variations with age, stature, and gender.

In the mid 1970s, UMTRI investigated the biomechanical properties of the head and neck using 180 "normal" adult subjects selected to fill eighteen subject groups based on age (young, mid-aged, older), gender, and stature (short, medium, and tall by gender). Lateral-view radiographs of the subjects' cervical spines and heads were taken with the subjects seated in a simulated automotive neutral posture, as well as with their necks in full-voluntary flexion and full-voluntary extension. Although the cervical spine and lower head geometry were previously measured manually and documented, new technologies have enabled computer digitization of the scanned x-ray images and a more comprehensive and detailed analysis of the variation in cervical spine and lower head geometry with subject age, stature, and gender. After scanning the radiographic images, 108 skeletal landmarks on the cervical vertebrae and 10 head landmarks were digitized. The resulting database of cervical spine and head geometry was used to study cervical spine curvature, vertebral dimensions, and head/neck orientation as functions of age, gender, and stature. The data were used to characterize neutral posture cervical spine curvatures using two methods: a curvature index and Bézier spline functions. Lateral-view vertebral dimensions were also calculated for each subject, and a cascading series of equations was developed to estimate vertebral size and shape for a selected age, stature, and gender. The orientation of the cervical spine was defined using a neck chord angle, where the neck chord was varied to use different anatomical landmarks and estimates of joint centers for the top and bottom of the neck chord. Results from the study have been incorporated into a MS-Access based software package that allows researchers and modelers to generate cervical spine geometries for occupants of a specified age, gender, and stature. The program allows selection of individual occupants from the database that meet age, stature, gender, or curvature criteria, or creation of a composite cervical spine geometry representative of the selected age, gender, and stature. This tool will allow researchers to configure and vary cervical spine geometry in computer models and experimental test setups used to study head and neck impact response and injury risk.

Journal Article↗