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Biomedical subjects

D C Smith

Publications and source records attributed to D C Smith.

At least 523 records · Page 29Linked to original sources
PubMedDate not supplied

Quality assurance in mammography: artifact analysis.

Evaluation of mammograms for artifacts is essential for mammographic quality assurance. A variety of mammographic artifacts (i.e., variations in mammographic density not caused by true attenuation differences) can occur and can create pseudolesions or mask true abnormalities. Many artifacts are readily identified, whereas others present a true diagnostic challenge. Factors that create artifacts may be related to the processor (eg, static, dirt or excessive developer buildup on the rollers, excessive roller pressure, damp film, scrapes and scratches, incomplete fixing, power failure, contaminated developer), the technologist (eg, improper film handling and loading, improper use of the mammography unit and related equipment, positioning and darkroom errors), the mammography unit (eg, failure of the collimation mirror to rotate, grid inhomogeneity, failure of the reciprocating grid to move, material in the tube housing, compression failure, improper alignment of the compression paddle with the Bucky tray, defective compression paddle), or the patient (e.g., motion, superimposed objects or substances [jewelry, body parts, clothing, hair, implanted medical devices, foreign bodies, substances on the skin]). Familiarity with the broad range of artifacts and the measures required to eliminate them is vital. Careful attention to darkroom cleanliness, care in film handling, regularly scheduled processor maintenance and chemical replenishment, daily quality assurance activities, and careful attention to detail during patient positioning and mammography can reduce or eliminate most mammographic artifacts.

Artifacts↗
PubMedDate not supplied

Perceptions of control at school among students in special education programs.

Data are reported on special and regular education students' perceptions of control at school and the importance to the students of having such control. For both special and regular education populations, comparisons were made between students enrolled in experimental and nonexperimental programs. Findings indicate comparability among the four groups with regard to areas in which control is valued. Perceptions of control at school for those in the standard special education group were lower than the ratings of regular education students and lower than those given by special education students in the experimental program.

Adolescent↗
PubMedDate not supplied

Malposition of a total parenteral nutrition catheter in the accessory hemiazygos vein.

A total parenteral nutrition catheter was surgically introduced into the left cephalic vein of a 31-yr-old man with regional enteritis. After placement, a frontal radiograph indicated malplacement of the catheter. Its left vertical paramedian position indicated a left internal thoracic vein, a persistent left superior cava, or a left superior intercostal-accessory hemiazygos vein position. The left internal thoracic vein is very anterior within the thorax, a persistent left superior vena cava is centrally located, and the left superior intercostal-accessory hemiazygos vein is quite posterior. A lateral radiograph revealed a markedly posterior catheter course, with its tip at the level of the vertebral bodies. A venogram confirmed its location within the left superior intercostal-hemiazygos vein. The catheter was removed and replaced. After placement of all total parenteral nutrition catheters, a chest radiograph should be obtained. A single frontal film is usually adequate; if not, a supplemental lateral view may be taken. If uncertainty still exists, a venogram through the catheter may be obtained for precise localization.

Adult↗
PubMedDate not supplied

A new concept in cancer care: the supportive care program.

This article describes the findings of a pilot program designed to enter advanced prostate cancer patients into the hospice benefit while they are still being actively treated, but in situations where treatment is known to be primarily palliative in nature. The supportive care program (SCP) combines the medical model's goal to prolong life with the goal of hospice to palliate symptoms and improve quality of life (QOL). The concept of a SCP was developed to create a team approach where advanced prostate cancer patients who are starting investigational chemotherapy are concurrently enrolled into a hospice program. The objectives were to identify whether SCP improved QOL and continuity of care while remaining cost-effective. Data were collected on patient quality of life, performance status, use of health care resources, and costs for the 36 enrolled patients. A comparison was made to a matched set of 23 control patients. Our findings indicate that the SCP contributes to continuity of care while being cost-effective.

Aged↗
PubMedDate not supplied

Assessment of the design and performance of the Sage syringe pump model 341A, with particular reference to its accuracy and stability.

Consideration of the timing circuitry employed in the Sage pump model 341A indicates that the pump's performance will be strongly affected by component tolerances, and our measurements have confirmed this impression. Thus, delivered flow rates may deviate considerably from those indicated on the calibration chart; our instrument was about 10% slow at all settings. For many applications it will be necessary to carry out a full calibration procedure, which should be repeated following any repairs to the electronic circuitry. The pump also suffered from drift at certain settings because an inappropriate component had been used in the timing circuitry. These findings will also apply to the Sage pump models 240A and 242A, which employ similar timing circuitry to the 341A. When precautions are taken to overcome these problems, the pump's performance is satisfactory for both clinical use and some laboratory applications.

Equipment Design↗
PubMedDate not supplied

An aid to visual pointing for children with severe physical handicap.

A simple system has been designed and built which gives an audio and a visual indication of when a child is looking at a specific object. This is a valuable motivation tool for use in both the assessment and the development of children with severe physical handicap.

Audiovisual Aids↗
PubMedDate not supplied

A versatile speech output communication aid.

A portable, battery-powered communication aid with speech output, which can be operated by patients with limited finger control, is described. The device is sufficiently versatile to try out different methods of selection of words or phrases in the search for an acceptable, portable communication aid for the speech impaired.

Communication Devices for People with Disabilities↗
PubMedDate not supplied

An instrument for testing external cardiac pacemakers.

Checking the function of an external pacemaker can be time consuming both as a routine maintenance task and after the repair of a fault. An instrument is described which is easy to use and contributes to a higher standard of maintenance by considerably reducing the time taken and by eliminating the need for the interconnection of specialized test equipment.

Biomedical Engineering↗
PubMedDate not supplied

A novel cervical dilatation force measurement instrument.

A simple and robust instrument for cervical dilatation force measurement is described which measures axial insertion force but is not affected by lateral loads. The instrument is battery-powered, self-contained and displays actual axial force and peak axial force on digital liquid crystal displays.

Cervix Uteri↗
PubMedDate not supplied

Effects of skin blood flow and temperature on skin--electrode impedance and offset potential: measurements at low alternating current density.

Skin--electrode impedance was determined at 100 Hz and 1 kHz between two disposable electrodes, 5 cm apart, at current densities < 65 microA.cm-2. Measurements were made on the volar skin of the forearm during cooling on cardiopulmonary bypass, and on the dorsum of the foot in the absence of skin blood flow during aortic aneurysm repair. Both the resistive and reactive components of the skin-electrode impedence showed an inverse linear relationship to temperature between 26 and 36 degrees C. The magnitude of the impedance change was different for each patient studied; resistance changes ranged from 0.03 to 23.2 k omega. Degrees C-1 at 100 Hz and from 0.03 to 2.7 k omega. Degrees C-1 at 1 kHz, while reactance changes ranged from 0.4 to 2.1 k omega. Degrees C-1 at 100 Hz and from 0.04 to 0.18 k omega. Degrees C-1 at 1 kHz. Changes in skin-electrode impedance were not due to changes in skin blood flow. There was no consistent change in offset potential with temperature. Although the skin-electrode impedance increases as temperature falls, it is concluded that temperature effects at the skin-electrode interface are not responsible for the observed failure of evoked electromyography during clinical monitoring of neuromuscular function.

Adult↗
PubMedDate not supplied

An evoked compound electromyogram simulator with external microprocessor control facility.

A circuit for an evoked electromyogram simulator is described, which produces a biphasic triangular waveform similar to the evoked compound action potential seen during clinical quantitative neuromuscular monitoring. The device can produce a fading train-of-four sequence, which can be controlled using a single externally-derived voltage. The simulator is useful for bench-testing of closed loop muscle relaxant administration systems, and for teaching aspects of neuromuscular monitoring in anaesthesia.

Action Potentials↗
PubMedDate not supplied

Effects of skin temperature on skin-electrode impedance: measurements at high direct current density.

Skin-electrode impedance was determined between two disposable electrodes 5 cm apart on the volar skin of the forearm in 20 patients during cooling on cardiopulmonary bypass. Measurements were made using a constant direct current pulse of 200 microseconds duration, at a current density of 25.6 mA cm-2. The mean inter-electrode resistance was 1.11 k omega, and the mean inter-electrode capacitance was 33.3 nF. In 19 patients there was no change in the inter-electrode resistance or the inter-electrode capacitance with changes in skin temperature from 27.5 to 36.0 degrees C. In one patient the inter-electrode resistance increased from 1.71 k omega at 35 degrees C to 1.94 k omega at 31.0 degrees C, while the inter-electrode capacitance increased from 19.6 to 26.6 nF. We conclude that temperature effects on the impedance of the stimulus electrodes are not responsible for the observed failure of evoked electromyography during clinical monitoring of neuromuscular function.

Body Temperature↗
PubMedDate not supplied

The characterisation of non-sperm cells in the ejaculates of fertile men using transmission electron microscopy.

The non-spermatozoal cells (NSC) in the semen samples of 20 fertile human males have been studied by transmission electron microscopy (TEM), in order to accurately distinguish between the different types of cell present and to give a quantitative profile of their relative proportions. The main seminal constituents of the average fertile man were found to be the germinal elements, accounting for 84.0% of the total NSC population. Of this percentage the anucleate bodies, designated "CM" in this study, were the greatest component (43.0%, SEM +/- 4.7). Spermatids were the next commonly occurring cell (22.2%, SEM +/- 2.9), the anucleate cellular masses with organelles, CM(O)'s and the spermatocytes making up the remaining 18.8%. Leucocytes accounted for 13% of the total NSC, respectively: neutrophils - 12% (SEM +/- 4.5); macrophages - 0.9% (SEM +/- 0.3) lymphocytes - 0.1% (SEM +/- 0.1). The remaining 3% consisted of 2.3% (SEM +/- 0.7) epithelial cells and 0.7% (SEM +/- 0.4) Sertoli cells. The principal conclusions reached were: that some normal ejaculates host active phagocytosis and possibly macrophage activation; that anucleate bodies which form a major component of the ejaculate merit further quantitative study and that the shedding of spermatids is an interesting and important aspect of ejaculation.

Cytoplasm↗