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Biomedical subjects

R Padgett

Publications and source records attributed to R Padgett.

9 recordsLinked to original sources
PubMed2006

Development and application of programs to measure modulation transfer function, noise power spectrum and detective quantum efficiency.

This project aimed to produce programs to calculate the modulation transfer function (MTF), noise power spectrum (NPS) and detective quantum efficiency (DQE) of digital X-ray systems, given a suitable digital image. The MTF was calculated using the edge technique and the NPS was calculated from a flat field image. Both programs require a suitably edited DICOM image as input. The DQE was then calculated from the output of MTF and NPS programs. This required data external to the DQE program to estimate the number of quanta per mm2 in the beam which formed the NPS image. All three programs run independent of each other on a PC and require no special software to be installed. Results for MTF, NPS and DQE for a Philips AC3 CR system are presented. In addition, the results for MTF from a Siemens Duo CT scanner with a specially designed PTFE edge are also shown.

Algorithms↗
PubMed2006

Trends in image quality in high magnification digital specimen cabinet radiography.

Advances in microfocus X-ray tube design together with the availability of high resolution charge coupled device (CCD) detectors have led to the introduction of high magnification digital specimen cabinets for the examination of tissue samples. This paper explores the effect that the high magnification geometry permitted by such units has upon image quality in terms of phase contrast edge enhancement, spatial resolution and the appearance of test phantom images. Phase contrast effects and spatial resolution were studied using a previously established method (using edge profiles) and by computing the system spatial frequency response at various geometries. It was demonstrated that the magnitude of the phase contrast enhancement effect reaches a stable maximum at a magnification of x 4. It has also been shown that a continual increase in both the spatial resolution together with an improved signal to noise ratio occurs up to the maximum permissible magnification geometry, with effects of focal spot blur being negligible. In practice, the limited size of the digital detector and the difficulty of object alignment can constrain the use of the very high magnification option.

Phantoms, Imaging↗
PubMed2004

Mammographic image restoration using maximum entropy deconvolution.

An image restoration approach based on a Bayesian maximum entropy method (MEM) has been applied to a radiological image deconvolution problem, that of reduction of geometric blurring in magnification mammography. The aim of the work is to demonstrate an improvement in image spatial resolution in realistic noisy radiological images with no associated penalty in terms of reduction in the signal-to-noise ratio perceived by the observer. Images of the TORMAM mammographic image quality phantom were recorded using the standard magnification settings of 1.8 magnification/fine focus and also at 1.8 magnification/broad focus and 3.0 magnification/fine focus; the latter two arrangements would normally give rise to unacceptable geometric blurring. Measured point-spread functions were used in conjunction with the MEM image processing to de-blur these images. The results are presented as comparative images of phantom test features and as observer scores for the raw and processed images. Visualization of high resolution features and the total image scores for the test phantom were improved by the application of the MEM processing. It is argued that this successful demonstration of image de-blurring in noisy radiological images offers the possibility of weakening the link between focal spot size and geometric blurring in radiology, thus opening up new approaches to system optimization.

Algorithms↗
PubMed2004

Assessment of the effects of pixel loss on image quality in direct digital radiography.

Modern digital radiographic 'flat panel' detectors can exhibit a progressive form of image degradation arising from non-functioning pixels. The effect of these 'dead pixels' on the quantitive image quality measures of modulation transfer function (MTF), noise power spectrum (NPS) and detective quantum efficiency (DQE) is investigated by a simulated degradation of images obtained from an Hologic EPEX system. The effects on the semi-quantitive measures obtained from contrast threshold test objects and resolution gratings are also investigated. Results suggest that the contrast-detail tests often employed in quality assurance measures are not sufficient to reveal the presence of dead pixels until well beyond the recommended replacement point for the flat panel detector. However, measurements of spatial resolution using a line pairs phantom were found to be more sensitive to pixel loss. Measurement of the MTF, NPS and DQE can reveal small changes in image quality with increasing pixel loss, with a distinctive pattern in the trend of the NPS.

Algorithms↗
PubMed1992

Registered nurses' perceptions of their communication with Spanish-speaking migrant farmworkers in North Carolina: an exploratory study.

Communication forms the foundation for all that nurses do. Recently, nurses working with migrant farmworkers have become challenged as the language of this population has become predominantly Spanish. To explore how nurses in North Carolina are managing communication issues, 55 nurses at 12 state health care agencies that serve migrant farmworkers was surveyed. Data were collected to determine what nurses believed about various communication issues involving these Spanish-speaking clients, including how they were presently communicating with them, in what areas of nursing functions they believed communication barriers were problematic, what they were doing to improve their communication, and what they envisioned the potential solutions were concerning communication barriers. Language differences proved to be substantial barriers to adequate nursing care for these individuals. Nurses cited many problems and said that they were receiving little assistance from their agencies to improve direct communication with the clients. Responses indicated a need for and a willingness by nurses to focus on improving communication with Spanish-speaking clients. Classes held at their agencies were seen as the most effective way of learning Spanish.

Adult↗
PubMed1989

Use of neuroleptics after an episode of neuroleptic malignant syndrome.

The authors report a case of unequivocal Neuroleptic Malignant Syndrome, in which the patient was successfully rechallenged with a different potent neuroleptic in substantial dosage during the recovery phase. The Neuroleptic Malignant Syndrome did not recur and the patient's psychosis cleared. Reference is made to the relevant world literature.

Adolescent↗
PubMed1980

Blood lead concentrations in a remote Himalayan population.

The lead content in the air at the foothills of the Himalayas in Nepal was found to be negligible. The concentration of lead in the blood of 103 children and adults living in this region was found to average 3.4 micrograms per deciliter, a level substantially lower than that found in industrialized populations.

Adult↗