Biomedical subjects

R T Ritchings

Publications and source records attributed to R T Ritchings.

7 recordsLinked to original sources

PubMed1980

Effect of smoothing brain scans: a study using receiver operating characteristic curves.

A sample of computed tomography (CT) brain scans containing marginal lesions with different degrees of spatial smoothing was shown to two groups of observers. One group consisted of radiologists who had considerable experience in the interpretation of CT brain scans, whereas those in the other group had only limited experience. Neither group showed any significant change in ability to detect the marginal lesions when the pictures were smoothed. The groups were able to make diagnostic decisions even on pictures with high degrees of smoothing.

Brain↗

PubMed1980

An evaluation of four rare-earth film-screen combinations.

Objective and subjective assessments are made on four film-screen combinations at 140 kV for use on an EMI body scanner. The combinations used were: 3M XD film + Trimax Alpha 8 screens; Agfa Gevaert RP film + MR600 screens; Kodak Ortho G film + Lanex regular screens and Ilford type S film + rare earth rapid R screens. The objective assessment is based on the optical density of the image of a test object on a radiograph. Receiver operating characteristic techniques are used in the subjective assessment. The best results in each assessment were obtained using the Kodak Ortho G film + Lanex regular screens.

Beryllium↗

PubMed1979

An analysis of the spatial distribution of attenuation values in computed tomographic scans of liver and spleen.

An autocorrelation analysis of the attenuation values in computed tomographic scans has been performed for a total of 35 normal and eighteen cirrhotic patients. The results confirm preliminary observations on a smaller sample which suggested that this technique may be used to separate normal and cirrhotic livers. The noise structure in a region within the spleen was also examined and found to change in the presence of cirrhosis.

Humans↗

PubMed1979

Receiver operating characteristic curves in the evaluation of hard copies of computed tomography scans.

Receiver operating characteristic curves have been used to compare a variety of pictures derived from a number of hard copy devices used with EMI computed tomography scanners. The pictures examined were obtained from (a) a Shackman camera with bromide paper, (b) a Polaroid camera and Polaroid film, (c) a Shackman backed camera with radiographic film, and (d) an EMI multiformat imager. The results show no significant difference in detectability of an experimental object close to noise values using the various hard copies. It is concluded that the choice of a hard copy device might be based on considerations other than its physical performance.

Data Display↗

PubMed1979

A technique for simultaneous dual energy scanning.

A method of deriving simultaneous dual energy scans on a conventional EMI CT5005 scanner is described. The only change that has to be made to the scanner involves the detector collimator where alternate slits are covered by a thin metal foil. The detector readings from the covered and uncovered slits are separated by software before picture processing to give two pictures from one scan--one at the usual X-ray energy and the other at a higher X-ray energy due to the beam hardening produced by the foil. A procedure is then outlined for converting these into pictures showing the effective electron density and the effective atomic number for the whole scan field.

Adolescent↗

PubMed1978

Radiation dose in neuroradiological procedures.

Radiation dose is cumulative in the radiosensitive organs. In neuroradiology the organ of particular interest is the eye. There is an immutable physical relationship between spatial resolution, signal-to-noise ratio (i.e., density discrimination), and dose: Dose alpha (formula: see text). Optimal imaging conditions require a compromise between these three factors. The factors concerned in the effective utilisation of dose are discussed and the various compromises considered. Radiation dose measurements are given for a wide variety of neuroradiological procedures, including CT employing the EMI CT1010 and CT5005.

Cerebral Angiography↗

PubMedDate not supplied

Pathological voice quality assessment using artificial neural networks.

This paper describes a prototype system for the objective assessment of voice quality in patients recovering from various stages of laryngeal cancer. A large database of male subjects steadily phonating the vowel /i/ was used in the study, and the quality of their voices was independently assessed by a speech and language therapist (SALT) according to their seven-point ranking of subjective voice quality. The system extracts salient short-term and long-term time-domain and frequency-domain parameters from impedance (EGG) signals and these are used to train and test an artificial neural network (ANN). Multi-layer perceptron (MLP) ANNs were investigated using various combinations of these parameters, and the best results were obtained using a combination of short-term and long-term parameters, for which an accuracy of 92% was achieved. It is envisaged that this system could be used as an assessment tool, providing a valuable aid to the SALT during clinical evaluation of voice quality.

Acoustic Impedance Tests↗