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Biomedical subjects

L R Manson-Hing

Publications and source records attributed to L R Manson-Hing.

At least 37 records · Page 2Linked to original sources
PubMed1978

Effect of mAs and kVp on resolution and on image contrast.

Two clinical experiments were conducted to study the effect of kVp and mAs on resolution and on image contrast percentage. The resolution was measured with a "test pattern." By using a transmission densitometer, image contrast percentage was determined by a mathematical formula. In the first part of the experiment, the density of the film was kept constant by changing the kVp and mAs. In the second part of the experiment, different mAs's were chosen, and for each mAs, several kVp's were used. Five observers read the radiographs. The first experiment showed that, when the film density is kept constant, the higher the kVp, the lower the resolution and image contrast percentage; also, the higher the mAs, the higher the resolution and image contrast percentage. The second experiment showed that when the film density is not kept constant, the correlation between kVp and resolution and between kVp and image contrast percentage was the same as in the first experiment. However, there was negligible correlation between mAs and resolution and between mAs and image contrast percentage. A high positive correlation was found between resolution and image contrast percentage, but a high negative correlation was found between resolution and film density.

Absorptiometry, Photon↗
PubMed1977

Radiation exposure and distribution measurements for three panoramic x-ray machines.

1. Exposures to internal sites in the phantom varied as follows: Panorex, 0.3 mr to 2.4 r; Orthopantomography, 0.4 mr to 0.8 r; Panelipse, 0.2 mr to 1.4 r. 2. With the phantom exposed for a normal-density radiograph at 65 KVP, the average radiation exposure at the sites measured were for the Panorex, Orthopantomograph, and Panelipse respectively: 8, 13, and 4 mr at the pituitary gland; 22, 62, and 8 mr at the superior area of the parotid gland; 13, 8, and 5 mr at the thyroid gland; 343, 425, and 365 mr at the submaxillary gland; and 50, 154, and 272 mr at the base of the tongue. 3. External exposures to the phantom and patients were found to be in good agreement at the low KVP. At the high KVP (using patients who were larger than the phantom), exposures at lateral and posterior sites showed relatively good agreement between phantom and patients, while exposures at anterior sites were less in patients. 4. The average stray radiation measurement at 1 meter from the phantom during pantomography with the three machines was 0.125 mr per exposure cycle. Individual averages were: Panorex, 0.10 mr; Orthopantomograph, 0.13 mr; and Panelipse, 0.15 mr.

Dental Equipment↗
PubMed1977

Densitometric evaluation of quick x-ray developing solutions.

1. A 1:2 dilution is the most effective concentration when Kodak developer-replenisher is used as a quick processing solution. 2. Clayton solution used at the manufacturer's recommended concentration with rapid processing times produces radiographs with greater densities than Kodak developer-replenisher or Dry-X-Sol. 3. Clayton, Dry-X-Sol, and concentrated Kodak developer-replenisher used as rapid developers produce radiographs with less image densities than standard Kodak developing solution used at conventional processing times. 4. Radiographic contrast is slightly less when rapid processing is utilized.

Absorptiometry, Photon↗
PubMed1976

A study of the resolution of dental films and screens.

From the study of the resolution produced by 156 screen-film combinations at a film density between 1.41 and 1.59, the following conclusions are drawn: 1. Resolution is affected by screens, films, and observers. 2. The effect of screens on resolution is much greater than the effect of films. 3. Screens varied greatly in resolving ability. 4. Films did not differ greatly in resolving ability. 5. Cronex Lightning Plus screen and Radelin super high-speed screen produced the lowest resolution and Cronex detail screen produced the highest resolution. 6. In general, the slower the screen, the higher is the resolution and vice versa. 7. There were two groups of films with significant resolution differences. 8. Films designed to be processed automatically did not differ significantly in their resolving ability when processed manually. 9. There is significant interaction effect of screens and films on resolution. 10. Individual visual resolving ability plays a significant role in measuring resolution.

Radiographic Image Enhancement↗
PubMed1976

Japanese tooth positions and their relation to panoramic radiography.

1. Tooth positions did not vary between ages and sexes in Japanese. 2. As the arches lengthened posteriorly, anterior tooth positions showed little variation. 3. Japanese tooth positions lie within the range shown for Caucasoid and Negroid persons. 4. Japanese tooth positions have a shorter anteroposterior dimension than their Caucasoid and Negroid counterparts. 5. The relationships of Japanese positions to the Panorex, Panelipse, and Orthopantomograph are similar to those found for Negroid and Caucasoid persons.

Adolescent↗
PubMed1975

Relations between tooth positions and focal troughs of panoramic machines.

A comparison of the established focal troughs of three panoramic machines with positions of the teeth in the dental arches of 240 patients. The patients, divided into twelve cells, were selected on the basis of race, sex, age, number of teeth, and occlusion. Occlusal registrations were made in fast-set acrylic. Tooth centers were identified and, with the midline-incisal point as a reference point, various composite drawings of tooth positions of patients were made. The total composite of all teeth revealed the striking similarity of the arches. Superimposition on the focal troughs showed that the focal trough of the Panorex easily encompassed all tooth positions. The focal trough of the Orthopantomograph encompassed all tooth positions, although tooth centers lie on the edges of the trough. The focal trough of the GE-3000 with profile index 10 extended so far buccally that many teeth are positioned lingual to the trough. The focal trough of the GE-3000, when reduced uniformly to profile index 7.5, encompasses all tooth positions although some positions fall quite near the borders of the trough.

Adolescent↗