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Biomedical subjects

M J Pharoah

Publications and source records attributed to M J Pharoah.

6 recordsLinked to original sources
PubMed1992

The radiographic characteristics of histiocytosis X. A study of 29 cases that involve the jaws.

The purpose of this study was to provide an objective analysis of the radiographic characteristics of histiocytosis X as it affects the jaws. The original radiographs of 29 cases were reviewed independently and objectively by three observers. The results suggest that seven characteristics, either alone or in combination, are useful in the identification of histiocytosis X. These include the appearance of solitary "intraosseous" lesions, the multiplicity of "alveolar bone" lesions, the "scooped-out" effect in the alveolar process, the well-defined periphery, sclerosis in the alveolar bone lesions, periosteal new bone formation, and slight root resorption.

Adolescent↗
PubMed1992

Reducing transmitted radiation in dental radiography.

A significant amount of radiation escapes the rear of an image receptor in conventional dental radiographic procedures despite the placement of a lead-containing backing at the rear of the film pack. The purpose of this investigation was to place additional layers of lead on the film pack in an attempt to reduce transmitted radiation to tissues behind the film. Reduction of dose to tissues behind the film causes a reduction in scatter radiation to critical organs such as the thyroid gland and salivary glands. A thermoluminescent lithium fluoride dosimetry system (TLD) was used and calibrated in both the beam of interest and tissue of interest. A tissue-equivalent anthropomorphic phantom was used for dose determination. Successive layers of lead foils were added to the image receptor, and dose was determined for each additional lead foil in the tissues behind the image receptor. Two sets of exposure conditions were used, namely: 70 kVp, 10 mA, and 0.6 s, and 90 kVp, 10 mA, and 0.6 s. The beam-film-patient orientation used was for a first molar bitewing radiographic projection. Four lead layers (three additional foils equalling 3.92 x 10(-3) mm of lead) on the conventional film package resulted in a significant dose reduction. Four layers of lead resulted in a dose less than one-third that of the conventionally shielded package.

Models, Structural↗
PubMed1991

Skin exposure and thyroid dose distribution using niobium filtration.

A thermoluminescent dosimetry system was utilized to investigate how much the radiation dose is reduced through the addition of a niobium-based accessory filter to an X-ray unit's conventional aluminum filter. A two-bitewing series was exposed in a tissue-equivalent human phantom. The skin exposures from an X-ray beam with the added niobium filter and a beam with the aluminum filter alone were measured and compared. Thyroid dose distribution was also measured and similarly compared. Utilization of the niobium filter resulted in a significant reduction in skin exposure (p less than 0.001) of 14.8 per cent. Thyroid dose was not lessened by using the niobium filter, however. In fact, in one region of the thyroid it increased significantly.

Filtration↗
PubMed1989

Presurgical radiographic assessment for implants.

A radiographic technique was developed to accurately assess bone available for the placement of intraosseous implants. Hypocycloidal tomographs were made at right angles to the long axis of the mandibular and/or maxillary alveolus while the patient was wearing a specially designed splint. Alveolar height and width measurements were obtained from the resulting films. Sensitivity results for this technique showed that the mean difference between the actual bone height and width and that measured in the radiographs was 0.49 mm and 0.35 mm, respectively. A paired difference test revealed a range of 0.25 mm to 0.73 mm in the expected error in the height and 0.20 mm to 0.50 mm in width measurements with a 95 confidence interval.

Alveolar Process↗