PubMed Health⌕ Search

Biomedical subjects

D R Dickson

Publications and source records attributed to D R Dickson.

14 recordsLinked to original sources
PubMed1979

Comparison of dosimetry and image quality in computed and conventional tomography.

Comparison was made of tomograms of a phantom head and a normal adult cadaver head on GE CT/T, Delta 50, EMI 5005, and CGR Stratomatic units. Image quality was ranked as follows: First, GE CT/T 8800 system; second, EMI; third, GE CT/T 7800 and Delta. The GE CT/T 7800 imaged 3.7 line pairs at high contrast with an exposure to the head phantom of 2.5 R (6.5 X 10(-4) C kg-1). The EMI exposure level was 5 R (13 X 10(-4) C kg-1) in the fast mode and 12 R (31 X 10(-4) C kg-1) in the slow mode, while the Delta 50 exposure level was fixed at 2 R (5.2 X 10(-4) C kg-1). The GE CT/T 8800 could image 6.1 line pairs/cm in a high-contrast phantom with exposures as low as 100 mR (25.8 muC/kg) but a typical operating exposure would be about 1--2 R (2.58 -5.2 X 10 (-4) C kg-1). Dosimetry ranged from 1.1 to 5.5 R/scan section (2.8--14.2 x 10(-4) C kg-1) in the CT units but never increased by a factor of more than 2, irrespective of the number of sections scanned. In conventional tomography, however, exposure increased almost arithmetically with the number of contiguous sections scanned.

Humans↗
PubMedDate not supplied

Anatomy of the normal and cleft palate Eustachian tube.

This report presents preliminary findings from a study of cleft palate and noncleft palate human fetuses to determine whether differences in Eustachian tube and cranial base structures could be found which might explain the universal appearance of otitis media in infants with cleft palate. Differences were found which are consistent with the previous hypothesis of reduced elasticity in the Eustachian tube. Principal findings included medial to lateral compression of the tube and reduced tubal width.

Abnormalities, Multiple↗
PubMedDate not supplied

Microfissure between the round window niche and posterior canal ampulla.

The microfissure between the round window niche and the posterior canal ampulla was examined in fetal, child, and adult human temporal bones. The communication which was filled with mesenchymal tissue and blood vessels extending from the middle ear, was observed between the round window niche and the posterior canal ampulla in 10 to 15-week human fetuses. The mesenchymal tissue in the communication was replaced by cartilage with advancing age of the fetus. No communication was observed at birth. From newborn to 12 months of age, no microfissure was observed. After one year of age, the microfissure was first observed and the frequency of the observation increased with increasing age of the patient. After six years of age, the microfissure was observed bilaterally in 100% of cases studied. The microfissure has its origin from the communication between the round window niche and the posterior canal ampulla in fetal life, and is a normal developmental and anatomical structure, and not a pathological finding.

Adolescent↗