Radiology, Vol 131, 509-514, Copyright © 1979 by Radiological Society of North America
Comparison of dosimetry and image quality in computed and conventional tomography
W Maue-Dickson, M Trefler and DR Dickson
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.
