Sensitometric response of the Sens-A-Ray, a charge-coupled imaging device, to changes in beam energy.
OBJECTIVE
To evaluate image density (pixel values) and image contrast due to variations in beam energy (kVp) for the Sens-A-Ray intra-oral radiographic sensor.


METHODS
Images of an aluminium step wedge were made at 50, 70 and 90 kVp. Mean pixel values (with standard deviations) for representative attenuator thicknesses were measured using region-of-interest histogram analysis. Corresponding entrance doses were measured using a beryllium-windowed ionization chamber.


RESULTS
The steepest response slopes were found with the lowest kVp settings; hence the CCD results mimic the behaviour of standard radiographic film, with the high contrast being found with low kVp. The entrance dose resulting in pixel saturation was less with low kVp than high kVp. It is suggested that this is due to the CCD receptor being most sensitive to X-ray photons of relatively low keV.


CONCLUSIONS
While the kVp needs to be selected in relation to both tissue and receptor characteristics, it is possible to use low kVp techniques with the Sens-A-Ray without increasing the entrance dosage.
Goshima
T
T
Division of Radiology & Imaging Sciences, School of Dentistry, University of Louisville, USA.
Goshima
Y
Y
Scarfe
W C
WC
Farman
A G
AG
D004560:Electricity; D011856:Radiographic Image Enhancement / Q000295:instrumentation*; D011861:Radiography, Dental / Q000295:instrumentation*; D019252:Radiography, Dental, Digital; D012815:Signal Processing, Computer-Assisted; D013679:Technology, Radiologic