Question

Concerning digital and computed radiography imaging systems: 

a. They have a similar dynamic range 

b. They are both unaffected by random noise 

c. With an analogue-to-digital converter (ADC), insufficient bits do not affect signal coding 

d. Digital and computed radiography imaging systems benefit from a reduction in image acquisition time compared with film-screen radiography 

e. Computer-aided detection (CAD) may be employed with digital images

Answer 1

a. True. Computed radiography has a dynamic range in the order of 10,000:1. Digital radiography has a dynamic range in the order of 1000:1 to 10,000:1. For both, the low end of the system is determined by noise. In digital radiography, the high end of the range is determined by the charge-holding capacity of the detector elements.

b. False. They are both affected by this. This is noise associated with the image receptor, which typically cannot be corrected for (so-called electronic noise). 

c. False. This is related to an insufficient number of grey-scale values that can be demonstrated. 

d. True. 

e. True. Post-image acquisition analysis and processing can help with diagnosis of pathology.