Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgements
- 1 Basic physics
- 2 Radiation hazards and protection
- 3 Imaging with X-rays
- 4 Film-screen radiography
- 5 Digital radiography
- 6 Fluoroscopy and mammography
- 7 Nuclear medicine
- 8 Computed tomography
- 9 Imaging with ultrasound
- 10 Magnetic resonance imaging
- Bibliography
- Index
5 - Digital radiography
Published online by Cambridge University Press: 05 July 2011
- Frontmatter
- Contents
- Preface
- Acknowledgements
- 1 Basic physics
- 2 Radiation hazards and protection
- 3 Imaging with X-rays
- 4 Film-screen radiography
- 5 Digital radiography
- 6 Fluoroscopy and mammography
- 7 Nuclear medicine
- 8 Computed tomography
- 9 Imaging with ultrasound
- 10 Magnetic resonance imaging
- Bibliography
- Index
Summary
Concerning a digital radiography system:
An early step in image acquisition is conversion of data from an analogue to digital format
The size of the image detector is not important, as the final image may be manipulated electronically
Detector sensitivity must be high
Pixel size influences image resolution
Noise is less significant than with film-screen radiography
The requirements of a digital radiography system are:
Good X-ray sensitivity
A small field size
A digital-to-analogue converter (DAC)
A narrow dynamic range
A locally based archive
Concerning the digital radiographic image:
It is represented numerically in digital form
The image is divided into a matrix consisting of multiple pixels
The greater the sampling frequency, the greater the spatial resolution
Decreasing the detector sampling frequency may reduce detector sensitivity
The image may be read out directly from the detector electronically
Concerning the digital radiographic image:
Signal digitization expresses the image as continuous grey-scale values
The function of the analogue-to-digital converter (ADC) is to digitize the input while maintaining resolution of the information
A binary system is used for signal digitization
Eight bits is typically sufficient for most images
Data compression for storage may lead to loss of data
The number of bytes of a digital image is dependent upon:
The number of pixels within the image
Pixel size, assuming matrix size is constant
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- Physics MCQs for the Part 1 FRCR , pp. 56 - 69Publisher: Cambridge University PressPrint publication year: 2011