7.2 Reporting Flashcards
it is a method by which digital radiography manufacturers provide feedback to the technologists regarding the estimated exposure on the detector, as a surrogate for image signal-to-noise ratio and an indirect indication of digital image quality
Exposure Index
The differences in the exposure indicators have created not only confusion but also frustration among users.
This provided the motivation for the development of a standardized EI by the ______
IEC (International Electrotechnical Commission) and the AAPM (American Association of Physicists in Medicine
The IEC standardized EI is _____ to the detector exposure and requires the user to establish EIT values for all examinations in order to ensure optimization of the dose to the patient without compromising the image quality
proportional
provides immediate feedback to the technologist as to whether the correct exposure was used for the examination
Deviation Index
3 Important Aspects of the New Standards
- Exposure Index (EI)
- Target Exposure Index (EIT)
- Deviation Index (DI)
the ability to image two separate objects and visually distinguish one from the other
Resolution
appears as an irregular granular pattern in all images and degrades image information
appears as an irregular granular pattern in all images and degrades image information
Noise can be discussed in terms of:
- Electronic noise (system noise)
* Quantum noise (quantum mottle)
determined by the number of X-ray photons falling upon the detector to create the image
Quantum Noise (Quantum Mottle)
is a measure of the efficiency and fidelity with which the detector can perform the task of receiving an input exposure and converting it into a useful output image
Detective Quantum Efficiency
The ideal detector would have a DQE of ____, meaning all the radiation energy or input exposure is absorbed by the detector and converted into useful image information. This means that there is no loss of information
1 or 100%
The DQE for CR is much ____ than film-screen (F-S) image receptors.
- This means that CR can convert an input exposure into a useful output image over a much wider range of exposures compared to F-S radiography
better
is any feature which appears in an image which is not present in the original imaged object
Image artifact
most common artifact
Motion artifact
devices that either convert x-rays into an electric charge
(direct conversion) or light (indirect conversion) which is then read out through TFTs (Thin Film
Transistors)
Flat panel are digital radiography (DR)
The flat-panel TFT digital detector is designed as a matrix of detector elements, each of which
can be regarded as a pixel. This design principle is referred to as _____
large area integrated circuit
The sensing/storage element of an indirect flat-panel TFT detector is the _____ (photosensitive
storage element)
photodiode
is a semiconductor device that converts light energy into electrical energy
photodiode
Aside from the matrix of pixels, there are other electronic components that are included in the flat-panel detector
gateline or data line
Typical Detector Dimensions
43 x 43 cm
30x 40 cm
18 x 18 cm
Different Matrix Sizes
1920 x 1536, 2000 x 2500, 2736 x 2736, 2560 x 3072, 2688 x 2688, 2836 x 2836, 3121 x 3121
The number of pixels can be obtained by multiplying the dimensions of the ____
matrix size
is the distance from the midpoint of one pixel to the midpoint of the adjacent pixel
Pixel Pitch
Pixel Sizes:
139 mm, 143 mm, 160 mm, 162 mm, 167 mm, 200 mm