Post-Processing Operations In Practice Flashcards
(38 cards)
What do all processing units of CR/DR have?
- Main screen to enter patient info
- Area to select procedure codes
- Areas for administration and/or support
Other than reviewing alignment and position, what is available to technologists on the review screen?
Ability to adjust the contrast, brightness, magnification and other image characteristics
What is the speed class of an image system based on?
Its sensitivity to radiation
What is the relationship between speed class and amout of exposure
Speed is inversely related to the amout of exposure required to provide adequate signal to the IR
- Faster the speed class, the less radiation is needed to create an image
What is the formula for speed?
Speed = 1/Exposure required
Historically, what was the standard speed class?
100 speed
What is the speed class used now?
200 speed
What are the exposure amounts by different speed classes?
- 100 speed = 2 mR
- 200 speed = 1 mR (half the radiation)
- 400 speed = 0.5 mR (quater the radiation)
What is the tradeoff when using a higher speed class?
The higher the speed class, the less radiation is used but the quality of the image goes down
What is the only digital image quality directly affected by the set technique?
Image noise
Now that digital images utilize processing techniques, where is the only indicator that can show the actual exposure/technique?
The Exposure Indicators (EI)
What is the relationship between EI number and exposure?
As the EI increases the exposure increases
As the EI decreases the exposure decreases
What does the EI indicate?
The actual exposure to image receptor which helps determine the correct technique since it cannot be determined by the image itself
What guildelines should be used when using EI?
- Avoid exremely high or low EI values
- High kVp and low mas techniques should be used
- Aim to stay within the department range
What do insufficient techniques result in terms of EI?
Low EI, which can produce unacceptable levels of mottle in an image
What do high EI values indicate?
Unacceptable levels of exposure to the patient
What is the EI value derived from in the generated image histogram?
The median pixel value of the main lobe between the Smin and Smax
What can skew the EI numbers?
The alignment of the patient, since the number is based on xrays passing through the patient and reaching the IR
What is a Deviation Index (DI)?
A standardized indicator that can be used across manufacturers to determine if the correct exposure/technique was used
What Deviation Index value will require a repeat?
Anything under -3.0, since it results in an excessive underexposure and causes excessive mottle in an image
What is saturation?
A condition of the detector elements where they reach their maximum electrical charge they can store
What happens with saturation?
The dels lose their data resulting in a black appearance on the image
What post-processing operations are done in practice by techs?
- Windowing
- Smoothing/Edge enhancement
- Masking (shuttering)
- Image reversal
- Resizing
- Image Stiching
What is masking?
A technique that allows for the darkening of collimation edges to make it less distracting when reading the image
