Chapter 26 - Simplifying & Standardizing Technique

Week 9

List the 3 general areas of standardization within a medical imaging department.

1. Standardization of Projections

2. Standardization of Exposure Factors

3. Standardization of Image Processing

______ reduces the probability of errors occuring in the first place.

Simplification

What is the standardization of projections?

A written routine as a guide in routine exam manual is recommended for every department

• Basic routine of projections

• Basic guidelines for each projection (centering, collimation & receptor plate size for CR)

• Protocol book!

What is the standardization of exposure factors?

Technique charts in every room and on every portable

• Should be created with the input of staff radiographers

What is the standardization of image processing?

• Post-processing algorithms can be manually changed by technologists which changes the appearance of the image (and cannot then be changed by the radiologist when dictating.)

A fixed kvp chart is a ____ based method.

film

Describe fixed kVp charts in film imaging.

• Did not have a wide latitude of kVp bc it DIRECTLY controlled the image contrast

• Was the minimum kVp that achieved full penetration of all anatomy of interest (provided for maximum image contrast and full penetration)

• Kept kVp constant across projections in the exam to keep contrast constant among the images

What were the 3 primary goals of a fixed kVp?

1. Assure sufficient penetration

2. Keep image contrast consistent

3. Simplify and standardize for accuracy

Why does digital imaging have more latitude of kVp?

Because it is now only affecting subject contrast (still important, but can adjust with computer processing whereas film cannot)

What is so good about variable kVp charts?

Reduction in pt exposure!

• increasing kVp has less impact on pt exposure than a corresponding increase in mAs

What do most variable kVp charts do in practice?

Nearly all kVp systems actually adjusted both kVp and mAs for each projection… making the whole approach more complex and complicated

What happens in variable kVp charts for thin patients?

• mAs had to be reduced rather than kVp bc of the risk of inadequate penetration through the tissues of the anatomy of interest

What happens in variable kVp charts for thick patients?

• kVp increases allowed for more exposure because

  • meeting minimum kVp requirements was not an issue

  • digital imaging’s image contrast is primarily controlled by the look-up table (processing algorithm)

    • our hands were no longer tied with increases in kVp affecting our image contrast

What is the best kVp chart to use in digital imaging? (for the test, not IRL)

Variable kVp chart to reduce pt exposure without affecting the visual qualities of the image

BUT

1. Minimum kVp must always be met in order to assure sufficient penetration of the anatomy of interest

2. Radiographers must use systematic calculation to achieve as much simplification and standardization as possible. (avoid guesswork)

Reduction in exposure should generally be made with a ____ in ___.

reduction, mAs

Increases in exposure should generally be made with ___ of ___.

increases, kVp

Technique charts have been proven to ____ exposure errors considerably.

reduce

Technique charts are a _____ point.

starting

Technique charts are used for ____ situations.

routine

No device can replace the need for the radiographer’s careful assessment of each individual patient and situation, adapting exposure factors as needed for pathology and unusual conditions.