Exposure Index

Exposure index is one of the key metrics used in digital radiography, it is often referred to as EI, it relates to the relative speed with which the incident x-rays reach out to the receptor. The exposure index also helps in evaluating the optimum ranges, in which a high-quality medical image can be obtained with a lower dosage of radiation. By carefully setting the exposure index the signal-to-noise ratio in the output image is also controlled.

Is your EI elevated or decreased from normal? (you don’t have to give values, just a general description)

The posteroanterior image of the hand was highly underexposed, thus the Exposure index was lesser than normal.

What indicators do you see in your image that support the out-of-range EI?  What does it look like? High contrast, low contrast, etc.?

The image was estimated to be fairly underexposed as:

1. It exhibited low contrast, i.e., the image was too light.
2. The anatomical boundaries were blurry.
3. The details were not evident; thus, the image was of little diagnostic credibility.
4. The output image displayed by the digital radiography exhibited a lower signal-to-noise ratio.
5. The underexposed image exhibited quantum mottle.

What does high/low EI mean?

The exposure index is a feedback metric, that lets the radiologist or operating technician know about the relative amount of the x-ray photons that were fortunate to an incident on the detector screen. This in turn specifies the quality defining parameters of the DICOM image, like the contrast. EI is a multifactorial parameter, which also depends on scanning speed and radiation dosage. A low EI value signifies that lesser X-rays have been made to reach the detector (quantum mottle), a low scanning dosage and underexposed image, and vice-versa.

What did you do wrong?

The radiation dosage was low to visualize the anterior anatomical structure of the hand, moreover, there was a considerable difference between the diversion index and exposure index value.

How will you fix it?

1. The standard radiation dosage recommended for visualizing the hands will be referred to and used.
2. The parameters on the DR console-like kV and mAs will be altered to reduce the discrepancy between the exposure and diversion index.

Will you make any additional changes?

The DR vendor’s instruction manual will be consulted to get to know how the EI feedback signal is translating to the image at that exposure intensity.

Provide an image that closely replicates your image’s inadequacies.