Radiographic Quality pt1

Understand Visibility 

Visbility is affected by brightness and contrast

Understand Sharpness

Sharpness is affected spatial resolution and distortion

What does this image tell you about contrast

1. This image shows how there isnt different types of material because there isnt differing structures attenuation which makes it look almost one color bascialyl no contrast

What does this image tell you about contrast

This image shows how the different itesm in the image show different attenuation giving more contrast to each other

What do these two images detail

Is this high contrast or low contrast

This image just shows how the shades can look more different this image is higher contrast and this would be considered high contrast

Is this high or low contrast

This would be low contrast

Purpose of x-ray image accuracy

When we take an x-ray, it is essential the image accurately represents anatomy and structures are easily visible.

Visibility of anatomic structures

Determined by brightness and contrast.

Accuracy of structural lines

Determined by spatial resolution and distortion.

Image Quality definition

Image quality = visibility factors + sharpness factors.

Brightness importance

The image must have enough brightness to visualize anatomical structures clearly.

Proper brightness example

An image with correct brightness is a good representation of diagnostic quality.

Overly bright image

Too much brightness hides thick anatomy; causes similar problems as low brightness because anatomy becomes difficult to visualize.

Low brightness (too dark) image

Image lacks brightness, appears dark, and makes anatomical parts difficult to distinguish.

Saturation definition

In digital imaging, saturation occurs when the image is severely overexposed or severely underexposed; results in loss of information.

Proper vs saturated image

The first image appears normal; the second shows severe overexposure with saturation.

Contrast definition

The number of brightness levels or shades of gray in the image.

Contrast depends on

Differential absorption of tissues and brightness differences needed to differentiate anatomy.

Digital image contrast requirement

The digital image must show differences in brightness levels (contrast) to differentiate anatomic tissues.

Subject contrast definition

Differences in x-ray attenuation due to tissue composition and beam quality (kVp).

What affects subject contrast

Tissue type (soft tissue, bone, fat) and beam energy.

Low subject contrast

Occurs when tissues attenuate similarly (e.g., abdominal imaging).

High subject contrast

Occurs when tissues attenuate very differently (e.g., forearm showing bone, muscle, fat).

Image contrast definition

The contrast seen on the final processed digital image.

Contrast and brightness levels

The ability to distinguish tissue types is based on differences in brightness (contrast).

High contrast definition

Big differences in brightness levels; fewer shades of gray; common with bony anatomy.

Low contrast definition

Small differences in brightness levels; many shades of gray; common in abdomen imaging.

Contrast resolution definition

The ability to distinguish between two tissues with similar subject contrast.

Limitations of x-ray contrast resolution

X-ray is not the best modality for differentiating tissues with similar contrast.

Gray scale definition

The number of brightness levels (shades of gray) displayed on an image.

Displayed image contrast processing

Computer algorithms adjust brightness and contrast before the image appears.

Radiologist post-processing

Contrast can be further adjusted after display based on what anatomy must be visualized.

Wide gray scale

More shades of gray.

Thin (narrow) gray scale

Fewer shades of gray.

Importance of low-contrast detection

Needed to visualize soft tissue anatomy.

Displayed image contrast depends on

Subject contrast + contrast resolution of digital detector + computer processing (pre- & post-display).