Bushongs Ch. 21

What is Medical Image Quality?

Refers to the fidelity with which the anatomy under investigation is rendered on the image receptor.

What is Spatial Resolution?

The ability to image small objects that have high subject contrast.

How does Spatial Resolution improve?

Improves with smaller pixel size.

What is Contrast Resolution?

The ability to distinguish anatomical structures of similar subject contrast.

What is Noise?

The random fluctuation of x-ray interaction on the image receptor.

What reduces Quantum mottle?

Reduced with use of high-mAs, low kVp.

What are the characteristics of fast image receptors?

Fast image receptors have high noise and low contrast resolution.

What accompanies slow image receptors?

Low noise accompanies slow image receptors and high contrast resolution.

What limits spatial resolution?

pixel size.

What is Magnification affected by?

Affected by SID and OID- MF = \frac{Image\ size}{Object\ size}


\- MF = \frac{source-to-image\ receptor\ distance (SID)}{source-to-object\ distance (SOD)}

What is Distortion?

Unequal magnification of different portions of the same object.

What does distortion depend on?

object thickness, position, and shape.

Are thick or thin objects more distorted?

Thick objects are more distorted than thin objects.

What is Foreshortening referring to?

Foreshortening.

What is Elongation referring to?

Elongation.

What is Spatial distortion referring to?

Spatial distortion.

What is Focal-spot blur?

Focal-spot blur occurs because the focal spot is not a point.

• Focal\ spot\ blur = effective\ focal\ spot \times \frac{OID}{SOD}

What is the Heel effect?

The focal-spot blur is small on the anode side and large on the cathode side of the image receptor.

What is Subject contrast?

Radiographic\ contrast = Image\ receptor\ contrast \times Subject\ contrast

What is a Patient thickness referring to?

Patient thickness

What is Tissue mass density referring to?

how closely packed the atoms are within a specific tissue type.

What is Effective atomic number referring to?

Effective atomic number

What is Object shape referring to?

Object shape

What is Motion blur?

Patient motion is usually the cause of motion blur.

What is Tools for Improved Radiographic Image Quality referring to?

Patient positioning

What is Tools for Improved Radiographic Image Quality referring to?

Image receptors

What is Tools for Improved Radiographic Image Quality referring to?

Selection of technique factors

What is Tools for Improved Radiographic Image Quality referring to?

Keep exposure time as short as possible.