RADT 311: Exam 2

requires sufficient brightness, sufficient contrast and a minimum presence of noise.

Visibility

The ideal amount of contrast is an optimum ___ level.

intermediate

_ is any undesirable input that interferes with the visibility of the subject of interest.

Noise

Scatter radiation, mottle, projection artifacts, image receptor artifacts and unwanted tissues are all examples of:

Noise

A is a solid white image of a subject against a darker background or vise versa.

silhouette image

Most radiographic images are displayed as _ images (lighter anatomy on a dark background).

Negative

is defined as the range of different densities (brightness) within an image.

Gray Scale / Contrast Scale

Scale (low contrast) presents many shades of gray

Long

Scale (high contrast) presents only a few shades of gray

Short

The gray scale or contrast of an image should be adjusted using window .

width

You would adjust the overall brightness by using window .

level

The most common form of noise at the IR is .

scatter radiation

The most common form of noise appearing in digital images is _.

quantum mottle

Image mottle is from:

Low beam penetration, low beam intensity (mAs) and/ or thick or dense anatomy

Background fluctuations, surges and dips in electrical current which are present in any electronic system, are classified as ___ noise in the image.

electronic

__ is all the desirable information carried by the subject contrast in the remnant x-ray beam.

Signal

_ is defined as the proportion of all useful diagnostic information to all obstructing disinformation.

SNR (Signal to Noise Ratio)

What are the 2 ways to improve SNR:

Reduce noise and increase signal (kVp, mAs)

Recognizability (Geometrical Integrity) requires:

Maximum sharpness of recorded detail, optimum magnification of the structure of interest, and minimum shape distortion of the structure of interest

___ is defined as the abruptness with which the edges of an image “stop.”

Sharpness of recorded detail

_ is a scientific term for the blurriness of image edges.

Penumbra

In radiography, a blurred image can result from movement during exposure of the:

x-ray tube, the patient, or the IR

Sharpness of detail is destroyed by:

1. Geometric penumbra 2. Motion penumbra

_ is also referred to as size distortion and the difference between the size of a real object and the size of its projected image.

Magnification

What is a pathological condition in which magnification can simulate and lead to diagnostic misinformation?

cardiomegaly

Magnification can be done purposefully in some cases (such as in angiography) for:

an aneurism or blood clot that is too small to recognize

is defined as the difference between the shape of a real object and the shape of its projected image.

Shape Distortion

Shape Distortion consists of either:

1. Foreshortening 2. Elongation

In radiography, shape distortion is caused by misalignment of the:

x-ray tube, body part, and the IR

is the most important component of the recognizability of an image.

Sharpness of Recorded Detail

__ is defined as the measured width of the penumbra, or the “spread of blur" and it can mathematically calculated.

Unsharpness

Equation to find SID:

SID = SOD + OID

Equation to find SOD:

SOD = SID - OID

Equation to find OID:

OID = SID - SOD

Unsharpness can be controlled by what three things?

1. SOD (source-to-object distance) 2. OID (object-to-image receptor distance) 3. Focal spot size

What is the Unsharpness Formula?

(Focal spot size x OID)/SOD

Unsharpness is directly proportional to _ size.

focal spot

Larger focal spot = _ (smaller/larger) penumbra

larger

Smaller focal spot = _ (smaller/larger) penumbra

smaller

What is the Percent of Magnification equation?

Image Size – object size/ Object Size x 100

__ is a shape distortion in which the length of the image in the direction of the tube angle measures longer than that of the real object.

Elongation

__ is a shape distortion in which the length of the image measures shorter than that of the real object from a tilt.

Foreshortening

___ is defined as the ability to distinguish two adjacent details as being separate from each other.

Resolution

The area of uniform darkness on an image pertains to the __.

umbra

Magnification can be completely eliminated within radiography by:

magnification will always inherently exists to some degree in radiographs

What is the equation used for the magnification of an object?

SID/SOD = Image/Object

What equation is used to find the factor of magnification?

SID/SOD