Spatial Resolution & Distortion Review Flashcards

A complete set of vocabulary flashcards covering spatial resolution metrics, distance factors, blur calculations, and types of image distortion based on the radiography lecture.

Spatial Resolution

The structural sharpness recorded in a radiographic image; also known as definition, detail, recorded detail, or sharpness.

Visibility of Detail

Determined by factors like scatter, contrast, exposure, and noise, which can hide recorded detail even if the system captured it.

Umbra

The structural sharpness recorded at the center of an image.

Penumbra

The blur or unsharpness recorded around the edges of an image.

Spatial Frequency

The number of line pairs in a given length, usually expressed in line pairs per millimeter ($lp/mm$).

Line Pair

A measurement unit for spatial resolution consisting of one black line and one white interspace.

Pixel Size

The primary determinant of spatial resolution in digital imaging; smaller pixels result in better spatial resolution.

Voluntary Motion

Patient movement that is under their direct control, best reduced through clear communication.

Involuntary Motion

Movement not under the patient's conscious control, such as peristalsis or pathology; best reduced using the shortest exposure time (reciprocity law).

SID (Source to Image Distance)

The distance from the x-ray tube to the image receptor; increasing this decreases penumbra and magnification while increasing spatial resolution.

OID (Object to Image Distance)

The distance from the anatomy of interest to the image receptor; increasing this increases magnification and decreases spatial resolution.

SOD (Source to Object Distance)

The distance from the x-ray tube to the anatomy being imaged, calculated as $SOD = SID - OID$.

Focal Spot Size (FSS)

Controlled by the filament; decreasing this decreases penumbra and increases spatial resolution.

Penumbra Formula

The mathematical calculation for blur: $P = \frac{FSS \times OID}{SOD}$.

Blooming

An increase in focal spot size (by up to a factor of 2) that occurs when high $mA$ causes electron repulsion at the filament.

Distortion

A misrepresentation of the size and/or shape of the anatomical part being imaged.

Size Distortion

Also known as magnification; the difference between the actual anatomy size and the imaged anatomy size.

Magnification Factor (MF)

The ratio used to determine size distortion, calculated as $MF = \frac{SID}{SOD}$.

Actual Object Size Formula

The formula used to find the size of the anatomy: $\text{Object size} = \frac{\text{Image size}}{MF}$.

Percent Magnification Formula

Formula used to describe how much larger the image is than the object: $\text{\% Mag} = \frac{\text{Image} - \text{Object}}{\text{Object}} \times 100$.

Shape Distortion

Misrepresentation caused by unequal magnification across the dimension of an object, occurring as elongation or foreshortening.

Elongation

Shape distortion where the object appears longer than it really is; caused by angulation of the x-ray tube or the image receptor (IR).

Foreshortening

Shape distortion where the object appears shorter than it really is; caused by misalignment or angulation of the anatomical part.