RAD 172 Final- Spatial Resolution

Spatial resolution

degree of geometric sharpness. The accuracy of the structural lines.

Spatial resolution is aka?

definition

sharpness

recorded detail

or detail

What's the primary unit of resolution?

Line pairs per millimeter (IP/mm) or cycles per mm.

AKA Spatial frequency

Higher spatial frequency

better spatial resolution

Increases SID

increases spatial resolution

Decrease SID

decreases spatial resolution

Nyquist Criterion

sampling the signal a minimum of twice per cycle.

Aliasing (morie Effect)

Occurs when the Nyquist criterion is not met. produces fluctuating, low frequency digital signal.

Visual appearance of two images slightly out of alignment.

Umbra

distinctly sharp area of a shadow or the region of complete shadow, aka geometric sharpness.

Penumbra

The imperfect, unsharp shadow surrounding the umbra, aka geometric unsharpness or edge gradient.

Modulation Transfer Function

The composite measure of image accuracy compared to the original object, on a scale of 0 to 1 referred to as MTF.

1=perfect

high frequency?

shorter wavelength signal, line pairs closer together better detail.

PSF

point spread function

LSF

line spread function

ESF

edge spread function

Increasing spatial resolution

increasing SID

Decreasing OID, patient thickness, focal spot size, motion, relative speed.

decreasing spatial resolution

decreasing SID

increasing OID, patient thickness, focal spot size, motion, relative speed.

Matrix

square series of boxes that gives form to image.

Pixel

picture elements, individual matrix boxes.

Gray scale bit depth

the number of shades of gray, ranges from 8-32 bits

More pixels per square equals ?

higher resolution

Small matrix

lower resolution

Quantum Noise

insufficient incoming data, not enough photons.