Technique Ch. 28

Front 1

Geometric properties

Back 1

Spatial resolution and distortion

Unlike the photographic properties of ir exposure and contrast, which control the visibility of detail, the ______ control detail itself

Front 2

Spatial resolution (recorded detail)

Back 2

Is one of the two geometric

properties of image quality.

Is the degree of geometric sharpness or accuracy of the structural lines actually recorded in the image

Is dependent on Matrix size, pixel size, and grayscale bit depth

Front 3

Definition, sharpness, recorded detail

Back 3

Spatial resolution is also referred to as

Front 4

Radiographic resolution tool

Back 4

Is composed of pairs of lines a set distance from one another

The point at which the viewer can discern the closest pair of lines from each other represents the 1p / mm reading.

Most humans visual limit is the range of 5 1P/mm

High spatial resolution represents a high-frequency signal that is capable of Imaging smaller objects

Low spatial resolution represents a lower frequency signal that can only image larger objects

Hint 4

Front 5

High frequency

Back 5

High spatial resolution is expressed as

Front 6

Spatial frequency

Back 6

High frequency (shorter wavelength signal) : represents pairs of lines that can be visualized very close together. AKA, high resolution

Low-frequency (long-wavelength signal) : represents pairs of lines that are further apart. AKA, low resolution

Front 7

Unsharpness

Back 7

Lack of sharp definition of fine detail

Front 8

Point spread function (PSF)

Back 8

Measures penumbra and is used to quantify digital system spatial resolution

Front 9

Resolution test tool

Back 9

Spatial resolution is usually evaluated during quality control testing by Imaging a _____.

In a clinical situation, small structures are the easiest to examine and evaluate spatia resolution.

The trabecular pattern of bone is an excellent guide post to image resolution

Front 10

Spatial resolution

Back 10

Describes the ability of an Imaging system to accurately display objects in two dimensions

Is higher when two objects can be demonstrated to be smaller or closer together

Front 11

Spatial frequency

Back 11

Determined by measuring distance between pairs of lines distinct from one another

Front 12

Measures of recorded detail (spatial resolution)

Back 12

Those used most often to describe and compare Imaging systems are

Spatial frequency

(PSF) Point spread function

(LSF) Line spread function

(ESF) Edge spread function

(MTF) modulation transfer function

Noise

Front 13

Point spread function (PSF)

Back 13

Expression of the boundaries of an image. Determined by a mathematical measurement of an image produced at a single point

Hint 13

Front 14

Edge spread function (ESF)

Back 14

Expression of the boundaries of an image

Front 15

(PSF) (ESF) (LSF)

Back 15

All Express the boundaries of an image

In film screen radiography this aspect was called penumbra or blur

Front 16

Test tools

Back 16

Are simply pairs of lines that are different distances from one another.

It is imaged by the system, and the viewer determines the smallest pair of lines that can be visualized.

The pairs of lines are then measured as line pairs per unit of length, usually in mm or cm.

Front 17

(MTF) Modulation transfer function

Back 17

Measures the accuracy of an image compared to the original object on a scale of 0 - 1.

Measurement of 1 represents perfect reproduction of original object (impossible with current tech)

Is comprised of spatial frequency components

PSF, LSF, ESF

As the spatial frequency of objects Rises, the ____ decreases

Hint 17

Front 18

Rises

Back 18

As the spatial frequency of objects Rises, the MTF..

Front 19

1

Back 19

In medical imaging, the goal is to produce an image with an MTF value as close as possible to ___, at high spatial resolution

Front 20

Imaging noise

Back 20

Background information that the image receptor receives

Is the total noise that the IR receives. It includes System noise, Ambient noise, and Quantum noise

Front 21

(SNR) signal-to-noise ratio

Back 21

Is a measure of signal strength relative to total noise.

Depends on the amount of radiation exposure to the detector and the detectors detective Quantum efficiency

Higher ___ is very desirable for optimum image quality

Front 22

(CNR) Contrast to noise ratio

Back 22

Is defined as the ratio of the difference of signal intensities of two regions of interest to the Imaging noise

Ratio of ROI signal differences to noiseCNR values are not possible without high SNR values, therefore these two metrics can be used to validate one another

CNR values are not possible without high SNR values, therefore these two metrics can be used to validate one another

CNR values are not possible without high SNR values, therefore these two metrics can be used to validate one another

Front 23

Noise

Back 23

Expressed as signal-to-noise ratio (SNR)

Quantified as a numerical value

Higher SNR is very desirable for optimal image quality.

Contrast to noise ratio CNR

Front 24

Noise level rises

Back 24

When this happens, more complex computer processing algorithms may be necessary. When their limits are reached, degradation of the image occur

Hint 24

Front 25

How to improve Recorded detail (spatial resolution)

Back 25

Eliminate motion, with shorter exposure time. Or synchronize exposure with motion

Reduce OID

Reduce focal spot size

Use detector with smallest detector element (DEL)

Reduce intensifying screen phosphor size and concentration film system.

Increase SID

Hint 25

Front 26

Voluntary motion

Back 26

Is best reduced through effective communication.

Technologist must establish atmosphere by being professional and competent

Front 27

involuntary motion

Back 27

Best reduced through short exposure time

Or

immobilization

Front 28

Motion

Back 28

Voluntary

Involuntary

Equipment

Front 29

Digital systems affecting recorded detail

Back 29

CR Imaging plates

-Limitations similar to intensifying screens. -Size of PSP Crystal.

-Also affected by image reader device (IRD)

DR

- primary limitation is size of detector element (DEL)

200 microns, 140 microns, 125 microns, Etc

Image processing system limits recorded detail depending on

- accusation and display matrix

- pixel size

- grayscale bit depth

Front 30

Focal spot size affecting recorded I detail (spatial resolution)

Back 30

Line Focus principle.

Creates a penumbra (P) and inherent loss of sharpness due to focal spot geometry and distances.

Focal spot size is a major factor in spatial resolution.

Smaller focal spot yield increased resolution

Hint 30

Front 31

Attenuation / absorption unsharpness

Back 31

Some degree of image unsharpness occurs due to shape and size of patient Anatomy.

Related to beam Divergence and incongruence with anatomical structures

Front 32

Assessing recorded detail (spatial resolution)

Back 32

Clinical evaluation

- Trabecular pattern of bone. - Cortex of bone.

- Bronchopulmonary markings of lungs

Front 33

Focal spot size

Back 33

Is controlled by the line Focus principle.

Is a major controller of spatial resolution because it controls penumbra

As it decreases in size, penumbra also decreases, thus increasing resolution

Hint 33

Front 34

Back 34

The width of the penumbra can be mathematically calculated using the following formula

Front 35

Umbra Vs. Punumbra

Back 35

Is the distinctly sharp area of Shadow or the region of complete shadow.

Versus.

Is the imperfect, unsharp Shadow surrounding the Umbra.