Ch.30 Flashcards by Sinead Zoellner

This screen usually includes erase cassette button, and options for entering patient and study data and for reviewing images.

Main Menu

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This is a set default procedure code and generic setting for the equipment, only accessible to QC technologists or supervisors with a password.

Key Operator Functions

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This screen is used to enter identification, demographics, and study information.

Study Data or Patient Data

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This button sends the patients whole file to the PAC system for storage.

Submit Study

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This is a screen used for windowing adjustments, presentation of histogram and exposure indicator.

Image Review Screen

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Most systems allow for adjustments of iamge brightness contrast or magnification by cursor movement. Left to Right is what? Up does what?

Left to RIght- Usually increases brightness
Up- Usually increases contrast
Down- Usually decreases contrast

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Extreme reduction of contrast by moving the cursor down can do what to the image?

Reverse the image making it black on white.

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A magnifying glass icon is usually presented for doing what on the image.

Zooming in or out

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From the image review screen, usually by touching the histogram, an image reprocessing screen can be accessed for what 3 things?

Applying alternate algorithms
Adding annotations, markers, arrows
Applying a “black” mask (border), reversing or making other changes to the image.

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This button dedicates the image to a particular study or series.

Assign or stamp view button

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This can be used to assign a study by scanning the bar codes into the system using a laser reader.

CR cassette

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This button sends the image with its current settings into a file in the PAC system.

Accept Image or Deliver

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This sends the entire study into the PAC system for storage.

Accept (All) Images

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This feature can be used to send an image directly to a printer without being saved into the PAC system.

Select Destination

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The ___ of any imaging system expresses its sensitivity to radiation and is always inversely related to the amount of exposure required to produce an adequate signal at the image receptor.

Speed

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What is the formula for speed?

1/exposure required

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If twice the exposure is required what do you do to the speed?

Half the speed

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What is the standard speed value that requires an exposure of 2mR to produce a density of 2.5

Speed value of 100

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No set _____ exists by which speed can be gauged.

Density

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Before the advent of digital imaging the most commonly used film/screen combinations in radiography had a speed of what?

400

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Early CR readers were typically installed to operate at what speed?

200

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This is the inherent speed of the photostimulable phosphor plate used as a CR image receptor.

200

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When the processing speed of the CR or DR system is doubled the IR plate need to only receive how much exposure for the whole system to produce the proper image?

one-half

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This speed assumes an average exposure of 2mR will penetrate through to the image receptor.

100

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This speed assumes an average exposure of 1mR will reach the image receptor.

200

This speed assumes an average exposure of .5mR will reach the image receptor.

400

Although the inherent speed of a CR reader is 200, the speed of the reader can be what?

Adjusted

Nearly all modern CR and DR systems can be operated at a speed class of 300,350,400 with out the appearance of what in the image?

Substantial Mottle

Digital images taken at increased technique sometimes turn out what in appearance.

Lighter in appearance

This is a number used to provide feedback to the radiographer on the exposure level to the image receptor.

Exposure Index

Exposure indicators are not related to what?

Brightness Level

Insufficient techniques resulting in low exposure indicators can cause an unacceptable level of what in the image.

Mottle Noise

High exposure indicators reflect an unacceptable level of what to the patient?

Exposure

This should be utilized for adequate penetration and low dose to achieve exposure indicators within the correct recommended range.

High kVp. Low mAs

This is the counting average rather than the arithmetic average of the pixel values.

Median

By using median rather than mean averaging in calculating the exposure indicator, the indicator is less severely skewed by what processing error?

Segmentation

This is a range of acceptable exposure indicator values centered around this median average, for guidance to radiographers as to whether an appropriate level of radiologic technique was used.

Target Range

What are the 3 types of scales used for exposure indicators?

1. Logarithmic Scales 2. Proportional Scales 3. Inversely Proportional Scales

In any logarithmic scale changes of .3 or a multiple thereof represent a change in exposure by what?

A facto of 2

These are the 4 types of logarithmic scales.

1. Carestream 2. Alara CR 3. Imaging Dynamics Corp and iCRo 4. Agfa- Log of Median (LgM)

What are the 4 types of proportional scales.

1. Hologic- Dose Area Product (DAP) 2. Siemans-Exposure Index (EXI) 3. GE- Detector Exposure Index (DEI) 4. Canon- Reached Exposure Value (REX)

What are the 3 types of inversely proportional scales?

1. Fuji 2. Konika Both are sensitivity numbers (S-value) 3. Philips- Exposure Index (EI)

A universal name for the exposure indicators recommended by the Americal Association of Medical Physicists is the?

Indicated Equivalent Air Kerma (Kind)

What is the standard Air Kerma unit?

Micrograys

What are the 4 recommendations for exposure indicators?

1. Base on median averaging rather than mean 2. Keep as independent as possible from a processed histogram, base as closely as possible on “raw” exposure data 3. Determine as early in processing chain as possible for higher validity and reliability 4. Use scales and units closely correlated to actual x-ray exposure (not inverted, not based on indicated processing speed, not based on systems for deriving techniques)

Who determines the acceptable range of exposures?

Management and Quality control technologists of the imaging department.

The common approach to determining ranges of acceptable exposures is to allow what?

Allow from one-half to 2 times the "ideal" or target exposure.

For a CR system that uses a lower processing speed class for extremities this technique is needed in order to provide sufficient signal to the receptor pate to avoid mottle.

Higher Radiographic Technique

These systems usually process all images at the same standard speed.

DR Systems

If there is excessive patient exposure of +1 what is the recommended action?

No repeat unless image burnout occurs from saturation. Management to follow up.

If there is over exposure to the patient of +5-+1 what is the recommended action?

Repeat only if burnout occurs.

If there is under exposure to the image of -.5 what is the recommended action?

Consult radiologist for repeat.

If there is excessive underexposure to the image of -1, what is the recommended action?

Repeat because excessive mottle is certain.

One way to adjust the contrast and brightness characteristics of an image is to re-process it under a different pre-set what?

Anatomical Algorithm

If a chest is processed as a foot what will the image look like?

Shows increased gray scale and improved detail.

If a chest is processed as an abdomen what will the image look like?

Show poorer detail.

This provides the best results for the great majority of images.

Default Processing Settings

When windowing of brightness and contrast is applied to an image and then it is saved into the PAC system, the range of windowing available to the radiologist is always what?

Narrowed

The loss of data from saving a re-windowed image is reflected in the histogram in what way?

By a shallower slope on the gray scale curve

In a Fuji System, S is what?

Originates as exposure indicator, adjusts brightness

In a Fuji System, L adjusts what?

Adjusts image latitude or gray scale level

As used in CT, MRI, and Angiographic imaging window level refers to what?

How dark the image is

As used in CT, MRI, and Angiographic imaging window width refers to what?

How long the gray scale is.

Increasing brightness is opposite to increasing what?

Window Level

Increasing contrast is opposite to increasing what?

Window Width

These can be used to suppress moderate amounts of mottle in the image.

Smoothing algorithms

This represents substantial underexposure which may include a loss of small details.

Severe Mottle

Smoothing algorithms will not recover lost information due to what?

Underexposure

What are smoothing algorithms sometimes called?

Noise Compensation

For an image already suffering from low contrast, smoothing may do what to the overall quality of the image?

Degrade

This reverses blank areas around he image to black border, reduces extraneous glare, improving apparent contrast.

Dark Masking

This reverses the image to "black on white" and produces no new information in the image but can make some details subjectively more apparent.

Image Reversal (Black Bone)

This zooms or reduces/expands features re-map image onto a smaller or larger matrix, it is automatically done to initially fit the display monitor.

Resizing

For scoliosis series, 3 CR plates can be exposed with a single exposure using a special wire mesh____.

Alignment Grid

This software accurately aligns the resulting images for a scoliosis series, using the grid to form a single body length image.

Image Stitching

DR has the same capability for scoliosis series as CR but it uses what?

A moving detector and only requires 2 exposures.

These should be balanced such that the number of details present in the image is maximized, and there is sufficient visual differentiation between adjacent details

Contrast and Gray Scale

All pixel brightness levels within the anatomy of interest should be neither completely white nor pitch black, but should possess an intermediate shade of gray along a broad range from very light to very dark gray is what?

Brightness

This is the maximizing penetration of the signal to reach the image receptor as well as minimizing mottle, electronic noise, and all other forms of noise.

Signal to Noise Ratio

To ensure adequate penetration of the signal sufficient what must be used?

High kVp

What tool is useful to evaluate the level of image mottle and other noise?

Magnification Mode (zoom)

The maximum spatial frequency should be aparent in electronic images with at least 8 LP/mm for static images and at least 6 LP/mm for digital fluoroscopy.

Spatial Resolution

Spatial Resolution is also called what?

Sharpness of Detail.

What 4 things are spatial resolution dependent upon?

1. Geometrical factors 2. Digital Processing 3. Vertical or Horizontal resolution of the display monitor 4. Zoom (magnification) Level

All of these must be absent.

Artifacts

This must be minimized such that accurate representation of the anatomy of interest is acheived

Distortion (shape and size)

What is distortion entirely dependent upon?

Geometry of original Projections

_____ of the digital image should not be so extreme that the image becomes pixelly where individual pixels become apparent and sharpness of detail is lost.

Magnification (size Distortion)

This uses high pass filtering improving image sharpness.

Edge Enhancement

This uses low pass filtering bringing out fine bony detail.

Smoothing