More on CR (Test 2)

Artifacts

What is the unavoidable extraneous information on the image that interferes with or distracts from the image quality?

A lighter or white area on the IR in the shape of the object

How does any object on the surface of the image receptor, like hair, dust, or adhesive, result in?

Cracks due to removing and replacing the imaging plate in the reader

As the imaging plate ages, what does it become more prone to and why?

As white areas on the imaging plate

How do cracks on the imaging plate appear?

The imaging plate must be replaced

When a crack appears on the imaging plate, what must be done with the imaging plate?

Adhesive Tape

What is used to secure lead markers to the cassette?

Can leave residue on the imaging plate

What can adhesive tape leave on the imaging plate?

Static that exists due to low humidity

What causes hair to cling to the imaging plate?

Backscatter

What is created by X-ray photons transmitted through the back of the cassette?

In CR and DR

What types of digital imaging does backscatter occur in?

Dark Line Artifacts

What type of artifacts can backscatter cause?

Scatter in those weaker areas

When areas of the lead coating of the cassette are worn or cracked, what does this allow on the imaging plate?

Problems with the electronics of the plate reader

What can the intermittent appearance of extraneous line patterns be caused by?

Dirt, dust, or scratches on the light guide in the plate reader

What are the horizontal white lines that are parallel to the direction of the plate caused by?

Service Personnel

If dust or dirt is on the light guide, who needs to be called to replace it?

A residual image left on the imaging plate before the next exposure

What does an insufficient erasure setting result in?

Ghost Images

What can occur with insufficient erasure settings, and is a faint, superimposed shadow of a previous exposure that appears on a new image?

- Erasure lamp is out or in need of repair

- High mAs techniques

What are the two causes of ghost images?

A deep erasure

In CR, after x-raying a hypersthenic patient, what should be done to the imaging plate after it is processed to ensure the imaging plate is clean?

Moiré Pattern

What do incorrectly oriented grids cause?

High frequency grids (103 lpi or higher)

What type of grids do vendors suggest to prevent the moiré pattern artifact?

Grid Replacement Software

What refers to software or algorithms that produce images that improve contrast by minimizing the effect of scatter?

No physical grids

What does grid replacement software not have?

- mAs can be decreased by up to 50%

- No grid lines/grid cut off

- No Moiré artifact

What are the three ways that grid replacement software can be useful?

Grid Suppression Software

What removes visible grid lines from an image taken with a grid?

- Insufficient collimation

- Cassette backwards

- Underexposure

- Overexposure

What are the four operator errors that can occur with CR imaging?

An improper calculation of the exposure indicator

What does insufficient collimation result in?

A misrepresentation of the displayed image

What can insufficient collimation do to the displayed image?

Artifacts from any hinges or other hardware on the back of the cassette

If the cassette is exposed with the back of the cassette toward the source, what does this result in?

Quantum Mottle

What does underexposure result in?

Reduced Contrast

What does overexposure result in?

The proper selection of technical factors

What is critical for both patient dose and image quality to ensure the appropriate production of light from the imaging plate?

A repeat

What does gross underexposure require?

Repeated unless it's a gross overexposure that causes saturation

Gross overexposure should not be what?

- Exposure field recognition errors

- Histogram analysis

- Grayscale analysis

During pre-processing, what are the three things that take place?

30% and exposure field recognition errors

If the imaging plate has less than ____% coverage, what will it result in?

Pixel Size = FOV / Matrix Size

What is the pixel size formula?

Pixel Pitch

What is defined as the distance between the pixels measured center to center?

Depends on the sampling or nyquist frequency

What does pixel pitch depend on?

Spatial Resolution

With CR systems, what does pixel pitch determine?

pixel pitch

The higher the sampling frequency the higher the ________ __________

The more pixels/mm the higher the spatial resolution

The higher the sampling frequency and pixel pitch, the what?

pixels/mm

In terms of pixel pitch, how is the sampling frequency expressed?

By the sampling frequency as the laser scans the plate

How is pixel pitch determined?

To one line or pixel pitch

As the red laser beam scans each line of the imaging plate, what does it correlate to?

Smaller / better

_________ pixel pitch = __________ spatial resolution

80% / 500%; the image will look the same

If the image is less than _____% underexposed or _____% overexposed, how will the image look?

An exposure index of less than 50% of the target EI

In digital imaging, what percentage of the exposure index is considered underexposed?

Repeat the image

If an image is more than 50% underexposed, what should the technologist do to correct it?

No it should not be repeated unless the radiologist finds the level of noise unacceptable

Although an exposure index of less than 50% is considered underexposed, should it be repeated?

Dose Creep

What refers to using more technique than necessary to ensure the image can be manipulated?

As Low As Reasonably Achievable

What does ALARA stand for?

100% / ALARA

Over ____% exposure violates ________

No unless saturation occurs

Should an overexposed image be repeated?

Excessive Radiation

What is defined as 3 times the level of radiation needed to produce a diagnostic-quality image?

Saturation

What is a condition in which detector elements (dels) in a particular area of the image receptor have reached the maximum electrical charge that they can store?

dynamic range

Saturation means the expsoure has exceeded the __________ _________ of the imaging receptor

8-10 / no

Saturation is ________ times a typical radiographic technique and a saturated image has ____ detail present

Changes in kVp and mAs will still affect patient dose

Although changes in kVp have a less direct effect on final image contrast due to digital post-processing, what is still very important to remember about kVp and mAs concerning the patient's dose?

Data drop or data clipping

What are other terms that describe saturation?

Technique Creep

What is an attempt to lower patient radiation dose by instituting higher kVp and lower mas techniques that correspond to ALARA?