Digital Radiography: Image Processing, Artifacts, and PACS

Expanding the digital grayscale to visible describes

window and level

A wraparound image or image aliasing artifact, occurs when what happens

failure to over sample digital signal

Ghosting on CR phosphors can be remedied by

primary erasure

This image artifact is the result of

dropped detector

The longer an image is stored in the CR cassette, the

more energy is lost by the active layer of the phosphor

As SNR increase, noise ________, but exposure ___________ to the patient

decreases; increases

Accentuation of the interface between different tissues and applies for high-pass filtering is

edge enhancement

The process of optimizing image appearance for better detecting pathology that can also have potential ethical ramifications

post-processing

Data collected within the collimated field on digital radiographic images are represented by a graphical representation known as a

histogram

______________ compression up to 2:1 generally is considered acceptable in digital imaging management

lossless

The difference between the K tgt and K ind in relationship to detector exposure recognition is known as the

deviation index

___________________ in digital imaging is directly related to the bit depth of the pixels in the image

contrast resolution

Also known as low pass filtering, this process of averaging the frequency of each pixel with surrounding pixel values to remove high-frequency noise is known as

smoothing

True/False: Dose creep, or the term Dr. Bushong prefers, technique creep, describes a needless overexposure to patients because of carelessness or more ability for post processing

true

Modality that generates the largest image file at approximately 200 MB and not a perfect choice for compression

mammography

What is the reason for this artifact

Nyquist Failure

The more manipulation of the image, the greater the

loss of information

True/False: the shape of the histogram is anatomy specific

true

Smaller pixels and larger matrix equals higher

detail

What preprocessing function will correct DR image lag

offset correction

FFS and OID affect image sharpness in which imaging systems

both film/screen and digital

Averaging the frequency of each pixel with surrounding pixel values to remove high-frequency noise is called

low pass filtering (smoothing)

In an effort to display the pixels for the area of interest when exposure is greater or less than what is needed to produce an image, __________ occurs

automatic rescaling

Loss of detail in a digitally processed image is the direct result of

the number of conversions

Gadolinium Detectors are also known as ____________ phosphors

unstructured/turbid

Which of the colors demonstrates a digital image

orange

What are the improvements made by virtual grids in comparison to standard grids

decreased dose and decreased artifacts

True/False: contrast improvement is no different between a standard grid and a virtual grid application

true

According to the AAPM, digital images should be repeated when they are ______% overexposed

25-30

True/False: Cesium Iodide Detectors and Gadolinium Oxysulfide detectors demonstrate the same DQE

false

In digital radiography, what is the controlling factor of contrast

LUT

Spatial Resolution of DR Units are affected by

detector material, pixel size, and material thickness

________ refers to the ability of the digital system to display subtle changes of gray

contrast resolution

According to the ACR, digital radiography monitors used for diagnotic purposes should be checked

monthly

What are the advantages of PACS in relationship to its acronym?

Picture Archiving and Communication System in healthcare: all components used to house, transfer, and manipulate a medical image (5 year storage)

What type of reading should the radiologists perform during downtime of the PACS system?

preliminary

The purpose of keeping a log of the reason for PACS/MIMPS system downtime is to

provide records of issues that would justify replacement or necessary additional service to PACS/MIMPS

A preprocessing calibration technique designed to make the response of the IR uniform

offset and gain images

_____________________ is the imaging system's ability to distinguish the adjacent structures separate from each other

spatial resolution

Which curve response demonstrates the most latitude

Film B

Refers to the ability of the digital system to display subtle changes in the shade of gray

contrast resolution

True/False: Systems with higher quantum efficiency can produce higher quality images at a lower dose

true

True/False: dynamic range of the image is the ability of the detector to respond to varying levels of exposure

true

True/False: Histograms are based on the initial 50 exams processed and will not be updated as new images from that detector continue to be processed

false

True/False: Phosphor layer thickness and pixel size determine resolution in a Photostimulable Phosphor

true

True/False: In PSP's, the thicker the phosphor layer, the higher the resolution

false (thinner phosphor limits the lateral spread of light and XR interactions)

True/False: Digital Image receptors are less sensitive than screen film radiography to scatter radiation

false

True/False: Loss of signal in digital imaging can result in quantum mottle

true

True/False: In reference to MIMPS , multiple radiologists can open the radiographic study at the same time with the intent to read it

false

Which of the below is not used to test digital monitor quality

SEMTE pattern

Which of the following is required for diagnostic Mammography monitors

2048 x 2560 (5K)

Measures how efficiently an imaging system converts photons into image data, considering system quality and noise

DQE

Refers to the range of light intensities that an imaging system can capture or display, from the darkest shadows to the brightest highlights

dynamic range

Refers to how much information each pixel can store, affecting how finely an image can represent colors and brightness levels

bit depth

How forgiving the system is to exposure errors, meaning how much variance in exposure can occur without creating a poor-quality image

exposure latitude

Brief definition of histogram equalization

enhances contrast by redistributing pixel intensity

Brief definition of windowing and Leveling: Adjusts contrast and brightness for better visualization of specific

Brief definition of noise reduction: Removes random noise from the image to improve

Brief definition of image stitching or reconstruction: Combines multiple slices or images into a single composite view for better

What quality measures occur moving from a gdox detector to a CSI detector?

superior image quality, higher resolution, and better dose efficiency

What is quantitative imaging?

the extraction of quantifiable features from medical images for the assessment of normal or the severity, degree of change, or status of a disease, injury, or chronic condition relative to normal

Explain the Nyquist Theorem

To accurately capture a signal, you need to sample it at a rate at least twice its highest frequency

What is actually happening when you change window level?

Adjusts the brightness and

contrast of the image by shifting the midpoint of the displayed grayscale values, making

the image appear lighter or darker overall

What is actually happening when you change window width?

Range of pixel values

What is another name for low-pass filtering?

Smoothing or blurring

Why does the 15% rule have more impact and application now than it ever has in the history of radiography?

Improved image quality with workload and speed, advances in digital imaging systems, and ALARA

What is happening when window width is widened?

the window is opened to utilize more shades of gray, and the image becomes less black and white with more grays

When high-pass filtering is applied to a completed image

the edges are sharpened, becomes more noisy, and the edges are enhanced

The bright, white light flash at the end of PSP processing is most like which of the following pre-processing techniques in FPD imaging?

lag correction

Dose creep is caused by which of the following?

LUTs can "fix" overexposure, but not underexposure; X-ray techs are influenced by wanting to avoid repeat exposures; lack of initial training for X-ray techs when digital was introduced; and radiologists' lack of understanding of the physics of digital imaging

The difference between Dynamic Range and Bit Depth can be described by

which of the following?

Dynamic Range describes the possible grays available in a digital system; Bit Depth describes the number of grays available in a pixel; Neither can be changed by mAs and kVp

What is depicted in these images (moving entire window)?

a change in window level

What is depicted in these images (changing the size of the window)

window width

Which of the following describes Exposure latitude?

the combinations of mAs and kVp that can produce a diagnostic image

Narrowing the window will decrease the shades of gray available. This ________ contrast

increases

Widening the window will increase the shades of gray available. This ________ contrast

decrease

This represents which post-processing tool

smoothing

Which of the following DQEs would indicate that no information was lost between the image detector and the resulting image?

1

What is responsible for the similarities in contrast between these 4 images that were created with different mAs?

LUTs

What idea best describes the danger exhibited by the above images?

increase patient dose

Data collected within the collimated field on digital radiographic images are represented by a graphical representation known as?

Histogram

A histogram displays the useful signal by locating what signals?

Minimum (S1) and maximum (S2) signals

What factors could contribute for pixel values to not be recognized, affecting the Deviation Index?

Hip prosthetic, shielding in the image, or failure of collimated border to be recognized

Target equivalent (Ktgt) is

a program from either the user or the manufacturer that represents the target exposure for each specific anatomical region

Indicated equivalent (Kind) is - a measurement of the radiation that was incident on the IR for a particular exposure; simply a value that aids in determining if an IR has been over- or underexposed for that particular anatomy

Raw data used to form each image histogram are referenced with what?

Normal range of each of those parts/previous histograms

Loss of detail in a digitally processed image is the result of what?

The number of conversions

What is Dynamic range?

The range of various X-ray intensities that can be imaged by the detector; describes the range of light a detector can capture without losing detail

What is Contrast Resolution?

the ability of the digital system to display subtle changes in the shade of gray

Contrast resolution in digital imaging is directly related to

the bit depth of the pixels/matrix in the image

What is DQE dependent on?

Radiation exposure, spatial frequency, MTF, and detector material

What is the advantage of detectors with a higher DQE?

they produce higher quality images at a lower dose

What detectors have the highest DQE and why?

amorphous selenium detectors because they do not have the light conversion step

The longer an image is stored in the computed radiography (CR) cassette, what will the result be?

Energy is lost (25% of stored energy lost in 8 hours)

A wraparound image or image aliasing artifact occurs when what happens?

the anatomy extends beyond the borders of the image receptor, causing the anatomy to appear on the opposite side of the image; occurs when spatial frequency is greater than Nyquist frequency

What is automatic rescaling and what is its relationship to exposure factors?

Preprocessing to alter image appearance for the purpose of improving image contrast; images are produced regardless of exposure amount

What would be the result it the event that an image has been manipulated/over manipulated?

Loss of information/decreased image quality/create artifacts