Production: QA/QC, Image Quality, & Digital Artifacts

Quality

A term that refers to a standard that healthcare institutions should abide by

The Joint Commission (TJC)

Accredits most healthcare institutions

Why is accreditation important?

It is voluntary but necessary to obtain medicaid certification, hold certain licenses, obtain insurance reimbursements, and receive malpractice insurance

Quality Assurance (QA)

A plan for the systemic observation and assessment of the different aspects of a project, service, or facility to make certain that standards of quality are being met

Quality Control (QC)

Part of the QA program; A comprehensive set of activities designed to monitor and maintain systems that produce a product. These activities are required by law to maintain the license for the room or department

QC activities

Ensures that procedures are performed safely, appropriate for the patient, performed efficiently, and produces a high-quality image to be read

QA vs QC activities

• Patient shielding: QA

• Image interpretation: QA

• Collimator light: QC

• PBL: QC

• Patient satisfaction surveys: QA

• Radiation monitor readouts: QA

Continuous Quality Improvement (CQI)

Focuses on the process rather than the people or the service. The belief is that is the process is good, the people will follow it and the service will then be good

QA/QC vs CQI

QA/QC programs focus on maintaining a certain level of quality, not necessarily improving to a higher quality. CQI focuses on improving the process or system in which the people function as a team rather than on the individual’s work

10 step quality assurance program

1. Assign responsibility

2. Delineate scope of care

3. Identify aspects of care

4. Identify outcomes that affect the aspects of care

5. Establish limits of the scope of assessment

6. Collect and organize data

7. Evaluate care when outcomes are reached

8. Take action to improve care

9. Assess and document actions

10. Communicate information to organization wide QA programs

Organizations that monitor or create QC standards

American College of Radiology (ACR), American Association of Physicists in Medicine (AAPM), and The Joint Commission (TJC)

Major categories of QC tests: Acceptance testing

Performed before newly installed equipment or when equipment has major repairs. This testing is performed by a designated tech, radiation physicist, or service personnel employed by the facility

Major categories of QC tests: Error maintenance

Performed when errors occur in equipment performance. Errors are detected by poor equipment performance or poor quality outcomes. This testing is performed by service personnel employed by the vendor

Major categories of QC tests: Routine (preventative) maintenance

Performed to ensure the equipment is performing as expected. This testing may be performed every few months by a tech, a radiation physicist, or a service personnel employed by the vendor

Physicists responsibilities of QC programs

Test filtration, collimation, focal spot size, kVp, exposure timer accuracy, exposure linearity, exposure reproducibility, and protective apparel

AAPM

Established a set of QC parameters to be followed for photostimulable phosphor systems

Beam alignment and collimator accuracy QC test

Performed semiannually. A bead is in each end of the cylinder. If it doesn’t line up exactly, the collimator is not accurate. The accepted range is within greater or less than 2% of the SID

Exposure timer accuracy QC test

Performed annually. A tool is exposed and it measures the time compared with the time of the exposure from the machine. The accepted range should be greater or less than 5% > 10ms, or greater or less than 20% < or equal to 10ms

Total beam filtration (HVL) QC test

Performed annually. This test verifies that the low energy photons are removed, but it is not a direct measure of total filtration. A beam is filtered by a glass envelope, a mirror, a plastic underside on the collimator, and any added filtration. All equipment operating at or above 70 kVp must have 2.5 mm of Al equivalent

Determining HVL

By plotting the thickness of aluminum attenuators that are added to the beam compared to the resulting exposures

Focal spot size QC test

Performed annually. The focal spot area is the surface area of the anode that is bombarded by the electron beam. Radiography machines range from 0.6-1.5mm. The focal spot size test limits are greater or less than 50% of the original specifications

Process of assessing the effective focal spot size

A resolution test pattern is used. The cylinder sits about 6 inches from the surface. You must count how many line pairs that are clearly visible. A star test pattern is another type of resolution tool, but it is more difficult to read. This is a qualitative test since it does not measure the true size of the focal spot

Slit cameras

A tool used to measure the focal spot size. The camera can actually see the physical focal spot on the anode, therefore it is much more accurate than the other tools

Exposure reproducibility (radiation output) QC test

Performed annually. The same results are attained every time the same exposure factors are used. The test must be within 5% of the kVp that was selected on the control panel

Exposure linearity (reciprocity) QC test

Performed annually. Different combinations of mA and time produce the same exposure. The test must be within 10% of the kVp that was selected on the control panel

Distance QC test

The actual distance must match what the automatic display shows. A tape measure is used for this test. The distance must be within 2% difference of the displayed distance to the actual distance.

AEC QC evaluation test

Evaluated by exposing an image receptor through various thicknesses of aluminum. Regardless of the material thickness, the brightness should always remain the same

Protective apparel QC test

Lead aprons are inspected annually by using fluoroscopy equipment

Fluoroscopy exposure rate

The exposure rate should not exceed 100 mGy per minute. It is determined by a radiation dosimeter

Society of Motion Pictures and Television Engineers (SMPTE)

Established a test pattern and performs tests at least monthly

Monitors

Often the weakest link. Not all monitors used in radiology are of high quality. Radiologists have monitors with the highest resolution. Monitors have a direct effect on the quality of the image because of pixels

Monitor tests

Performed daily, monthly, and quarterly by a trained tech or physicist. Initial and annual tests are performed by physicists to evaluate distortion, reflection, luminance, and resolution

Geometric distortion

A displayed image that is geometrically different from the original image. The displayed image should not be over 5% variation, and the borders and lines of the pattern should be clear and straight

Monitor reflection

The generation of mirror images of light sources surrounding the monitor

Monitor luminance

A measure of the luminance response and uniformity of the monitor. A photometer is used to measure the luminance on the center. 5 readings should be in 30% of one another

Monitor resolution

Evaluated in terms of visibility. The center and 4 corners (5 total) should appear the same

Artifacts

Any undesirable objects on the processed image other than those caused by scatter and fog. Artifacts interfere with accurate diagnosis

Image receptor artifacts

Dust, dirt, scratches/lucent cracks, pixel malfunctions, and ghost images

Software artifacts

Histograms, range/scaling, and image compression

“For processing” images

Raw data

“For presentation” images

Raw data that has been manipulated

Interpolation

Used for preprocessing in case of defective pixels

Flatfielding

Used to equalize the response of each pixel to a uniform x-ray beam

Image compression

Performed to reduce the size of image files produced so the image can be transmitted easier. Consists of lossless compression and lossy compression

Loseless image compression

An image data file can be reconstructed to be exactly the same as the original image. It reduces the data file to 10% (10:1) to 50% (2:1)

Lossy image compression

Can be used on images in which exact measurement or fine detail is not required. It reduces the data file to 100:1 or greater

Histogram

A graph of the frequency of digital values. The Y axis is the number or amount. The X axis is the digital value (the density or brightness of each pixel)

Object artifacts

Patient positioning, collimation/partition, and dark line backscatter

Object artifact: Collimation/partition

Used to avoid exposure field recognition errors, which could lead to histogram errors. Proper collimation has the added value of defining the image histogram

Object artifact: Partitioning

Allows two or more images to be projected on a single image receptor. They must have clear, collimated edges and margins between each field. Partitioning recognizes even number exposures

Object artifact: Patient positioning

The body part being imaged must be centered to the IR because digital image receptors normally recognize images in the center of the IR.

What organization accredits most hospitals in the United States?

The Joint Commission

A systemic observation and assessment of different aspects of a radiology department

Quality assurance

A comprehensive set of activities designed to monitor and maintain systems that produce a product

Quality control

What is done after the installation of new equipment to determine if the equipment is performing to vendor specifications?

Acceptance testing

True or false: Continuous quality improvement tends to focus on the people or the service rather than the process

False

What device is used to measure the luminance of a monitor?

Photometer

What can be used to determine if the monitor is displaying any distortion over the display?

SMPTE pattern

True or false: Printer quality is of no importance in a digital environment

False

Which of the following is a quality control activity performed in a digital imaging environment? Image transfer speed, image processing speed, or data integrity measure

Image transfer speed, image processing speed, and data integrity measure

What CQI activity documents images that are of poor quality?

Recognition of nondiagnostic images

What organization developed the standards for acceptance testing and quality control of PSP imaging systems?

American society of Physicists in Medicine

Which of the following are daily QC duties of a technologist? Hinge and latch inspection, erasure of imaging plates, or image inspection for artifacts 

Hinge and latch inspection, erasure of imaging plates, and image inspection for artifacts

True or false: An imaging plate should be erased when it has not been used for an extended period of time

True

Which of the following are weekly QC duties of a technologist? Clean imaging plates, clean air intake on reader, or perform a reject analysis

Clean air intake on reader

True or false: The EPA regulates the disposal of PSP imaging plates

True

True or false: The physicist is responsible for performing the preventative maintenance on the digital imaging systems

False

How often does a physicist perform an accuracy test between the exposure indices and the ion chamber?

Semiannually

Which of the following should not be used to clean the PSP imaging plates? Camel hair brush, photographic lens cloth, or corrosive solution

Corrosive solution

True or false: The display monitors should be cleaned on a monthly basis

False

Whose responsibility is it to maintain the quality of digital images?

The technologist, physicist, and radiologist