Quality Control and the ACR's MRI Accreditation Program

The zipper artifact is caused by outside RF getting inside the scanning room. What are some reasons that could be the cause of this?

- door could be open - have the wrong kind of light in the scan room - malfunction in the Faraday Cage

Low-contrast detectability

-Ability of an imaging system to discriminate small differences in physical properties -Slice used dependent on Bo field strength -Will get more contrast to noise detectability the higher the field strength -Suggestive of: reduced stability of system

What does the ACR phantom look for?

-Geometric Distortion --Slice thickness & position -Factors affecting image SNR (resolution, bandwidth, ghosting) - image uniformity

If QC test fails, what are 4 common errors?

-check for magnetic objects in bore -re-seat head coil -reposition & landmark phantom -make sure scan room door is securely closed

If a QC test fails we need to _____________

-repeat QC procedure -record data and report problems to service -have service record problems and solutions in a service log

To pass the ACR quality control, for a 1.0mm spatial resolution, you want to make sure you see _____ dots in the vertical direction and ______ dots in the horizontal direction.

4 and 4 - this shows we have high contrast, high resolution detectability

What does ACR stand for and what is its purpose?

American College of Radiology - its purpose is to help assure your patients that you provide the highest level of image quality and safety by documenting that your facility meets requirements for equipment, medical personnel and quality assurance.

What is quality control?

Deals with techniques that we use in maintenance and monitoring of the MR technical systems. Example: Think of the gradients and the inhomogeneities and make sure they are functioning within a certain parameter so the quality stays the same.

To have a successful MRI QC program, technologists need to run QC scans on a daily basis? True or False?

False - need to be run on a weekly basis, however daily is recommended.

If you get a geometric accuracy failure from phantom mispositioning, you need to _______________

Go in and reposition your phantom. Make sure its level and sitting within the coil evenly.

What is geometric accuracy?

It measures distance along main axes of phantom and compares with known values.

Who is the measurement of central frequency performed by?

MRI technologist

Who's responsible for the routine visual inspection of equipment?

MRI technologist

Who's responsible for weekly quality control of hard copy and soft copy images?

MRI technologist

Who's responsible for weekly magnetic resonance image quality control procedures?

MRI technologist - (daily is recommended but weekly is mandated)

Is it the MRI tech's responsibility to get MRI accredited?

No

Not all hydrogen processes in the same frequency due to it not always being "free" hydrogen. It is bonded to different molecules which shield it from the magnetic field more or less and we get a slightly different ____________?

Processional frequency

Who is responsible for MRI equipment performance review and perform acceptance testing (baseline measurements)?

Qualified medical physicist or MRI scientist

Who is responsible for setting up daily/weekly QC tests?

Qualified medical physicist or MRI scientist

Who is responsible for writing purchase specifications and determining action limits?

Qualified medical physicist or MRI scientist

Who's responsibility is it to arrange staffing and scheduling so that quality control tests can be carried out?

Radiologist

Who's responsibility is it to ensure that an effective quality control program exists for all MRI?

Radiologist

Who's responsibility is it to ensure that appropriate test equipment and materials are available to perform the technologist's QC test?

Radiologist

Who's responsibility is it to select a qualified medical physicist or MRI scientist to ensure that records are properly maintained and updated in the MRI QC procedures manual?

Radiologist

Who's responsibility is it to select the technologist to be the primary quality control tech?

Radiologist

If a QC test fails, what should you do?

Repeat daily QC scan procedures and record results again in the QC notebook.

Why is ACR important?

So that we can create uniform quality scanners all over the United States.

What is Transmitter Gain/Attenuation?

The attenuator controls the gain of the amplifier so that the proper current and voltage are sent to the coil to generate a B1 field of appropriate magnitude.

What is the ACR phantom?

The phantom body is marked with a NOSE and CHIN to aid in orienting the Phantom for scanning. Inside of the Phantom are various fixture used to facilitate testing of scanner performance.

What are these tests and who is responsible for them? -Center frequency -Table positioning -Setup & Scanning -Geometric accuracy -High contrast resolution -Low contrast detectability -Artifact analysis -Visual checklist

These are weekly quality control tests done by the MRI technologist

Why is it important to measure the central frequency over time?

To make sure the scanner is working properly and has no magnetic drift, and is staying homogenous over time. We need to document it so that if we see that something is changing, we need to call to have it serviced and make some adjustments.

What reflects power required to optimize RF pulse? It depends on coil, phantom, pulse, sequence, etc. and should remain constant over time if nothing in pulse sequence or hardware has changed.

Transmitter Gain/Attenuation

According to the ACR MRI Accreditation Program, you have to agree to use the ACR MRI phantom. This is to ensure that your scanner is good. Also need to agree to provide all documentation requested by the survey team. True or False?

True

Inhomogeneities or something that creates the field to be uneven in any way is going to cause a lot of different failures on the geometric accuracy test. True or False?

True

The measurement of Central Frequency is the frequency at which the hydrogen protons are processing & majority of water within the body. True or False?

True

The qualified medical physicist or MRI scientist is responsible for annual survey tests such as: -slice position accuracy -slice thickness accuracy -radio frequency coil checks -inter-slice RF interference -soft copy displays (monitors) True or false?

True

Because we get a slightly different processional frequency due to hydrogen being bonded to different molecules, we tend to center on ____________

Water

For high contrast resolution, if there is a reduction in # of holes seen, this is suggestive of ____________ (select all that apply) - increased eddy currents - poor gradient calibration - poor Bo uniformity - reduced stability of system - all of the above

all of the above

What is the ACR MRI Accreditation Program?

evaluates staff qualifications, quality control, MR safety policies and image quality.

These are potential causes of ______________ failures. -phantom mispositioning -gradient miscalibration -inhomogeneity -gradient non-linearity -inappropriate receiver bandwidth -poor eddy current compensation -combo of two or more above

geometric accuracy

Water is really close to ________________ processions which is why we center on water.

pure hydrogen

Who is responsible for overseeing the equipment quality control program? - qualified medical physicist - the MRI technician - medical doctor

qualified medical physicist

The ACR phantom is a short scan that must be done at least _________ to comply with ACR standards. - daily - weekly - monthly - yearly

weekly