How to Evaluate a SMPTE Pattern
What is a SMPTE pattern?
SMPTE is an acronym that stands for the Society of Motion Picture and Television Engineers. It’s a test pattern used in medical imaging to evaluate the quality of the imaging monitors.
Watch the video above on our YouTube channel as Eric walks you through how to evaluate a SMPTE pattern when completing your monthly visual quality control checklist for CT scanners.
So, why is this important to understand?
First, visually inspecting the SMPTE pattern can identify any problems with the quality of the imaging monitor. As a radiologic technologist, it’s critical that the monitor is providing consistent and accurate results.
Second, checking the SMPTE pattern on a CT scanner is part of the monthly visual quality control checklist for the scanner required by the ACR or the American College of Radiology.
On page 48 of the ACT CT Quality Control Manual, available here, they provide the specific procedures for testing the gray level performance of CT scanner acquisition display monitor.
You can also download the ACR CT Equipment Quality Control Data Form to record your daily and monthly inspections.
What do you need to look for?
There are three main areas to visually check when inspecting the SMPTE pattern on the imaging monitor.
1. The 5% patch
You want to be able to clearly identify the 5% patch within the 0%-5% square, ensuring it’s discernible.
The 5% patch is found directly to the right of the 0% gray level box, which is solid black.
2. The 95% patch
You want to be able to clearly identify the 95% patch within the 95%-100% square, ensuring it’s discernible.
The 95% patch is found directly to the left of the 100% gray level box, which is solid white.
Each of these patches must be discernible in order to pass the monthly quality control check.
3. The gray level steps
You can identify the distinct gray level steps throughout the SMPTE pattern.
On the SMPTE pattern, you should be able to identify eleven (11) distinct gray scale boxes from solid black to solid white.
There are also two (2) boxes of 50% gray – both of these squares should be identical.
On the right hand side of the ACR CT Equipment Quality Control Data Form you will find a box for the Monthly Display Monitor Gray Level.
As you check each of the three above areas, indicate its passing with a checkmark or “P” for Pass. For a failing test, you may enter “F” for Fail.
What do you do if you can't see those patches? Or you don't have distinct grade level steps?
Here are several tips:
- Ensure you use the same lighting conditions every time you evaluate the SMPTE pattern for your monthly visual inspection.
- Ensure that the monitor is positioned so that there’s no glare from existing lighting or excessive ambient light.
- Ensure that the monitor hasn’t entered an automatic power-saver or economy mode.
- A common issue is incorrect adjustment of the monitor’s contrast and brightness settings. If you suspect this may be the case, perform the manufacturer’s recommended procedure for adjusting the monitor’s contrast and brightness.
If you’re still having issues seeing the distinct 5% and 95% patches or cannot observe the gray level steps after going through the above tips, you will want to contact your service engineer or medical physicist. They can provide recommendations on how to correct the issue. Alternatively, the monitor may need to be repaired or replaced.
Now that you understand what a SMPTE pattern, you can confidently evaluate it during your CT scanner monthly inspection.
If you have any questions or comments, we welcome you to reach out at info@olympichp.com
Also, check out our Resources page for further information on quality control documentation, forms, and manuals.
Your medical physicist is a great resource for you when designing your CT Scanner Quality Control Program. You can also always reach out to us if you have questions or want more information on CT Quality Control or want to see why you should partner with us. We also offer Annual CT Physics Testing.