CT Ring Artifacts Explained

Everything CT technologists need to know about CT scan ring artifacts in under sixty seconds.

What Is a CT Ring Artifact?

A CT ring artifact is a visible ring pattern that appears in a CT image. It looks like a circular or oval shape with different shades of gray. These patterns can occur in both single-slice and multi-slice CT machines.

Ring artifacts in CT scans are circular or ring-like image distortions characterized by black or white edges that can degrade the diagnostic quality of images and can lead to misinterpretation or misdiagnosis.

Cause of CT ring artifacts

So, what exactly causes ring artifacts? These image distortions are produced when one or more detector channels generate spikes or dips in the scan data.

A ring artifact appears in images when image data in one or more detector channels registers outside of the system’s tolerance levels.

Common causes of CT ring artifact

The most common causes of ring artifacts in CT scans are:

• Faulty detector components
• Noisy power supplies
• Calibration errors
• Obstructions in the X-ray beam
• Physical damage to detector modules.
• Faulty X-ray tube.

Insufficient Data Acquisition

The first cause is insufficient data acquisition. This happens when the CT machine does not collect enough data during the scan. CT scans use X-rays to create images of the body. The X-ray tube rotates around the patient, and detectors measure the amount of X-rays that pass through the body. The CT machine then uses this information to create an image. If there are gaps in the data, the image will have artifacts.

Detector Malfunction

The second cause is detector malfunction. In multi-slice CT machines, there are many detectors that measure the X-rays passing through the body. If one or more of these detectors malfunction, it can cause a CT ring artifact. The affected detectors will not measure the X-rays correctly, leading to an inaccurate image.

Now the question everyone wants to know: How do you fix CT ring artifacts?

How to fix CT ring artifacts?

To resolve ring artifacts, troubleshooting and corrective action is required. This may involve removing obstructions in the path of the X-ray beam or replacing faulty detector components. After performing corrective action, the system will need to be recalibrated In order to resolve the CT ring artifact.

It is important to note that performing calibrations before addressing the underlying issue can mask the appearance of the ring artifact but will complicate troubleshooting the root cause.

If you are currently experiencing a CT scan ring artifact, here’s a few things to know:

1. Ring artifacts in CT scans may not appear on every image and often occur only with specific scan parameters selected.
2. When ring artifacts first appear (noticed), it’s useful to run test scans with DQA phantoms to assess your system’s limitations. Perform multiple test series, adjusting different scan parameters. Start by switching the focal point: if you’re using a large focal point, switch to a small one, or vice versa. Next, adjust detector configuration settings, such as slice thickness and images per rotation. You may find that only certain protocols are affected, or that all of them are. However, this quick 5-minute evaluation is invaluable for assessing current scan limitations and determining which patients can still be scanned without concerns about ring artifacts.

Troubleshooting tips

To effectively resolve a CT scan ring artifact, it is advisable to conduct a thorough examination of the patient database to identify when the artifact first appeared and track the frequency of occurrence.

Once this information is obtained, promptly notifying the CT scan service provider with these details would be the recommended course of action. By doing so, the service provider can be informed of the artifact’s history and take appropriate measures to resolve the ring artifact effectively. Short, sweet, and to the point. Follow for more.

Key Takeaways

CT ring artifacts are visible ring patterns that appear in CT images. They happen due to insufficient data acquisition or detector malfunction. CT ring artifacts can affect the accuracy of the CT scan and may require further investigation.

If you have any concerns about CT ring artifacts, speak to your CT scanner repair service provider.

If you want to learn more about CT ring artifacts, click here: Cause of Image Artifacts in CT

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