CBCT Artifacts | Basic CBCT| CBCT basic understanding | Cone beam computed tomography

Summary

This dental radiology video explores the various artifacts that can affect CBCT image quality, categorizing them into inherent, procedural, introduced, and patient motion artifacts. It explains how physical limitations, such as X-ray geometry and image reconstruction methods, contribute to inherent artifacts like cone beam artifacts and quantum noise. Procedural artifacts stem from under sampling and scanner issues, leading to misregistration and distortion. Introduced artifacts are caused by beam hardening, resulting in cupping and streaks. Lastly, patient motion artifacts can cause data misregistration, appearing as shading or streaking. The video also offers tips to minimize these artifacts for clearer dental imaging.

Takeaways

• 🌟 Dental radiology image artifacts in CBCT can be categorized into inherent, procedure-related, introduced, and patient motion artifacts.
• 🔍 Inherent artifacts stem from physical limitations such as the geometry of the X-ray cone, its trajectory, rotational arc, and the image reconstruction method of the software.
• 📈 Quantum noise, or strict artifacts, and the cone beam effect are examples of inherent artifacts that can degrade image quality.
• 📊 The partial volume artifact occurs in both CT and CBCT, where a single voxel contains multiple tissue densities, leading to an averaged, inaccurate representation.
• 🛠 Procedural artifacts can result from under-sampling, causing misregistration and streaking artifacts, or scanner issues leading to circular artifacts.
• 🌀 Beam hardening artifacts occur when the X-ray beam's energy changes after passing through dense objects, causing distortions in the image of metallic structures.
• 🏥 To mitigate beam hardening artifacts, adjust the field size, modify patient positioning, or separate the dental arc to avoid scanning metallic dental implants or restorations.
• 🚫 Removing metallic objects like jewelry before scanning can help reduce peripheral beam hardening effects on the region of interest.
• 🏃‍♂️ Patient motion artifacts arise from movement during the scan, leading to misregistration and potential shading or streaking in the image.
• 📢 The video emphasizes the importance of understanding and managing these artifacts to ensure accurate diagnostic imaging in dental radiology.

Q & A

What are the main factors that affect CBCT image quality?

The main factors affecting CBCT image quality are image artifacts and distortions, which can be unrelated to the object or artificially appearing on the image but not part of the tissue being examined.

How can dental radiology image artifacts in CBCT be classified?

Dental radiology image artifacts in CBCT can be classified into inherent artifacts, procedure-related artifacts, introduced artifacts, and patient motion artifacts.

What are inherent artifacts in CBCT?

Inherent artifacts arise from limitations in physical processes due to the geometry of the X-ray, such as the cone-beam effect, trajectory, rotational arc, and image reconstruction method of the software.

What is the cone beam effect and how does it affect image quality?

The cone beam effect, or V artifact, occurs because the X-ray beam is cone-shaped and has divergence. This results in less data collection at the periphery compared to the center, leading to streaking artifact and noise at the edges of the image.

What is a partial volume artifact and how does it appear in CBCT?

A partial volume artifact occurs when different tissue densities are present in one voxel, causing the final density displayed to be an average rather than the real density of the individual tissues.

What are procedure-related artifacts and how do they occur?

Procedure-related artifacts include under sampling artifacts and scanner-related artifacts. They occur when there is a large interval between projections or sections, causing misregistration of data and visible artifacts like fine hypodense and hyperdense strips.

What is a circular artifact in CBCT and what causes it?

A circular artifact in CBCT is caused by a detector being out of calibration, resulting in a constantly reading error at each angulation of the tube, which manifests as a circular pattern in the image.

How does beam hardening affect CBCT images?

Beam hardening occurs when the X-ray beam passes through dense objects, causing lower energy photons to be absorbed and the mean energy to increase. This can result in artifacts such as distortion in the image of metallic structures and dark streaks between dense objects.

What are introduced artifacts and how can they be reduced?

Introduced artifacts include cupping artifact, streaks, and dark bands caused by beam hardening. They can be reduced by adjusting the field size, modifying patient position, or separating the dental arc to avoid scanning regions with metallic objects.

What are motion artifacts and how do they appear in CBCT images?

Motion artifacts are caused by patient movement during the scan, leading to misregistration of data and appearing as shading or streaking in the image, sometimes causing a double contour of bones.

Why is it important to remove metallic objects before scanning in CBCT?

Removing metallic objects like jewelry before scanning in CBCT is important to reduce peripheral beam hardening effects that can superimpose on the region of interest and degrade image quality.