CT-Scan Artifacts and their Types .pptx

CT-SCAN
ARTIFACTS
PRESENTED BY :
ANKITA KUMARI
MMRIS 2ND
YEAR

WHAT IS ARTIFACT IN CT-SCAN???

 Definition: Artifacts in CT scans
are distortions or errors in the
reconstructed images that reduce
diagnostic quality and can
obscure important anatomical
details.

IMPORTANCE: Identifying artifacts helps improve diagnostic accuracy.
MOTION ARTEFACT BEAM HARDENING
NOISE ARTEFACT ALIASING ARTEFACT
A
B
N
O
R
M
A
L
N
O
R
M
A
L

CLASSIFICATION OF ARTIFACTS:
ARTIFACTS
PATIENT BASED
ARTIFACTS:-
caused by patient motion or
the presence of metal on or in
the patient
PHYSICS BASED
ARTIFACTS:-
Physics-based artifacts
are distortions or patterns in
medical images that are caused by
the physical processes used to
acquire the images.
HARDWARE &
SCANNER BASED
ARTIFACTS:-
Image irregularities caused by
issues with the CT scanner
itself.

Patient based artifacts
MOTION
ARTIFACT
OUT OF
FIELD
ARTIFACT
CLOTHING
ARTIFACT
JWELLERY
ARTIFACT

1-MOTION ARTIFACT:
Cause: Patient movement during the scan.
Appearance: Blurred or double images.
Prevention: Immobilization devices, faster scan times.

2-OUT-OF-FIELD ARTIFACT:
Cause: Anatomy extending beyond the scan field.
Appearance: Streaks or shading near image edges.
Prevention: Proper positioning within the scan field.

3-JEWELRY ARTIFACT:
Cause:presence of metallic jewelry (necklaces, earrings, piercings, rings) within or near the scan field which block or
scatter x-ray beams
Appearance: Bright streaks or starburst
patterns radiating from the jewelry.
Prevention: remove all jewelry before the
scan, especially near the area being imaged.

4-CLOTHING ARTIFACT:
CAUSE:Presence of clothing with dense or metallic components such as zippers, buttons, hooks etc.
Appearance:Bright streaks,
shadows, or irregular areas of
attenuation on CT images.
Prevention:remove all clothing
containing metal before the scan.

Physics-based Artifacts
Beam H
ardening
Partial vol
ume Avera
ging
Photon
Starvation
Aliasing
Truncation
artifact
quantum
mottle
(noise)
Metal
Artifact
Streak
and dark
bands
Cupping
Artifact

BEAM HARDENING ARTIFACTS:Occurs when low-energy x-rays are absorbed as the beam
passes through dense structures (like bones), leaving behind a harder (higher-energy) beam.
• CUPPING ARTIFACT:
• Cause:Occurs when the X-ray beam is
attenuated more at the edges of a dense
structure (like the skull) than at the center,
leading to uneven attenuation.
• STREAKING ARTIFACT:
• Cause:Caused by abrupt changes in X-ray
attenuation within the scan field.
• METALARTIFACT:
• Cause:Occur due to the presence of metal
objects (implants, dental fillings, surgical clips)
within the scan field.
Appearance:The central area of a structure appears
darker than its periphery, creating a "cupped"
appearance.
Appearance:Bright or dark lines radiating across
the image, often between dense objects. remove
metallic objects and use artifact reduction
algorithms when metal is unavoidable
Appearance:Bright streaks or starburst patterns
radiating from the metal object.
Prevention:Use beam-hardening correction
algorithms,with use pre-patient filter.
Prevention: remove metallic objects and use artifact
reduction algorithms when metal is unavoidable
Prevention:Remove external metal objects before
scanning.
• Use metal artifact reduction (MAR) algorithms.

PARTIAL VOLUME AVERAGING ARTIFACT:
Causes:-Occurs when a voxel contains multiple tissue types with different densities or
signals.
• Common in low-resolution scans or thick-slice imaging.
 Appearance:-Blurred edges and loss of detail in small structures.
• Misrepresentation of tissue density or signal intensity.
 Solution:-Use thin-slice imaging and high-resolution protocols.
• Apply multi-planar reconstruction (MPR) and optimize patient positioning.

TYPE OF PARTIAL VOLUME AVERGING ARTIFACT:
QUANTUM MOTTLE/ NOISE ARTIFACT:
 Cause:Occurs due to an insufficient number of X-
ray photons reaching the detector in CT, X-ray, or
fluoroscopy imaging.
• Often results from low radiation dose, short
exposure time, or high-speed imaging.
 Appearance:Grainy or speckled texture reducing
image clarity.
• Can obscure fine details, leading to diagnostic
challenges.
 Solution:Increase radiation dose (mAs) while
balancing patient safety.
• Use image averaging, iterative reconstruction, or lower
noise protocols.

PHOTON STARVATION ARTIFACT:
 Causes:Occurs in CT scans when X-ray photons are excessively absorbed,
especially in dense areas like bones.
• Common in obese patients, metallic implants, or thick body parts.
 Appearance:Streak artifacts, primarily in highly attenuated regions.
• Dark bands or noise in areas with insufficient photon penetration.
 Solution:Increase tube current (mA) or use iterative reconstruction.
• Use adaptive filtration or dual-energy CT to enhance image quality.

ALISING ARTIFACT:
Cause:Occurs when the sampling rate is too low, leading to misrepresentation of high-
frequency structures.
•Common in helical CT scans with insufficient projection data or rapid motion.
Appearance:Wavy, streaky, or repeating patterns in the image.
•Loss of fine details, making structures appear distorted.
Solution:Increase the sampling rate by using finer detector collimation.
•Use higher-resolution reconstruction algorithms and reduce patient motion.

HARDWARE & SCANNER BASED ARTIFACTS:-
ring artifact tube arcing out of field artifact
air bubble artifact
helical and multichannel artifact
windmill artifact
cone beam effect
multiplanar reconstruction
(MPR) artifact
stair step artifact
zebra artifact

RING ARTIFACT:-
 Cause:Results from detector calibration errors or malfunctioning detector
elements in a CT scanner.
• Occurs when certain detector channels consistently report incorrect values.
 Appearance:Concentric circular or ring-like artifacts centered around the
scanner's rotation axis.
• More noticeable in head and brain CT scans.
 Solution:Perform detector recalibration and quality control checks.
• If persistent, replace faulty detector elements or apply correction algorithms.

HELICALAND MULTICHANNELARTIFACT:-
Causes:
Helical Artifacts: Incomplete data reconstruction, pitch too high, or motion.
Multichannel Artifacts: Detector calibration errors, cross-talk between channels.
windmill artifact cone beam effect
Cause:Occurs in multi-detector CT (MDCT) when using a high pitch value in helical
scanning.
Caused by the overlap and rotation of detector rows, leading to aliasing effects.
Appearance:Repeating fan-shaped or windmill-like streaks across the image.
Most noticeable in high-contrast areas, causing distortion.
Solution:Reduce pitch value to minimize excessive interpolation errors.
Use advanced reconstruction algorithms to correct the artifact.
Cause:Occurs in multi-detector CT (MDCT) and cone-beam CT (CBCT) due to the wide
cone-shaped X-ray beam.
More prominent in scanners with more detector rows, where standard reconstruction
algorithms struggle with peripheral data.
Appearance:Streaks, shading, or distortion at the edges of the image.
Can cause blurring and inaccurate structure representation, especially in 3D reconstructions.
Solution:Use cone-beam reconstruction algorithms like Feldkamp-Davis-Kress (FDK).
Reduce cone angle or use central slices for more accurate imaging.
Windmill artefact
Windmill artefact Normal image

MULTIPLANAR RECONSTRUCTION ARTIFACT:
 Cause:Occurs when thick slices or low-resolution data are used for MPR in CT and
MRI.Results from partial volume averaging and interpolation errors.
 Appearance:Blurring, stair-step effect, or jagged edges in reconstructed sagittal or coronal
images.
• Loss of fine details, making small structures appear distorted.
 Solution:Use thin-slice imaging to improve resolution.
• Apply higher-quality interpolation algorithms to enhance reconstruction accuracy.
ZEBRA ARTEFACT

TUBE ARCING:
Causes:Electrical discharge (arcing) in the X-ray tube due to gas buildup,
oil contamination, or tube aging.
Appearance:Bright streaks, random noise, or sudden image degradation
in CT scans.
Solution:Power cycle the scanner, allow tube cooldown, and recalibrate
the system.
If persistent, replace the X-ray tube to prevent further artifacts.

Summary of Imaging Artifacts in CT
1.Causes: CT artifacts arise due to physical limitations, patient movement, hardware
issues, or reconstruction errors, affecting image quality and diagnostic accuracy.
2.Types: Common artifacts include partial volume averaging, photon starvation,
aliasing, ring, windmill, helical, multichannel, cone beam, and MPR artifacts,
each with distinct causes and appearances.
3.Appearance: Artifacts can manifest as streaks, blurring, rings, noise, or distortion,
often obscuring important anatomical details.
4.Impact: These artifacts can compromise diagnosis, misrepresent tissue densities,
and reduce the effectiveness of medical imaging.
5.Solutions: Reducing artifacts involves optimized scanning parameters (lower pitch,
higher resolution), proper calibration, advanced reconstruction techniques, and
patient positioning adjustments.

CT-Scan Artifacts and their Types .pptx

CT-Scan Artifacts and their Types .pptx

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CT-Scan Artifacts and their Types .pptx