When MRI Image Quality Is Reduced by Artifact

A limitation in the scan is not necessarily a problem in your body

MRI reports sometimes begin or end with language that sounds uncertain: image quality is reduced by artifact, within the limits of the study, or the examination was incomplete. These statements can be unsettling, especially when the report also describes a disc, joint, or gland as normal or abnormal.

Often, however, the caution reflects a technical limitation of the images rather than uncertainty about your symptoms. Radiologists document these limits so that the clinician reading the report knows which areas were seen clearly, which were partly obscured, and whether an important question remains unanswered.

A report can be reliable for one body part or finding while being limited for another. The key question is not simply whether artifact was present, but whether it affected the area that mattered.

What does “artifact” mean on an MRI?

An artifact is a feature on an image that does not represent the body’s actual anatomy. It can appear as blur, distortion, signal loss, duplicated edges, or streak-like changes. Artifacts may come from metal, movement, blood flow, breathing, scanner settings, or other technical factors.

Some artifacts are minor and do not interfere with interpretation. Others hide a specific structure. The report should ideally describe both the cause and its effect, such as reduced evaluation of tissues near a hip implant.

Metal-related artifact

Metal can disrupt the magnetic field and distort nearby MRI signals. A hip replacement, spinal hardware, dental work, surgical clips, or other implanted material may produce a dark or blurred region. The effect is usually strongest close to the metal.

For example, a lumbar MRI may state that image quality is reduced by artifact from a metal hip replacement and then describe the visible spinal discs. This does not automatically make every disc finding unreliable. Upper or central portions of the lumbar spine may remain well seen, while the lower spine, pelvis, or tissues closest to the implant may be harder to assess.

Radiology teams can sometimes reduce metal artifact by changing sequences or scanner settings. In some situations, another imaging method may answer the clinical question better. The presence of an implant must also be reviewed for MRI safety before scanning; image artifact and implant safety are related but separate issues.

Motion artifact

MRI sequences take time to acquire. Moving a knee, shifting position, swallowing, breathing, or being unable to remain still because of pain or anxiety can blur the images. Motion may affect only a few sequences or much of the examination.

A knee report might say that its conclusions are made within the limits of the study because of motion. This wording means the radiologist interpreted the available images but could not evaluate everything with the usual confidence. A recommendation to repeat the MRI later may be intended to obtain clearer images, monitor an uncertain finding, or both. A suggested interval such as three months is specific to that clinical situation and is not a general rule for motion-limited scans.

Does an open or low-field MRI change image quality?

MRI field strength is measured in Tesla. Some open MRI systems use a lower magnetic field than commonly used closed scanners. Open designs can be more comfortable for people with claustrophobia, larger body size, pain, or difficulty fitting into a conventional scanner.

Lower-field imaging may provide less signal or fine detail for certain examinations, although image quality also depends on the scanner design, coils, sequences, body part, and protocol. A scan should not be dismissed solely because of its field strength.

A report from a 0.33 Tesla open MRI might include a footer stating that printed images are not suitable for reporting and that the images on the CD should be used. This usually describes the limitations of the paper printouts, which may contain selected, compressed, or lower-resolution pictures. It does not necessarily mean the original digital examination was unusable. Radiologists generally interpret the full digital image set, where brightness, contrast, magnification, and individual slices can be adjusted.

What an interrupted contrast examination can and cannot show

Some MRI studies include images before and after an injected contrast agent. Certain examinations, including pituitary MRI, may use rapid or dynamic images during and immediately after injection. These sequences can help show how a small structure or lesion enhances over time.

If a patient stops the examination during the injection, the radiologist may still report the completed sequences as unremarkable. That conclusion applies only to the images obtained. If the dynamic series or other post-contrast images are missing, the examination may be unable to answer the original question fully, particularly when looking for a subtle abnormality that is best seen with contrast timing.

An incomplete exam is therefore different from a completed normal exam. It also does not mean an abnormality is present. It means that some intended evidence was not collected.

Common limitation language translated

• “Image quality is reduced by artifact”: Part of the image is blurred, distorted, or obscured. Look for wording that identifies the affected region.
• “Evaluation is limited by motion”: Movement lowered the clarity of one or more sequences. Small or subtle findings may be harder to assess.
• “Within the limits of the study”: The conclusions are based on what could be evaluated, but confidence is not the same as it would be in an optimal examination.
• “Clinical correlation is recommended”: The images should be considered alongside symptoms, examination findings, and other tests. This phrase does not by itself mean the scan must be repeated.
• “Printed images are not for diagnostic use”: Paper copies are not adequate for formal interpretation; the original digital files remain the relevant images.
• “Examination terminated” or “study incomplete”: Planned sequences were not obtained. The report should identify what was available and what limitation remains.

How clinicians decide whether a repeat is needed

Not every limited MRI needs to be repeated. The decision depends on the original clinical question, the location of the artifact, the importance of the missing sequences, and whether the visible findings already provide an answer.

A repeat or different test may be considered when:

• Artifact hides the exact structure responsible for the symptoms being investigated.
• Motion prevents assessment of a ligament, nerve, small lesion, or other key feature.
• Required contrast or dynamic sequences were not completed.
• The report directly recommends follow-up imaging.
• Symptoms and examination findings remain concerning despite a technically limited scan.

By contrast, repeating an MRI may add little when the limitation is outside the area of concern or when the needed anatomy is still clearly visible. The radiologist’s impression, rather than the artifact warning alone, usually gives the best summary of what can be trusted.

When to talk to your doctor

Ask your clinician to review which body region was limited, whether the report answered the original question, and what any recommended follow-up is intended to clarify. Prompt discussion is especially important if symptoms are worsening or new neurological symptoms develop. This article provides general education and cannot diagnose a condition or determine whether any individual scan should be repeated.