The term “artifact” in healthcare refers to any signal, image, or result produced during a diagnostic procedure that does not truly represent the patient’s biological state or underlying disease. These false findings are generated by external interference, technical errors, or the patient’s own physical reactions during the test. Recognizing these anomalies is a fundamental skill for clinicians. A misinterpreted artifact can lead to misdiagnosis or unnecessary treatment.
Defining Medical Artifacts and Their Origin
Medical artifacts arise from three distinct categories of source, all of which interfere with the accurate reading of a test. One common source involves factors related to the patient themselves, such as movement, which can blur an image, or the presence of metallic implants and dental work that distort magnetic or X-ray fields. These patient-related issues introduce false data that the equipment cannot distinguish from the body’s own signals.
A second major source comes from the testing environment or other external factors, such as electrical interference from nearby equipment or a room’s temperature causing a patient to shiver and generate spurious signals. Equipment itself constitutes the third source, where issues like poor calibration, detector failure, or software processing errors can incorrectly generate or display data. Understanding the origin of the interference is the first step in correcting the error and obtaining a valid result.
Visual Interference in Diagnostic Imaging
Artifacts are prominent in diagnostic imaging, where they can obscure anatomical structures or mimic disease. In computed tomography (CT) scans, beam hardening occurs when the X-ray beam passes through a dense object like bone or metal, selectively filtering out lower-energy photons. This results in dark streaks between two dense objects or bright streaks around metallic implants (metallic streak artifacts), making interpretation difficult.
Magnetic Resonance Imaging (MRI) is susceptible to motion artifacts, which appear as blurring or “ghosting” across the image, even from involuntary movements like breathing or blood flow. Another common MRI distortion is the susceptibility artifact, caused by localized magnetic field distortion near materials with different magnetic properties, such as surgical clips or air-tissue interfaces. This distortion causes a loss of signal, often appearing as a dark void or geometric warping near the offending material.
Ultrasound imaging produces unique anomalies due to how sound waves interact with different tissues. An acoustic shadow artifact appears as a dark area devoid of signal deep to a structure that strongly reflects or absorbs the sound, such as a gallstone or bone. Conversely, a reverberation artifact occurs when the ultrasound beam bounces repeatedly between two highly reflective surfaces, creating bright, parallel echoes that suggest structures which are not actually present.
Distortions in Clinical Monitoring and Specimen Analysis
Artifacts frequently compromise numerical data from physiological monitoring and laboratory samples. Electrocardiograms (ECG or EKG) are often affected by muscle tremor artifacts, which appear as a rapid, erratic vibration of the baseline that can mimic a cardiac arrhythmia. Poor electrode placement or loose contact can cause a wandering baseline, where the tracing slowly drifts across the graph, potentially obscuring subtle changes in the heart’s electrical activity.
In laboratory medicine, artifacts are a common pre-analytical error that affects test results before the specimen reaches the analyzer. A classic example is hemolysis, the rupture of red blood cells, often caused by a traumatic blood draw or vigorous shaking of the sample tube. Since red blood cells contain high concentrations of potassium, hemolysis releases this content, leading to a falsely elevated potassium result, known as pseudohyperkalemia.
Specimen contamination also presents an artifactual challenge, particularly in microbiology and chemical analysis. A urine sample can be contaminated by external skin flora or vaginal secretions during collection, leading to a culture result that suggests a urinary tract infection when one may not exist. Foreign materials like textile fibers or talcum powder can also appear in microscopic analysis, requiring the technician to differentiate these items from actual pathological findings.
Recognizing Artifacts and Minimizing Misinterpretation
Identifying an artifact is a trained skill that prevents harmful clinical errors, such as misdiagnosis or unnecessary treatment. Clinicians differentiate a true finding from a false one by correlating the test result with the patient’s overall clinical presentation and history. For example, an ECG arrhythmia caused by muscle tremor will not correlate with a patient who is calm and clinically stable.
Mitigation strategies vary but often involve simple, practical steps. In imaging, this might mean repositioning the patient, ensuring they remain perfectly still, or changing the imaging sequence to one less prone to a specific type of interference. For laboratory work, reducing artifacts relies on strict adherence to proper collection protocols, such as using the correct order of draw for blood tubes or providing detailed instructions for clean-catch urine samples. If an artifact is suspected, the most direct action is to repeat the test with technical adjustments or under optimized conditions.