What artifact is caused by a falsely low reading when calibration fails or a detector drifts in PET?

The artifact associated with a falsely low reading in positron emission tomography (PET) due to calibration failure or detector drift is indeed the ring artifact. This phenomenon occurs when there are inconsistencies in the detection system, such as miscalibration of detectors or variations in detector sensitivity. As a result, these issues can mimic the appearance of rings on the final reconstructed image, creating an unexpected pattern that can mislead interpretation.

The presence of these rings can distort the quantitative accuracy of the PET images, leading clinicians to make flawed clinical decisions based on inaccurate data. Understanding and identifying ring artifacts is crucial as it emphasizes the importance of regular calibration and maintenance of PET systems to ensure accurate imaging and reliable quantification of radiotracer uptake.

The other types of artifacts, although relevant in imaging, do not specifically account for the falsely low readings caused by calibration issues in PET. Beam hardening typically refers to the phenomenon where lower-energy photons are absorbed more than higher-energy photons in a material, causing artifacts primarily in CT imaging. Motion artifacts arise from patient movement during imaging, which can blur the resulting images, while noise artifacts are associated with fluctuations in the signal that contribute random background noise rather than systematic errors. Therefore, recognizing ring artifacts in the context of calibration errors underscores the