signal dropout
Loss of MRI signal in specific tissue regions due to technical or physiological factors.
Full Definition
Signal dropout refers to the complete or partial loss of MRI signal intensity in localized areas of an image, resulting in dark or absent signal regions where tissue should normally be visible. This phenomenon can occur due to various factors including magnetic susceptibility differences at tissue interfaces (particularly near air-filled sinuses or metallic objects), motion artifacts, RF coil positioning problems, or technical sequence limitations. In neuroimaging, signal dropout commonly affects the orbitofrontal cortex, temporal poles, and brainstem regions in echo planar imaging sequences. Recognition of signal dropout is important to distinguish it from true pathological signal loss and to assess image quality for diagnostic interpretation.
Usage
Usage note: Use 'signal dropout' as a compound noun; avoid 'drop-out' hyphenated form in medical contexts.
In Context
- "Significant signal dropout in the orbitofrontal region limited evaluation of the anterior temporal lobes." — Image quality assessment
- "The apparent lesion in the brainstem was determined to be signal dropout rather than true pathology." — Diagnostic interpretation