signal void

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sig·nal void

in magnetic resonance imaging, a region emitting no radiofrequency signal, because there are no activated protons in the region (such as flowing blood), because a different element predominates, particularly calcium, or because of uncompensated dephasing, such as occurs at air-tissue interfaces in the lung.

signal void

A dark or blank space in a radiographic image of a fluid-filled structure. See: filling defect
See also: signal
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References in periodicals archive ?
However, a distinct flow-related signal void usually indicates a spinal AVF.
Biliary stones and biliary gas both produce signal void on MR; however, nondependent positioning suggests biliary gas.
Methemoglobin, with its shortT1 relaxation time on T1-weighted imaging, is easily identified in the membranous labyrinth because of the distinct contrast between it and the surrounding bony signal void of the otic capsule.
If present, a signal void extending from the ASA into the left atrium would also indicate an associated PFO.

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