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 ?
Nondependent signal voids in the urinary bladder suggest air, which is only normal if iatrogenic (eg, recent Foley catheter placement or cystoscopy).
No atrial thrombi were seen and no signal voids adjacent to the atrial septum were found to suggest the presence of a patent foramen ovale (PFO).
A patent lumen with rapidly flowing blood will result in a signal void that may be visualized on T1- or T2-weighted images (1,2) (Figure 2).

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