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.
Farlex Partner Medical Dictionary © Farlex 2012

signal void

A dark or blank space in a radiographic image of a fluid-filled structure. See: filling defect
See also: signal
Medical Dictionary, © 2009 Farlex and Partners
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Conforming to safe RF power limits, this is the first work reporting MRI sequence dependent artifact size of DBS leads in refractory Parkinson's patients and exploring various sequence limits to minimize the artifactual signal void within clinically feasible image resolution and hardware limitations for PD patients.
However, a distinct flow-related signal void usually indicates a spinal AVF.
Also, MRI can demonstrate multiple areas of signal void in the hemangiomas, which represent vessels.
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.
A keen search is advised when assessing for the signal void of gas, as can be seen in the setting of pneumatosis or free air; extraluminal gas is more difficult to identify on MR compared to CT.
On MRI, arteriovenous malformations are composed of large tortuous often serpiginous arterial and venous vessels with multiple areas of signal void due to the rapid blood flow (Figure 1).

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