Pitfalls of MR Angiography due to slow flow in large Aneurysm

This case illustrates a potential pitfall of Non contrast 3D TOF MRA imaging. Contrast enhanced CT study shows a focal aneurysmal dilatation of basilar, but the non contrast 3 D TOF MR Angiography of Brain of same patient fails the aneurysm is not depicted well on lateral view.

The non visualization of aneurysm may be due to slow flow owing to its large size or thrombus formation in the aneurysm because vascular imaging in Non contrast 3D TOF MRA depends on flow related signal from a rapid blood flow in a vessel. In this study the ICAs and basilar show normal flow related signals but the large aneurysm sac appears nearly isointense with nearby static brain.
CT Angiography or MR Angiography with contrast has considerable value in such cases because it is not dependent on flow velocity to create contrast and signals.

Reference: Practical MR Physics and case file of MR artifacts and pitfalls, Alexander C. Mamourian, MD

MRI Artifact secondary to embolisation glue

A 55 y o male came for follow up imaging with history of endovascular embolization for dural AV fistula.

MRI Axial FLAIR, T2*GRE and DWI

This is his follow up MRI images show susceptibility artifact in left temporal region from glue used for endovascular embolization, the abnormal vessel is blocked by injecting a glue by placing a small catheter inside the blood vessels that supply the AV. Among the variety of materials used commonly include liquid tissue adhesives (glues) which get polymerised and become hard on coming in contact with blood.

Susceptibility artifact of glue refers to susceptibility of a material in it, the tendency of the material to become magnetised when placed in a magnetic field, create local disturbances in the magnetic field resulting in non-linear changes of resonant frequency, which in turn creates image distortion and areas of signal void.

Other common causes such artifacts in daily practice are Dental implants, hair pins, dirt and grim in hairs, bindi, post traumatic subcutaneous implants.