Classification of a Pseudotumor Adjacent to a Joint Prosthesis Based on Its Appearance in a MARS MRI

A pseudotumor associated with a metal-on-metal (MoM) joint prosthesis can be classified by its appearance on MARS MRI.

MARS = metal artifact reduction sequence

Parameters:

(1) wall thickness

(2) contents on T1 and T2

(3) shape

Wall Thickness	Contents	Shape	Type
thin	T1 hypointense, T2 hyperintense	flat	1
thick or irregular	T1 hypointense, T2 hyperintense	not flat	2a
thick or irregular	T1 hyperintense, T2 variable	any shape	2b
solid	mixed	any shape	3

where:

• T1 hypointense and T2 hyperintense is “fluid-like”.

• Flat indicates that the walls are primarily (> 50%) in apposition

• One variation might be to have subtypes for Type 1 based on shape.

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