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Our next topic is a discussion of masses.

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And a mass is a three-dimensional space

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occupying lesion, with a convex outward contour.

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We evaluate these on pre and post-contrast scans, and we want to evaluate the shape,

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the margin and internal enhancement characteristics.

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Shape can be described as oval, round or irregular.

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An oval is elliptical or egg shaped and can have two or three gentle undulations.

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Round would be spherical, ball shaped, circular or globular.

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An irregular is neither round nor oval.

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Here's an example of an oval mass indicated by the yellow arrow.

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You can see that nice margin, may be

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an undulation here in the middle, but basically an oval mass.

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This is a round mass about the same dimension on all sides.

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And here's an example of an irregular mass.

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So kind of an irregular shape,

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and neither round nor oval.

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Margins can be described as circumscribed or not circumscribed.

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And if not circumscribed, then the two descriptors are irregular and spiculated.

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A circumscribed margin should be sharply

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demarcated from the surrounding tissue, with an abrupt transition between

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the lesion and the tissue outside of the lesion.

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And the entire lesion must be well defined to classify as circumscribed.

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Not circumscribed includes irregular, which has uneven or jagged edges,

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and spiculated, which has lines radiating out from the mass.

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This is a circumscribed mass indicated by the yellow arrow.

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You can see the edges are very easy to see

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and very sharply demarcated from the surrounding tissue.

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This is an example of an irregular margin,

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kind of jagged edges. Irregular.

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And a spiculated margin,

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this mass has lines radiating out in a circular fashion from the mass.

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We can also look at internal enhancement

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characteristics and the descriptors for internal enhancement are homogeneous,

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heterogeneous, rim enhancement and dark internal septations.

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Here's an example of a homogeneously enhancing mass.

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We can see that it has a uniform signal

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intensity throughout the interior portion of the mass.

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This is a heterogeneously enhancing mass.

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So there's a range of signal intensities

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within that mass. Some bright, some darker areas.

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This is an example of rim enhancement.

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You can see a high signal intensity lesion

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on STIR imaging and then rim of enhancement.

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And another example of rim enhancement.

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This is a cyst.

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So this is a fluid filled cyst and sometimes the edge of a cyst can

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be a little bit inflamed and can demonstrate thin rim enhancement.

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So that's rim enhancement.

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And then the last

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descriptor is dark internal septations or non enhancing internal septations.

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And we can see those in this oval enhancing mass.

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There are some lines going through it that don't enhance. So these thin

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dark lines. And that's fairly typical of a fibroadenoma.

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This is another example, an enhancing mass with dark lines going through it.

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Benign features of a mass include round or oval shape, circumscribed margins,

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homogeneous internal enhancement, internal fat, such as a lymph node or fat

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necrosis or a hamartoma, and persistent kinetics.

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Suspicious features include irregular

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shape, irregular or spiculated margin heterogeneous internal enhancement,

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rim enhancement and wash out or plateau kinetics.

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And back to our abbreviated MRI training algorithm.

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This is looking at a unique mass.

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And for patients with a mass that's either

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not circumscribed or has rim enhancement, we'll usually biopsy these.

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And a rim enhancing mass,

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I'm not referring to a cyst with a thin rim of enhancement around the edge.

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It would be more of a thicker rim,

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or if the size of the internal features doesn't match with a cyst.

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So non circumscribed or rim enhancement, we're definitely going to biopsy.

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For a circumscribed mass, we're going to look at the T2

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characteristics, whether it's high T2 or not.

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And for high T2, we may be able to follow those. Not high T2,

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if it's homogeneously enhancing, we may be able to follow those.

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Heterogeneous enhancement, we're going to biopsy.

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And then for these other things, the inflammatory cyst, obvious fibroadenoma or

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lymph node, we just consider those to be benign.