Interactive Transcript
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The fourth set of sequences that I look at
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when evaluating liver lesions are the T1
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weighted pre- and post-contrast sequences.
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Now, the post-contrast sequences are obtained in
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the arterial, portal venous, and delayed phase.
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But if you're using an agent with partial
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hepatobiliary, you're going to get a fourth
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additional phase at about 20 minutes.
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These sequences are fat-suppressed isotropic T1
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weighted gradient echo sequences, and they're
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performed with patients holding their breath.
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Performing this with fat saturation, as can be
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seen over here in the subcutaneous fat, allows
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for increased conspicuity of enhancement.
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And obtaining them as isotropic sequences
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allows to get greater signal-to-noise ratio.
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It will also allow you to get multi-planar
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reconstructions without losing spatial resolution.
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Now, this example here is the pre-contrast
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sequence, and I used this as a baseline
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for subsequent contrast-enhanced imaging.
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I also use it to assess for the presence of
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any liver lesions with intrinsic hyperintense
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T1 content, such as methemoglobin or melanin.
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If we do see a liver lesion with high T1 content, we
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need to make sure that we have good subtraction sequences
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to assess for any enhancement within that lesion.
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On this sequence over here, we can see that
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the liver has pretty homogeneous signal.
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And it is relatively hyperintense on the
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T1-weighted images compared to the spleen.
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And that's due to its relatively low water content.
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