0:00

The fourth set of sequences that I look at

0:02

when evaluating liver lesions are the T1

0:04

weighted pre- and post-contrast sequences.

0:07

Now, the post-contrast sequences are obtained in

0:09

the arterial, portal venous, and delayed phase.

0:13

But if you're using an agent with partial

0:14

hepatobiliary, you're going to get a fourth

0:18

additional phase at about 20 minutes.

0:20

These sequences are fat-suppressed isotropic T1

0:23

weighted gradient echo sequences, and they're

0:25

performed with patients holding their breath.

0:26

Performing this with fat saturation, as can be

0:29

seen over here in the subcutaneous fat, allows

0:31

for increased conspicuity of enhancement.

0:34

And obtaining them as isotropic sequences

0:37

allows to get greater signal-to-noise ratio.

0:40

It will also allow you to get multi-planar

0:42

reconstructions without losing spatial resolution.

0:45

Now, this example here is the pre-contrast

0:47

sequence, and I used this as a baseline

0:50

for subsequent contrast-enhanced imaging.

0:53

I also use it to assess for the presence of

0:55

any liver lesions with intrinsic hyperintense

0:58

T1 content, such as methemoglobin or melanin.

1:02

If we do see a liver lesion with high T1 content, we

1:06

need to make sure that we have good subtraction sequences

1:09

to assess for any enhancement within that lesion.

1:12

On this sequence over here, we can see that

1:14

the liver has pretty homogeneous signal.

1:17

And it is relatively hyperintense on the

1:20

T1-weighted images compared to the spleen.

1:22

And that's due to its relatively low water content.