0:00

I would be remiss if I didn't mention the marker for

0:04

hyperacute hematoma, and that is oxyhemoglobin.

0:08

Oxyhemoglobin is diamagnetic.

0:11

By that, we mean that it has no characteristics of Proton

0:15

Relaxation Enhancement, nor proton-electron dipole interaction.

0:20

Oxyhemoglobin effectively looks like water,

0:23

and therefore, is dark on a T1-weighted scan

0:25

and bright on a T2-weighted scan.

0:28

It is incredibly uncommon to see oxyhemoglobin on MRI.

0:33

Because of the rapid conversion of

0:35

oxyhemoglobin to deoxyhemoglobin,

0:38

we usually see acute hemorrhages as dark on T1

0:42

and dark on T2 because of the proton relaxation enhancement

0:46

of deoxyhemoglobin.

0:48

Remember, however,

0:49

that that proton relaxation enhancement characteristic is

0:53

field strength-dependent,

0:55

and therefore, at 1.5T and 3T,

0:59

we see the conversion of oxyhemoglobin to deoxyhemoglobin

1:03

relatively easily,

1:04

and therefore, hemorrhages are rarely

1:07

seen as dark on T1 and bright on T2.

1:10

However, if you are using a low field strength magnet,

1:15

which is less sensitive to the conversion

1:17

of oxyhemoglobin to deoxyhemoglobin,

1:20

you may get fooled by seeing something that looks like edema

1:25

but is actually a hyperacute hematoma

1:28

dominated by oxyhemoglobin.

1:31

So, this is a potential pitfall at low field strength.

1:34

You see something,

1:35

it looks just like edema, not a hematoma,

1:39

because you are less sensitive to the presence of

1:42

deoxyhemoglobin than at high field strength.