0:01

The technical aspects of imaging a patient who has head

0:05

trauma are important and I want to emphasize

0:09

with respect to the CT imaging,

0:11

which is usually done as the primary mode of evaluation

0:14

of the patient in the emergency room,

0:16

that thin section images are critical.

0:20

At our institution, we see the 0.75 millimeter or

0:26

0.6 millimeter thin sections on all of our CT scans

0:31

for patients who have head trauma.

0:33

The technologist may reconstruct them in 2-3 millimeter

0:37

thick sections in the axial, coronal or sagittal plane.

0:41

But because sometimes the imaging findings of traumatic

0:47

head injury are relatively subtle,

0:50

I highly recommend that you look at the thin sections

0:53

for this indication. Not only that,

0:56

but I usually will make my own reconstructions in coronal

1:00

or sagittal plane, rather than using the thicker section

1:04

3 millimeter thick sections that the technologists provide.

1:08

And that's because small subdural hematomas or

1:12

epidural hematomas may be 1-2 millimeters thick,

1:15

and therefore, the potential for partial volume

1:18

averaging is quite high.

1:20

In addition with traumatic brain injury,

1:23

we usually say that you have

1:24

to look at the brain with multiple windows.

1:27

And by that, I mean both a brain window,

1:30

as well as a broader window and centered image

1:34

that will allow you to detect those subtle

1:37

subdural collections, as well as the bone windows in

1:41

order to see fractures. So at the very least,

1:44

you should be looking at three separate windows,

1:46

that is brain subdural window, and bone window,

1:51

as well as

1:53

multiple planes, be it axial, coronal and sagittal planes.

1:58

With regard to MR imaging,

2:00

at a very basic, we need our T1 and T2 weighted scans

2:03

to be able to detect the hemorrhage

2:05

and to be able to characterize its age.

2:08

However,

2:09

susceptibility weighted imaging has become a mainstay

2:12

of imaging for head trauma because of its

2:17

increased sensitivity to blood products,

2:19

both deoxyhemoglobin for acute hemorrhage,

2:22

as well as hemosiderin for the chronic effects of hemorrhage,

2:28

as well as methemoglobin,

2:30

which is our marker for subacute hemorrhage.

2:33

Some facilities will do an MR technique that highlights

2:39

the bone marrow in order to detect fractures.

2:42

This is true in particular if you have a policy of using

2:46

MR in pediatric cases to avoid any type

2:50

of radiation of the patient for CT.

2:53

So in some instances, the emergency department

2:56

is ordering MR imaging in children

2:59

as the first and initial evaluation of the patient

3:03

rather than CT, in order to avoid irradiating young brains.

3:07

As with CT, it's best to do multiplanar imaging.

3:13

I mentioned susceptibility weighted MRI,

3:16

and this is a technique

3:21

which was developed by Mark Haacke.

3:23

It's a wonderful technique for evaluation of

3:28

blood products. It is, as he says here,

3:31

a 3D velocity compensated gradient echo sequence that

3:35

combines magnitude information as well as phase

3:38

information and accentuates the visibility of susceptible

3:42

foci such as small veins and hemorrhage.

3:45

We usually will reconstruct this in what is called

3:49

a minimum intensity projection, a MIP,

3:52

which refers to not the maximum intensity projection,

3:54

but the minimum intensity projection,

3:56

to see all the darkest signals that represent hemorrhage.

4:00

In this situation,

4:01

we have a gradient echo scan on the left side

4:04

which shows lots of little black dots of hemorrhage,

4:08

in this case hemosiderin,

4:10

because there's no edema around them.

4:12

But note that on the exact same slice,

4:15

using susceptibility weighted imaging,

4:18

we see so many more little dots of these hemorrhage,

4:21

these foci of hemosiderin with this technique.

4:24

So, although gradient echo technique used to be our

4:28

best masterpiece for looking for hemorrhage,

4:30

we've now replaced that with susceptibility

4:34

weighted imaging, which is far superior.

4:36

Thank you to Mark Haacke.