 The technical aspects of imaging a patient who has head trauma are important. And I want to emphasize with respect to the CT imaging, which is usually done as the primary mode of evaluation of the patient in the emergency room, that thin section images are critical. At our institution, we see the 0.75 millimeter or 0.6 millimeter thin sections on all of our CT scans for patients who have head trauma. The technologists may reconstruct them in two to three millimeter thick sections in the axial, coronal, or sagittal plane. But because sometimes the imaging findings of traumatic head injury are relatively subtle, I highly recommend that you look at the thin sections for this indication. Not only that, but I usually will make my own reconstructions in coronal or sagittal plane rather than using the thicker section, three millimeter thick sections that the technologists provide. And that's because small subdural hematomas or epidural hematomas may be one to two millimeter thick, and therefore the potential for partial volume averaging is quite high. In addition, with traumatic brain injury, we usually say that you have to look at the brain with multiple windows. And by that, I mean both the brain window as well as a broader window and centered image that will allow you to detect those subtle subdural collections as well as the bone windows in order to see fractures. So at the very least, you should be looking at three separate windows, that is brain subdural window and bone window, as well as multiple planes, be it axial, coronal, and sagittal planes. With regard to MR imaging, at a very basic, we need our T1 and T2 weighted scans to be able to detect the hemorrhage and to be able to characterize its age. However, susceptibility weighted imaging has become a mainstay of imaging for head trauma because of its increased sensitivity to blood products, both deoxyhemoglobin for acute hemorrhage as well as hemesidarin for the chronic effects of hemorrhage as well as methemoglobin, which is our marker for subacute hemorrhage. Some facilities will do a MR technique that highlights the bone marrow in order to detect fractures. This is true in particular if you have a policy of using MR in pediatric cases to avoid any type of radiation of the patient for CT. So in some instances, the emergency department is ordering MR imaging in children as the first and initial evaluation of the patient rather than CT in order to avoid irradiating young brains. As with CT, it's best to do multi-planar imaging. I mentioned susceptibility weighted MRI and this is a technique which was developed by Mark Hakey. It's a wonderful technique for evaluation of blood products. It is, as he says here, a 3D velocity compensated gradient echo sequence that combines magnitude information as well as phase information and accentuates the visibility of susceptible foci such as small veins and hemorrhage. We usually will reconstruct this in what is called a minimum intensity projection, a MIP which refers to not the maximum intensity projection but the minimum intensity projection to see all the darkest signals that represent hemorrhage. In this situation, we have a gradient echo scan on the left side which shows lots of little black dots of hemorrhage, in this case hemacidrin because there's no edema around them. But note that on the exact same slice using susceptibility weighted imaging, we see so many more little dots of these hemorrhage, these foci of hemacidrin with this technique. So although gradient echo technique used to be our best masterpiece for looking for hemorrhage, we've now replaced that with susceptibility weighted imaging which is far superior. Thank you to Mark Hakey.