Introduction to MRI Head Imaging Ryan Hakimi, DO, MS Director, Critical Care Neurology Assistant Professor Department of Neurology The University of Oklahoma Health Sciences Center January 16, 2015

DISCLOSURES FINANCIAL DISCLOSURE UNLABELED/UNAPPROVED USES DISCLOSURE Nothing to disclose UNLABELED/UNAPPROVED USES DISCLOSURE

Objectives Describe the pros and cons of MRI versus CT when imaging the head Discuss some common MRI sequences Illustrate the appearance of acute ischemic stroke on various MRI head sequences Present MRI head imaging of other common neurological diagnoses 3

Principles of Magnetic Resonance Imaging Uses a magnet and radio waves to create an image based on changes in alignment of protons in the tissue Terminology Hyperintense (bright, white) Hypointense (dark, black)

Advantages of MRI over CT Head No radiation Can image in multiple planes (axial, sagital, coronal, oblique) Superior soft tissue imaging Can image some vessels without contrast (MRA head) Many different sequences allow for specialized imaging Can image the brainstem and cerebellum

Disadvantages of MRI vs CT Head Inferior bone imaging Cost Longer study time Images degraded by motion Can not image patient with pacemaker, claustrophobia, metallic foreign bodies (bullet)

Axial T1 T1 looks like a CT CSF is black (hypointense) orbit pons

Sagital T1 atrophy corpus collosum pons cerebellum

Coronal with contrast (gadolinium) With contrast can see hyperintensity of the blood vessels Good for visualization of hyppocampi

Axial T2 T2 has white (hyperintense)CSF lateral ventricles frontal horn occipital horn

DWI brainstem Breakdown of blood brain barrier acute ischemic stroke acute demyelination acute trauma Right pontine ischemic infarction T2 shine through

T2* acute ICH (gradient echo) Blood will appear black (hypointense)

Acute Ischemic Stroke DWI T1

Acute Ischemic Stroke T2 FLAIR (fluid-attenuated inversion recovery)

Acute Ischemic Stroke T2* petechial hemorrhages within the ischemic tissue

MRA (LMCA patent) anterior cerebral artery middle cerebral artery L R Image can be rotated, left is not always on the right side of the screen, must look at labels anterior cerebral artery middle cerebral artery L R internal corotid artery

Normal Pressure Hydrocephalus Central atrophy (large ventricles) out of proportion to peripheral atrophy (minimal atrophy)

Meningioma Extraaxial brain tumor (outside of the brain) displacing Enhances with gadolinium Has a dural tail

Multiple Sclerosis Periventricular white matter hyperintensities, some of which enhance, from National MS Center

GAD with NSF Puts patients at risk for nephrogenic systemic fibrosis Fibrosis of skin, eyes, organs Gadolinium can not be administered in patients: Glomerular filtration rate (GFR) of 30 or less On dialysis

Questions Thank you OU Neurology