NeuroImaging Dr. Norman Pay

CT Transmission

CT Transmission Density differences Ionizing radiation Iodinated contrast material Spatial resolution Fast scanning times and acquisition Appropriate in emergent situations, claustrophobic patients, body coverage Utilization for contraindications in MRI as aneurysm clips, cardiac pacemakers, etc. Biopsies Workstation compatibility CT angiography

RADIATION Sv (Sievert) – absorbed dose in biological tissue 2 mSv/ year – background radiation 24 mSv/ year –background radiation for airline cruising altitude 6.8 mSv – chest CT scan mSv – single full body CT scan 21 Sv – fatal dose

CT Angiography CAROTID STENT CAROTID TRAUMATIC ANEURYSM

MRI Proton Relaxation Signal intensities Contrast resolution Gadolinium (Gd) contrast Nephrogenic Systemic Fibrosis (NSF) – Gd contraindicated in Low GFR states (<30) and renal failure Non-ionizing, non-invasive Workstation compatibility More complex, longer acquisitions and set-up Magnet bore - claustrophobia MR angiography

MR Angiography CAVERNOMACAROTID DISSECTIONCAROTID OCCLUSION

T1 T2Flair Diffusion GRE Contrast

MR sequences T1 – anatomy, CSF dark T2 – screening, CSF bright FLAIR (fluid attenuated inversion recovery) – similar to T2 MR diffusion – bright signal for restriction GRE (gradient echo) – susceptibility- dark signal Gadolinium, T1 – bright signal MR angiography and perfusion – Gadolinium utilization

Anatomy of the Brain Spatial Resolution –CT Density Contrast Resolution –MR Signal Intensity Intravenous Contrast –Iodinated contrast –Gadolinium contrast

NEURONAL MIGRATION

CORTICAL DYSPLASIA FLAIR T2

Stroke Acute ischemic stroke (AIS) – 3 rd leading cause of death, leading cause of disability in adults 700,000 ischemic strokes annually in the U.S. Reperfusion therapy is the only proven treatment of AIS

CT and MR Time to infarct Time to treatment Extent of infarct Hematoma Recovery

PRE THROMBUS LYSIS POST THROMBUS LYSIS

PRE THROMBUS LYSIS POST THROMBUS LYSIS CT

MOYA-MOYA FLAIR

Pattern Recognition Diagnostic Neuroradiology, pg Osborn, Anne G., M.D. Mosby – Year Book, Inc., 1994.

Pattern Recognition Diagnostic Neuroradiology, pg Osborn, Anne G., M.D. Mosby – Year Book, Inc., 1994.

MR DIFFUSION Diffusion refers to the general transport of molecules, mixing through agitation and randomly The driving force is the motion of water within water, driven by thermal agitation called Brownian motion If restricted as in acute infarcts, decreased diffusion results Decreased diffusion displayed as bright MR signal

MR DIFFUSION Failure of Na+/K+ ATPase and other ionic pumps – net shift of water from the extracellular to the intracellular space Cell swelling with decrease in extracellular space Increased intracellular viscosity and cell membrane permeability Temperature decrease Decreased diffusion in acute stroke

CTMR DIFFUSION CEREBELLAR INFARCT

CTMR MIDDLE CEREBRAL ARTERY INFARCT

DIFFUSION BASILAR ARTERY OCCLUSION MRA

FLAIR DIFFUSION ACUTE INFARCT

EMBOLIC DISEASE – ATRIAL FIBRILLATION MR DIFFUSION

T1 T2 CONTRAST POSTERIOR CEREBRAL ARTERY INFARCT

FLAIR T2 VASCULITIS

FLAIR DIFFUSION STATUS POST AORTIC VALVE SURGERY HYPOTENSION

Neuroimaging in acute ischaemic stroke: insights into unanswered questions of pathophysiology. Wardlaw, J. M. Journal of Internal Medicine 267; 172–190. Blackwell Publishing Ltd

MR DIFFUSION Neuroimaging in acute ischaemic stroke: insights into unanswered questions of pathophysiology. Wardlaw, J. M. Journal of Internal Medicine 267; 172–190. Blackwell Publishing Ltd

CTMR MIDDLE CEREBRAL ARTERY INFARCT

Hematoma Hemorrhagic transformation – dreaded complication Exclusion of hematoma -prerequisite for treatment Cue for emergent intervention

CT INFARCT HEMORRHAGE INTO INFARCT

EPIDURAL SUBDURAL HEMATOMA

ISODENSE REBLEED SUBDURAL HEMATOMA

Magnetic Resonance Imaging of the Brain and Spine, 3rd ed., Vol. 1, pg 788. Atlas, Scott W., M.D., editor. Lippincott Williams & Wilkins, 2002.

HEMATOMA GREFLAIR

CT T1T2 SUBDURAL HYGROMA AND HEMATOMA

SUBDURAL HEMATOMA T1CTT2 CHRONIC

CT FLAIR SUBARACHNOID HEMORRHAGE

ANTERIOR COMMUNICATING ARTERY (ACA) ANEURYSM

T1 FLAIR VENOUS THROMBOSIS AND VENOUS INFARCT

SIDEROSIS GRE

FLAIRCT BENIGN MALIGNANT HEMATOMA

MALIGNANT HEMATOMA T1T2CONTRAST

T1 GRE CT T2 CYST

SUMMARY CT and MR utilize different technologies, often complementary Advantages and disadvantages of CT and MR CT and MR advances pari-passu with computing capabilities Moore ’ s Law

REFERENCES Diagnostic Neuroradiology, pg Osborn, Anne G., M.D. Mosby – Year Book, Inc., Magnetic Resonance Imaging of the Brain and Spine, 3rd ed., Vol. 1, pg 788. Atlas, Scott W., M.D., editor. Lippincott Williams & Wilkins, Neuroimaging in acute ischaemic stroke: insights into unanswered questions of pathophysiology. Wardlaw, J. M. Journal of Internal Medicine 267; 172–190. Blackwell Publishing Ltd