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• 10-30 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

CAVERNOMA CAROTID DISSECTION CAROTID OCCLUSION

T1 T2 Flair

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) – 3rd 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 130-131.Osborn, Anne G., M.D. Mosby – Year Book, Inc., 1994.

Pattern Recognition

Diagnostic Neuroradiology, pg 130-131.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

CT MR DIFFUSION

CEREBELLAR INFARCT

CT MR

MIDDLE CEREBRAL ARTERY INFARCT

DIFFUSION DIFFUSION DIFFUSION

BASILAR ARTERY OCCLUSION

MRA MRA

FLAIR DIFFUSION

ACUTE INFARCT

EMBOLIC DISEASE – ATRIAL FIBRILLATION

MR DIFFUSION

T1 T1 T2

CONTRAST

POSTERIOR CEREBRAL ARTERY

INFARCT

FLAIR FLAIR T2

VASCULITIS

FLAIRFLAIR DIFFUSION DIFFUSION

STATUS POST AORTIC VALVE SURGERYHYPOTENSION

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

Blackwell Publishing Ltd. 2010.

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. 2010.

CT MR

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 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 T1 T2

SUBDURAL HYGROMA AND HEMATOMA

SUBDURAL HEMATOMA

T1 CT T2

CHRONIC CHRONICCHRONIC

CT FLAIR FLAIR

SUBARACHNOID HEMORRHAGE

ANTERIOR COMMUNICATING ARTERY

(ACA) ANEURYSM

T1 T1 FLAIR

VENOUS THROMBOSIS AND VENOUS INFARCT

SIDEROSIS

GRE

GREFLAIR CT

BENIGN MALIGNANT MALIGNANT

HEMATOMA

MALIGNANT HEMATOMA

T1 T2 CONTRAST

T1GRECT

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 130-131. Osborn,

Anne G., M.D. Mosby – Year Book, Inc., 1994.• Magnetic Resonance Imaging of the Brain and

Spine, 3rd ed., Vol. 1, pg 788. Atlas, Scott W., M.D., editor. Lippincott Williams & Wilkins, 2002.

• Neuroimaging in acute ischaemic stroke: insights into unanswered questions of pathophysiology. Wardlaw, J. M. Journal of Internal Medicine 267; 172–190. Blackwell Publishing Ltd. 2010.