ct and mri interpretation

CT and MRIINTERPRETATION

SAMIR EL ANSARY

ICU PROFESSOR

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A midline Post-contrast Sagittal T1 Weighted MRI

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Identify anatomical structures 1 - 24

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A midline Post-contrast Sagittal T1 Weighted MRI

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1. Scalp fat2. Bone3. Inferior sagittal sinus4. Corpus callosum5. Internal cerebral vein6. Vein of Galen7. Superior sagittal sinus8. Parietal lobe9. Occipital lobe10. Straight sinus11. Vermis12. IV ventricle13. Cerebellar tonsil14. Cervical cord15. Medulla16. Pons17. Midbrain18. Mass intermedia of thalamus19. Anterior III ventricle 20. Optic chiasm21. Pituitary gland22. Sphenoid sinus23. Nasopharynx24. Frontal lobe

Coronal Section of the Brain at the level of IV VentriclePost Contrast Coronal T1 Weighted MRI

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Identify anatomical structures 1 - 8

Coronal Section of the Brain at the level of IV VentriclePost Contrast Coronal T1 Weighted MRI

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1 1. Cerebellar tonsil2. Cerebellar hemisphere3. IV ventricle4. Superior vermis5. Tentorium6. Posterior temporal lobe7. Choroid plexus within lateral ventricle8. Posterior frontal lobe

Coronal Section of the Brain at the level of Pituitary glandPost Contrast Coronal T1 Weighted MRI

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Coronal Section of the Brain at the level of Pituitary glandPost Contrast Coronal T1 Weighted MRI

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1. Frontal lobe2. Corpus callosum3. Frontal horn4. Caudate nucleus5. III ventricle6. Optic nerve7. Pituitary stalk8. Pituitary gland9. Internal carotid artery10. Cavernous sinus11. Sphenoid sinus12. Nasopharynx

Coronal Section of the Brain at the level of the orbits.Post Contrast Coronal T1 Weighted MRI.

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Coronal Section of the Brain at the level of the orbits.Post Contrast Coronal T1 Weighted MRI.

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1. Frontal lobe

2. Orbital Fat

3. Globe

4. Nasal Cavity

5. Maxillary Sinus

Post Contrast Axial MR Image of the brain

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Post Contrast sagittal T1 Weighted M.R.I.

Section at the level of Foramen Magnum

Answers

1. Cisterna Magna2. Cervical Cord3. Nasopharynx4. Mandible5. Maxillary Sinus


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Post Contrast sagittal T1 Wtd M.R.I.

Section at the level of medulla

Answers

6. Medulla7. Sigmoid Sinus


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Post Contrast sagittal T1 Wtd M.R.I. Section at the level of Pons

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8. CerebellarHemisphere9. Vermis10. IV Ventricle11. Pons12. Basilar Artery

13. Internal Carotid Artery14. Cavernous Sinus15. Middle CerebellarPeduncle16. Internal Auditory Canal17. Temporal Lobe


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Section at the level of Mid Brain

Answers18. Aqueduct of Sylvius19. Midbrain20. Orbits21. Posterior Cerebral Artery22. Middle Cerebral Artery


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Post Contrast sagittal T1 Wtd M.R.I. Section at the level of the

III Ventricle

Answers23. Occipital Lobe24. III Ventricle25. Frontal Lobe26. Temporal Lobe27. Sylvian Fissure


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Post Contrast sagittal T1 Wtd M.R.I. Section at the level of Thalamus

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28. Superior Sagittal Sinus29. Occipital Lobe30. Choroid Plexus within the occipital horn31. Internal Cerebral Vein32. Frontal Horn

33. Thalamus34. Temporal Lobe35. Internal Capsule36. Putamen37. Caudate Nucleus38. Frontal Lobe


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Section at the level of Corpus Callosum

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39. Splenium of corpus callosum40. Choroid plexus within the body of lateral ventricle41. Genu of corpus callosum


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Section at the level of Body of Corpus Callosum

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42. Parietal Lobe43. Body of the Corpus Callosum44. Frontal Lobe


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Post Contrast sagittal T1 WtdM.R.I.

Section above the Corpus Callosum

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45. Parietal Lobe46. Frontal Lobe

Brain Imaging: “The Big 10”

• Infarction

• Hemorrhage

• Infection

• Tumor

• Trauma

• Dementia

• MS

• Epilepsy

• Cranial neuropathy

• Orbits / Ophtho dx

Acute Ischemic Stroke Imaging

Confirm diagnosis

Triage for therapy (risk / prognosis)

– Rule out hemorrhage

– Assess damage: location, pattern, extent

– Is there salvageable brain (“penumbra”)?

Follow outcome

– Vessel patency, ultimate infarct size, hemorrhagic transformation

CT Signs in Early MCA Ischemia

Hyperdense MCA Insular Ribbon Lentiform Nucleus

Pathophysiology of Ischemic Injury:Duration and Degree of CBF

Normal neuronal function

Reversible injury

(penumbra)

Infarction

25

20

15

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0

CBF

ml /

100g /

min

Time (hrs)1 2

Pipes Perfusion Parenchyma

MRA Perfusion MR Diffusion MR

“Penumbra”

MRI in Stroke Intervention“The 4 P’s”

MCA Infarct

MCA

PCA Infarct

PCA

ACA Infarct ACA


• Infarction

• Hemorrhage

• Infection

• Tumor

• Trauma

• Dementia

• MS

• Epilepsy



Cerebral Hemorrhage

• Trauma• Ruptured aneurysm • Hypertensive• Hemorrhagic transformation of ischemic infarction

(esp. venous)• Venous infarction• Tumor • Vascular malformations• Angioinvasive infection• Amyloid angiopathy

Acute intraparenchymal hematoma

Cerebral Hemorrhage

Hemorrhagic melanoma metastases

Cerebral Hemorrhage

Acute subarachnoid hemorrhage

(and intraventricular)

Cerebral Hemorrhage

Subdural vs. Epidural Hematoma

Acute subdural hematoma

Cerebral Hemorrhage

Acute epidural hematoma

Cerebral Hemorrhage

Subdural: Follows inner layer of dura

“Rounds the bend” to follow falx or tentorium

Not affected by sutures of skull

Tendency for crescentic shapes

More mass effect than expected for their size

Typical source of SDH: cortical vein

Epidural: Follows outer layer of dura (periosteum)

Crosses falx or tentorium

Limited by sutures of skull (typically)

Tendency for lentiform shapes

Typical source of EDH:

skull fracture with arterial or sinus laceration

Subdural vs. Epidural Hematoma

*

Mixed acute/chronic subdural hematoma

Cerebral Hemorrhage

ACUTE

CHRONIC

Hematocrit level!

Cerebral Hemorrhage

MRI of Hemorrhage

MR appearance of hematomas depends on image type.

Magnetic properties change over time (Hgb breakdown products), allowing approximate dating

T1 T2 T2*


• Infarction

• Hemorrhage

• Infection

• Tumor

• Trauma

• Dementia

• MS

• Epilepsy



Infection

• Meningitis

• Encephalitis

• Cerebritis and parenchymal abscess

• Empyema (subdural/epidural)

Leptomeningitis: pia-arachnoid

Meningitis

Pachymeningitis: dura

Most common imaging findings in meningitis: NONE !!

Herpes Encephalitis

Cerebritis w/ Bacterial Abscess

T1 + Gd T2 Diffusion

Cerebritis w/ Subdural Empyema

T1 + Gd T2 FLAIR Diffusion


• Infarction

• Hemorrhage

• Infection

• Tumor

• Trauma

• Dementia

• MS

• Epilepsy



Brain Tumor ImagingDiagnosis

• Location: Intra- / Extra-axial, Supra- / Infra-tentorial, Grey / white matter, etc.

• Single or multiple?• Tumor or tumor-like alternatives?• Histology: Type and grade?

Treatment Planning• Surgery, radiation, chemo tx• Functional MRI for eloquent brain mapping• 3D scans to guide surgery, radiation

Follow-up • Stable vs. recurrence / progression• Complications

T1 + Gd T2

Intra- or Extra-axial?

Intra- or Extra-axial?

Tumor vs. Other MassesArachnoid Cyst

Abscess

Hematoma

“Tumefactive” MS

GBM

Tumor vs. Stroke

Cytotoxic Edema Vasogenic EdemaCellular swelling

Gray-white margin lostLeaky capillaries

Gray matter is spared

T1 T1 + Gd

T2T2 FLAIR

Tumor?Stroke?

Encephalitis?

3D Imaging for XRTor Surgical Guidance


• Infarction

• Hemorrhage

• Infection

• Tumor

• Trauma

• Dementia

• MS

• Epilepsy



Fractures: CT not MRI !

Traumatic Brain Swelling

Cerebellopontine angle

PontineCerebellomedullary (Cisterna Magna)

Know your basal cisterns!


Know your basal cisterns!

QuadrigeminalInterpeduncular

SuprasellarAmbient

Effacement of basal cisterns

Traumatic brain swelling with downward herniation


Traumatic brain swelling

Extra-axial Hemorrhage

Subdural Epidural Subarachnoid

Intra-axial Hemorrhage

Hemorrhagic contusions



Mechanism

Direct contact with skull

Shear-strain deformation

Lesion locations

Commonly located along inferior, lateral, and anterior

frontal and temporal lobes

Often above bony prominences (petrous pyramid,

sphenoid wing, orbital roof)



Appearance of cortical contusions

Overlying cortex, by definition, always involved (vs. DAI)

“Salt and pepper” appearance due to intermixed hemorrhage

and edema

Non-hemorrhagic contusions often not initially seen on CT scans

Lesions often more visible days after injury as edema and

hemorrhage increase

Acute lesions much more conspicuous on T2 or T2-FLAIR MRI

Diffuse Axonal (Shear) Injury (DAI)



T2: Reveals non-hemorrhagic lesions occult on CT


T2: Increased sensitivity to hemorrhage


• Tissues w/ differing elastic properties shear against each other, tearing axons

• Caused by rapid deceleration/rotation of head • Locations:

• Cerebral hemispheres near gray-white junction• Basal ganglia• Corpus callosum, especially splenium• Dorsal brainstem

• High morbitity & mortality – common cause of post-traumatic vegetative state

• Initial CT often normal despite poor GCS• Lesions often non-hemorrhagic and seen only on MRI


• Infarction

• Hemorrhage

• Infection

• Tumor

• Trauma

• Dementia

• MS

• Epilepsy



Dementia

• Primary role of imaging is to exclude treatable causes, e.g.:

–Hydrocephalus

–Subdural hematoma

–Neoplasm

Dementia

Irreversible dementias (imaging non-specific):• Alzheimer’s disease• Multi-infarct dementia • Dementias associated with

Parkinson’s disease and similar disorders

• AIDS dementia complex

Alzheimer’s: Temporal-Parietal Lobe Atrophy (Late)


• Infarction

• Hemorrhage

• Infection

• Tumor

• Trauma

• Dementia

• MS

• Epilepsy



Multiple Sclerosis (MS) Imaging

• MRI is the imaging study of choice

• Help establish “dissemination of lesions in time and space”

• Estimate disease burden

• Identify acute (inflammatory) vs. chronic lesions (enhancement = active inflammation)

Tumefactive MS


• Infarction

• Hemorrhage

• Infection

• Tumor

• Trauma

• Dementia

• MS

• Epilepsy



Seizure Imaging

• MRI is the imaging study of choice

• Identify and localize offending lesion

• New onset vs. chronic epilepsy

• Younger vs. older patients

• Search may be guided by EEG / clinical sx

• Preoperative planning

e.g. language lateralization before temporal

lobectomy

Congenital anomalies: Polymicrogyria

Congenital anomalies: Schizencephaly

Mesial Temporal Sclerosis

Most common pathology found in medically refractory epilepsy patientsRare under age 10 or with new seizuresPathogenesis unknown

- Post ictal / kindling?

Pathology: Hippocampal atrophy / gliosis

MesialTemporal Sclerosis

FLAIR

T1

T2

• Atrophy• Loss gray-white•↑T2 / FLAIR


• Infarction

• Hemorrhage

• Infection

• Tumor

• Trauma

• Dementia

• MS

• Epilepsy



Cranial Nerve Imaging

FIESTA

CN-5CN-8

CN-7

Vestibular Schwannoma

Intracochlear Schwannoma

30 y/o F with 6wk

h/o blurred vision

Craniopharyngioma

CT vs. MRI

Wide doughnutOpening

10-20 minutesLength

Adjust windowTechnique

AialPlane

Bright Bone

Long, narrow

30-60 min

T1, T2, Pd

3-D

Dark

Magnetic fldX-ray beamObtained

MRICT

Advantages to CT

• Costs less than MRI

• Better access

• Shows up acute bleed

• A good quick screen

• Good visualization of bony structures and calcified lesions

Disadvantages to CT

• Resolution

• Beam-hardening artifact

• Limited views of the posterior fossa and poor visualization of white-matter disease

Advantages to MRI

• Good resolution—excellent view of brain structure

• 3 dimensions

• Good gray-white differentiation

• Adjust settings based on characteristics of the lesion

• Good view of the posterior fossa

Advantages to MRI

• No radiation exposure

• Gadolinium contrast is relatively nontoxic

• Capacity for quantitative imaging, 3-D reconstruction, angiography, spectroscopy

Disadvantages of MRI

• Cost

• Some patients ineligible because of pacemakers, other metal

• Claustrophobia

• Long exam

• Access

What Is Bright

on CT?

• Blood

• Contrast

• Bone

• Calcium

• Metal

What Is Dark

on CT?

•Air

•CSF/H20

Artifacts

• Beam hardening

• Bone

• Foreign body

• Motion

Uses for SPECT and PET

• Acute stroke

• Identify a seizure focus-increased flow during sz and decreased interictal flow

• Dementia-frontal pattern in FTLD, temporo-parietal pattern in AD

• Ligand imaging in PD, others

Landmarks

• Axial views

– Fourth ventricle

– Petrous bone and sphenoid ridge

– Aqueduct

– Third ventricle

– Lateral ventricles

– Frontal horns

– Calcifications in the choroid plexus, pineal, basal ganglia and falx

– Caudate, putamen and globus pallidus

Landmarks (Cont.)

– Internal capsule—anterior and posterior limbs– Thalami– Sylvian fissures

• Sagittal views– Severity of cortical atrophy– Corpus callosum and cingulate gyrus

• Pituitary– Coronal views– Hippocampus and amygdala

NormalHippo-

Campus

Atrophic

Hippo-campus

in AD62 year old

woman with

rapid

progression of

memory loss

Introduction to Scan Interpretation

• Is the scan

– Contrast or noncontrast?

– Good quality?

• Describe the abnormality

– Size—small, punctuate, medium, large

– Shape—round, well circumscribed, ovoid, irregular, patchy

Introduction to Scan Interpretation (Cont.)

• Signal intensity

– High signal, hyperdense

– Low signal, hypodense

– Isointense, isodense

– Mixed signal

• Location

Vascular DementiaThree types of vascular dementia

Multiple large

Vessel infarctions

Bilateral strategic

thalamic infarctsBinswanger’s

Disease

Normal Pressure Hydrocephalus: NPH

• Cognitive Impairment

• Gait Disturbance

• Bladder Control

• May Have:

Behavior Problems

Parkinsonism

MRI findings

• Ventricular enlargement disproportionate to the amount of atrophy

• Bowing of the corpus callosum• Smooth rimming of high signal around the ventricles

due to transependymal flow of CSF

NPH: pre-op NPH: post-op-130 mm H2O

Types of fMRI

• BOLD-fMRI which measures regional differences in oxygenated blood

• Diffusion-weighted fMRI which measures random movement of water molecules. Diffusion tensor imaging (DTI) measures diffusion of water in different directions and is a good test for studying white matter tracts.

• MRI spectroscopy which can measure certain cerebral metabolites non-invasively

DTI reconstruction of the corpus callosum

3D reconstruction

with functional

overlay

fMRI:Visualstimulation

MR Spectroscopy

MR spectroscopy of N

acetyl aspartate

(NAA) showing

decline of NAA over

time in patients with

Alzheimer’s disease

(lower line)

compared to age-

matched controls.

GOOD LUCK

SAMIR EL ANSARYICU PROFESSOR

AIN SHAMSCAIRO

ct and mri interpretation

Health & Medicine

nasopharynx coronal

level of medullaanswers6

level of ponsanswers8

level of thalamusanswers28

superior sagittal sinus8

superior sagittal sinus29

level of mid brainanswers18

inferior sagittal sinus4