LECTURE – 4 RHPT – 485

THE CENTRAL NERVOUS SYSTEM – CT/MRI SCAN

COURSE COORDINATOR – SEKARLECTURER, M.P.T, SPORTS, MAJMAAH UNIVERSITY ,

MINISTRY OF HIGHER EDUCATION, CAMS, DEPT OF PT&HR ,KINGDOM OF SAUDI ARABIA

PLAIN RADIOGRAPHS

•Plain X-ray is essential modality for initial assessment of the spine.

•Good display of bony details•Limited value in evolution of head trauma since it

may not reflect underlying CNS damage.•Skull radiograph helps in classification of skull

fractures and its extent and therefore further management.

Computerized TomographyCT

•Readily available fast modality for evaluation of intracranial structures.

•Rapid acquisition of axial images.•The procedure of choice for evaluation of

patients with head trauma and stroke patients.

•Provides fine details of the bony structures.

Magnatic Resonance ImagingMRI

•Provides fine details of the brain and spine.•Does not involve irradiation.•Needs special equipment for patient

monitoring.•Few specific contraindication, e.g.

pacemakers, old cerebral aneurysms clips, cochlear implants.

NEURO-IMAGING TECHNIQUES

.1StructuralPlain Skull RadiographyPneumo-encephalography CTStructural MRI

.2FunctionalMagnetic resonance spectroscopy (MRS)Functional MRI (fMRI)Positron emission tomography (PET)Single photon emission computed tomography (SPECT)Brain electrical activity mapping (BEAM)Evoked Potential

USES OF NEUROIMAGING

Indications in Clinical Practice

•Neurological Deficits

•Dementia

Indications in Clinical ResearchIndications in Clinical Research

Analysis of Clinically Defined Analysis of Clinically Defined Groups of PatientsGroups of Patients

Analysis of Brain Activity during Analysis of Brain Activity during Performance of Specific TasksPerformance of Specific Tasks

COMPUTED TOMOGRAPHY (CT)

INTRODUCTION

•Revolutionized diagnostic neuroradiology by permitting imaging of the brain tissue in live patients

•The first CT Scanner was developed in 1972 by Godfrey Housenfield of UK.

•Allan Cormark developed the mathematics used to reconstruct the CT image.

•The invention of CT Scanner earned Housenfield & Allan Cormark the Noble Prize for Medicine in 1979.

BASICS

Normal CT Brain

POINTS TO REMEMBER

•CT images determined only by degree to which tissues absorb X-ray

•Bone, clotted blood, calcified tissue, contrast material appear white & CSF black

•The only component of brain better seen on CT scan is Calcification, which may be invisible on MRI

…Contd

¤ Plain• Diagnostic accuracy 82%

¤ Contrast• IV iodinated contrast medium• Diagnostic accuracy 92%

CRITERIA FOR CONTRAST•Patients with H/O seizure•Patients with H/O cerebro-vascular accident•Suspicion of intracranial SOLs including granulomas,

CNS tumours, metastatic lesions

…Contd

CLNICAL INDICATIONS OF CT BRAIN IN PSYCHIATRY

•Confusion &/ or dementias of unknown cause•First episode of psychosis•First episode of major affective disorder after 50 years of age•Personality changes after 50 years of age•Psychiatric symptoms following head injury•Prolonged catatonia•To rule out complications due to possible head trauma•Co existence of seizure in psychiatric symptoms•Movement disorders of unknown etiology•Focal neurological signs accompanying psychiatric symptoms

…Contd

Weinberg 1984; Beresford et al 1986

ADVANTAGES v/s DISADVANTAGES

ADVANTAGES

•Simpler, cheaper, more accessiblecheaper, more accessible

•Tolerated by claustrophobicsTolerated by claustrophobics

•No absolute contraindicationsNo absolute contraindications

•Fewer pitfalls in interpretationFewer pitfalls in interpretation

•Better than MR for bone detailBetter than MR for bone detail

…Contd

DISADVANTAGESDISADVANTAGES

Ionizing radiationIonizing radiation

IV contrast complicationsIV contrast complications

Limited range of tissue contrastsLimited range of tissue contrasts

MRI

Liquid Helium Cooled1.5 Tesla Solenoid Magnet

Patient Platform

RadiofrequencyTransmitter/Reciever

Coil

INTRODUCTION

•Felix Bloch, working at Stanford University, and Edward Purcell, from Harvard University, discovered NMR

…Contd

WHAT IS AN MRI ?WHAT IS AN MRI ?

Safe & noninvasive testSafe & noninvasive test

Produces pictures of structures inside Produces pictures of structures inside the bodythe body

Images : slices of an organ or part of Images : slices of an organ or part of bodybody

MRI’s computer: 3-D imagesMRI’s computer: 3-D images

HOW IT WORKS ?HOW IT WORKS ?

Body Body strong magnetic field strong magnetic fieldMachine uses Machine uses strong magnetic field & strong magnetic field & pulses of radio wavespulses of radio wavesMachine creates an image Machine creates an image how how hydrogen atoms reacthydrogen atoms reactUsually images are created as single Usually images are created as single slices of organs or structuresslices of organs or structuresMRI computer combine them to give a MRI computer combine them to give a 3-D image.3-D image.

BASIC PRINCIPLE OF MRI

…Contd

Strong magnetic

field

PrecessionSpin

S

N

Emitted photon

Spin down

Spin up

• In a magnetic field, spinning nuclei precess at the Larmor frequency.• The spin-up and spin-down nuclei have different energies.• Transitions between levels lead to emission of photons, which we can detect.

…Contd

THE NORMAL HUMAN BRAIN AS SEEN BY MRI…Contd

Data sources : The Whole-brain Atlas, K. A. Johnson and J. A. Becker, Harvard

TYPES OF IMAGES

T1 WEIGHTED IMAGES

–An SE sequence with a short TR (200 – 1000 milliseconds) and a short TE

(20-25 milliseconds)

–CSF, cortical bone, air & rapidly flowing blood have negligible signals

appear dark

–Fat & bone marrow have high signal intensity appear white

–Useful in evaluation of cerebropontine angle cistern &

pituitary fossa

…Contd

T2 WEIGHTED IMAGEST2 WEIGHTED IMAGES

AAn SE sequence with a long TR (2000 n SE sequence with a long TR (2000 – 2500 milliseconds) and a long TE (>75 – 2500 milliseconds) and a long TE (>75 milliseconds)milliseconds)

CSF has bright signal intensity & CSF has bright signal intensity & relative to a dark signal from grey & relative to a dark signal from grey & white matterwhite matter

Useful in demyelination, edema & Useful in demyelination, edema & tumour infiltrationtumour infiltration

Reveal brain pathology most clearlyReveal brain pathology most clearly

T1 WEIGHTED IMAGES T2 WEIGHTED IMAGES

IMPORTANT POINTS

INDICATIONS

•To rule out organic cause of psychiatric

illness

•Abrupt change in mental state

•New onset memory loss

•New onset dementia

ADVANTAGESADVANTAGES

Does not expose the Does not expose the patient to ionizing patient to ionizing radiationsradiations

Generates images in Generates images in three planesthree planes

Demyelinating disease Demyelinating disease can be assessed reliablycan be assessed reliably

To study posterior fossa To study posterior fossa structuresstructures

DISADVANTAGESDISADVANTAGES

Avoided in patients Avoided in patients wearing metallic deviceswearing metallic devices

ClaustrophobiaClaustrophobia

Does not pick up bony Does not pick up bony abnormalitiesabnormalities

Difficult in Difficult in uncooperative patientsuncooperative patients

IV CONTRAST IN NEURO-IMAGING

•CT Iodine based–Iodine is highly attenuating of X-ray beam (bright on CT)Iodine is highly attenuating of X-ray beam (bright on CT)

•MRI Gadolinium based (Gadolinium DTPA)–Gadolinium is a paramagnetic metal that hastens T1 relaxation of nearby Gadolinium is a paramagnetic metal that hastens T1 relaxation of nearby

water protons (bright on T1-weighted images)water protons (bright on T1-weighted images)

•Tissue that gets brighter with IV contrast is said to be “enhanced”

•Enhancement reflects the vascularity of tissue, butEnhancement reflects the vascularity of tissue, but……–The blood-brain barrier keeps IV contrast out of the brainThe blood-brain barrier keeps IV contrast out of the brain–Enhancement implies BBB is absent or dysfunctionalEnhancement implies BBB is absent or dysfunctional

FLAIRFluid Attenuated Inversion Recovery

POINTS TO REMEBER•Special type of MRI scan

•T1 image is inverted & added to the T2 image

•Doubles the contrast between grey & white matter

•Special indications.1Temporal lobe epilepsy causing sclerosis of hippocampus.2Localizing the areas of abnormal metabolism in degenerative neurological

D/Os

…Contd

MRS

PRINCIPLE

…Contd

Basic principle similar to MRI

MRS can detect several odd-numbered nuclei

Permits study of many metabolic processes

φ Nuclei align themselves in the strong mag. field

φ A radiofrequency pulse causes the nuclei of interest to absorb & then emit energy

φ Readout on MRS in the form of a spectrum Can be converted into a pictorial image of the brain

NUCLEI USED IN MRS

…Contd

NUCLEINUCLEI USESUSES

H¹H¹ Decreased aspartate (NAA) in dementia & other neural lossDecreased aspartate (NAA) in dementia & other neural loss

Li Li 7 Pharmacokinetics of LithiumPharmacokinetics of Lithium

C¹³C¹³ Study of metabolic pathwayStudy of metabolic pathway

F 19F 19 • Pharmacokinetics of certain drugs like SSRIs (Fluoxetine, Pharmacokinetics of certain drugs like SSRIs (Fluoxetine, Fluoxamine)Fluoxamine)

• Analysis of glucose metabolismAnalysis of glucose metabolism

P³¹P³¹ Tissue metabolism (compound containing high energy Tissue metabolism (compound containing high energy phosphates like ATP, ADP etc.)phosphates like ATP, ADP etc.)

fMRI

What is an AXIAL section?

TOMOGRAPHIC IMAGES ARE

IN A SPECIFIC PLANE

SAGITTALAXIAL CORONAL

RT RT

Lateral ventricles

Brain CT…•Note that we take axial slices beginning from the skull base.,

parallel to a standard line (orbito-meatal or canthomeatal line).• The thickness of the slice (the distance between a slice –picture-

and the following slice –picture-) is 10mm or as determined.

•The skull base is a bony area with much small details, so we take the slices with less thickness (5mm) to show al the details.

•You have to recognize the following: 1 -Cerebral hemispheres 2 -Brainstem 3 -Ventricular system 4 -Basal ganglia and thalamus 5 -Basal cisterns (subarachnoid space)

Cerebral Hemispheres (Lobes) & Brain Stem…

•Lobes in the cerebral hemispheres are the frontal, temporal, parietal, and occipital

lobes.•Note that the white matter appears grey,

and the grey matter appears white.•Brainstem is composed of the mid brain,

Pons & medulla oblongata .

Ventricular System…•It is composed of the lateral ventricles, 3rd ventricle and

the 4th ventricle.•Remember that the ventricles contain the choroid

plexuses which maybe normally calcified so appears white in CT.

•The lateral ventricle is composed of the frontal horn (anterior horn), ventricular body, occipital horn (posterior

horn) and the temporal horn (inferior horn).•Normally, the temporal horns can’t be seen in CT. So,

when they appear we call them “prominent temporal horns”; If they are dilated, this indicates hydrocephalus.

•4th ventricle is situated behind the pons .

Basal Ganglia & Thalamus…

•You need to recognize: 1 -thalamus 2 -caudate nucleus 3 -lentiform nucleus 4 -internal capsule (it’s anterior limb and

it’s posterior limb)

Basal Cisterns (Subarachnoid Space)…•They contain cerebrospinal fluid (CSF), so they

normally appear black in brain CT.•Basal cisterns are :

1 -prepontine cistern 2 -cerebellopontine cistern 3 -interpeduncular cistern 4 -ambient cistern 5 -quadrageminal cistern 6 -sylvian cistern (sylvian fissure)

CT Brain Bone Window…

•It’s done by just giving an order for the CT machine to give us a CT brain- bone window.

•You have to recognize the following: 1 -Frontal, parietal, temporal & occipital bones (Bone

appears white on CT scan). 2 -Bone sinuses (Sinuses are full of air)

Brain edema

Appears as hypodense area on CT scan. Two main types:

Cytotoxic:▪ Results from cell death.▪ Involves the gray matter.

Vasogenic:▪ Results from disruption of the BBB.▪ Mainly involves the white matter.

Axial injury: Concussion:

▪ Brain damage at the microscopic level.▪ Usually associated with normal imaging

Contusion:▪ Focal area of edema that can be associated with

hemorrhage..▪ Usually involves the fronto-temperal lobes

Trauma

Shear injury(diffuse axonal injury): significant brain damage results from

acceleration/deceleration mechanism. Associated with poor prognosis. MRI is more accurate in evaluating the extent

of injury.

Trauma

Extra-axial injury: Blood can accumulate in different spaces

around the brain. Subarachnoid hemorrhage is usually has a

benign self-limiting course. Its presence is suggestive of significant trauma.

Trauma

Subdural hematoma: Usually of venous origin. Slowly enlarging blood collection between the

dura and the subarachnoid space. Has the characteristic crescent shape. It crosses the suture line.

Trauma

Extradural (Epidural) hematoma: More than 90% occurs supratentorial and

more than 95% are unilateral. Usually attain their final size quickly. Only 23% of EDH will enlarge, mostly within 36

hours. Has the characteristic lucent period.

Trauma

Extradural (Epidural) hematoma: Usually associated with skull fracture(85-95%). Results from injury to middle meningeal artery

or one of its branches. About 10% are of venous origin. It has the characteristic biconvex shape. Limited by the suture lines.

Neoplasm

Divided into two major categories: Intra-axial:

▪ The tumor is within brain parenchyma.▪ Metastasis is the most common etiology in adults.

Extra-axial:▪ Arising from the brain coverings or nerve sheaths.

Inta-axial Tumors

•Primary brain neoplasm:–Gliomas are the most common types.–Wide variety of pathological types: astrocytoma,

oligodendroglioma, ependymoma.•Metastasis:

–Lung, breast and colon are common primary sites.–Usually multiple, can be hemorrhagic.

Extra-axial tumors

•Meningiomas are the most common pathological type.

•Nerve sheath tumors are less common, e.g. schwannoma, neurofibroma.

•Metastasis is less common than intra-axial ones.

        MRI is a noninvasive imaging technique that does not use x-rays.   The process involves passing a strong magnetic field through the head.  The magnetic field used is 30,000 + times that of the earth's magnetic field.  It's effect on the body, however, is harmless and temporary.  The MRI scanner can detect radiation from certain molecules, which are present in different concentrations in different tissues. 

Tumor in Wernicke’s Area

CNS Infection•Meningitis is the most common form of CNS

infection.•Its clinical and lab diagnosis.•Imaging is helpful in excluding secondary

complications.•Diffuse meningeal enhancement is a common

finding.•Normal CT or MRI does not exclude the diagnosis .

CNS infections

•Sub-dural effusion:–Common in children especially with H. influenza

meningitis.–Can be treated conservatively.

•Brain abscess:–Usually secondary to hematogenous spread of

microbes.–May not be distinguished from brain tumor.

CNS infections

•Viral infections:–MRI is very sensitive for diagnosis of viral

encephalitis.–Herpatic encephalitis has a characteristic bilateral

temporal lobe involvement.

Vascular Disorders

•Stroke is a major source of mortality and morbidity.

•Most stokes are ischemic, result from vascular occlusion by a thrombus or embolus.

•CT is usually the initial modality to evaluate these patients.

Vascular Disorders

•CT:–Usually becomes positive in 12-24hours after

onset of neurological deficit.–Edema in a vascular distribution.–Helpful to rule out ICH or hemorrhagic conversion.

Vascular Disorders

•MRI:–It becomes positive earlier than CT.–Diffusion weighted images can become positive in

few minutes from onset.–MRA can be obtained at the same time to

evaluate vascular occlusion.

Vascular Disorders

•Vascular abnormalities:–Aneurysms:

• usually manifest in the form of subarachnoid hemorrhage.

–AVM :•presents with either ICH or headache.•Can be diagnosed with enhanced CT or MRI.•Angiogram is diagnostic and therapeutic.

MRI Weighting

T1 Weighted MRI T2 Weighted MRI

Axial FLAIR

Brain MRI

Most brain lesion are seen by T2 or FLAIR MRI.

Usually, we use T1 MRI to visualize brain anatomy, while T2 MRI & FLAIR is used for visualizing brain pathology.

Coronal Brain MRI

You have to recognize: 1- sella turcica: which contains the

pituitary gland 2- cavernous sinus 3- sphenoidal sinus 4- optic chiasma

Sagittal T1 with contrast

4th ventriclr

Body of lateral ventricle Body

Genu

RostrumSplenium

Sagittal Brain MRI…

In a sagittal MRI, you have to recognize: The Corpus callosum that is composed of:

rostrum, genu, body and splenium.

  The patient presented confused after falling on his head. On examination there were right-sided neurological signs present.

Section of a computed tomographic (CT) scan of the brain.

A high attenuation abnormal area is seen in the subdural space on the left side.

This is compressing the normal left cerebral hemisphere and is causing a masseffect such that there is compression of the left lateral ventricle and a shift of the midline to the right.

These are the features of an acute subdural haematoma.

CNS haemorrhage

Head injuries are a common clinical problem especially in casualty departments.

The investigation of choice in patients with neurological signs is a CT scan.

Although skull X-rays may show a fracture, they do not provide information about the brain parenchyma.

In addition, there may be quite significant brain pathology in the absence of fractures on the skull radiograph.

often due to ruptured middle meningeal arteryExtra-dural haemorrhage -

The following may be seen following trauma:

CT scan shows a high attenuation (white) mass (fresh blood) peripherally around the brain adjacent to the cranial vault. The inner margin is often convex. Requires urgent neurological drainage

Subdural haemorrhage :-

may present following a fall (often in alcoholics) with fluctuating consciousness .

CT scan shows areas of crescentic peripheral high attenuation (white) with

1 .a concave inner border

2. midline shift may be seen to the opposite side of haemorrhage

3. mass effect may compress ventricles

4. if subdural > 2 weeks old, the blood may be hypodense (grey)

Intra-cerebral haemorrhage.

1. focal area of increased attenuation (white) fresh blood

2 .may cause mass effect with midline shift

3. blood may extend into the ventricles

Cerebral contusion

1. high attenuation areas in the brain are accompanied by brain swelling

2. may be multi-focal

3. haemorrhage may be present in areas of contusion

4. due to shearing of white matter tracts, cerebral swelling may cause compression of ventricles and effacement of sulci

CT scan showing low attenuation fluid collection around the right cerebral hemisphere.

Fluid collection is in the right subdural space and it is causing a minimal amountof mass effect.

The appearances are those of a chronic right subdural haematoma.

The right lateral ventricle is not clearly seen.

Section of a CT scan showing a very large right-sided intra-cerebral haematoma.

The blood is fresh because the attenuation is white.

Fresh bleeding causes a mass effect with a midline shift to the left side, away from the lesion.

In addition, as seen, there is high attenuation (white) area in the lateral ventricles.

This is due to the fact that there has been intraventricular haemorrhage.

 

CT scan of brain. There is an abnormal area of isodense attenuation seen in the left subdural space.

This area is not white (i.e. it is not fresh blood).

It is not of low attenuation either (i.e. it is not chronic). This density is almost similar to that of normal brain tissue.

This is due to the fact that this haemorrhage is perhaps ~ 1 week old and is passing through the phase where the blood goes from appearing bright white to dark on the scan.

These subdurals are easy to miss.

Look very carefully for the mass effect.

One can see that there is no left lateral ventricle clearly seen.

In addition, one can see that the sulci are not clearly seen on the left side becausethere is a subdural collection at this site that is compressing the normal brain tissue scan of the brain.

CT scan of the brain. Note the soft tissue abnormality outside the left occipital bone.

This is a soft tissue haematoma in the superficial tissues of the skull at the back.

The patient has been attacked and hit on the back of the head.

There are patchy areas of increased attenuation (white) seen diagonally in the right frontal lobe that represent areas of contusion and haemorrhage at this site. This is called a contra-coup injury.

The patient presented with a sudden onset of headache.

Subarachnoid haemorrhage

CT scan of the brain and this section shows a marked high attenuation material in the cisterns of the brain and in the subarachnoid spaces.

These are the appearances of a large subarachnoid haemorrhage.

Hydrocephalus (communicating)

Re-bleed

Complications of subarachnoid

Arterio-venous malformation

Rupture of intra-cerebral aneurysm

Causes of subarachnoid haemorrhage

Cerebral infarction

CT scan of the brain showing a section at the level of the thalamus.

There is a generalized atrophy noted.

In addition, a low attenuation area is in the left side of the brain involving the left basal ganglia.

This low attenuation region is not causing any significant mass effect.

The appearances are those of an infarction of the left basal ganglia.

CT section of the brain showing marked low attenuationin the left hemisphere with sparing of the left frontal lobe and left occipital lobe.

These are the appearances of massive infarction of the left side of the brain due to an occlusion involving the left middle cerebral artery.

CT scan of the brain at the level of the occipital lobes showing a low attenuation (dark) area in the left occipital lobe.

This is due to an infarct involving the left posterior cerebral artery.

Cerebral infarction

Cerebral infarction is due to an impaired circulation of the brain.

A thrombus or an embolus causes it (often from the carotid vessels).

The clinical presentation is that of a stroke.

CT scan - used to identify an infarct and to rule out a haemorrhage as the cause of a stroke. In the early stages (first 24 h) the scan may be normal in an infarct1. early signs include loss of grey-white matter interface

2. a reduced density is noted in the brain, and the area involved usually corresponds to the arterial supply affected (e.g. anterior, middle or posterior cerebral artery territories)

3. oedema and swelling in the early stages with mass effect

4. infarcts may be haemorrhagic

5. old infarcts show areas of low attenuation

MRI scan1. shows an area of increased signal on a T2-weighted image of the site of the infarct

2. posterior fossa and brain stem infarcts are better seen using MRI

Carotid ultrasound - allows visualization of the common carotid and internal carotid arteries to look for plaque (soft or calcific) and narrowing of the vessels

CT scan of the brain showing features of atrophy.

These include the prominent sulci and slightly dilated ventricles present in an atrophic brain.

Brain atrophyBrain atrophy is due to the irreversible loss of brain tissue. Atrophy of the brain occurs with ageing and in elderly patients it is common to see the loss of brain tissue.

Radiological signs on CT/MRI

1. Increased cerebro-spinal fluid (CSF) space with widening of the sulci

2. Prominent ventricles

3. Prominent basal cisterns and temporal horns of lateral ventricles

4. In Alzheimer's disease there may be cerebellar sparing

Causes of atrophy

a. Ageing

b. Alzheimer's disease

c. AIDS

d. Trauma long-term sequelae

e. Congenital diseases of the brain

f. Alcohol abuse (chronic)

g. Radiotherapy

h. Degenerative diseases

This patient presented with a history of confusion following treatment of bronchial carcinoma.

MRI scan of a section of the brain showing multiple ring enhancing regions in the brain.

Some are associated with oedema (dark grey area).

This scan has been performed with intravenous contrast to demonstrate the ring enhancement of metastatic disease.

Ring enhancing lesions identified on a MRI or CT scan are due to:

1. Metastases

2. Cerebral abscesses

3. Primary brain tumour

On a CT scan the lesions may be associated with cerebral oedema identified by areas of lower density around the lesion.

On an MRI scan, oedema appears as bright signal on T2-weighted images. The swelling may cause compression of the ventricles and midline shift.

Section of a brain scan in a patient with AIDS.

It has been performed with intravenous contrast showing a ring enhancing abscess, which in patients with AIDS is usually due to toxoplasmosis.

The dark area around the abscess is due to oedema in the frontal lobe.

A 25-year-old patient presented with a history of visual disturbances and pins and needles on two separate occasions.

Axial sections of an MRI study of the brain.

This is in fact a T2-weighted sequence (the CSF and the ventricle appear white).

There are areas of increased signal (white) in the white matter of the brain.

These have the appearances of plaques of de-myelination and in someone of this age group a diagnosis of multiple sclerosis would be considered.

In elderly patients these areas of increased signal (hyper intensities) are quite commonly seen and are often due to vascular changes in an elderly brain.

Multiple sclerosisMultiple sclerosis is a disease predominantly of the young adult characterized by plaques of de-myelination in the brain and spinal cord.

Relapse and remission characterize it, although it may show progression to chronic disability in a number of cases.

Imaging has revolutionized the diagnosis of this disease although a detailed history and examination are of paramount importance, as imaging is not always specific.

MRI findings1. Multiple high signal areas are seen in the brain on T2-weighted images

2. High signal areas < 2 cm

3. High signal areas have smooth margins, are ovoid and are often periventricular in location

4. High signal areas may be present in the spinal cord or optic nerves

5. The most sensitive MRI sequence for detecting lesions is the fluid attenuated inversion recovery (FLAIR) sequence

The patient presented with transient ischaemic attacks and underwent the following test.

Doppler investigation of the carotid artery.

The section shows a calcified plaque at the originof the internal carotid artery that appears to be causing some narrowing of the internal carotid artery.

The plaque is causing some shadowing.

This is the feature of a calcified plaque.

The appearances are those of a plaque causing some narrowing of the internal carotid artery.

Both the carotid bulb and the common carotid artery appear normal.

Cerebrovascular diseaseCerebrovascular disease is a major cause of morbidity and mortality in the Western world.

Investigation of the carotid arteries may be helpful in identifying plaques and narrowing in the carotid bifurcation.

Until recently, investigation of the carotid bifurcation required invasive carotid angiography.

Today, however, the first line investigation is a noninvasive carotid Doppler ultrasound investigation. Doppler ultrasound involves three steps:

1. Inspection of the carotid vessels in a longitudinal plane on standard grayscale images

2. Colour Doppler to outline the stenoses

3. Spectral Doppler to measure velocities of blood flow in vessels to enable quantification of stenosis

Doppler ultrasound can demonstrate

1. Narrowing

2. Plaques

3. Intimal thickening

Magnetic resonance angiography

1. can identify the carotid bifurcation

2. stenoses overestimated

PET measures the emission of positrons from the brain after a small amount of radioactive isotopes, or tracers,  have been injected into the blood stream.  A common example is a glucose-relative with embedded fluor-18.   With this molecule, the activity of different regions of the brain can be measured.  The result is a three-dimentional map with the brain activity represented by colors. 

PET

SCANS

P

E

T

S

C

A

N

S

Dopamine

After Implant of Dopamine-secreting Tissue

Brain Development in First Year of Life

Normal Brain ADHD Brain