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Transcript of Byrne 2008 Medicine
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7/30/2019 Byrne 2008 Medicine
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InvestIgatIons
MeDICIne 36:10 545 2008 elir Ld. all rih rrd.
NuroradioloyJ v Byr
Abstract
adc i urrdily, lik m mdicl imi pcili, r
dri by chicl imprm d cliicl rm ii-
i prdim. tchiclly, h mphi h lwy b impr
im quliy whil rduci h u iizi rdii. thi h ld
rr rlic cmpur p-prci h im d u
mdlii h d il iizi rdii, uch MRI d
Dpplr ulrud. I h l w yr ub-pcilizi urrdi-
li h ccurrd wih pcili i pdiric urrdily, hdd ck imi, d iril urrdili mri rm
rduci umbr rli. thi chpr dcrib i dil h mi
imi mdlii ud i cliicl prcic. th ii i hw
hw ch chly i dplyd r iii d rm. th
mphi i hlpi h rdr udrd which i h m
pprpri yp imi i dir circumc,wh cr
hcm c i dd (d wh i i ) d hw dir-
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ud chiqu r i cx wihi urrdily d pcili
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Kywords irphy; cmpurizd mrphy; mic rc
imi Dpplr ulrud; mylrphy; prui imi; pirmii mrphy; rdiuclid ciNeuroradiology uses planar scanning, i.e. computerized tomog-
raphy (CT) and magnetic resonance imaging (MRI), alone or
in combination, to identiy most central nervous system (CNS)
pathologies. Traditional radiographic techniques (e.g. plain
radiography, myelography and angiography) are now second-
line modalities. Skull radiography has a role in the emergency
department, but not in general medical or neurology out-patient
departments. Myelography with intrathecal injection o radio-
graphic contrast media is now reserved or patients who areunable to undergo MRI because o implants (e.g. cardiac pace-
makers) or extreme claustrophobia, and is generally used in
combination with CT. Techniques such as Doppler ultrasound
(carotid, transcranial and intra-operative), radionuclide scanning
and unctional MRI have specic indications and are important
research tools with limited roles in routine practice.
JV Byrne FRCS FRCR is Consultant Neuroradiologist at the John Radcliffe
Hospital and Professor of Neuroradiology at the University of
Oxford, UK. His specialist interests are cerebrovascular disease and
interventional neuroradiology. Competing interests: none declared.
CT
Since its introduction in the mid-1970s, CT has been the main-
stay o neuroradiological diagnosis. Its role has evolved in the
last decade with the introduction o aster multislice scanners,which generate considerably more data than previous machines,
allowing better-quality three-dimensional (3D) image displays.
Tcniqu
The basic principle o CT involves rotating an X-ray source and a
series o detectors around the patient and making multiple mea-
surements o radiation attenuation. The measured attenuation
(amount o radiation absorbed) by small volume-elements (vox-
els) o the subject is calculated by computer and used to build
a two-dimensional (2D) picture composed o a matrix o pixels.
Each pixel is assigned a grey-scale value (in Hounseld units),
which is based on the measured attenuation and thereore refects
the density o the scanned tissue. Hounseld units, named aterthe inventor o CT, are scaled with the attenuation value o water
set at zero and maximum density +1000 and minimum density
1000. High-density structures (e.g. bone or calcication) are
depicted in white and low-density tissues (e.g. air) in black; inter-
mediate densities are depicted in grey. By this means, the inher-
ent contrast resulting rom density dierences between tissues is
displayed on a cross-sectional image (Figure 1).
In order to obtain non-axial views it was previously necessary
either to alter the patients position or angle the scanner gantry.
The extent to which the latter can be achieved was limited by the
engineering o the scanner. The problem has been solved by spi-
ral scanning and the introduction o multiple detector systems.
The original scanners collected data or each 2D slice in a single360 rotation using a single detector. Multiple 2D images could
be re-assembled by computer reconstruction to obtain images in
3D displays but the quality was relatively poor. Current scan-
ners move the X-ray source and patient simultaneously, and scan
in a helical pattern to produce volume data images in seconds.
These speeds are achieved using multiple detectors, which col-
lect data as they move. Current multidetector scanners employ
up to 64 detectors and can scan the entire brain in less than
3060 seconds. These speeds reduce arteacts caused by the
patient moving and are ast enough to scan during the rst pass
o a bolus o intravascular radiographic contrast media. This has
been a major advance or neuroradiology.
nw mulilic Ct cr r ud r Ct irphy,
which i rpidly rplci chr irphy
Diui-wihd MRI bl rlibl, ulr- dii
ichmic rk
thr i icri rd ilr MRI quc
pcic phli
Cmpur rcruci diilizd MRI d rdirphic
im prid -cr diply i hr dimi
Wats nw?
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InvestIgatIons
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CT wit contrast mdia
A water-soluble iodine-containing agent is injected intrave-
nously and accumulates in areas o bloodbrain barrier break-
down. Contrast agents are used to highlight tumours and areas
o infammation (e.g. meningitis, abscesses). The eect o uptake
by a lesion is to increase its density so that it appears brighter
(relative to the surrounding brain). This is termed enhancement
and refects the vascularity o the tissues, i.e. it is increased in
vascular tumours and reduced in areas o inarction.
Contrast media can also be injected into arteries as well as
veins to show vessels, i.e. angiography, or intrathecally by lum-
bar puncture to show the spinal cord, i.e. myelography. CT is thenused to image the structures outlined by the density dierences
within the injected body compartment. This is the principle o
traditional radiographic myelography which CT has replaced
because it is more sensitive than X-ray lm and CT angiography
(CTA). The images are acquired as digital 3D data, which makes
their interpretation easier (Figure 2).
Fast scanning during injections allows the rate o contrast
uptake by a tissue to be measured and is the basis o perusion
scanning. This technique is used to estimate blood fow and
blood volume within tissues by comparing time/density curves
between dierent parts o the brain. It is used to identiy areas o
under-perusion ater stroke.
MRI
MRI is now the modality o choice or the investigation o most
neurological disease because it does not use ionizing radiation
and is extremely sensitive to small changes in tissue watercontent (Table 1).
Principls of MRI
In MRI, imaging is based on the phenomenon o magnetic res-
onance, in which elements with an odd number o subatomic
particles (protons and electrons) can be induced to resonate
Calcification
Frontal horn
Cyst
Cyst
Axial CT scan without contrast,
showing calcification in an
oligodendroglioma that was
found to be partially cystic at
surgery. The calcification was
not evident on MRI
Fiur 1
A coronal view of the frontal lobes (computed tomography angiography) showing a haematoma and the nidus of a brain arteriovenous
malformation (AVM). The scan is performed during the passage of a bolus of radiographic contrast so that the arteries are enhanced and
reconstructed by computer to produce this display.
Draining veins
Nidus of arteriovenousmalformation (AVM)
Haematoma
Anterior cerebral arteriesdisplaced by haematoma
Middle cerebral artery
Enlarged middle cerebralartery and branchessupplying AVM
Fiur 2
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when placed in a strong magnetic eld. Clinical MRI is perormed
at the resonance requency o hydrogen nuclei because they are
abundant in biological tissue. Resonating hydrogen protons are
perturbed by electromagnetic energy, applied as a radiorequency
pulse. This causes the protons to emit a weak signal, which is
detected, amplied and, ater computer processing, used to con-
struct an image. Dierent tissues contain dierent amounts o
hydrogen (largely in water) in various molecular environments;the appearance o the image depends principally on the concen-
tration and molecular environment o the perturbed hydrogen
protons and the applied radiorequency pulse.
The appearance o the image can be changed by manipulat-
ing the radio-requency pulse, using electronic protocols (termed
sequences). The parameters commonly measured are T1, T2
and T2* relaxation times (Figure 3),
Images relying principally on contrast produced by T1
relaxation are termed T1-weighted (T1 W) and show cere-
brospinal fuid (CSF) darker than the brain. These sequences
are designed to show the anatomical detail o the brain andspinal cord. They are used with contrast enhancement or simi-
lar indications to CT. The contrast medium used in MRI is a
paramagnetic substance, such as gadolinium, which alters the
Head of caudate nucleus
a Axial T2W and b T1W MRI showing the basal ganglia.
Lentiform nucleus(comprisingputamen,globus,pallidius)
Thalamus
Trigone region oflateral ventricle
White matterof frontal lobe
Sylvianfissure
Externalcapsule
Internalcapsule
Frontal horn oflateral ventricle
Subcutaneous fat
Sulci of
Sylvian fissure
External
capsule
Posterior partition of
lateral ventricle (trigone)
Head of caudate
nucleus
Lentiform
nucleus
Thalamus
Third
ventricle
Interhemispheric
fissure and falx
a b
Fiur 3
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magnetic properties o blood and appears brighter on T1 W
images (Figure 4).
Water (and thereore CSF) appears white on T2-weighted (T2 W)
images. T2 W images are very sensitive to increases in cerebral
water, which occur in most infammatory and neoplastic diseases
o the CNS. Cerebral white and grey matter can be distinguished
because o dierences in their water and at content.
T2 star (T2*) is the term used to describe the eects on the scano molecules with inherent magnetic properties. The best example
is the iron contained in haemoglobin (Hb). Ater acute haemor-
rhage, the magnetic resonance signal rom a blood clot is aected
by the extravasated Hb. The magnetic eect, termed susceptibility,
causes local dierences (inhomogeneities) in the magnetic gradi-
ent and loss o signal. T2*-weighted sequences are sensitive to any
magnetic eld inhomogeneity and are best at showing the eects o
both acute and chronic cerebral haemorrhage (Figure 5).
Hydrogen protons in bone or in areas o calcication return
little signal and thereore appear dark on both T1 W and T2 W
sequences. MRI is not as sensitive to brain calcication as CT.
MRI squncs and tcniqusA typical brain scan comprises several sequences designed to
image the brain in three orthogonal planes using a combination
o sequence types. The spine is imaged in the sagittal plane with
axial scans at levels o interest. Any plane o scan can be desig-
nated on MRI (unlike CT). Contrast medium (e.g. gadolinium)
a
b
a Saggital T1-weighted MRI
after administration of
intravenous gadolinium. A
cystic cerebellar tumour shows
partial enhancement.
b Magnetic resonance
angiography enhanced with
gadolinium and reconstructed
in the axial plane. The tumour
is only moderately vascular.
This was confirmed at surgery;
histological examination
revealed a cerebellar
astrocytoma rather than a
more vascular
haemangioblastoma.
Trigone of
lateral ventricle
Enhanced
lateral sinus
Non-enhancing
cystic element of
cerebellar tumourEnhancing
component of cerebellar tumour
Basilar artery
Jugular bulb
Sigmoidsinus
Lateral sinus
Torcula
Posteriorcommunicating artery
Internal carotidartery
Posteriorcerebralartery
Tumour incerebellar
hemispherewithout evidence ofvessel hypertrophy
Fiur 4
Diffrntial dianosis usin MRI
Multifocal wit mattr (i-sinal) lsions on T2-witd
squncs
Mulipl clri
Ici prri mulicl luccphlphy,
Lym di, pprui ici
Ifmmry cu dimid cphlmylii,
rcidi, chric ifmmry plyurii
Crbrculr di miri, xmi prcy,
ubcu hrclric cphlmylii
vculii rulmu, ymic crizi, rhumid
nplm mi
txic pi mylilyi, prdii ch
Matrials rturnin i sinal on T1-witd squncs
F (icludi -cii umur prduc)
subcu hmm (mhmlbi)
Mlm (mli i prmic)
Flwi bld m quc Prmic cr (.. dliium)
Tabl 1
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is administered intravenously to highlight tumour and infam-matory lesions that have interrupted the bloodbrain barrier
(Figures 4 and 6).
CSF signal-suppressing sequences: Since T2 W sequences are
best or demonstrating ocal lesions causing increases in cerebral
water, lesions in the periventricular brain (e.g. multiple sclerosis)
may be obscured by the high signal returned by adjacent CSF. A
fuid low-attenuation inversion recovery (FLAIR) sequence was
developed to show periventricular plaques because it produces
a T2 W image with dark CSF but has proved to have wider uses
including tumour ollow-up (Figure 7). It is usually included in a
standard brain scan protocol.
Fat-suppression sequences: Fat appears bright on standard T1W and T2 W sequences. Sequences that suppress the at signal
are used to investigate suspected at-containing tumours and
lesions in areas containing at (e.g. the orbit, Figure 8).
Diffusion-weighted MRI: Physiological and pathological changes
in the Brownian motion o water in the cellular and extracel-
lular compartments o tissue can be distinguished by diusion-
weighted MRI. These movements are detected on ultra-ast scans
which measure the rate and direction o water diusion. Acute
cell swelling ater ischaemic stroke (due to cytotoxic oedema)
restricts normal diusion. DWI scanning can demonstrate this
change and can demonstrate hyperacute inarction (Figure 9),
a Axial T2 W MRI showing an acute haematoma in the frontal lobe. The centre of the haematoma contains deoxyhaemoglobin which distorts the
magnetic field locally and reduces the signal return. This results in a dark area on the image. b is the same patient scanned 2 weeks later when
the effect has reduced as the clot breaks down and the centre now returns a higher (brighter) signal.
a
b
Vasogenic oedema
surrounding haematoma
Signal loss due to magneticeffect of acute haematoma
Third ventricle containing
cerebrospinal fluid
Internal cerebral veins
Early low signal rim to
haematoma due to
haemosiderin
Vasogenic oedema
Bright centre of
subacute/chronic haematoma
Falx
Anterior cerebral arteries
Fiur 5
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beore changes are detectable on CT. It is also used to distin-
guish brain abscesses rom tumours since pus in the ormer is
associated with restricted diusion, which is not seen in areas o
tumour-induced vasogenic cerebral oedema.
Functional MRI: Sequences that allow production o images in
less than 1 second can be used to perorm dynamic scanning and
real-time imaging. Fast-scanning techniques such as echoplanar
imaging can show areas o increased brain activity and are used
in unctional MRI or research and to locate eloquent areas o the
brain in patients beore neurosurgery. Perusion imaging tech-
niques (i.e. scanning immediately ater an intravenous injection
o contrast medium) is used with DWI so that reduced perusion
(i.e. contrast uptake) can be compared with areas o restricted
diusion on DWI to identiy ischaemic brain that is potentially
salvagable brain ater stroke.
a
b
c
Axial T1W a and b and sagittal c MRI showing a tumour which enhances after intravenous gadolinium injection b and c. This is a meningioma
which has grown from the anterior margin of the pituitary fossa. Note how the pituitary gland is bright c because it is outside the bloodbrain
barrier and, therefore, also enhances.
Anterior falx
Tumour
Optic tractMid-brain
Enhancement of tumour
Corpus callosum
Straight sinus (enhanced)
Tumour arising from planum sphenoidale
Mid-brain
Pituitary gland
Pons
Sphenoid air sinus
Fiur 6
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Magnetic resonance spectroscopy (MRS): Since the MR sig-nal refects the chemical composition o tissue it can measure
cerebral metabolites. This is done by producing a display show-
ing the requency spectrum o chemical composition o an area
o tissue. MRS is used in various specic clinical situations
(e.g. to distinguish radionecrosis rom recurrent neoplasms) and
to assay cerebral levels o drugs (e.g. lithium). Despite its theo-
retical potential, its clinical role has proved limited.
Magnetic resonance angiography (MRA): Because moving
hydrogen atoms in fowing blood return dierent signals rom
those in static tissue, sequences have been designed to capital-
ize on the eect o blood fow and highlight vessels. There are
two types o sequence in clinical use: time-o-fight and phase-contrast. Both rely on computer post-processing o images to
produce an angiogram (i.e. images showing blood vessels). They
can selectively demonstrate arteries (MR arteriography) or veins
(MR venography), based on the velocities and direction o blood
fow, and can be used to demonstrate the patency o intracranial
vessels. No injected contrast is needed, but MRA is increasingly
perormed ater injection o gadolinium to improve the resolution
o vessels and to obtain the temporal dimension. Fast scanning
allows the use o 3D data collection and is now used extensively
or the diagnosis and ollow-up o treated vascular lesions such
as aneurysms and arteriovenous malormation, and to show
tumour vasculature and vessel occlusions (Figure 4).
CSF in frontalsulci
Lateral ventricle
Demyelination
Demyelination
CSF ininterhemisphericfissure
Lateral ventricleDemyelination
a Sagittal T2-weighted and b axial fluid low-attenuation inversion recovery MRI in a patient with multiple sclerosis. In a, plaques of
demyelination return high signal (bright), as does CSF. The sequence used in b is designed to show plaques as high-signal lesions, but with low
signal returned by CSF. The resulting image clearly shows areas of demyelination, against dark CSF in the adjacent ventricles.
a
b
Fiur 7
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Wn to us CT or MRI
During CT the patient is more accessible and overall scanning is
quicker, thus CT is saer ater recent trauma and or imaging in
very ill patients.For almost all other indications brain and spine
scanning uses MRI because o the absence o ionizing radiation,
high sensitivity to CNS pathology and the ability to image in anyplane directly. The last is especially useul when imaging the
spine (Figure 10)
The strong magnetic elds used in MRI can aect cardiac pace-
makers and may disturb metal implants. Patients with pacemak-
ers, some types o aneurysm clips or retained metallic oreign
bodies (particularly in the eye) cannot be scanned and so they are
imaged with CT. Other problems that limit the use o MRI are the
claustrophobic nature o the scanner and the need or patients to
remain quite still during scanning. For these reasons, sedation or
general anaesthesia may be required to scan children and patients
who suer claustrophobia. Monitoring patients under general
anaesthesia is more complicated during MRI than CT.
CT is better at showing intracranial calcication (Figure 1),
bone and recent intracranial haemorrhage (Figure 11), particu-
larly subarachnoid haemorrhage, though it seems likely that the
capabilities o MRI will continue to expand. Recent technical
improvements in 3D scanning with CT have increased its use or
angiography, especially ater spontaneous intracranial haemor-
rhage. CT angiography has replaced emergency catheter angiog-raphy in many departments and its complementary role assures
it a place in neuroradiology or the oreseeable uture.
Radiorapic aniorapy
Tcniqu
Cerebral intra-arterial angiography is usually perormed by selec-
tive catheterization o the carotid or vertebral artery. Following
percutaneous emoral or brachial artery puncture, a catheter is
positioned under fuoroscopic control and radio-opaque con-
trast medium is injected rapidly. Passage o the contrast bolus
through tissues rom artery to vein is recorded by a series o
Coronal MRI of the orbits obtained with a T2-weighted sequence
(hence bright CSF), showing the orbital optic nerves. The external
ocular muscles can also be seen, contrasted against the low signal
returned by fat on this sequence. The right optic nerve (arrow)returns the bright signal characteristic of optic neuritis.
(By courtesy of P Pretorius).
Maxillary sinus
Middleconcha
Inferiorconcha
Anterior hemispheric fissure
Orbitaloptic nervesurroundedby externalocularmuscles
Frontal lobe
Fiur 8
Axial diffusion-
weighted MRI at
the level of lateral
ventricles.
Anatomical detail
is vague
compared with
T1-weighted
images (e.g.
Figure 4b), CSFappears dark, and
grey matter is
lighter than white
matter (note the
crossing fibres of
the anterior
corpus callosum).
This scan shows
restricted water
diffusion caused
by infarction in
the left centrum
semiovale, it was
performed within
hours of the onset
of hemiplegia.
Cortical grey matter
Anterior corpus callosum
White matterof frontal lobe
Frontal hornof lateralventricle
Infarct in
centrumsemiovale
Trigone oflateralventricle
Third ventricle
Fiur 9
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radiographic exposures timed to show the maximum opaci-
cation o each component o the vascular tree. Subtraction o
each digitized image rom a baseline image (obtained beore
the arrival o intravascular contrast) is perormed electronically,
i.e. by digital subtraction angiography (DSA). This process
removes details o the baseline image (i.e. cranial bone) rom
subsequent images so they show only the opacied vessels.Because digitized systems are sensitive to lower concentra-
tions o contrast medium, images can be obtained ollowing
both intravenous (IV-DSA) and intra-arterial (IA-DSA) injection.
Improved computer reconstruction techniques now allow 3D
image post-processing in DSA. To acquire enough data or 3D
displays, a technique called rotational angiography is used. This
involves rotating the X-ray gantry in a similar way to CT during
the injection o contrast medium.
Pros and cons
IA-DSA carries a risk o arterial damage caused by the catheter or
inadvertent introduction o emboli. IV-DSA is thereore attractive
because it is less likely to cause stroke, but it lacks the precision
o IA-DSA. It has been replaced by CTA and MRA. MRA can
provide images o adequate diagnostic quality without expos-
ing patients to the risks associated with ionizing radiation and
radiographic contrast agents. However, CT angiography is more
robust, provides better bone detail and is quicker in acutely ill
patients.Along with the general shit to less invasive imaging, CT and
MR angiography are replacing catheter angiography or diagnosis
and IA-DSA is increasingly perormed only during endovascular
embolization procedures or the treatment o brain arteriovenous
malormations and aneurysms (Figures 2 and 12).
Plain radiorapy and mylorapy
The chest radiograph is the most important plain radiograph in
neuroradiology. Spinal radiography has a limited role as a primary
investigation, except ater trauma. Radiographic tomography and
myelography have largely been replaced by planar scanning.
a
b
Sagittal T1W (dark CSF) and
T2W MRI (bright CSF) of the
lumbar canal in a patient with
spina bifida. a A tract between
the spinal canal and skin
surface containing fat
(therefore bright on the image)
is best seen. b The spinal cord
extends low into the lumbarcanal and is tethered in the
region of the bony defect
(L5/S1).
L2 vertebral body
Low spinal cord
Lipoma in lumbar canal
Tethered cord and filum
White cerebrospinalfluid in expandedlumbo-sacral canal
Lipoma in lumbar canal
Fat-containing tract to skin dimple
Dark cerebrospinal fluid
S1 vertebral body
Fiur 10
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Radionuclid scannin
Brain and spine scanning or the diagnosis o tumours, using
radionuclides such as technetium-99m, has been generally
replaced by CT and MRI. The principle o radionuclide scanning
is that tissues and neoplasms concentrate a substance labelled
with a radioactive isotope (i.e. a radiotracer) and the patient is
scanned at a suitable interval ater its injection. The technique
is most commonly used to identiy sites o metastatic tumour
but tissue metabolism and blood fow can also be assessed with
positron emission tomography (PET) and single-photon emission
computerized tomography (SPECT).
Tcniqus
Positron emission tomography (PET) involves the detection o
two high-energy photons emitted by the annihilation o a posi-
tron rom a radiotracer. The radionuclides used have short hal-
lives and a cyclotron is required to produce them; this, and the
need or a dedicated detector, has previously limited its avail-
ability, but the recent introduction o networked radionuclide
production and systems that are combined with a CT scanner
(i.e. PET-CT) has seen an expansion in its use in oncology.
Single-photon emission computerized tomography (SPECT)
uses gamma ray-emitting radionuclides and can be perormed
using a standard gamma camera. Technetium-99m-labelled
Axial CT scan showing an acute haematoma in the right frontal lobe a. The clot is hyperdense and so appears whiter than the brain. It has
extended into the adjacent ventricle b.
a
b
High-density haemorrhage
in frontal lobe
Calcification in pineal
Part of left lateral ventricle
Haemorrhage in the frontal lobe
Cerebrospinal fluid in left
lateral ventricle
Haemorrhage in the right
lateral ventricle
Falx
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hexamethylpropylene amine oxime (HMPAO) is commonly usedor scanning the brain. This substance is lipophilic and crosses
the intact bloodbrain barrier to bind to unspecied receptors. Its
distribution refects cerebral blood fow and remains stable or
about 1 hour, during which scanning is perormed.
Uss
Both techniques are used to measure cerebral blood fow, but
PET provides unique inormation about cerebral metabolism o
oxygen and glucose, using oxygen-15 and fuorine-18 respec-
tively. They are used to investigate patients with seizure disor-
ders, dementia, neoplasms or ischaemic disease. PET research
has been benecial in the development o SPECT, and both are
used to complement and validate unctional MRI.
Ultrasonorapy
Tcniqu
Ultrasonography is based on the transmission and detection o
refected sound rom tissue planes within the body. Because
bone is relatively impervious to sound, ultrasonography is useul
in the CNS only when perormed through a bone deect (e.g. an
open ontanelle) or ater laminectomy. Duplex ultrasonography
combines high-resolution real-time imaging with Doppler fow
analysis and is used to evaluate the cervical carotid arteries. TheDoppler principle is used to determine the velocity o blood fow
based on requency changes in a continuous sonic signal.
This technique has been rened by the addition o colour
to the displayed images, and high-power instruments are now
available or transcranial use, which are capable o estimating
blood fow velocity in intracranial arteries.
Uss
Transcranial ultrasonography is used to evaluate hydrocephalus
and neonatal haemorrhage in young children. It is simple to use,
but less simple to interpret. Duplex scanning has replaced angiogra-
phy or screening patients with suspected carotid biurcation steno-
sis. It may be combined with MRA, and most vascular surgeons usethe combination or preoperative imaging, instead o IA-DSA.
FURTheR ReADINg
Dmrl P, d. Rc dc i diic urrdily. Brli:
sprir-vrl, 2001.
grm RI, Yum DM. nurrdily: h rquiii (rquii i
rdily). oxrd: Mby, 2003.
obr a, Blr s, slzm K, l. Diic imi: bri, 1 d.
amiry, 2004.
a b
c
2D a and c and 3D b digital subtractionangiography frontal views showing an
aneurysm of the anterior communicating
artery before a and c and during treatment
by coil embolization. The 3D view is
obtained by rotating the X-ray source
during intra-arterial contrast injection and
is used for pre-operative evaluation of the
aneurysm and anatomy.
Pericallosal artery
Aneurysm
Anteriorcerebral artery
Internal
cerebral artery
Middle
cerebral artery
Coils in aneurysm
Microcatheter at
the internal
cerebral artery
termination
Fiur 12