817

MR Angiography in Children with Cerebral Neurovascular Diseases: Findings

in 31 Cases

H

.

American Journal of Roentgenology 1992.159:817-823.

Thomas J. VogI1 JOrn 0. Balzer1 Joachim Stemmler1 Clifford Bergma&

E. Egger Josef

Lissner1

OBJECTIVE. We evaluated the suitability of MR angiography for routine use in children with suspected intracranial vascular disease. SUBJECTS AND METHODS. Thirty-one children, 6 months to 14 years old, with intracranial lesions or clinically suspected vascular malformations were studied prospectively with conventional MR imaging and time-of-flight MR angiography. In nine cases, MR angiographic findings were verified with digital subtraction angiography or conventional angiography All MR studies were performed on a 1.5-T MR system using a circularly polarized head coil. RESULTS. Arterial MR angiography, performed in 24 cases, revealed congenital abnormalities of the arterial vessels in 20 cases. Vessel stenosis was observed in nine patients, and displacement of intracranial arteries due to tumors could be seen in 10 patients. Seven children had no abnormal findings. Venous MR angiography was performed in seven children, with depiction of sinus thrombosis in six cases. The comparative analysis of MR angiography and digital subtraction angiography showed equivalent results in nine patients; in one patient the degree of stenosis was overestimated with MR angiography. CONCLUSION. MR angiography, when combined with MR imaging, reveals information about soft-tissue and vascular structures in a single setting. At this point, MR angiography can replace invasive conventional angiography or digital subtraction angiography only in selected cases because of software and hardware limitations. Arterial or venous MR angiography can be helpful as an additional scan in MR examinations of children with suspected cerebral neurovascular diseases, and its noninvasive nature makes it well suited for routine use in children. AJR

159:817-823,

Although

October

conventional

1992

X-ray

angiography

and

digital

subtraction

angiography

(DSA) are the gold standards for the assessment of intracranial vessels [1 -3], the invasiveness of these procedures makes them difficult to perform, particularly in children. Thus, they are not routinely available for use in children in many centers. Among the noninvasive methods of imaging blood flow, MR angiography is an attractive alternative. It can be used to evaluate vessel patency, flow magnitude,

Received March 12, 1992; accepted s/on April 30, 1992.

after revi-

1

Departmentof

Radiology,

University

1 , 8000 Munchen

of Munich,

2, Germany. Ad-

dress reprint requests to T. J. yogi. 2

Pediatric

Munchen

Hospital,

0361 -803x/92/1 CAmerican

University

2, Germany.

594-0817

Roentgen

Ray Society

As an adjunct

raphy can provide tumors that would

information otherwise

zation.

This study was supported by a grant (no. 842501) of the Wilhelm Sander Foundation. ZiemssenstraBe

and flow direction.

of Munich,

8000

MR angiography

to conventional

MR imaging

studies,

about blood supply and vascular be available only through angiography

exploits

the intrinsic

properties

of flowing

MR angiog-

topography of via catheteri-

blood so that

catheterization and the need for contrast material are eliminated. Because of its safety, it is likely that MR angiography will play an increasingly significant role in the workup of children with suspected neurovascular disease. Nevertheless, MR angiography is still subject to a number of technical limitations, because of motioninduced artifacts and artifacts caused by alterations in flow behavior through

abnormal vessels. Furthermore, it is not yet possible to consistently visualize vessels smaller than 1 mm in diameter [4, 5]. We present the MR angiographic findings in 31 children, correlate the findings

81 8

VOGL

ET AL.

AJR:159, October 1992

with those of conventional angiography or digital subtraction angiography, when available, and briefly summarize the ex-

amination

strategies

and parameters

we found most useful. C U:

Subjects

and

Methods

6

Thirty-one children 6 months to 14 years old with suspected intracranial lesions or vascular malformations seen on conventional spin-echo MR images were studied prospectively with MR

.

angiography. MR imaging examinations were carried out with the patient under general anesthesia in 27 cases. All MR studies were performed on a 1 .5-T MR system (Magnetom SP 63, Siemens AG, Erlangen, Germany) with a circularly polarized head coil 30 cm in diameter. Conventional

MR

imaging

was

performed

according

to the

.

$

thickness

3-1 0 mm, 256 x 256 matrix,

images (600/i 5, i 3 slices, slice thickness

x 256 matrix,

acquisitions)

two

one acquisition)

c .

following

were obtained.

and then Ti

3

.

American Journal of Roentgenology 1992.159:817-823.

For all axial images,

a saturation

plane

below the imaging slices to eliminate motion artifacts.

c

coronal

. .

was placed

The total width

of the field of view (FOV) was 20 cm in all cases. In i 1 children with intracranial tumors, Ti-weighted images were obtained after IV bolus injection of gadopentetate dimeglumine (dosage: 0.1 mmol per kilogram body weight). MR angiography was performed by using three-dimensional (3D) Fourier transformed, rephased gradient-recalled echo sequences. Three-dimensional

fast

imaging

with

steady

ing was used to depict vessels with dimensional (2D) or 3D fast low-angle

precession

fast shot

(FISP)

> -E (‘

I-.

w .

imag-

blood flow, and (FLASH) imaging

‘-

-

>

we had previously found gave the best results in visualizing fast-

.

..

flowing blood with 3D FISP imaging. A TRITE of 36/iO was best for

,

E

placed arterial venous The tracing

adjacent or venous or arterial 3D or 2D algorithm

(Table

i

).

Presaturation

slices

intensity projection (MIP) images [6, 7]. Rotatable projections of the MR angiograms were usually calculated with a range increment of i 50 The computing time required for image reconstruction was 3-

i 2 mm, depending For each

on range increment

scale

of 0 to 3: grade

were not depicted

data

0, vessels

on MR images;

-

c#{176}

0

0

I

.

5

U: .

.

9)



5

.-

C’)



‘ (,

9



.

c

c

L

*1)

.

and resolution.

set of MR angiographic

and corresponding

MIP

images, the quality and extent of vessel visualization within the slab were ranked by a concensus of three independent observers on an ordinal

o

o o I

were

to the imaging volume in order to suppress either blood flow as appropriate to produce more purely MR angiograms, respectively. data set was processed by using a computer rayon an integrated workstation to provide maximum

o

(#{176}

.

the dural sinus system

‘-

#{176}-

twowas

used for vessels with slow flow. For arterial MR angiography, we used a TE of7 msec, a TR of4O msec, and a flip angle of iS#{176}, which

visualizing

X

X

-

or sagittal images were acquired as needed to show any lesions seen on axial images.

3

X X

3-i 0 mm, 256

Ti-weighted

.

-

scheme: After a preliminary sagittal image was obtained, axial T2weighted spin-echo images (3000/22,60,120 [TRITE], 17 slices, slice weighted

,



that lay within

grade i

,

vessels

!



?

i

< 2.

the FOV but

j

that could be

detected only over a short distance; grade 2, vessels that could be visualized over a greater distance but had interruptions in flow signal; grade 3, vessels that were imaged over their entire length within the

C’)

C’)

u

FOV and without signal interruption. The following arteries were evaluated: internal carotid, anterior cerebral, middle cerebral, anterior communicating,

ophthalmic,

ebral, superior cerebellar,

posterior

communicating,

anterior inferior cerebellar,

posterior

posterior

cer-

inferior

cerebellar, basilar, and vertebral (Table 2). On venous MR angiography, depiction of the following segments of the sinus system was evaluated: superior sagittal sinus, inferior sagittal sinus, straight sinus, confluens of sinuses, transverse sinus,

sigmoid sinus, cavernous sinuses,

the sphenoparietal

vein (Table

3).

sinus and its draining sinus,

and

the superior

superior bulb

and inferior of the jugular

cs

.

,

c

.

U-




Z

MRA

1992

OF

AJR:159,

October

TABLE Imaging

2: Delineation of Intracranial Arteries Quality on Arterial MR Angiography

Could Not Be

Vessel8

CEREBRAL

NEUROVASCULAR

and Evaluation

of

TABLE 3: Delineation Evaluation of Imaging

Grade 1 Grade 2 Grade 3

(%)

(%)

(%)

0 0

i 5 20

25 35

60 45

0 5

10 20

45 5

45 70

70 45

20 25

5 25

0 5

90 95 I 00

0 5 0

10 0 0

0 0 0

0 0

20 0

25 25

0 70

65

25

5

0

50 40

20 iO

0 15

0 0

0

20

i0

40

Evaluated

DISEASES

of Intracranial Sinus System and Quality on Venous MR Angiography

V esse I

(%) Internal Anterior

carotid artery cerebral artery

Middle cerebral artery Posterior cerebral artery

ACA PCA Ophthalmic artery Thalamostriate artery Choroid artery

Vertebral artery Basilar artery Superior

cerebellar

artery

AICA PICA Abnormal

vessels

819

Could Not Be Evaluated

Grade

1 Grade

2 Grade

(%)

(%)

(%)

0 0 50 66 0 0 0 17 0 0 17 0 0

33 0 17 17 17 0 0 17 17 17 53 33 17

50 100 17 17 83 100 83 0 0 0 17 67 50

3

(%) Superior sagittal sinus Straight sinus Inferior sagittal sinus Vein of Galen Confluens of sinuses Transverse

Sigmoid Cavernous

sinus

sinus sinus

Superior petrosal sinus Inferior petrosal sinus Sphenoparietal sinus Superior bulb of jugular vein Abnormal vessels

17 0 17 0 0 0 17 67 83 83 13 0 0

Note-Seven patients were examined; 14% had no abnormalitses. Grade 1 poor visualization, grade 2 = good visualization with some flow-signal interruption, grade 3 = optimal visualization.

American Journal of Roentgenology 1992.159:817-823.

=

Note.-24 patients were examined; 30% had no abnormalities. Grade 1 = poor visualization, grade 2 = good visualization with some flow-signal interruption, grade 3 = optimal visualization. a ACA = anterior communicating artery. PCA = posterior communicating artery, AICA = anterior inferior cerebellar artery, PICA = posterior inferior cerebellar artery.

Results Arterial

MR Angiography

Arterial

MR angiography

was

the nine cases in which results

performed

in 24 children.

of angiography

In

via catheteri-

zation were available, depiction of the vascular structures on MR angiograms compared favorably with depiction on DSA

images, although vessels smaller than 1 mm in diameter could not be visualized consistently on MR angiograms (Table 2). The anterior cerebral artery could be seen as far as the high cortical segment in nine patients, the middle cerebral artery could be followed to the angular gyrus in eight patients.

Excellent for

the

imaging upper

quality

segments

could of the

be achieved internal

in 1 2 patients

carotid

artery,

in

1 4 patients for the entire posterior cerebral and basilar artery, and in one patient for the posterior communicating artery. Smaller arteries such as the anterior communicating

Fig.

1.-3-year-old

with

venous malformation encephalocele. A, Coronal

intracranial

arterio-

and a frontoethmolds

Ti-weighted

(600/15) MR Image of frontal lobe. FISP (40/7, 15#{176})

shows #{149}ncephalocele (arrows) B, Axial,

three-dimensional

arterial MR anglogram shows a network of abnormal vessels (arrowhads). Ophthalmic art#{149}ries (0) can be seen because they are dilated.

artery, the ophthalmic artery (Fig. 1), the superior cerebellar artery, the anterior inferior cerebellar artery (AICA), and the posterior inferior cerebellar artery (PICA) could be visualized in only a few cases. On arterial MR angiograms, vessel stenoses were detected in eight cases involving the middle cerebral artery (n = 4; Figs. 2-5), the anterior cerebral artery (n = 2; Figs. 2 and 3), the posterior cerebral artery (n = 1 ), and the internal carotid artery (n = 1 , Fig. 5). Correlation with DSA findings was available in four patients and confirmed the diagnosis based on MR angiographic findings in three cases (Figs. 2B and 3B). In one case the grade of stenosis was overestimated on the basis of MR angiographic findings (Figs. 4B and 4C). In a fifth patient with hemiparesis, stenosis of the middle cerebral artery, consistent with clinical findings, was seen on MR angiograms; in the remaining three patients, infarcts evident on the spin-echo images corresponded to the areas of flowsignal loss as seen on the MR angiograms. Displacements of the anterior cerebral artery by an astrocytoma in one case and of the middle cerebral artery by a large hydrocephalus in

820

VOGL

ET AL.

AJR:1 59, October

1992

Fig. 2.-2-year-old with an astrocytoma in frontal lobe and stenoses of both anterior cerebral arteries and right middle cerebral artery. A, Axial, three-dimensional FISP (40/7, 15#{176}) arterial MR anglogram, rotated to a more sagittal view, artery

reveals stenosis of right middle cerebral (arrowhead) and stenosis of anterior cerebral arteries (arrows). m = middle cerebral ar-

tery, I

=

internal carotid

artery.

B, Conventional angiogram (lateral view) of rightintemal carotid artery verifies the diagnosis of stenosis of right middle cerebral artery made by MR anglography (arrowhead). Comparison of

American Journal of Roentgenology 1992.159:817-823.

stenosis on MR angiography and conventional anglography shows that MR angiography overestimates grade of stenosis.

Fig. 3.-2-year-old with right-sided hemiparesis and local vascular lesion (infarct) in left internal capsule. A, Axial, three-dimensional FISP (40/7, 15#{176}) arterial MR angiogram. Axial > coronal -30#{176} rotated maximum intensity projection angiogram reveals stenosis of both anterior cerebral arteries (arrowheads) and of left middle cerebral ar tery (arrows). B, Digital subtraction angiogram of left Internal carotid artery verifies resufts of MR angiography in this patient stenosis of anterior and middle cerebral arteries (arrowheads). a = anterior cerebral artery, m = middle cerebral artery, i = internal carotid artery.

C FIg. 4.-6-year-old with idiopathic hemorrhage in region of right internal capsule. A, Coronal TI-weighted (600/15) MR Image shows hemorrhagic lesion in region of right internal capsule (arrowheads) B, Axial, three-dimensional ASP (40/7, 15#{176}) arterial MR anglogram. Coronal rotated maximum intensity projection angiogram of right middle cerebral artery (arrows). C, Digital subtraction angiogram of right Internal carotid artery confirms stenosis of right middle cerebral artery (arrowheads).

shows

suspected

stenosis

MRA

October 1992

AJR:159,

OF CEREBRAL

and middle

American Journal of Roentgenology 1992.159:817-823.

intensity

cerebral

arteries. Ax15#{176}) arterial 30#{176} rotated angiogram shows

projection

821

bacterial

hemisphere (arrowheads). B, Axial, three-dimensional

FISP (40/7, 15#{176}) arterial MR angiogram. Coronal > sagittal -30#{176} rotated maximum intensity projection anglogram shows displacement of right middle cerebral artery due to occlusive hydrocephalus (arrowheads). Additionally, a common anterior cerebral artery is detected (arrows). a = anterior cerebral artery, m = middle cerebral artery.

ial, three-dimensional FISP (40/7, MR angiogram. Coronal > sagittal maximum

DISEASES

Fig. 6.-12-year-old with enlargement of right ventricle due to occlusion of foramen of Monro after meningitis, resulting in displacement of vessels. A, Coronal Ti-weighted (600/15) enhanced MR image shows an occlusive hydrocephalus In right

Fig. 5.-i4-year-old with giant-cell arteritis (Takayasu’s syndrome) and stenoses of upper segments of left internal carotid artery and origin of left anterior

NEUROVASCULAR

stenoses

of upper segments of left internal carotid artery (arrows) and at origin of left anterior and middle cerebral artery (arrowhead). a = anterior cerebral artery, m = middle cerebral artery, i = internal carotid artery, b = basilar artery.

another case were clearly seen on the MR angiograms. In one case, an occlusion of both middle cerebral arteries was seen. MR angiograms showed anatomic variations in five patients.

These

included

primitive

trigeminal

arteries

(three),

a

common anterior cerebral the internal carotid artery

artery (one, Fig. 6) and kinking of (one, Fig. 7). In the patient with the

occlusive

and a common

artery,

hydrocephalus a displacement

was suggested, additional

with

but this was excluded

projections

anterior

superimposition

and rotated

cerebral

of both

arteries

after we examined

the angiograms

(Fig. 6). In

one patient with a frontoethmoidal encephalocele, MR angiograms showed an arterial network in the area of the anterior cerebral artery. Dilatation of both ophthalmic arteries resulted in particularly erwise findings

good

visualization

of these

vessels,

which

are not usually seen on MR angiograms (Fig. confirmed the presence of a primitive trigeminal

oth-

1 ). DSA artery

in one case and kinking of the internal carotid artery in another case (Fig. 7). In one case, the mass effect of an astrocytoma resulted in displacement of the anterior cerebral artery and occlusion

superior

of

and confirmed

Venous

the

high

curvature;

cortical

this was

segments

observed

of

with

the

ascending

MR angiography

with DSA (Fig. 2).

superior sagittal, straight, transverse, and sigmoid and the bulb of the internal jugular vein were visualin all patients (Table 3). The cavernous sinus and its

ized draining superior and inferior petrosal sinus were in most cases ranked with grade 0 or grade 1 , largely because these sinuses lay at the edge of the imaging slices. Detection of the sagittal

sinus

abnormal

with kinking

of both internal

carotid

arteries

and no

findings.

Axial, three-dimensional FISP (40/7, 15#{176}) arterial MR angiogram. Sagittal > coronal 30#{176} rotated maxium intensity projection angiogram reveals kinking of left internal carotid artery (arrows).

Venous MR angiography was performed in seven patients with suspected sinus thrombosis and showed sinus thrombosis in six cases; collateral drainage could be seen in one. In one patient, venous MR angiography revealed no pathologic findings. Sinus thrombosis involved the transverse sinus in four of the seven cases. One patient with extensive throm-

bosis of the transverse and sigmoid sinuses was examined before and after treatment with heparin; venous flow improved

MR Angiography

The sinuses

inferior

Fig. 7.-2-year-old other

and the vein of Galen

was inconsistent.

markedly after administration of heparin (Fig. 8). Complete and partial sinus thrombosis could be differentiated by including the original MR angiographic data set in the review.

Use of gadopentetate dimeglumine in 1 1 children did not improve the overall imaging quality of angiography, although the relationship depicted in five

of tumor to adjoining cases. Large tumors

vessels was better or tumors with high

822

VOGL

ET AL.

AJR:159, October 1992

Fig. 8.-14-year-old girl under chemotherapy for acute myelogenous leukemia with sinus thrombosis before (A and B) and 1 month after (C and D) application of hepann. A, Coronal, two-dimensional (2D) FLASH (36/ 10, 60#{176}) venous MR angiogram. Coronal view shows occlusion of right transverse sinus (t), right sigmoid sinus (5), right jugular bulb (jb),

and jugular vein B, Coronal,

(fl.

2D FLASH

(36/10,

60#{176})venous MR

anglogram. Sagittal view shows thrombosis of superior sagittal sinus (arrowheads) as well. st = straight sinus, g = vein of Galen, t = transverse sinus, s = sigmoid sinus, j = jugular vein.

American Journal of Roentgenology 1992.159:817-823.

C, Coronal, 2D FLASH (36/10, 60#{176}) venous MR angiogram after heparin application shows reperfusion of right sigmoid sinus (s) and jugular bulb (jb). D, Coronal, 2D FLASH (36/10, 60#{176}) venous MR angiogram. Sagittal view after heparin applicahon shows imperfect reperfusion of superior sagittal sinus (arrowheads). is = inferior sagittal sinus, St = straight sinus, g = vein of Galen.

enhancement

reduced

MIPs in six cases, neighboring

proved giography,

angiographic

lesions

Use

of contrast

vessels.

the visualization especially

the

as these

imaging material

of small vessels in three

infants

quality

were superimposed slightly

in venous

where

3D

in

on im-

MR an-

FLASH

im-

aging was used. We achieved the best results by using the sequence parameters for 3D FISP and 2D FLASH imaging listed in Table 1. Visualization of smaller intracranial veins, such as the great vein of Galen and the inferior sagittal sinus, was better on 3D

FLASH than on 2D FLASH images. Discussion

Time-of-flight MR angiography is a useful technique for imaging intracranial vessels, although it does have several limitations. Because it depends on the refocusing of inflowing unsaturated spins, it may suffer from increasing saturation within a large imaging volume and incomplete refocusing [2, 5, 8]. Alterations in flow dynamics can cause partial signal

loss, because from from

these spins are dephased.

Dephasing

the random, tumbling motion in areas of turbulence the increased duration of stay in the measuring

Because of signal loss induced by poststenotic vessel stenosis cannot be graded appropriately

results and slice.

turbulence, on the basis

of MR angiographic findings [5, 9]. Nevertheless, the grade of stenosis or occlusion as seen on MR angiograms could

more accurately be assessed by including conventional MR images and the original 3D FISP data set in the review. Another source of error stems from the lack of signal from partially thrombosed aneurysms, which may lead to underestimation of aneurysm size [1 0, 1 1 ]. However, spin-echo images obtained during the same examination usually provide more information on true size and composition of the aneurysm; indeed, MR angiography together with conventional MR imaging may yield more information than DSA alone. Progressive saturation within an imaging volume occurs sooner with slow-flowing blood (e.g., venous blood) but also depends on the vessel’s course (perpendicular, oblique, or parallel to the imaging volume). Slice thickness and the RF deposition, which are operator-controlled parameters, also

cause saturation effects [8, 12]. As scanning parameters depend on the Ti relaxation of blood, a variation of these parameters

is possible

within

a narrow

Before this study, we determined

range

optimal

only [6, 8].

scanning

param-

eters in healthy children. We found that a TR of 40 msec and a flip angle of 1 5-20#{176}produced the maximum contrast-tonoise and signal-to-noise ratios. Slice thickness must be held to a minimum to decrease saturation effects; however, this also reduces the length of the vessel segment that can be imaged during a given examination [5, 8, 1 2-1 4]. A difficulty arises in positioning small axial planes in order to achieve maximum

be kept

information

as small

about

as possible

vessels,

as slice

in order

thickness

to increase

must

spatial

MRA

October1992

AJR:i59,

resolution. To increase slice thickness ration effects, two 3D volumes can

partitions

and 25% overlapping

A more

severe

problem

vessels

in the process

Imaging

of small

NEUROVASCULAR

while minimizing satube used with half the

[101.

is the loss of visualization

of acquisition

vessels

OF CEREBRAL

or reduced

of small

and MIP reconstruction. venous

flow

in partially

thrombosed sinuses requires an increase of in-plane spatial resolution, which can be achieved if the FOV is kept as small as possible. The best achievable in-plane resolution in our study was 1 mm, with a loss of signal from smaller vessels. A further problem arises in image reconstruction. When a vessel’s size is small compared with pixel size, small vessels may be lost completely on MIP reconstruction because of partial volume averaging and statistical fluctuations in background noise [1 0, 15]. This problem can be overcome by including the original MR angiographic data set in the review, as small vessels or restricted venous flow in partial sinus

American Journal of Roentgenology 1992.159:817-823.

thrombosis

is documented

on these

images

be

effect (e.g., TE = 7 or 1 1 msec), combined with the smallest possible slice thickness and field of view. In 89% of our healthy children and five of our patients, we found

partial

signal

loss from

the confluens

of sinuses

that

seemed not to correlate with pathologic changes. in stenosis or sinus thrombosis, the extent of the be overestimated, because the atheromatous thrombus creates a poststenotic turbulent flow loss adjacent to vessel boundaries, simulating a occlusion. It has been reported that fresh thrombus a high signal intensity, mimicking that of flowing

Particularly lesion can plaque or with signal high-grade can have blood, re-

suIting

[1 3]. How-

in missed

diagnosis

of sinus

thrombosis

ever, we found that in evaluating the original sections of the MR angiographic sequences, we had no difficulty in differentiating

between

Despite graphic

thrombus

the reasonable findings

with

DSA

and the laminar

anatomic findings,

flow of blood.

correlation MR

of MR angio-

angiography

is not

likely to be sufficient for the preoperative staging of aneurysms. At the current state of the art, small vessels arising near an aneurysm, knowledge of which is crucially important in planning neurosurgical strategies, are likely to be missed [10, 14]. For the evaluation of MR angiograms, rotatable projection images in two planes are recommended, and the original data set as well as conventional MR images should be included. This reduces the risk of overestimating the degree of a stenosis or underestimating the size of an aneurysm. The cine technique facilitates detection perimposed vessels can be easily

of vessels, distinguished

because from

sequences

jection for depiction not. Use of contrast

suone

another and their identification verified by rotating the images. Use ofcontrast material contributed little to the visualization of intracranial vessels in MR angiography. Whereas 3D

823

required

gadopentetate

dimeglumine

in-

of vessels, 3D FISP and 2D FLASH did material improves the depiction of vessels

only in patients with an intact blood-brain barrier, that is, when contrast material remains intravascular [1 6]. In patients with tumor, contrast-enhanced MR angiography can be an excellent tool for visualizing the lesion and adjacent vessels, but is not applicable for tumors with strong contrast enhancement

or tumors lying near the nasal cavity, as the high signal intensity of the lesion or the mucosal tissue can interfere with the vascular

signal.

As a noninvasive technique, MR angiography can be added to routine MR imaging, providing additional information about intracranial vessels and soft tissues in a single setting. It may be useful as a screening method when vascular disease is suspected, as a mapping technique before surgery or catheterization of abnormal vessels, or as a method for diagnosis and follow-up

but is eliminated

by the MIP algorithm on projection angiograms. High-resolution 3D FISP or FLASH sequences can be used to depict small intracranial vessels such as the anterior inferior cerebellar artery (AICA), posterior inferior cerebellar artery (PICA), anterior cerebral artery, and ophthalmic artery or small intracranial veins. A disadvantage of the 3D FLASH sequence is the simultaneous visualization of subcutaneous fatty tissue, which is superimposed on vessels in MIPs. This can diminished by using echo times that induce a fat-suppressive

FLASH

DISEASES

of sinus

thrombi

[1 0, 1 7]. Additional

clinical

experience and improvements in flow-compensation technique will expand the role of MR imaging in the diagnosis of intracranial vascular abnormalities. REFERENCES 1 . Brown DG, Riederer SJ, Jack CR, Farzaneh F, Ehman RL. MR angiography with oblique gradient-recalled echo technique. Radiology 1990;176:

461-466 2. Edelman RR, Mattle HP, Atkinson

DJ, Hoogewoud

HM. Magnetic

reso-

nance angiography. In: Cardiovascular imaging: ARRS categorical course syilabus. Reston, VA: American Roentgen Ray Society, 1990:51-60 3. KrayenbUhl H, Yasargil MG. Zerebrale Angiographie f#{252}r Klinik und Praxis.

Stuttgart:

Thieme Verlag, 1979:71-211

4. Edelman RR, Wentz KU, Mattle HP, et al. Intracerebral arteriovenous malformations: evaluation with selective MR angiography and venography. Radiology i989;173:831-837 5. Edelman RR, Hesselink JR. Clinical magnetic resonance imaging. Philadelphia: Saunders, 1990: 1 1 0-i 82 6. Angiography Numaris Il/Version A 2.1 . In: Magnetom SP user guide, 5th ed. Erlangen, Germany: Siemens AG, 1990 7. Ehricke H-H, Laub G. Integrated 3D display of brain anatomy and intracranial vasculature in MR imaging. J Comput Assist Tomogr 1990;14: 846-852 8. Lissner J, Solderer M. Klinische Kernspintomographie. Stuttgart: Ferdinand

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MR angiography in children with cerebral neurovascular diseases: findings in 31 cases.

We evaluated the suitability of MR angiography for routine use in children with suspected intracranial vascular disease...
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