between

the needle

sound needle

shaft

beam decreases echogenicity.

diameter

enhances

and

the ultra-

from 90#{176}, so will Increasing needle

needle

shaft

echo-

genicity as does axial rotation of a nonsymmetric needle (3). Physical alterations consisting of surface scratches of both the needle shaft and obturator in-

crease needle echogenicity creased scattering of sound

by inwaves

Injection

of an echogenic

tune into

the needle

to increase sonically

needle echogenicity active needle-stylet

rendering

ultrasound

it a passive

used

(4). A combina-

by coupling crystal,

the

mix-

has also been

tion has been created needle to a piezoclectnic ceiver

(4).

aim-jelly

the thus me-

(6).

Although it is important to visualize shaft of a biopsy or drainage nec-

die,

it is needle

tip localization

that

1.

is

of the utmost importance. However, for the tip to remain within the beam duning its passage, the shaft must be aligned parallel to the beam. Bobbing the needle-stylet combination, that is, moving the tip back and forth quickly

over

a short

quently

distance,

used

tip’s

maneuver

location.

We

maneuver the needle stylet

echogenicity

is thought microbubbles en aspects

find

in and

out.

of

needle

the

fre-

to confirm

now

the

to be less traumatic tip never moves,

moves

hanced

is the most

the pump

shaft

shaft

alignment allowing

and

of the constant

tip allows shaft tip

and

Dedicated

tip

Coil

Charles M. Anderson, MD, David Saloner, PhD Ralph E. Lee, RT Alexandra Fortner, MD

outen-

the

needle

tion.

U

1.

3.

which has previously adjunct

shaft

and

en-

tip

visualiza-

Sonographic guidance

biopsy

and

needle

in the

drainage:

for Carotid

N

for

4.

versus computed percutaneous

Intervent

Radiol

Ultrasound localizing

1985;

Radiol

the

90.1214, surface nology

arteries,

MR studies,

172.1214 #{149} Magnetic resonance (MR), coils #{149} Magnetic resonance (MR), tech-

EARLY

From the Department of Radiology San Francisco Veterans Administration Center, 4150 Clement St. San Francisco,

Radiology

868

1990; 176:868-872

#{149} Radiology

Received

requested

quests

The sonographic enhancement of

J Clin Ultrasound

needles.

1983;

JW, James percutaneous

EM. Sobiopsy

of small

masses.

1988;

(3 cm

or less)

AJR

6.

McDicken

WN,

MacKenzie

Ultrasonic

WE,

identification

in amniocentesis.

Anderson

of needle

Lancet

1984;

tips

2:198-199.

MR Angiography’

60% of all surgically accessistenoses of the carotid and vertebral arteries occur at sites other than the carotid bifurcation (1). Dopplen ultrasound (US) often cannot depict these sites because of overlying bone that obscures the vessel origins and the distal internal carotid artery. Magnetic resonance (MR) angiography could be useful in screening patients for cervical arterial disease because it has the potential to depict the entire extent of the carotid and vertebral arteries, includ-

April

R, Seidel KJ. and contrast

12-25.

ble

94121.

ultrasound.

24:555-560.

biopsy

segment.

Carotid

tip echo-

real-time

Reading C, Charboneau nographically guided

ing

the

origins.

ly available

suited

(114), Medical CA

January 2; accepted

to C.M.A.

c RSNA,

1990

November 25, May

21, 1990;

1989;

revision

8. Address

revision received

reprint

re-

However, imaging

for MR

imal

arteries.

specifically of-flight

commercial-

are not well of the prox-

coils

angiography We

have

developed

designed for MR angiography

a coil

carotid with

timecoronal

sagittal excitation, and which can be used to screen the entire extent of the carotid and vertebral arteries for stenotic disease. The ideal coil for MR angiography of the carotid arteries must have many ator

tributes.

First,

it must

vide

the

best

ond,

the

sensitive

common

terms:

phantip af-

Berlin:

1

Index

the and

15 1:189-192.

guided

image.

above shaft

J. Needle

with

1989;

Heckmann appearance

T.

sonographic

Springer-Verlag,

PhD

5, Kwela

a study

Invest

5.

needle puncture. Semin 1986; 3:254-263. Otto RCH, Wellwer J.

2.

Bondestain

genicity:

(1),

that

of equal echogenicity of the night needle

puncture 11:265-268.

Wittich GR. tomographic

beam,

A magnetic resonance imaging coil was developed to improve contrast in direct coronal and sagittal time-of-flight carotid angiograms. The sensitive volume of the coil extends from the carotid origins to the siphons. Angiographic contrast can be optimized for an arterial segment of interest by repositioning the coil to minimize presaturation of blood before it enters

atnaumatic

hances

of

easier

with the visualization.

maneuver, described

needles echogenicity

References

increased

to be due to the formation along the inner and of the needle shaft. This

The pump been cursorily is a useful

in that while the

The

2.

Figures 1, 2. (1) Sonogram of two 21-gauge tom target (an olive). (2) Distinct increased ten the needle stylet has been pumped.

cluding

the it is

bral can from should

be

small

signal-to-noise

to

ratio.

volume

must

pro-

Seccoven

sites

of vascular disease, inat the aortic arch, bifurcation, and the siphon. Third, useful if the coil includes the cereocciput, so that dunal sinus blood be saturated to eliminate signal jugular veins. Fourth, the coil the

be

origin

capable

of providing

September

direct

1990

Ca

Cb

Figure 4. 1.

2.

Figures

1, 2. (1) Circuit diagram of carotid coil. Ca 10 zF, Cb = 30 MF, and Cc = 0-25 zF. By making Ca smaller than Cc, a wide latitude of tuning and matching is achieved, although some symmetry among the four circuit segments is lost. Conducting elements are made of copper

strips.

(2)

Carotid

imaging

coil,

consisting

of

nearly

elliptical

loop

that

rises

at

caudal

end to pass over sternum or neck. Grooves along sides of coil allow it to slide longitudinally on tracks. Height of tracks is adjustable with wing nuts. Coil is shown positioned to image proximal

MR angiogram

of aortic

arch

in

the right posterior oblique projection. Placement of coil edge oven upper sternum limits excitation of blood in ascending arch. Pixel intensity of ascending arch is 170 (arbitrary scale), while that of transverse arch is 1,120. Axial saturation band (arrow) has been applied to eliminate venous signal. BC brachiocephalic artery, CC = left common carotid artery, SC left subclavian artery, J = jugular vein.

carotids.

Materials

and

Methods

Computer simulations of the transverse magnetic field were performed

with

a program

authors

written

by one of the

(C.M.A.).

The

coil frame

was made

of oak for

strength and ease of construction. Coil circuitry was enclosed in plastic conduit set into the undersurface of the coil. The circuit consisted of a 19 X 40-

cm elliptical loop with high-voltage fixed capacitors (Voltronics, East Hanover, NJ) distributed in four segments, a. Figure

b. 3.

Contour

plot

of transverse

magnetization,

for

and

carotid

imaging

coil,

ed in midsagittal (a) and coronal (b) sections. Contour levels are equally spaced on an arbitrary scale. Coil has heterogeneous excitation and sensitivity in head and neck but adequate sensitivity along course of carotid artery. Note that is zero at the edge of the coil (an-

row). In this area, tissues

variable

Rochelle,

calculat-

the carotid view. Furthermore, tion by the body

tients

raphy

with

wide

variations

in body

habitus.

Coils available for conventional imagdo not meet all of these requirements. The sensitive range of the head coil does not extend proximally to the aortic arch and may not include the carotid bifurcation in patients with high shoulders. Coronal or sagittal excitation with the body coil pnesaturates blood before it enters the carotid arteries, mesuiting in a loss of image contrast. The body coil also has a relatively poor signal-to-noise ratio. Although receiveonly surface coils improve the signal-tonoise ratio, they have a limited field of ing

Volume

176

#{149} Number

3

presaturation

they rely on excitacoil, again resulting in

of thonacic

We have

found

studies

that

of the

carotid

MR angiogarteries

fail

because of inadequacies in coil design. After examining computer simulations of coil sensitivities calculated for a vanety of proposed coil geometries, we designed and built a dedicated transmitreceive carotid imaging coil that improves contrast in MR angiography. The important features of this coil are that the sensitive volume extends as far as the aomtic arch proximally, and that the

coil

cunately

can

excitation

flow interest.

be quickly

translated

set the proximal

contrast

volume,

which

in the arterial

edge

and

mounted translated

to ac-

of the

optimizes

segment

New

matching

artery

in-

of

(Fig 2). The

This

could

be done

out removing the patient magnet by pulling on the calibrated rod (not shown). platform was designed to existing cushions for the Imaging was performed Siemens Magnetom unit

Federal

coil was

on a track so that it could be longitudinally with respect

to the patient.

blood.

many

(Polyflon,

(Fig 1). The coil was bent anteriorly so that the caudal edge of the coil could pass above the upper sternum while the body of the coil was positioned more posteriorly along the course of

are not excited.

coronal and sagittal images of the neck without saturating blood proximal to the arterial segment of interest. Finally, the coil must be easy to position on pa-

capacitors

NY) for tuning

Republic

with-

from the coil with a The coil be used with head coil. with a 1.5-T (Erlangen,

of Germany).

Carotid

angiograms (2) and maximum-intensity projections (3) were obtained with software provided by Gerhard Laub, PhD, of Siemens Medical Systems (Iselin, NJ). MR angiognams were acquired with three-dimensional Fourier transform, FLASH (fast low-angle shot) sequences with velocity compensation in the section-select and frequency-encod-

Radiology

#{149} 869

id coronal two-dimensional FLASH with velocity compensation in the section-select and frequency-encoding directions, a TR of 22 msec, a TE of 12 msec, a flip angle of 30#{176}, one acquisi-

ing directions and with a repetition time (TR) of 30-40 msec, an echo time (TE) of 7-8 mscc, a flip angle of 20#{176}30#{176}, one acquisition, a 256 X 256 X 32 or 64 matrix, and a voxel size of 1 X 1 X 1 .25 mm. A coronal saturation band

was applied venous grams,

to the occiput

signal. For composite the field of view was

corresponding 1.37

icd

to a voxel

tion,

of 1.37

X

from

mm. Acquisition times van4 to 9 minutes. After selection

number the vessel

maximum-intensity

matrix,

and

An axial

Results The

a pixel

presatura-

transmit-receive

carotid

imaging

tion

coil is an elliptical loop placed in the coronal plane around the patient’s

nal

head

a parasagittal plane arch, then combined

X 1.25

of the minimum that contained

X 256

algo-

rithm.

band was applied to eliminate sigfrom the jugular veins. Sections 4 mm thick were obtained every 2 mm in

angio350 mm,

size

a 256

size of 1 X 1 mm.

to eliminate

projection

maximum-intensity

(Fig 2). The

longitudinally

coil can be translated

on an adjustable

track.

When the coil is moved toward the feet, the caudal edge of the coil is sus-

through the aortic by means of the

of sections of interest,

projections

were

calculated on a 256 X 256 grid. A typical examination consisting of two coronal acquisitions and one sagittal acquisition, with translation of the coil and calculation of preliminary projections, could be accomplished in less than 40 minutes.

Images of the aontic arch were obtamed with a sequence written by one of the authors (D.S.), consisting of rap-

Figure 5. MR angiograms of vertebral antery origins. Caudal edge of coil has been placed over clavicles. (a) Sagittal image of left common carotid (CC) and proximal vertebral

(V)

artery

origin

tery (SC). Arteries rower more distally ration

of blood

bilateral

from

appear

subclavian

because

nan-

of partial

(4). (b) Coronal

subclavian

an-

progressively

image

and proximal

satuof

vertebral

arteries.

a.

a.

b.

Figure 6. Lateral mon carotid artery, applied to occipital reaches bifurcation. tions

of projection.

dal edge

just below

ty does not project 870

b.

#{149} Radiology

c.

ulceration of the sinus (arrow). CC = cornIC internal carotid artery, EC external carotid artery. (b) MR angiogram obtained with head coil. Saturation band was blood to eliminate jugular signal. Contrast is poor because weak inflow leads to partial saturation of blood before it Note that proximal extent of common carotid artery in excitation volume is not seen because it is not included in 5cc-

angiograms

(c) Contrast

bifurcation. over artery

of

carotid

is much

bifurcation.

improved

Submandibular in lateral view

(a)

in MR

Conventional

angiogram

angiogram

obtained

shows

with

signal intensity from fat (arrow) and can be removed from projection

same

shallow

sequence

is the result in frontal

but

with

carotid

coil

of proximity of coil to chin. view by choice of sections.

positioned

This

with

signal

September

cau-

intensi-

1990

pended above the patient’s sternum and the cephalic edge of the coil is positioned at the skull vertex. When the coil is moved toward the chin, the caudal edge of the coil is just above the hyoid

The

bone.

coil is translated

to determine

the proximal edge of the excitation ume, which can be used to optimize flow contrast for a chosen segment the artery. Contrast between blood

volinof and

stationary tissues in time-of-flight imaging is due to a short TR, which mcsuits in saturation of stationary tissues (2). Blood entering the volume is not

in the

volume

before

the arterial segment of A calculated contour transmitted field strength coil is shown in Figure zero at the caudal edge miffing precise placement of the saturation volume. is not Figure 7. Sagittal MR angiogram of carotid siphon (arrow), acquired with thin, three-dimensional sagittal slab (40 mm) medial to the common carotid arteries, to prevent presatunation.

homogeneous

volume

arch

only

and

not

to the

in images

of the

origins

with

was performed twice, once with the coil over the sternum to optimize contrast of proximal vessels, then, without moving the patient, with the coil pulled up to the pa-

is obtained

tient’s chin to image distal vessels. Selected sections from each acquisition were projected, after which the two resulting images

were projected Acquisition

Volume

to form the composite time

176

was

less

#{149} Number

than

3

20

image.

minutes.

the

head

coil.

After

utes,

the lower edge of the carotid below the bifurcation, greaten with

the

same

slab

positioned

medial

to identify lesions in if endartenectomy of a lesion is under consid-

projection.

image

required

illustrating

Acquisition

less than

the

feasibility

20 mmof per-

forming screening of the entire length of the carotid in a reasonably short cxamination time. Discussion The carotid coil shown in Figure 2 can be used to image all segments of the carotid artery with direct coronal or

of

as-

of the

adjustment

midline

mum-intensity

vertebral arteries (Fig 5), with strong contrast. If the coil is pulled back farther, so that the caudal edge is near the chin, presaturation of the carotid bifurcation is minimized. In Figure 6, a convcntional angiognam of the bifurcation is compared with MR angiognams obtuned with the head and carotid coils. In this patient, poor inflow results in reduced contrast on images obtained Figure 8. Coronal MR angiogram of carotid arteries with large field of view used to display entire course of vessels. Sequence

An MR angiognam of the carotid siphon (Fig 7) was obtained with a thin

of this

cending arch or the heart. The sharp definition of the saturated volume is achieved by positioning the coil over the upper sternum. The neck vessels are clearly depicted. If the coil is pulled slightly cephalad, so that the caudal edge is over the clayides, one can minimize presaturation of the subclavian arteries. This position results

in

tissue.

two

the aortic arch in the right posterior oblique projection. This image demonstrates that excitation is limited to the transverse

resulted

two

of

imaging. angiogram

have

of stationary

emation. Figure 8 is a composite of coronal images obtained with the carotid coil first over the sternum, then pulled up to the chin. The first image demonstrates strong contrast in the proximal vessels, while the second shows strong contrast distally. The projection images were then combined in a maxi-

the head and neck. Rather, it delivers the largest flip angles and has the greatest sensitivity along the anterior neck. It would not be adequate for spin-echo imaging of the neck, which requires precise 90#{176} and 180#{176} flip angles. It is suitable, however, for gnadient-refocused angiographic Figure 4 shows an MR

would

it is important this distribution more proximal

reaching

the

but this suppression

to the common carotid arteries, so that blood was not excited proximal to the intrapetnous segment. The siphons and intracranial circulation arc generally not amenable to surgical connection, but

interest. plot of the of the carotid 3. Excitation is of the coil, perof the edge The coil field

oven

less

sagittal

yet saturated and appears bright. If the blood must follow a long course in the excited volume or is moving so slowly that it is subjected to many pulses, it will become saturated, resulting in poor contrast. Saturation of blood may be minimized by careful placement of the edge of the excitation volume so that the blood travels only a short distance

angle,

of

coil to just contrast

sequence.

The path length that the blood traversed in the common carotid artery before reaching the bifurcation was 9 cm in the head coil but only 4 cm in the carotid coil. Saturation of blood in the head coil could have been reduced by choosing a longer TR or a smaller flip

sagittal cause

time-of-flight of the small

size

sequences. Beof the coil, sig-

nal-to-noise ratio is adequate, yielding images with good contrast. The coil overcomes common reasons for failure of MR angiognaphy encountened with of conventional coils. First, the unique design of the carotid coil allows imaging of artery bifurca-

two

use

tions body

and origins regardless habitus. This is not

of patient always possi-

ble with the transmit-receive head coil, which may not extend proximally enough to include even the bifuncation. Second, coronal on sagittal excitation with the carotid coil does not mesuit in saturation of thoracic blood. Saturation

is a problem

when

the

body

coil is used to excite and a receive-only surface neck coil to detect. This prob1cm is solved with the carotid coil by positioning

the

caudal

edge

mal to the arterial segment Other investigators have specialized pulse sequences tions

to the

problem

just

proxi-

of interest. proposed as solu-

of proximal

satu-

ration. Two of these arc sequential axial thin-section acquisition followed by coronal reconstruction (5) and axial slab

excitation

followed

by coronal

sec-

tion readout (6). The carotid coil described here could be used together with these pulse sequences but does not require them to eliminate presaturation. Direct coronal and sagittal acquisitions en in-plane

have the resolution

advantage than

does

Radiology

of greatse#{149} 871

quential

thin-section

Furthermore,

reformation.

they

have

than both thin-section and excitation-coronal readout thereby

minimizing

ous

shorter

axial slab sequences,

turbulent

This may be disadvantageous if strong subcutaneous fat signal obscures underlying vessels in projection images. Because the coil also transmits, tissues

to the coil are more saturated, offsetting this disadvantage. one may “edit out” subcutane-

partially

Further,

Monorail System of the Greenfield Diana F. Guthaner, MD James 0. Wyatt, MD John Thomas Mehigan, Allan M. Wright, MD Jerome F Breen, MD Lewis Wexler, MD

terms:

plications,

nae cavae,

al-

clipping

projection approach

the coil wider,

calculawould

1.

thereby

in-

obese. The extended range of the carotid coil highlights one of the key advantages of MR angiography. It can be used to visualize carotid origins and phons

and

the

vertebrobasilar

which

are not accessible

US. A screening MR ing bilateral origins,

1990; 176:872-874

angiognam bifurcations,

includsi-

ning.

of a Gncenficld

infe-

malpositioning

of the

filter,

or the

sub-

sequent migration on embolization of the filter. Because the small hooks at the feet of the filter legs are sharp and pierce the wall of the vena cava, mcor repositioning

of a malposi-

tioned filter is difficult. Several recent case reports in the literature have descnibed the percutaneous retrieval of a Greenfield filter (1-7). The technique we have developed is simple and also allows repositioning of the filter in some

cases.

Case

Reports

the

Departments

Radiology,

Mayo 13; revision

Medical

of Diagnostic

Center,

872

RSNA,

1990

#{149} Radiology

Pasteur

(D.F.G.,

LW.)

Dr. Rrn H2321,

pulmonary

presence

and

Surgery

Stanford,

embolus

of a Mobin-Uddin

(J.O.W.,

J.T.M.),

CA 94305; Department

Samaritan Hospital, San Jose, Calif (A.M.W.); and Department of Diagnostic Clinic, Rochester, Minn (J.F.B.). Received January 12, 1990; revision requested received April 23; accepted April 26. J.F.B. supported in part by National Heart

March Lung Blood Institute Cardiovascular print requests to D.F.G. C

Radiology 300

a new the

Radiology

Research

Training

203:961-968. MT, Ruggieni

Three-dimensional aging of the carotid clinical experience.

(volume)

Rossnick

grant

HLO

bifurcation:

Radiology

S, Laub

PM,

C, Braeckle

dimensional

display

Proceedings

of the

of blood IEEE

et al.

gradient-echo impreliminary 1989; 171:801-806. R, et al.

Three-

vessels

in MRI.

Computers

in Cardiol-

ogy Conference, Boston, 1986. New York: IEEE Publication Services, 1986; 193-196. Anderson CM, Saloner D, Tsuruda JS, et al. Artifacts in maximum intensity projection display of MR angiograms. AJR 1990; 154: 623629. Keller

PJ, Drayer

BP,

Fram

EK, et al.

MR

angi-

ography with two-dimensional acquisition and three-dimensional display. Radiology 1989; 173:527-532. Masaryk TJ, Laub G, Modic T, Ruggieni P. Ross Js. 3DFT MR angiography of the carotid bia comparison

of time-of-flight

tech-

niques (abstr). In: Book of abstracts: Society of Magnetic Resonance in Medicine 1989. Vol 1. Berkeley, Calif: Society of Magnetic Resonance 1989;

164.

Repositioning

vena caval filter (Mcdi-tech/ Boston Scientific, Watertown, Mass) under fluoroscopic guidance is now a standard procedure performed with percutaneous techniques. Occasionally, optimal positioning of the filter is not achieved because of premature ejection of the filter from the carrier device,

despite

tions. JAMA 1968; Masaryk TJ, Modic

in Medicine,

HE placement

tnieval

Hass WK, Fields WS, North RR, et al. Joint study of extracranial arterial occlusion. II. Arteniography, techniques, sites, and complica-

furcation:

U

developed

From

6.

phons, and vertebral arteries can be accomplished in less than an hour, which compares favorably with US scan-

33-year-old woman with pulmonary arterial hypertension secondany to chronic pulmonary emboli

1

5.

Doppler

Case 1.-A

Stanford University of Radiology, Good

3.

si-

nor

MD

2.

4.

system,

with

References

be

creasing the distance between coil and subcutaneous fat. A wider coil would also permit excitation deep to the sternum in patients who arc unusually

T

Interventional procedure, corn949.458 #{149} Venae cavae, filters #{149}Veinterventional procedures, 949.1299

Radiology

a regional

for Percutaneous Vena Caval Filter’

The authors describe a technique for removing or repositioning a malpositioned Greenfield inferior vena caval filter. A “monorail” system was used, in which a wire was passed from the femoral vein through the apical hole in the filter and out the internal jugular vein; the wire was held taut from above and below and thus facilitated repositioning or removal of the filter. The technique was used successfully in two cases. Index

with

before the alternative

to construct

dephas-

ing signal loss. In our experience, axial slab excitation-coronal readout acquisition works well for visualizing the distal carotid arteries but very poorly for the carotid origins, even with a low-lying surface coil. The close-fitting carotid coil enables detection of subcutaneous tissues near the coil elements with great sensitivity.

adjacent

tissues

gonithm tion. An

TEa

7425.

Address

re-

umbrella placed in the infranenal

fenion

vena

many years previously inferior vena cava. In-

cavography

occlusion

of the

demonstrated

inferior

vena

cava

dis-

tal to the umbrella, with development of large lumbar and gonadal collateral veins draining into the cava and renal veins and bypassing the occlusion. In the operating suite, a Greenfield filter was placed at the level of T-12, above the renal veins, in a position considcred satisfactory in this patient. After surgery, the filter was found to have

migrated. Twenty-four hours after placement, the filter had moved to the level of L-1 and had an oblique orientation; at least 2 cm of the filter extended into

the

right

gonadal

vein

Because the filter tive in this oblique tioning

was

(Fig

la).

would be ineffecorientation, neposi-

indicated.

The

right

inter-

nal jugular vein was cannulated and a balloon catheter partially inflated in the inferior vena cava above the level of the renal veins to prevent embolization of the filter into the right atrium. A 0.035-inch Amplatz wire (Cook, Bloomington, md) was introduced from the left femoral vein, and, with the assistance of a Benenstein catheten-with an angle near its tip that facilitates directional control-traversed the lumbar collateral vessel into the infcmion vena cava above the occlusion.

The

wine

was

then

through

the

ten. The

balloon

placed

wine,

with

and

hole

manipulated in the

catheter

apex

was

a doubled-over

the Amplatz

of the

then

fil-

mc-

exchange

wire

protruding

September

1990