Relocatable

Glanturco

Toshiyuki Irie, MD Shigeru Furui, MD Teiyu Yamauchi, MD Kohzoh Makita, MD Satoshi Sawada, MD Eiichi Takenaka, MD,

Expandable

terms:

Interventional procedures, exVenae cavae, grafts and prostheses, 982.1299 #{149} Venae cavae, interventional procedure, 982.1299 penimentab

#{149}

Radiology

1991;

178:575-578

a. various types of metallic stents have been designed and used for vascular and nonvascular intervention (1-10). One problem encountered so far has been the inability ECENTLY,

to move the stents after placement. solve this problem, we modified tunco expandable metallic stents (GEMSs) relocatable.

to make

Materials

them

and

Figure

1.

0.018-inch

space

Stents’

AAAA AA AAAA/ AAAA vVVVv

PhD

The authors modified Gianturco cxpandabie metallic stents to make them relocatable. Two tandem designs were made. The first design had long struts and, thus, more evenly distributed cxpansive force; the second had short struts and more flexibility and was betten suited for use in curved strictures. Both designs (two to four in tandem, 0.012-, 0.014-, and 0.018-inch wire) were tested successfully in vitro, and both designs (two to four in tandem, 0.012-inch wire) were successfully placed, retrieved, and relocated in the inferior vena cava of five dogs. Index

Metallic

Photograph

b. (a) and cut and opened

wire.

struts

between

Long

receive

the

view

expansive

(b) of long force

strut

of all stents

design and

made

transmit

‘I

from it to the

stents.

To Gian-

retrievable

and

Methods

We made two types of relocatable stents in tandem with use of original single GEMSs, wire struts, and monofilament line. Original single GEMSs with six bends were made from 0.012-, 0.014-, and 0.018-inch stainless steel wine. Stents made from 0.012and 0.014-inch

Abbreviations: abbe metallic

stent,

GEMS IVC

Gianturco =

inferior

expandvena

cava.

I From the Department of Radiology, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359, Japan (TI., S.F., T.Y., KM., E.T.), and the Department of Radiology, Tottoni

University (5.5.).

School Received

of Medicine, March

26,

Tottoni,

1990;

quested April 30; final revision tember 7; accepted September print requests to TI. RSNA,

Volume

received 10. Address

Japan re-

Sepre-

a. Figure

1991

178

revision

0.018-inch

Number

#{149}

2

b. 2.

Photograph wire.

(a) and

cut

and

opened

view

(b)

of short

strut

design

made

Radiology

from

#{149} 575

3.

Figure

Photograph

of short

made from 0.014-inch wire. strut has a hinged structure, this

stent

more

strut design

One side of each which gives

F I SI

flexibility.

a

‘I

Is

II

SI

I

II SI S ‘I S II I SI S S

wine were 1.5 cm in diameter and 1.5 cm long, and those made from 0.018inch wine were 2.5 cm in diameter and 2.5 cm

long

tail

stent

and

(Fig

flexibility

GEMS had long all cephalic bends all caudal

1). Long but,

in

bends

struts

our

I

II

I

(1).

One modified that connected others

I

struts of the

I I

S

I

s

of the

have

little

judgment,

have

the advantage of evenly distributing expansive force because the long struts seem to receive the expansive force of all stents and transmit it to the gaps between stents. The other modified GEMS had short struts

that

connected

all caudal

and

cc-

phalic bends between One side of each strut

stents (Fig 2). had a hinged

structure,

which

the

flexibility

(Fig 3).

Struts

wire with

were

gave made

as the stents silver solder.

small

rings

from

stent the

were

made

in diameter

same

size

and were connected In both designs, by closing

caudal bends of the tail stent yen solder. These rings were with a circle of monofilament thread (nylon or polypropylene, mm

more

for

0.012-

the

with sibjoined surgical 0.15

and

inch wire stents and 0.20 mm in diameten for 0.018-inch wire stents). A small draw loop (1 mm in diameter) was made in the circle to connect the stent to a holding line (fluorocarbon monofilament

line,

0.2 mm

size of the compressed same for both tandem Stents

were

placed

in diameter).

use

Figure

4. rod

pusher

ered (e).

Method of retracting is advanced (b). The

(c). The sheath

the stent into the sheath. Stent is placed (a). The hollow holding line is pulled and the bends of tail stent are gathover the stent (d). The stent is now retracted into the sheath

is advanced

The

stent was the designs. with

e

0.014-

of con-

The stent its position

was then checked

placed (Fig 4a) and fluoroscopically by

and 0.018-inch wire stents, respectively (Medikit, Tokyo, Japan). A hollow pusher rod was made by cutting off the sharp tip of the Teflon dilator included

means of injection of contrast medium through the hollow pusher rod via the Y-shaped connector. If retrieval or relocation is necessary, the pusher rod is advanced beyond the end of the sheath (Fig 4b), the holding line is pulled, the

in the

bend

ventional angiographic Teflon sheath sets of 7-, 9-, and 12-F for 0.012-, 0.014-,

set.

Before insertion sheath, a holding through through

the the

small hollow

of the stent into line was looped

draw 1oop and run pusher nod, which

was capped by a Y-shaped with a hemostatic valve. the the the

the

connector The ends of

holding line were passed through valve, knotted, and held to control stent. The sheath was positioned, and the stent and pusher nod were inserted.

576

Radiology

#{149}

rings

of the

stent

are

drawn

to-

gether (Fig 4c), and the stent is retracted by advancing the sheath over it (Fig 4d, 4e). The stent can now be retrieved by pulling

the

holding

cated by moving to a new position. tached by cutting ing line pusher.

and

Six stents four

in tandem,

line

on relo-

the

line

nal

aorta

retrieved

out

of the

three

and

(IVC)

long made

struts, from

0.012-,

its

first-order

branches.

and

relocated

in the

of five

immediately

inferior

af-

vena

cava

dogs.

Results All

with

and

Two stents with long struts (three and four in tandem) and three stents with short struts (two to four in tandem) made from 0.012-inch wire were ten placement

the tip of the sheath The stent was dethe knot in the hold-

drawing

0.014-, and 0.018-inch wire and nine stents with short struts, two to four in tandem, made from 0.012-, 0.014-, and 0.018-inch wine were placed, retrieved, and relocated in a silicone vascular model simulating the human abdomi-

stents

were

retrieved,

and

vascular

model

successfully

relocated

and

placed, in

the

IVCs

the

silicone

of five

February

1991

b.

Figure upper Stent mild

e.

d.

C.

5. Venacavogram shows relocation of long strut stent part of IVC (a). Stent is partially drawn into the sheath is relocated 4 cm below the previous position (d). Another intimab hyperplasia.

(four in tandem, 0.012-inch wire) (b). The tip of the sheath is placed venacavognam obtained 60 days

6). No evidence tion was found

of pulmonary at this time.

infanc-

hollow

were our modified to make retrieval

intervention.

of placement

the ability stent after

and

expand

little

stent

5. Both

and the covered

the

metallic

part

monofilament by the tunica

circle intima.

the of

dog the

(arrow)

(Fig 5a-5d). Venacavograms of of the dogs obtained 60-75 days placement showed patency of the and development of mild intimal (Fig 5e). Results of necrop100-115 days after placeshowed both the metallic part of stent

and

be covered

Volume

178

the

monofilament

by the

Number

#{149}

tunica

2

circle

intima

(Fig

flexibility

ity,

expansive

stricture force

unless

is used,

stent unit

can

be

checked

remaining

with in

the

with

position the sheath

prior

to

full

expansion.

ing line was looped of the tail stent and

or polypropylsome

weeks

cause

(12) and,

danger

to the

toxic-

thrombo-

pulmonary

by intima

after

therefore,

poses

patient.

we believe

our

modi-

fied GEMSs can be advantageously used for connection of obstruction the arteries, veins, bile ducts, and cheobronchial trees. U

of tra-

of tail for

easier retraction. This is particularly useful in cases of IVC obstruction immediately below the night atrium and common bile duct obstruction near the papilla duodeni major and in other cases where the lead stent must be precisely placed at the site of the lesion. The position and expansive effect of the stent should be checked after full expansion. We also tested our modified GEMSs without a monofilament circle. This design can be retracted and relocated only

may

be

relocate the gives the op-

has little

it is covered

In conclusion,

which

design

it has

which

embolism,

will

However,

in therapeutic

nylon

line

though

several

the

GEMSs

situations.

The

monofilament

the

of

greater

genicity,

model

circle

to retrieve and full expansion

ene

more flexible tandem stent short struts can be used. For clinical use, the initial

IVC

in many

enaton

intro-

into

the modified

stents (10,11). The modified GEMS with long struts has more evenly distributed expansive force and is better suited for use in straight strictures. This design will not

in a curved

retracted

a monofilament

adequate

of additional

were

vascular

relocated.

We believe

ed by means

stents

expanded while keeping in the sheath. The stents

and

without

can cause undesirable stress on the wall of the stricture. In curved strictures, the

opened

The

the silicone

successfully

sheath

and relocation possible. If the expansive force of a stent is insufficient, it can easily be replaced with another. Misbocation or insufficiency of expansive effect has previously been correct-

strong

and

into

and partially the tail stent

To our knowledge, GEMSs are the first

Cut

pusher.

duced

Discussion

6.

in the IVC of a dog. Stent is placed in the at a bower position after full retrieval (c). after placement (e) shows good patency and

The

hold-

through one run through

ring the

Acknowledgments: his

aid

We

in our

preparation

thank

E. T. Mirtin

of the

for

manuscript.

Tadaharu Kojima for his photographic work, and Hiroshi Akuzawa for his aid in expenimentab work.

References 1.

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2.

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Radiology

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Index terms: Angiography, 91.1299, 95.1299, 951.1299, 952.1299 . Angiography, technology Filters

of angiographic

images

density A wedge

commonly but it may

used create

have filter

limited is the

compensating filtration

efmost

filter, artifacts and,

depending on how much of the filter is placed in the path of the primary beam, it may require in exposure.

A good

compensating

produce ty, cause position, crease in

Texas

a considerable

increase

filter

M.D.

Anderson

Cancer

open-floored concentric

Center,

structed shoulder

ogy, tional

the

Section

Department

of Diagnostic

of Angiography

Radiology,

Box

57,

and the

as M.D. Anderson Cancer Center, combe Blvd. Houston, TX 77030. 30,

1990;

revision

requested

Interven-

University

August

of Tex-

1515 HobReceived May 6; revision

received September 13; accepted September Address reprint requests to C.H.C. c RSNA, 1991

578

Radiology

#{149}

20.

161:295-298. Furui 5, Sawada

5, brie

vena

of two metallic

Dahbke

H, Dociu

genicity

edge hole

and

of the filter was conthe

(eg, same

the outby 2.5 by 6

was

with

used

two

[T;o

of which

Lanex

film

Figure

were

regular

(Eastman

1.

Schematic drawing compensating

floored concave (top) and lateral

peak

made

and

with

was

by

the

and

filter.

In

the

usually

to

tion

x

this

vary

man-

out” of adjusted the

institution, a field to

celiac without

Thus,

angiogra-

the

the

are included

entire

lateral

area

walls

in the field

performed

(25

X

of

of the

in

small patients and excluded in larger patients. The standard exposure factors for celiac angiognaphy are 75 kVp and

size.

time den-

The

filter

collimator.

with

a magnifica-

of 1.3 times and a field of 12 (30 X 30 cm), which may

according

timal

magnifica-

of 10 X 13 inches

include

patient’s the

to liven

size.

The

dand exposure factors used in of both sexes are 75 kVp and station to obtain a small focal duce image unshanpness. To

density. is performed

on

factor 12 inches

loss in den-

ner, the filter prevented “burn the less dense areas while the milliampere second maintained

a given

with an exposure an optimal film

Selective hepatic angiognaphy is performed after catheterization of the hepatic artery or one of its branches. It is

the comkilovolt

adjusted

for the overall

caused

milliam-

at 75 kVp,

second

compensate

an optimum

When used, the

maintained

milliampere

views.

screens

a variable

pene second technique. pensating filter was

(bottom)

of the openfilter. Frontal

Kodak,

for

vessel.

as

microsco14:251-268.

17.7 cm2 of It has an

is centered

abdomen

electron Res 1980;

in

sity

the

Thrombo-

materials

demon-

decreased reduced

were

with

K.

suture

revealed by scanning py. J Biomed Mater

Exposures

cm)

expandable 1990; 176:665-

N, Thurau

of different

mA station will produce

32.5

Hepatic treatment

670.

12.

600 that

tion

T, et al.

obstruction:

types with Gianturco stents. Radiology

Rochester, NY). Selective celiac, hepatic, shoulder, and pelvic angiography was performed with use of the filter.

sity

cava

ex1986;

for Anglography’

wedge,

with

TMH-1

was

prelimi-

5,

diameters thickness

both

equipped

kilovolt

cava:

concave design with a wedge with a slope of 1/3

Conn),

and

vena

of treatment with stents. Radiology

Methods

in the concentric

ton,

of the

assessment pandabbe metallic

inferior

imagems, the General Electric MSI 1250 IV (GE Medical Systems, Milwaukee) and the Philips Poly Diagnost I (Shel-

phy

Radiob-

that,

has

for some applications angiognaphy) with

At our From

a filter

boned through the center (Fig 1). A smaller version

overall 1

Wallace

starting 2.5 cm from the outer terminating in a 5.1-cm radius

peak

should

a radiograph of uniform densino artifacts due to its shape or and require little on no inexposure. At the University of

CH,

was made from stock aluminum.

en and inner cm, and the mm. The filter

is often less than optimal because variations in body density result in aneas of oven- or underexposure within a field. Most filters designed to equalize

radiographic fectiveness.

and

The filter 1.3-cm-thick

slope

178:578-579

quality

11.

Filter

constructed

Materials

HE

C, Carrasco

most of its applications, strated these characteristics.

An open-floored concave compensating filter was designed that produced a radiograph of uniform density, caused no artifacts due to its shape or position, and required little or no increase in exposure in most applications. Selective celiac, hepatic, shoulder, and pelvic angiography was performed with use of the filter; image quality was noticeably improved.

T

R, Dondebinger

Compensating we have

James M. Johnston, RT(R) C. Humberto Carrasco, MD William R. Richli, MD Lee M. Marsh

1991;

A, Dick

175:97-102.

167:727-728. H, Joffre F, Railbat

Open-floored

Radiology

Adam

Stenosis

nary

RF, Lunderquist A, Roche A. Gianturco expandable metallic bibiary stents: results of a European clinical trial. Radiology 1989; 172:321-326. Strecker EP, Liermann D, Barth KH, et al. Expandable tubular stents for treatment of arterial occlusive disease: experimental and clinical results. Radiology 1990;

G Jr. Wright KC, Charnsangavej C, 5, Gianturco C. Flexible balloonstent for small vessels. Radiobo-

1987;

et al.

170:773-778.

160:723-726.

5.

stent in expeniRadiology 1989;

density,

the

exposure

time

varies according to the patient’s size. Magnification is not possible in patients with abdomens thicken than 27 cm because the required exposure time exceeds the safety limits of the small focal spot. The filter is positioned so that

a

film

stan-

patients a 160 mA spot to meobtain op-

penior

its

thickest and

lateral

portion portion

is over of

the the

February

su-

liver.

1991