Donald G. Mitchell, Keith Haidet, MD

MD #{149}Simon Vinitski, PhD Matthew D. Rifkin, MD

#{149} Feroze

B. Mohamed,

BS

Comparison ofKaopectate for Negative and Positive Contrast at MR Imaging’

T

with Enteric

evolution of clinical magnetic resonance (MR) imaging of the upper abdomen has been impeded by the tack of a suitable orally administened contrast agent. It is often difficult to distinguish between normal and pathologic bowel tissue; a pathologic condition intrinsic to the bowel can rarely be imaged adequately at

tional

MR.

containing

from

0%

to 100% attapulgite or barium preparations were compared by using spinecho and spoiled-gradient-echo techniques

to estimate

Ti,

T2,

and

T2*

relaxation times. In vivo spin-echo and gradient-echo images were obtamed of 10 healthy volunteers and of five patients with pancreatic disease after oral administration of 12-16 oz of attapulgite preparation. Ti and T2 relaxation times obtained with use of attapulgite were slightly lower than those obtained with kaolin-pectate at both 50% and 25% concentrations.

Compared

with

barium,

attapulgite had shorter Ti, T2, and 12* relaxation times, and concentration-dependent relaxivity was greater by

nearly

an order

subjects

were

able

of magnitude. to drink

All

the

atta-

pulgite, and the only complaints were of bad taste and mildly loose stools. Index

terms:

Contrast

Abdomen,

media,

tines,

MR

(MR),

contrast

Radiology

studies,

MR

comparative 70.1214

studies, studies

Magnetic

70.1214 #{149} Intesresonance

enhancement 1991;

19107.

181:475-480

Received

PhD

replaced computed tomography (CT) as the primary screening modality for the abdomen (1-3). In addition, MR imaging is rarely performed to enable detection, characterization, or staging of pancreatic disease, for which CT is often performed. Dilute preparations of barium or iodinated contrast agents, routinely administered orally prior to CT imaging of the abdomen, greatly increase the ability of CT to depict and enable characterization of extrahepatic pathologic conditions (4). These agents are widely used because of their high contrast relative to other tissues, as well as their safety and tow cost. These important attributes should be considered in the search for an orally administered contrast agent for use at MR imaging. The choice between increasing the signal intensity of intestinal contents (“positive contrast”) or suppressing it (“ negative contrast”) depends on the pulse sequence used. On T2-weighted images,

whether

HE

Therefore,

negative

MR

imaging

contrast

has

not

is prefera-

ble, since this decreases artifact and prevents confusion between normal bowel tissue and pathologic bowel tissue that has high signal intensity

, From the Department of Radiotogy, Thomas Jefferson University Hospital and Jefferson Medical College, 11th and Sansom Sts, PhiladelPA

MD,

wall. In addition, suppressing the signat of bowel, as welt as that of fat, neduces artifact and optimizes dynamic range, impnoving depiction of Ti contrast (9,10). The diamagnetic properties of clay compounds such as Kaopectate (kaotin-pectate; Upjohn, Kalamazoo, Mich) have been described by Listinsky and Bryant (5). The low cost and established safety of this class of agents are significant advantages over other orally administered contrast agents proposed for use at MR imaging, such as magnetic particles (8), paramagnetic solutions (11), and perfluorocarbon fluids (7). By binding water, clay compounds shorten Ti and 12 relaxation times, resulting in low signal intensity in the bowel on conventional spin-echo MR images. If echo time (TE) is short enough, howeven, 12-shortening effects may be minimized, “unmasking” Ti -decreasing properties. The goals of this study were (a) to determine whether the current formutation of Kaopectate (attapulgite) is as effective as the old formulation of Kaopectate (kaolin-pectate), which was evaluated by Listinsky and Bryant (5); (b) to compare the Ti- and 12-decreasing properties of attapulgite with those of barium, another low-cost contrast agent for use at MR imaging (6); and (c) to determine

(5-8).

phia,

F. Mammone,

Barium

In an evaluation of safe, inexpensive, orally administered contrast agents for use at magnetic resonance imaging, different concentrations of the clay agents kaolin-pectate and attapulgite were compared in an in vitro phantom by performing spin-echo imaging with variable echo times to estimate 12 relaxation time. Addiphantoms

#{149} Joseph

#{149}

March

27,

1991;

revi-

sion requested April 30; revision received June 10; accepted June 17. Address reprint requests to D.G.M. RSNA, 1991

On

Ti-weighted

images,

how-

ever, normal bowel tissue with tow signal intensity may mimic pathologic tissue with tow signal intensity. Therefore, it may be preferable to increase the signal intensity of intestinal contents on conventional Tiweighted images. With fat suppression, however, negative contrast may produce a double contrast” effect, improving depiction of the bowel “

attapulgite

enha

nces

lumen effectively on spin-echo ultrashort-TE, gradient-echo ages. MATERIALS Kaopectate

AND was

bowel

and MR im-

METHODS

purchased

in a super-

market for approximately $5.00 per i2-oz bottle. Alt MR examinations were performed with a 1.5-1 unit (Signa; GE Medicat

Systems,

Abbreviations: tion

Milwaukee).

TE = echo

Three

time,

phantoms,

TR = repeti-

time.

475

each

consisting

were

imaged

and

of a vertical with

transmit

agitated

use

of vials, receive

attenuation.

Alt

approximately

to the

onset

vials

tate (kaolin, mg/mm )

vials

The

prior

first

mg/mm3,

scnibed

Kaopec-

and

and new-formula

pectate,

above.

4.3

Kaopectate

ing

a three-point

was

calculated

(attapulgite, 37.5 mg/mm) in 100% , 50%, and 25% concentrations. These phantoms were imaged in the sagittat plane by using

(1,500/9,

a single-section, repetition time

above. The the relaxation

20 msec

spin-echo (TR) of 400

(TRITE

to estimate each vial

wt/wt; volume

This

tions.

contained

and

E-Z-Em, at both

barium

Westbury, 100% and

phantom

imaged

to estimate

and

1,600

50,

msec.

with 100,

by using

ages.

partial-echo sampled

was measured background.

=

Since much

p

(S)

in spin-echo less

than

(in which approximate

T2*

deviation imaging,

of we

(1)

experiments

TR,

we

used

Equation

(I)

12)

to were

to provide a comparison among of these solutions at MR imagthan to provide a definitive

measure

of the

actual

relaxation

the

comparison

barium

water

wt/wt

found

In

to be

precipitated

containing 60%

E-Z-Em)

taming preparations 40%, 60%, 80%,

#{149} Radiology

for within

a premixed

(Novapaque;

for

and

dilution.

wt/wt was

this

The

was

experiment,

20%

or more

minutes.

There-

preparation

used.

White in these

dependence 1/12, and

correlated

a. of

1/12*

with

Fisher

the using Softsusvis-

Scientific,

the exact shear measurements,

tow because experiments.

Human subjects investigation

(2,500/50, were

of the were approved

prior

after bottles)

shear

stress

imaged as part by our institu-

of C.

Conventional TIand T2-weighted

100) images

obtained

low

of 10 volunteers to and

approximately

administration of attapulgite.

with

Vials

of 0%, 10%, 20%, 100% concentrations

quences bottle

after ingestion of attapulgite.

of 16 oz Higher

pancreatic

The

b.

rate is it is rel-

of the contrast agent, use of which may have improved imaging, were not given because of concern regarding patient compliance. Subjects were polled for any adverse effects within 48 hours

for time-of-flight tionat TI- and ages

and

of barium

unsuitable

all dilutions

of

of concentrations;

used

was

using

Figure

1.

tamed

with

In vitro TR

spin-echo

of 2,000

images

msec

ob-

compare

kaolin-

pectate (old-formulation Kaopectate) and attapulgite (new-formulation Kaopectate) at 25%, 50%, and 100% concentrations with tap water. W = water, A = attaputgite, K = kaolin-pectate, /4 = 25% concentration, /2 = 50%

concentration.

Both

formulations

are

msec, msec.

= 40

(b) TE

100%

signal

msec,

concentration

voids.

(a)

and

(c) TE

TE

=

20

= 80

cancer imdif-

of a single 12-oz first gradient-

quence and in the axial plane at the end of the examination. Single-section, gradient-echo (27/7.4) images with a 20#{176} flip angle were obtained of each subject

to expand

attapulgite

preparation

water

476

imaged

range

was

since fore,

was between

at a wider

distilled

85%

times.

the validity of measurements time that use truncated radiopulses has not, to our knowl-

edge, been proved. A third phantom

a two-point

echo sequence consisted of 12 radio-frequency-spoiled (101/2.3) images acquired within a 14-second suspended respiration. These images were obtained in the coronal plane as an initial localization se-

TE is

obtained properties ing rather particular, relaxation frequency

using

and one with pancreatitis underwent aging with use of spin-echo and two ferent breath-hold gradient-echo se-

‘#{149}

is substituted with T2. The measurements

and

after ingestion. Four patients

is

I2(1

t

us-

time

quantities

image.

for a 90#{176} radio-frequency intensity

cal-

was estimated by technique described

(Canon-Fenske;

30 minutes (two 8-oz

dephasing of transby radio-frequency

Thus,

S

im-

measurements noise, which

as the standard In gradient-echo

signal

of

by using full echo

the

20-msec

intensity to system

assumed complete verse magnetization

spoiling.

while

the

for

Therefore, these were normalized

pulse,

acquisitions 20)

by

tional review board. weighted (400/12-14)

was

achieved

sampling,

an

800,

(4,000/12,

was

was obtained TR by

double-spin-echo

images

plotted

atively in these

msec

relaxation

separate

12 msec

400,

time

images variable

concentration rates 1/Ti,

shear rate. unknown

TI reof 2.1

200,

T2

spin-echo of

TE

TE

150,

Finally,

single-section,

was

T2* relaxation.

estimated

of 25,

estimated

a

pulses. TR was 100 msec, varied (2.1, 3, 4, 6, 8, 10, and

was TRs

with

from

ar-

Pittsburgh) at 20#{176}C.For strictly quantitative measurements, the use of a capillary viscometer assumes that the fluid obeys Poiseuille law. This assumption is not entirety valid for suspensions in which the apparent viscosity varies according to the

NY) in an equal 50% concentra-

was

relaxation

fit. T2 relaxation

18)

cometer

of 85%

use of a single section and Prototype short-TE softthat employed truncated

radio-frequency while TE was

and

not

vials

was

barium,

fit of the linear regression curve by Cricket Graph 1.3 software (Cricket ware, Malvern, Pa). Kinematic viscosity of the various pensions was measured in a capillary

gradient-echo

technique, with a 90#{176} flip angle. ware was used

15 msec)

40 of

(HZ-HD,

radio-frequency-spoiled,

taxation

2,000/20,

time our experishorter TE was

phantom

attapulgite

and

TI

fit. T2* relaxation the gradient-echo

with TE of

T2 relaxation times use of region-of-interest

At the performed,

available. The second both

400/20)

=

TI and through

measurements. ment was

technique, msec and

and

rows, were imaged technique de-

culated from spin-echo with TE of 9 msec and

phantom

of original-formula

194

of attapulgite

ranged in two separate with the single-section

were

15 minutes

of imaging.

contained

by volume

row

of constant

con-

were

flow imaging. Conven12-weighted spin-echo

obtained

for

the

normal

im-

volun-

teers, as well as TI-weighted images in which fat was suppressed with a combination of selective saturation and opposed-phase techniques (9,12). The signal intensity of the mens was noted,

gastric and duodenat tuas was visibility of the

head, body, and tail of the pancreas. Because of the limited time between ingestion of the contrast material and imaging and because of the small volume of contrast agent remainder evaluated.

that was administered, of the small bowel

was

the not

RESULTS Alt curve tions

fits

resulted

mated

Ti and

tamed

with

tions

than

Table

1). The of too

the

relatively

in

this

the

The

.99.

>

12 relaxation and

slightly

pulgite

were

relaxation

r

50%

were

times

for in

for

25%

shorter

for

to tong

atta(Fig

1;

12 relaxation

full-strength

experiment.

concentra-

kaotin-pectate

Ti and

short

estimaestitimes ob-

formulations

be

estimated IRs

and

Because

with TEs

used

of limited November

1991

a.

b.

Figure

2.

In vitro images contain 100%, 80%, 60%, nat intensity than distilled (1,000/6) image. All tubes signal ing

intensity

than

60%-I00%

C.

compare attapulgite and barium (60% wt/wt). lop 40%, 20%, 10%, and 0% concentrations. (a) Ti-weighted, water. Tubes containing 20%-60% attapulgite have containing barium have higher signal intensity than

water.

(c)

attapulgite

(1,500/18)

Spin-echo

have

lower

signal

image.

intensity

Alt tubes

than

with

row

= barium,

bottom

gradient-echo the highest signal water, while tubes

barium

have

higher

row (100/2.2) intensity. containing

signal

= attapulgite.

From left to right, image. Alt samples have higher (b) T2*weighted, gradient-echo 60%-I00% attaputgite have

intensity

than

water,

while

tubes

tubes sigtower

contain-

water.

20

200 :;

150

100

50 t006’08’01#{224}0 20

,

40

a. Figure 60%

60

80

100

Concentration

%

%

3. wt/wt

Relaxivity

plots

show

the

concentration

dependence

of (a) 1/Ti,

(b) l/T2,

(c) 1/T2*

for 50% dilution (4.0 msec vs and 8.3 msec, respectively, for 12* relaxation time and 10.2 msec vs 11.4

attaputgite

varied

centration,

but

and

tapulgite

29.1

msec,

of

two Even

data points, the accuracy of these relaxation measurements is limited, but it is sufficient to establish that attapulgite is at least as effective an MR contrast

as kaolin-pectate. had shorter 12,

agent

Attapulgite

Ti relaxation

times

12*,

barium Compared with either attapulgite or barium alone, the mixture of the two preparations had shorter 12* relaxation time (i.8 msec vs 2.4 and 3.6 msec, respectively) and 12 relaxation time (4.3 msec vs 5.5 and 6.5 msec, concentrations

respectively).

Volume

for attapulgite

similar

the

all

rates

4.9

cause

at

relaxation

(U)

and

barium

(#{149}).

respectively,

for

12

relaxation time). The 50% concentration of attapulgite had approximately the same catculated 12 in the first two experiments (11.0 msec vs 11.4 msec), but the calculated Ti was different (118 msec vs 78 msec). This may be be-

and

Concentration

C.

LI

This

181

than

(Figs

#{149} Number

relationship

2

2, 3).

was

tated ium

technical

between

experiments. though the vials were agiprior to imaging, the 50% bar-

mixture

Repeated 85%

differences

imaging

separated

noticeably.

experiments

wt/wt

barium

confirmed settled

that

within

minutes when diluted to 20% or more water by volume. No gross evidence of settling of any of the other solutions

was

noted

at

imaging

or

an

order

dilutions cause The

1/12*

relaxation

rates

i/T2, for

used

and

at-

be calculated

wt/wt

60%

barium

wt/wt

greater

than

at high

concentrations

too

of

was

barium,

especially

(Table

drank

for

be-

rapidly.

attapulgite

that

All subjects

at or

barium,

precipitated of

by for

concentration,

of 85% they

for

viscometers

the

2).

attapulgite,

but all found it unpleasant. objected to both the taste

Subjects and consistency, and some stated that it became increasingly difficult to drink because of a feeling of gastric fullness. There were no reports of constipation or pain

after

ingestion,

stools In

although

reported

that

were

volunteers, resulted

except

in

an

distention

anterior

of

loose

accompanied

ingestion in

five

mildly

not

ach and duodenum virtual signal void

and

barium

not

60%

viscosity

gite

for the third experiment. The calculated i/Ti,

than

10 volunteers

visual

therefore

or

greater

con-

nearly

greater

capillary

attapulgite

ods

were

the

with

was

3).

could

Viscosity

cramps.

and

magnitude

(Fig

using

inspection within 1 hour of mixing. Dilutions of 60% wt/wt barium nemained in suspension for longer penof time

of

linearly

the slope

by

of

attaput-

of

the

and produced at MR imaging, layer of fluid Radiology

stom-

a

#{149} 477

with intermediate to high signal intensity. Depiction of the pancreas was improved after administration of attapulgite (Fig 4). In four of five patients, the bowel lumen demonstrated a near signal void on images obtained with TE not tess than 7.4 msec. The fifth patient had partial obstruction of the gastric outlet, which resulted in dilution of attapulgite with gastric secretions. In this patient, the bowel lumen demonstrated high signal intensity on alt images obtained with TE of not more than 12 msec, but the signal intensity of bowel was low on images obtained with TE of not less than 50 msec. In all patients, the pancreas, stomach, and small bowel were delineated

clearly

on

all enhanced

a.

b.

images

(Fig 5). Benign and malignant pancreatic tissue could be clearly diffenentiated. The stomach and the duodenum demonstrated the same signal intensity. d.

C.

DISCUSSION Attapulgite

Figure

is a safe,

inexpensive,

and readily available orally administered contrast agent with promising effects on shortening Ti and 12. Retaxation is enhanced even when attaputgite is diluted, as might occur in the presence of intestinal secretions. There the

are

abundant

broad

margin

administration other

of of

clay

The

data

establishing

safety

for

preparations

oral

Li

et

at (6).

because

preparations

appear of

their

to

be

at

unsuitable

tendency

to

precipi-

tate with even mild dilution, presumably because of the limited amount of suspending agents. Paramagnetic (11), supenparamagnetic (8), and perfluorocarbon (7) agents have shown promise in clinical trials, but the production and investigation of these agents may be expensive. For 12-weighted images, in which it is desirable to decrease the signal intensity of the bowel lumen, attapulgite was effective as a contrast agent in alt cases, including in a patient with

gastric

distention

that

was

the

of partial obstruction of the tric outlet. In 12-weighted images tamed with barium as the contrast agent, signal intensity was higher the calcutated 12 and 12* relaxation result

478

#{149} Radiology

were

with

(5).

Barium

times

on

relaxation

wt/wt

of the pancreatic

et

properties of attapulgite appear to be significantly supenion to those of even the most concentnated solutions of barium in use clinically. For our concentration-dependent nelaxivity data, we used a 60% wt/wt preparation of barium, which was reported to be optimal by 85%

piction

consistent

and

attapulgite

4. (a, c) Ti-weighted (400/14) images tamed (a, b) prior to and (c, d) approximately by a volunteer. Except for a thin layer of high tow signal intensity on both TI- and T2-weighted

gasoband

longer, with

at that 12-weighted orally

signal

body

and

findings the

images administered

tail (P).

that

observation

reduction

were of

was

Li

limited

enhanced barium

(6).

Li et at noted that barium provided the best negative contrast on 11weighted images, but water alone also could provide good negative contrast because of its long 11 relaxation time. For Ti-weighted images, the deci-

to increase or decrease the signal intensity of the lumen is tess obvious. Achievement of negative contrast decreases the potential for the appearance of ghost artifact on TI-weighted images, but ghost artifact can be avoided by decreasing TE and imaging time, especially if respiration can be suspended. White we occasionally note significant bowel-related artifact on conventional spin-echo images obtained with TE of 12 msec (probably because of respiratory-induced motion of hypenintense fluid), we have not noted this artifact on breathhold images obtained with TE of 2.3 msec. The high signal intensity of bowel can also potentially obscure vessels on MR angiognams. In our series, the 12* relaxation time of attapulgite was sufficiently short to produce low intraluminal signal intensity on att images obtained with TE of not less than 7 sion

and (b, d) T2-weighted (2,500/100) images ob30 minutes after ingestion of 16 oz of attapulgite signal intensity at the top, the gastric lumen has images after ingestion, which improves de-

msec,

except

struction

the

in of

the

patient

gastric

with

outlet.

ob-

Nega-

tive contrast Ti-weighted

was also beneficial images acquired

on with fat suppression; the bowel watt was depicted as having high signal intensity relative to fat on one side and relative to the contrast agent on the other. White it is possible that intermediate signal intensity might result from the use of certain pulse sequences, this did not occur in our series. Positive contrast can be beneficial on Ti-weighted images because of increased differentiation of the bowel lumen from most other tissues. In all subjects,

bowel

the

lumen

demon-

strated

high signal intensity on images obtained with TE of 2.3 msec because of the short Ti relaxation time of the clay agent. The pancreas was depicted as hypointense to fat and bowel lumen but hypenintense to tumors

or

other

abdominal

viscera.

Although all subjects drank the attapulgite in this series, tack of palatability remains a significant obstacle to routine use of currently available clay-based formulations. The high viscosity

of

attapulgite,

which

is even

greater

than that of barium, contnibutes to the unpleasant experience of ingesting large quantities. Variable patient toterance is already a limitation with MR imaging because of the November

1991

a.

b.

d.

C.

e.

Figure

5.

creatitis. duodenat intensity

(101/2.3) image was obtained with a flip angle of 90#{176}. Attapulgite within the gastric (G) and (D) lumens has high signal intensity, allowing clear depiction of the mural folds of both structures. A pseudocyst (C) with high signal is adjacent to but separate from the lesser curvature of the stomach. The pancreatic head (P) is prominent. Small-bowel contents arrows) also have high signal intensity. Black lines at fat-water interfaces indicate partial volume effects between fat and water, the of which are opposed at TE of 2.3 msec. Large arrow indicates susceptibility artifact from metallic clips in the gallbladder fossa. (b) Coro-

(small

Images (a) Coronal,

obtained after Ti-weighted,

administration gradient-echo

of 12 oz of attapulgite

in a patient

with

pancreatic

pseudocysts

that

occurred

after

acute

pan-

phases nat, gradient-echo (27/7.4) image obtained with a flip angle of 20#{176} corresponds to the image in a. Attapulgite within the gastric (G) and duodenat (D) lumens has low signal intensity. As in a, the walls of each viscus are depicted clearly. C = pseudocyst, P = large pancreatic head. Fluid in the small intestine (arrows) also has low signal intensity. The celiac trunk, superior mesenteric artery, and other vessels are depicted as haying high signal intensity. (c) Axial, fat-suppressed, Ti-weighted (400/i4) image. Attaputgite within the gastric lumen (C) has tow signal intensity, which allows clear depiction of the gastric wall with “double contrast” relative to lumen and fat. The pseudocyst (C), with high signal intensity, can be clearly distinguished from the stomach and from the left adrenal gland (arrow). (d) Axial fat-suppressed image at a tower level reveals a pseudocyst (C), with tow signal intensity, anterior to the left psoas muscle. Attapulgite, with tow signal intensity, facilitates detineation of the duodenal (D) and gastric watts. The superior mesenteric vein (white arrow) and duodenum (D) mark the lateral borders of the enlarged pancreatic head (tong black arrow). Short black arrows indicate the pancreatic duct within the pancreatic head. (e) Axial T2-weighted (2,500/100) image corresponding to the image in d reveals a signal void (white arrow) within the duodenum and stomach. Black arrow mdicates the pancreatic duct. The pseudocyst has high signal intensity.

for long examination times in an enclosed space, accompanied by acoustic noise. We are, therefore, reluctant to add to the possible unpleasantness of MR examinations. In our practice, attapulgite is restricted to use in patients referred primarily for imaging of the pancreas, in which use of orally administered contrast matenat is especially important. Thus far, we have not optimized oral administration of contrast agents, which ne-

comthat have but are more palatable. Some clays, such as bentonite, have especially efficient relaxation properties (5), which might allow them to be used in much tower concentrations than are necessary with attapulgite. Rectally administered clay agents are effective as contrast material because lack of palat-

cessitates

The benefit tered clay-based

necessity

patients

arriving

early

a large volume of contrast nat in divided doses during the preceding the MR examination. drink

Volume

181

#{149} Number

2

to

matehour

Perhaps

pounds similar

ability

other

clay-based

may be developed relaxation properties

is not

a problem

(13).

of using orally adminisor other contrast agents for MR imaging of the abdomen may be greatest for imaging of

the pancreas, which bowel. The pancreas relaxation time, and

is surrounded by has a short Ti its signal inten-

sity

images

on

Ti-weighted

is even

higher than that of the liver (9,10). Pancreatic neoplasms thus have significantly lower signal intensity than normal parenchyma. Motion-artifact correction and fat suppression have been shown to improve depiction of normal and pathologic pancreatic anatomy by unmasking the high tissue contrast available in this region (9,10). As demonstrated herein, use of breath

tered

holding

contrast

and

material

orally

adminis-

at MR imaging Radiology

#{149} 479

may be beneficial. Further evaluation of techniques designed to optimize MR imaging of the pancreas and comparison with other modalities is therefone indicated. U

3.

4.

5.

ACknowledgments: Listinsky, MD, vice; to Esmond

We are grateful to Jay for valuable comments and adMapp, MD, for assistance with barium preparations; to Ken Goodman and Fred Ross for photography; and to Pam Bittle for secretanial

6.

assistance. 7.

References 1.

Barakos J, Goldberg H, Brown JJ, et at. Comparison of computed tomography magnetic

2.

480

resonance

tion of focal Radiol 1990; Chezmar JL, et at. Liver patients with ing. Radiology

#{149} Radiology

hepatic

imaging

lesions.

in the

and

evalua-

Gastrointest

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