Didier

Mathieu,

Catherine

MD

Beges,

#{149} Alain

MD

Focal Nodular Assessment TurboFLASH Twenty-two

patients

focal nodular proved with

hyperplasia pathologic

Rahmouni,

#{149} Pierre

with

25 cases

of

imaged with a TurboFLASH (fast low angle shot) sequence combined with bolus administration of gadolinium tetraazacyclododecanetetraacetic (DOTA), spin-echo (SE) T2-weighted sequences, and postcontrast Ti-

quantified;

the

acid

of the

central

scar were qualitatively SE T2-weighted images, were

hyperintense;

central

scar

intensity

tense

exhibited

associated

areas

analyzed. On all FNHs in two cases the a high signal with

corresponding

tissue within Unenhanced

the branches TurboFLASH

hypoin-

40-80

seconds

(GRE)

RADIENT-ECHO

injec-

magnetic proved

evaluation

of liver

However, the are sometimes

results limited

tumors

our

combined

(1-6).

of this technique because the

study

was

this

to study

characteristics of this trast material-enhanced MR

images

and

180:25-30

I From the Department of Radiology, H#{244}pital Henri Mondor, 51 Avenue du Mar#{233}chal de Lattie de Tassigny, 94010 Cr#{233}teil,France (D.M., AR., M.C.A., B.F., C.B., PG., J.J.M., NV.); and Siemens Medical Systems, Paris (B.F.). From the 1990 RSNA scientific assembly. Received December 21, 1990; revision requested January 23, 1991; revision received March 1; accepted March 13. Address reprint requests to D.M. C RSNA, 1991

In a project mors at high referred to

field

1-year

period

with

the same

since

implementation

sequence.

strength,

all the

our MR imaging underwent

We

have

cases and

drium cases;

prompted a palpable

patients.

of FNH were pain in the

These

right

lesions

were

patients

a used

fortu-

hypochon-

located

patients

dynamic

corn-

after

intravenous

of contrast lesion.

All

bo-

medium the

in

patients

to our institution underwent MR with a 1.5-T magnet (Magnetom Siemens). The study was performed

1. T2-weighted

images

were

obtained

with a TR of 2,2.00 msec and a TE of 45 and 90 msec (TRIFE = 2,200/45, 90), a matrix of 256 x 256, two acquisitions, and an 8-mm with

a gap

sections

with

of 0.8 mm

and

inter-

an acquisition

Artifacts

TurboFLASH

TB/FE

matrix of 128 mm (Fig 1).

re-

in the found

and

of the

follows:

discovered

discovery mass was

plane

2.

viewed the MR imaging characteristics of 25 cases of FNH proved with pathologic examination in 22 patients. These patients were 21 women (mean age, 34 years; range, 18-52 years), 19 of whom had used oral contraceptives, and one man who was 42 years old with no history of steroid use. Eight itously,

before

such

images

with a multisection covering the entire pended respiration nous injection. The

TurboFLASH

retrospectively

ob-

time of

as motion

and

flow were suppressed by means of flow and respiratory artifact obliteration with directed orthogonal pulses in 20 patients (9), with a presaturating band 2 cm thick close to the ventral subcutaneous fat.

hi-

that had been of the

with

puted tomography (CT) performed in other medical centers. In all cases, adjacent axial CT scans 8 or 10 mm thick were

leaved

examination

protocol

and

17 minutes.

unit during

mean

proved of samples

in all these

sonography

thickness

the

liver

were

The

4-12 cm). All

by means of the same protocol with a body coil and axial views in all patients. These successive images were obtained:

in compar-

different

and in the left

included

referred imaging SF 63;

METHODS

studying

PhD

tamed at surgery. Initial examination

the

ison with other previous reports, the features of FNH on spin-echo (SE) MR images in this large group of lesions proved with pathologic examination.

AND

of FNH examination

lus administration

lesion on conTurboFLASH

to discuss,

MD,

lobe in 12 patients

obtained

technique

twofold:

right

these cases pathologic

acquisition time is too long to perform a suitable hemokinetic study of these lesions (6). TurboFLASH (fast low angle shot) (Siemens Medical Systems, Paris) MR imaging techniques have recently been developed to obtain very fast acquisition of images (7,8). have

Falise,

MD

lobe in the other 10 patients. diameter was 6.8 cm (range,

contrast agents have imthe capability of MR imaging

PATIENTS

1991;

in

T2-

Index terms: Liver, focal nodular hyperplasia, 761.3119 #{149} Liver neoplasms, MR studies, 761.1214 #{149} Magnetic resonance (MR), pulse sequences #{149} Magnetic resonance (MR), rapid imaging #{149} Magnetic resonance (MR), tissue characterization Radiology

sequences

magnetic resonance (MR) imaging reduce measurement time by virtue of short repetition times (TRs). GRE sequences enhanced with para-

with the injection of paramagnetic contrast agent in the evaluation of 22 patients with focal nodular hyperplasia (FNH) of the liver. The purpose of

after

with

G

#{149} Beatrice

Vasile,

Liver:

We

scar.

lion. Both unenhanced and enhanced TurboFLASH sequences produced the best signal-difference-to-noise

ratios in comparison weighted images.

MD

#{149} Norbert

MD

of the images

central scar as a hypointense area within the lesion. After bolus injection, arterial enhancement of FNH was clearly seen, and in 10 of 25 lesions, enhancement within the scar

seen

Anglade,

Mollet,

to fibrous

always demonstrated the FNHs as hypointense and always depicted the

was

J.

#{149} Jean

in the

FNH-liver sigratios were

features

#{149} Marie-Christine

MD

Hyperplasia ofthe with Contrast-enhanced MR Imaging’

(FNH) study were

weighted sequences. nal-difference-to-noise

MD

Gheung,

other in seven

in the

3. A bolus

of 7/4, x 128, of 0.2

were

obtained

sequential acquisition liver without susand without intraveparameters were as a flip

angle

mLlkg

sous

bois,

(Laboratoire France)

of 10

of gadolinium

tetraa.zacyclododecanetetraacetic

(DOTA)

of 10#{176}, a

and a thickness

acid

Guerbet,

Aulnay

in a concentration

mol/L Gd-DOTA was injected antecubital vein, followed by sion of saline. With the same as in the previous paragraph, FLASH sequence was started

of 0.5

through an a rapid infuparameters this Turboin the plane

Abbreviations: DOTA = tetraazacyclododecanetetraacetic acid, FLASH = fast low angle shot, FNH = focal nodular hyperplasia, GRE gradient echo, SD/N = signal-difference-tonoise ratio, SE = spin echo, TE = echo time, TI = inversion time, TR = repetition time.

=

25

a.

c.

b.

f.

g.

d.

h.

e.

j.

i.

Figure 1. Images of FNH. (a) TurboFLASH image obtained with an inversion time (TI) of 100 msec (TRTIE,ffI = 7/4/100). Banding artifacts (arrow) and presence of high signal intensity in the aorta and inferior vena cava were caused by flow-related enhancement. The central scar is not seen. In a-g, the flip angle was 10#{176}. (b) TurboFLASH image (7/4/400). FNH is hypointense, with a good visualization of the central scar. (c) TurboFLASH image (7/41600). The FNH-liver signal-difference-to-noise ratio (SD/N) is decreased. (d) TurboFLASH image (7/411,000). Note the area of signal isointensity between FNH and the surrounding liver. (e) TurboFLASH image (7/41400) obtained 10 seconds after injection of GdDOTA. Hypervascularization of the lesion is seen with identification of the hepatic artery (arrow). (f) TurboFLASH image (7/4/400) obtained 18 seconds after injection of Gd-DOTA. Hypervascularization of the lesion is seen with identification of the right portal vein. (g) TurboFLASH image (7/41400) obtained 50 seconds after injection of Gd-DOTA. Note enhancement of the central scar (arrow). (h) Ti-weighted SE image (420/ 15). The lesion is isointense relative to the surrounding parenchyma. Note signal hypointensity of the central scar. (i) T2-weighted SE image (2,200/90). The lesion is hyperintense, with high signal intensity of the central scar. (j) Contrast-enhanced Ti-weighted SE image (420/15). Note enhancement of the central scar with a small area of signal hypointensity (arrow) that could not be explained at pathologic examination.

of the lesion immediately after injection and lasted 2 minutes. After the end of the bolus

injection,

every 4.

an

image

2 seconds for Then, 4 minutes

was

a total after

8

acquired

of 60 images. the bolus injec-

tion, a delayed contrast-enhanced weighted sequence was started

6 0

z

TIwith the

0

z

0

0

Cl)

CI)

following parameters: 256 x 256 matrix, and with an 8-mm thickness, and

interleaved

tion

time

sections

of 7 minutes

TurboFLASH

acquisition

an

Cl)

small

flip

very

small

provides nique,

described by that allows

angles.

With

such

TI relaxation

Haase very

TI

short

et al, short

place TE.

before

before To gener-

inverts one

the

short

im-

as the time and the beHence, the

relationship

the

TI and

of the TurboFLASH on the spin-lattice

of the tissue and is similar inversion recovery sequence. The shortest TR and TE

26

#{149} Radiology

times

3000

0

2000

1000

Inversion

( TIs

Times

3000

( TIs)

b.

a.

Figure 2. (a) Mean values (b ) Mean values of FNH-liver bottom

are

of liver-spleen SD/N versus

SD/N versus Tis in three

TIs in five healthy volunteers. cases of FNH. In a and b, numbers

at

milliseconds.

a

age acquisition. TI is defined between the inversion pulse ginning of the GRE sequence. between

Inversion

2000

and thus

contrast. In this techis also minimal, because

a 180#{176} pulse

magnetization

TRs,

occurs

dephasing takes with a very short

ate Tl contrast,

strength depends

2

1000

times

a poor T2 contrast

little T2* sampling

z

::

acquisi-

30 seconds.

(7,8). This ultrafast of images is obtained by means sequences with short TRs and

acquisition of GRE

spins

with

4

a

Technique

This sequence, a new technique

is data

TRII’E of 420/15, four acquisitions a 0.8-mm gap,

signal

sequence Ti relaxation

were for

fixed a 128

at 7 and x

128

gle

of 10#{176}; with appears. used, 128 lines msec.

signal

To and

obtain to study

We

respectively, chose

enhancement of the lesions, the SD/N between the liver with different TIs. With TIs

in an

300 msec, the from 300-600

on

system

tamed

and

700

a flip

an-

a smaller angle, a loss of When a TRItE of 7/4 is of data are acquired in 900

heavily Ti-weighted the paramagnetic

to that our

4 msec,

matrix.

SD/N msec,

dropped

was this for

poor. ratio TIs

images contrast we compared and the spleen shorter than Ranging was mainlonger

than

msec

(Fig

2a).

Because

we

wanted

to

study FNH of the liver, we established the same curve for the SD/N between FNH and liver. To determine the best contrast, we measured SD/Ns of three typical cases of FNH normal

(ie, central surrounding

examination).

This

for short TIs (less Hence, we chose of 400

msec,

which

scar and lesion with liver at pathologic contrast

was

than 600 msec) the compromise provided

trast of FNH and liver. The ratio of signal difference FNH and surrounding liver

good

obtained (Fig 2b). of a TI Ti

con-

between to noise was

July

1991

b.

c.

e.

f.

Figure 3. FNH of the left lobe. (a) Dynamic perintense signal corresponds to the central with low signal intensity of the scar (arrow).

CT scan shows scar within the (d) TurboFLASH

g.

hypervascular mass without central scar. (b) T2-weighted SE image (2,200/90). Hylesion. (c) TurboFLASH image (7/4/400, flip angle of 10#{176}) shows hypointense lesion image (7/4/400, flip angle of 10#{176}) obtained 12 seconds after injection of Gd-DOTA.

At the

arterial phase, tumor shows high enhancement. The scar remains hypointense. (e) TurboFLASH image (7/4/400, flip angle of 10#{176}) ob20 seconds after injection of Gd-DOTA. The scar remains hypointense relative to the tumor. (f) TurboFLASH image (7/4’400, flip angle 10#{176}) obtained 60 seconds after injection of Gd-DOTA. The scar (arrow) shows high signal intensity within the tumor. (g) Contrast-enhanced Ti-weighted SE image (420/15) shows high signal intensity within the scar.

tamed

computed

as follows:

tensity

of lesion

-

SD/N

signal

(signal

=

in-

intensity

different

of

liver)/standard deviation of background noise. Measurements of signal intensities

in the homogeneous the central scar were ages

by

interest

use

area of FNH outside obtained from im-

of operator-defined

encompassing

Noise

was

of interest

with

large

that encompassed

method

offers

regions

of interest

ences

regions

ventral

and are more

measurement

of noise

tient

respiratory

includes

the entire

average ventral

Second, to the

motion

pa-

artifacts

that may degrade image quality in the region of the liver. As a result, our noise measurement

reflects

both

incoherent

noise and coherent motion 12). MR images were thus evaluated for FNI-I signal

graded

tensity of surrounding TurboFLASH images, jection of paramagnetic FNH. quences

Student

were t test

characteristics

Volume

liver on SE and before and after contrast agent,

of the contrast

SD/Ns

for

the

enhancement

various

compared for paired of the

180

(10-

intensity and with the signal in-

in comparison

the peak

artifacts quantitatively

#{149} Number

pulse by means samples.

central

scar

1

inat

of seof a The

on

the

plain were

and

en-

also

cases

present

in the

lesions

were

SD/Ns

between

hyperintense,

FNH

with and

surround-

ing liver higher on the first echo at 45 msec than on the second echo at 90 msec (9.4 msec ± 3.2 [standard deviation] and 5.8 msec ± 3.1, respectively). of FNH

were

same

lobe

in three

patients

differ-

reproducible.

Twenty-five

were

First, large small

on

images

demonstrated with the different imaging techniques. Two cases of FNH

regions

to the patient, bands. This

two advantages:

and

RESULTS of

at least 25 pixels.

measured

image background out of the presaturated

SE images

hanced TurboFLASH qualitatively assessed.

of

The

differences

in the

of lesion-liver 2,200/45 and not statistically

absolute

values

SDINs on both SE SE 2,200/90 images were significant (Figs ii, 3b,

and were visualized on the same plane at MR imaging. One FNH, 1 cm in diameter, adjacent to a large 7-cm main FNH tumor, was diagnosed at pathologic examination only and was not found retrospectively with the different imaging techniques. Furthermore, three patients had associated hemangiomas, 3 and 4 cm in diameter, that were resected along with FNH. These hemangiomas had been previously diagnosed at sonography, dynamic CT, and MR imaging. Furthermore, at pathologic

4).

examination

changes in the large septal vessels and the presence of loose connective tissue within the branches of the scar without necrosis. These vascular changes were observed in two

in two

patients,

hemo-

siderosis without obvious cause was present within the surrounding liver resected with FNH. On SE T2-weighted images, all the

The

fled

central

with

peared

scar

these

was

hyperintense

(24 cases)

always

sequences

identi-

and

ap-

as a thin

or as a network

band

pattern

(one case). The scar was identified CT scans in 18 of 25 cases of FNHs

(72%).

However,

(10 and

7 cm

hypomntense were

noticed

in two

large

in diameter),

radiating on

on

lesions

associated

linear

areas

T2-weighted

SE im-

ages (Fig 4a, 4b). In these two cases, pathologic examination demonstrated prominent

obliterative

vascular

Radiology

#{149} 27

a.

b.

d.

c.

e.

f.

Figure 4. Large lesion of the right lobe in a patient with hemosiderosis at pathologic hypointense band (arrow) and hyperintense bands within the tumor. (b) T2-weighted bands within the tumor. (c) TurboFLASH image (7/4/400, flip angle of 10#{176}) shows slightly surrounding liver. Hypointense bands are present within the tumor. (d) TurboFLASH after bolus injection, shows hypervascular mass at the arterial phase. (e) TurboFLASH after bolus injection, shows persistence of hypointense bands within this hypervascular (420/20) shows high enhancement of the previously hypointense bands with a network

women

who

contraceptives

had for

been taking oral 8 and 10 years, re-

cases were then hyperintense on sequence (Fig 40. The high signal intensity of the scar was homogeneous in 23 cases of FNH, and in two two

this

spectively. On

unenhanced

TurboFLASH

im-

ages obtained with the parameters previously described, all the lesions were recognized as hypointense masses in comparison with the liver (Figs lb. 3c, 4c). The SD/N was equal to -14.7 ± 2.3. The scar was always demonstrated as a hypointense area within the tumor on these precontrast images (Figs lb. 3c). On

contrast-enhanced

cases

In our

Turbo-

to the

#{149} Radiology

because

of

study,

both

the

unenhanced

accumulation

lesions.

of

with

Because

facts

can

ages

of the

degrade

that

Recent methods have permit MR imaging of

upper

the

quality

abdomen,

motion of MR

shot

a modified

ery-type

of paramagnetic

contrast

agents

The

and

not et al and

or GRE systems used

ation single-shot

first consists

These

with

very

GRE short

allows

seTRs

For the

inversion

TurboFLASH,

of on

prepulses.

This

desnap-

available

(7,8).

of Ti-weighted

than

generally

called

technique

a 180#{176} prepulse images.

yet

TurboFLASH,

radio-frequency

less necessitates

Haase

are

ample,

times

technique technique,

FLASH

different

this

described imaging

Echo-planar

Another by

im-

characterization

tumors.

has

authors

been with

less.

hardware

scribed

quences

of hepatic

sequences

imaging

but

available.

anti-

numerous

or

permits

msec,

techniques have been developed to reduce these different artifacts. Breathholding with fast imaging and panticularly GRE sequences has been used for role

i second

specialized

respiratory

fast

by different

(1-6).

100

vanliver

these

emphasized

times

MR imaging has been used with ous degrees of success for studying

SE

associated

been

imaging

DISCUSSION

paramagnetic contrast agent was observed within the scar (Figs lj, 3g). Furthermore, the hypointense areas noticed on T2-weighted images in 28

heterogeneous

and enhanced TurboFLASH images produced the best SD/Ns (-14.7 ± 2.3 and 21.0 ± 5.3, respectively), in cornparison with the poor SD/N of the enhanced Ti-weighted images (4.3 ± 2.1). Comparison of unenhanced and enhanced TurboFLASH images with the SE T2-weighted images obtained with a TE of 45 msec (9.4 ± 3.2) showed significant differences (P < .01) (Table).

2 minutes

Ti-weighted images, all areas of FNH were hyperintense to the liver, with an SD/N equal to 4.3 ± 2.i. In all 25 cases of FNH, high signal intensity corresponding

it was

the presence of a hypointense area less than 0.5 cm in diameter (Fig lj). In these two cases, pathologic examination did not reveal peculiar features within the scar.

FLASH images, the peak of contrast enhancement was observed 10-24 seconds after bolus injection (Figs le, 3d, 3e, 4d, 4e). All the lesions were then hyperintense, with an SD/N between FNH and liver equal to 21.0 ± 5.3. In 10 cases, an enhancement was visualized within the scar 40-80 seconds after injection (Figs 1g. 3f). In the remaining 15 cases of FNH, the scar remained hypointense after bolus injection. On delayed contrast-enhanced

examination. (a) T2-weighted SE image (2,200/45) shows SE image (2,200/90) shows persistence of hypointense hypointense lesion in relation to hemosiderosis of the image (7/4/400, flip angle of 10#{176}), obtained 18 seconds image (7/4/400, flip angle of 10#{176}), obtained 24 seconds mass. (f) Delayed postcontrast Ti-weighted SE image pattern.

technique

ex-

cre-

recovof

acquiring

all

July

1991

lines

of data,

has

different

advantages:

on the

plain

TurboFLASH

multisection sequential acquisition and a short imaging time allowing a suitable

thin hypointense of lines within

study

for

i28

ment

(13). Another

dynamic

segmented

been

contrast

technique,

k-space

called

TurboFLASH,

has

by Edelman et al (14). This method spans k space in four segments of 32 steps each to generate

recently

enhance-

a 256

described

x 128-pixel

breathhold

image

of 12-14

method offers different comparison with the

FLASH technique ter tissue contrast,

during

seconds.

advantages single-shot

in Turbo-

: high resolution, and diminution

artifacts.

The

with this to buildup

technique are probably of unspoiled transverse

netization. technique

banding

a good

tumors

Ti

without

contrast

tion

by

time,

the

the

from

300

subsecond

an enhancement in

40-80

3f).

This

after

and/or

stant

visualization

or into

and

the

In the other is usually

cases

of FNH

at 0.6

frequency

T on Ti-weighted

always

appeared

high signal ter injection)

lowed

at the portal

phase,

described

slightly

hyperintense

one would of hyperplastic, hepatocytes study,

all

of

these

with

2,200/45

images

than

SE 2,200/90

significant

lesions

a higher

on

the

images,

statistical

on

difference

The reason

contrast quence

first echo unclear:

has

were

comparison with

an The

Volume

slightly

with SD/N

central

180

the

ratio scar

surrounding

was

#{149} Number

to 4.3 always

1

resolution

intensity

of the

of the scar

on Ti-weighted intensity on T2-

images

images

can be explained

of slow

blood

flow

contains fibrous the vessels, and (22). However,

characteristics can

be

observed

of these also

by within

tissue the bile MR vascular

in

been

ages

in

liver, ± 2.i.

identified

did

not

become

(19,23). carcinoma

hyperintense

In

on

long TRTFE SE images (24). On T2weighted images in two cases of FNH, we also observed the presence of hypointense areas corresponding to fibrous tissue and obliterative vascular changes at pathologic examination 4a, 4b). This finding was previously

mentioned

by of FNH on the tamed at 1.5 T correspond to FNH,

particularly

(Fig

Schiebler et al in one case long TRITE images ob(20). These findings could a complex appearance of in large

lesions,

(25).

with

a

vascular

inthe

malforma-

Finally,

on the

images, demonstrated

scar and

in the previ-

hypointense

areas

to the stagnation contrast agent fibrous

hy-

tissue.

of this

cor-

of the within The

the

incon-

enhancement

during contrast-enhanced TurboFLASH MR imaging can be explained by the relative short time (2 minutes) of the acquisition.

In a recent

letter,

Tham

et al

reported one case of FNH on Tiweighted images obtained 6 minutes after administration of gadopentetate dimeglumine ing septa

that demonstrated as structures with low

intensity

separating

high

signal

(26).

In

nodular

intensity

lobules

within

the

fact, as demonstrated the

contrast

radiatsignal

of

tumor

in our

agent

is present

within the scar delineating the lesion and not in the nodules with lower sig-

nal intensity In

DOTA

ij, 3g. 4f).

(Figs

conclusion,

enhancement

significantly

Gd-

with

improves

lesion-

liver contrast when dynamic scanning performed with this TurboFLASH se-

reported by Titelbaum et al, the scarlike area hypointense on short TRTFE im-

of this seAt pathologic

equal

CT in

no

of this higher

hyperintense

The

with

the central mentioned

study,

ence of proteinaceous fluids fibrolamellar hepatocellular

hy-

examinations of these resected tumors, no necrosis was observed despite their large size. On Ti-weighted images obtamed 4-12 minutes after bolus injection of paramagnetic contrast agent, the lesions

18 of 25

SE

second-

although

demonstrated. on the remains

were SD/N

in

in all le-

in

both hepatocellular carcinoma and giant hemangioma, which present with frequently inflammatory scar tissue marked by edema, hypercellularity, and the presscars

composed

in

on CT scans.

better

presence

imaging

but otherwise normal, (i5-i7,i9-2i). However,

perintense,

echo

with

a finding

in a lesion

the

the scar, which accompanying duct proliferation

or

lesion,

expect

to

present in FNH and high signal the

previous images

isointense

due

weighted

surroundinjection)

as described

as an

a

new CT scans. The low signal

of isointense

FNH and the seconds after

CT (18). In different FNH on T2-weighted

reports,

our

arterial

images

this study is higher than the 43.5% frequency in our previously described series of 23 cases of FNH (18). It is probably

seconds afphase, fol-

MR

study,

of this observation

bo-

lesions with

(10-24

by an area

signal between ing liver (30-50 dynamic

After

the

hyperintense

intensity at the

rapidly

was

images.

of Gd-DOTA,

and

images.

the scar

on

as in our

(72%)

thick-

reports,

analyzed

images

at

authors

the scar was identified MR

dis-

of six

obtained

of the

published

sequences

injection

interval

on CT scans,

which

three

the

Ti-weighted was always

responding paramagnetic

pat-

women

or the hepatocytes.

ously

in

et al have

the section

gap

better

nodules

network

Mattison

not mentioned

on

lus

into

a peculiar

in one case.

sions

0.35

the lesion

thromboand was cords, as

and Medline these findings

in two

postcontrast perintensity

T2-weighted images in our study, scar was always identified as a thin

dividing

of previous

of either

tion

fibrous of some

of oral contraceptive is known to stimulate

vessels

than

performed by Butch et al (15) by El Rahman et al (16) at 0.15 T on Ti-weighted images and in one of the six FNH lesions reported by Matisson et al (17) at a field strength of

history which

On the

(Figs

T and

observed

long take,

within

have

in only three cases to on inversion recovery

were

In the previous reports, this scar appeared hypointense relative to liver on Ti-weighted images and hyperintense on T2-weighted images (i5-i7,i9-21).

tinguished this scar in only cases of FNH on SE images 0.35 T (i7). However, these

been

Evidence

reported by Wanless It is noteworthy that

ig,

could be due to blood flow within scar contains nu-

enhancement

in the

thrombosis

sis was seen in 45% of lesions prominent in 22% with fibrous

of the (Figs

scarring

organized

arteries.

25 lesions

injection

and

growth

tern

had

10 of the

by dense

body

merous dilated, thin-walled vascular channels among dense and/or loose connective tissue and occurs as a result of vascular malformation in FNH (22).

ness

already reported our knowledge:

seconds

24 cases

studies

hypointensity

seen

the presence of slow the scar. This vascular

On unenhanced TurboFLASH images in our study, FNH always appears hypointense with a TI equal to 400 msec This

was

marked

as a

of enhanced

scar

the

performed.

i, 3).

By use

TurboFLASH,

to 700

acquisi-

dynamic

x 128 matrix.

band

liver

by the images.

the

enhanced

easily

related mag-

degrading

supported

Furthermore,

observed

in

artifacts

information

betof

however, demon-

for a TI ranging

msec

are

artifacts

In our study, of TurboFLASH

strates

a

This

image

band or as a network the lesion despite a

quence,

particularly

in cases

of FNH.

In

our study, the unenhanced FLASH sequence permitted visualization of the central

Turboconstant scar, which

was

in only

identified

on CT scans

is

72%

of the cases. With this sequence, the enhancement characteristics of this tumor are similar to those on dynamic CT scans.

The

delayed

weighted

sequence

all cases

in showing

enhanced

Ti-

appeared

useful

the

persistent

in en-

hancement of the scar, probably in relation to the stagnation of the paramagnetic contrast and/or in the

the scar.

agent fibrous

within tissue

the vessels present in

This

sequence permitted the in two cases in which hypointense bands, associated with hyperintense bands, were present on T2weighted images, because late enhancement of these areas was shown. Therefore, these MR imaging sequences (unenhanced, enhanced TurboFLASH, and delayed Ti-weighted sequences) diagnosis

of FNH

demonstrated

constant

patterns

when

findings

were

atypical

T2-weighted studies

images. that

include

helpful

present

However, assessment

tocellular adenomas and hepatocellular carcinomas

on

larger of hepa-

fibrolamellar with these Radiology

#{149} 29

a.

c.

b.

Figure image flip

Al. (a) Dynamic CT scan, (2,200/90) shows hyperintense

angle

obtained 15 seconds and homogeneous

sequences

will

be helpful

ADDENDUM

A 62-year-old

hepatitis

man with

B without

B

virus

chronic

replication

underwent

of the

MR

hep-

imaging

ac-

cording to our protocol for a focal liver mass. Previous sonography and dynamic CT demonstrated a well-limited tumor of the right lobe of the liver (Fig Ala). The

a-fetoprotein level was normal. T2weighted MR images showed a homogeneous and hyperintense lesion with a hyperintense seconds

central scar after intravenous

(Fig Aib). Ten injection of Gd-

DOTA, the lesion was markedly enhanced on a TurboFLASH image (Fig Aic). On the TurboFLASH image obtained 2 minutes after injection of contrast material, the enhancement

ever,

of the scar

was

a rim enhancement

also

seen

(Fig Aid).

weighted

the lesion

features

tence

of a rim enhancement finding

ries

as FNH was

of 25 FNHs,

not

was Ti-

exhibited

except

capsule

with

the persisin our

the patient

numerous

composed

Se-

under-

vessels,

of fibrous

and

tissue.

a true

Patho-

for must

is a well-known

of a capsule feature

cellular carcinoma and has been described in rare cases of hepatocellular adenomas

this

#{149} Radiology

This

this presence

In our

14.

on

emphasizes

be

This

misleading

2.

Yoshida

3.

4.

5.

6.

Edelman

RR,

1990;

8.

Siegel

JB, Singer

A, Matthaei 0, Bartowski Leibfritz D. Inversion recovery

Edelman

RR,

FRODO ology Stark

flow

DJ, Silver

a new and

method

of hepatic

metastases:

Crooks Magnetic

12.

Wehrli

LE, Arakawa resonance

20.

21.

22.

field strength. FW,

MacFall

JR. Clover

GH,

scars

in primary

liver

CT

5, et al.

tumors:

hyperplasia

of the liver.

MR fea-

J Comput

24.

25.

BA, nod-

Assist

AC, Gyi B.

HY, Burke

hepatocellular

J Comput Wanless

Hepatocellular

OR, Saul carcinoma:

Assist Tomogr IR, Medline A.

carcinoma:

SH.

nodular

hy-

ML,

Fibrolamel-

MR appearance. 1988; 12:588-591.

The

role of estrogens

as promoters of hepatic neoplasia. Lab Invest 19fi2; 46:313-320. Tham RTOTA, Holscher HC, Falke THM, Arndt JW, Lamers CB. Focal nodular hyperplasia of the liver: features on Gd-DTPA-enhanced MR (letter). AIR 1989; 153:884-885.

27.

Ebara

28.

small hepatocellular carcinoma: correlation of MR imaging and tumor histologic studies. Radiology 1986; 159:371-377. Rummeny E, Saini 5, Wittenberg J, et al. MR imaging of liver neoplasms. AJR 1989; 152:493499. Hosoki T, Chatani M, Mon S. Dynamic com-

of

-

29. N.

IR,

Tomogr 1987; 11:651-654. Nokes SR. Baker ME, Spritzer CE, Meyers W, Herfkens RJ. Hepatic adenoma: MR appearance mimicking focal nodular hyperplasia. Comput Assist Tomogr 1988; 12:885-887. Wanless IR, Mawdsley C, Adams R. On the pathogenesis of focal nodular hyperplasia of the liver. 1-lepatology 1985; 5:1194-1200.

sis

Grigsby

dynamic

160:53-58. R, Sironi

specificity, and pathologic correlation. Radiology 1989; 171:323-326. Schiebler ML, Kressel HY, Saul SH, Yeager Axel L, Gefter WB. MR imaging of focal

lar

-

hyperplasia:

MR appearance mimicking focal perplasia. AJR 1987; 149:721-722. Titelbaum OS, Hatabu H, Schiebler

in MR imaging.

1984; 151:12

nodular

Wilbur

RR, et al.

Radiology

of

LE, Francis

23.

Radi-

et al. of ma

focal

ular

MS.

M, HoenningerJ, imaging: effects

GM, Quint

study. Radiology 1986; Rummeny E, Weissleder

Kressel

E,

analysis

MR imaging

tures,

Tomogr

artifact.

GR, Glazer

Central

for elimination

wrapround

pulse sequence performance Radiology 1986; 159:365-370. netic 133.

Assist

i988; 166:231-236. DO, Wittenberg J, Edelman

Detection

11.

19.

26.

Atkinson

pulses:

of motion,

10.

K,

R, Duhmke snapshot

J Comput

RA.

Bree RL, Ensminger WD. MR imaging of hepatic focal nodular hyperplasia: characterization and distinction from primary malignant hepatic tumors. AIR 1987; 148:711-715. Mathieu 0, Bruneton JN, Drouillard J, Pointreau CC, Vasile N. Hepatic adenomas

and

MRI: applications imaging. Magn

Haase

DD, Malt

Mattison

18.

153:1213-1219.

Haase A. Snapshot FLASH to Ti, T2, and chemical-shift Reson Med 1989; 13:77-89.

1990;

17.

HE. Dynamic MR imaging of the Gd-DTPA: initial clinical results. AJR

FLASH MR imaging. 1989; 13:1036-1040. 9.

A, Dupuis

of the

Radiology

16.

T, Mi-

nami M, Yashiro N. Small hepatocellular carcinoma and cavernous hemangioma: differentiation with dynamic FLASH MR imaging with Gd-DTPA. Radiology i989; 171:339-342. Hamm B, Fischer E, Taupitz M. Differentiation of hepatic hemangiomas from metastases by dynamic contrast-enhanced MR imaging. Comput Assist Tomogr i990; 14:205-216. Marchal G, Demaerel P. Decrop E, Van Hecke P, Baert AL. Gadolinium-DOTA enhanced fast imaging of liver tumors at 1.5 T. J Comput Assist Tomogr 1990; 14:217-222. Van Beers B, Demeure R, Pringot J, et al. Dynamic spin-echo imaging with Gd-DTPA: value in the differentiation of hepatic tumors. AJR 1990; 154:515-519. Longmaid liver with

177:515-521. Butch RJ, Stark

MR imaging

contrast.

focal nodular hyperplasia. J Comput Tomogr 1986; 10:874-877. El Rahman M, Li KCP, Ros PR. Hepatic focal nodular hyperplasia: new MR findings. Magn Reson Imaging 1989; 7:687-688.

sign

K, Kokubo

flexible

Assist

Ohtomo K, Itai Y, Yoshikawa K, et al. Hepatic tumors: dynamic MR imaging. Radiology 1987; 163:27-31. Y, Ohtomo

for breath-hold with

RR. Firstwith ultra174:757-762. Atkinson

hepatic

known.

H, Itai

Atkinson DJ, Burstein 0, Edelman pass cardiac perfusion: evaluation fast MR imaging. Radiology 1990; Edelman RR, Wallner B, Singer A, DJ, Saini S. Segmented TurboFLASH: liver

15.

(b) T2-weighted image (7/4/400,

intensity of the scar. (d) Turboa rim enhancement can be the surrounding liver paren-

method

the

lesion has mimicked of a capsule is atypical

diagnosis.

M, Ohto

M, Watanabe

Y, et al.

Diagno-

of

puted

tomography

noma.

AIR

1982;

of hepatocellular

carci-

139:1099-1106.

The dependence nance (NMR)

of nuclear magnetic resoimage contrast on intrinsic and pulse sequence timing parameters. Magn Re-

son

30

scans.

1.

on MR of hepato-

CT

was not visualized

References

parenchyma.

The visualization images

dynamic

images.

Although FNH, the

7.

logic signs of mild chronic hepatitis without cirrhosis were demonstrated in the surrounding

on

role of contrast-enhanced TurboFLASH and postcontrast Ti-weighted images.

the

went surgery. Pathologic examination of the resected right lobe demonstrated a well-differentiated hepatocellular carcinoma with a scar containing edematous fibrosis

the capsule

(Fig Aie).

observed

and

(29),

patient,

How-

the delayed

same This

obvious.

of the lesion

On

images,

scribed T2-weighted

Since the acceptance of our manuscript, we have obtained contrast-enhanced MR images in which the findings simulate those associated with FNH in a case of a well-differentiated hepatocellular carci-

noma.

13.

(27,28). This case illustrates the enhancement of the capsule, as previously de-

for further

#{149}

evaluation.

with a central scar. scar. (c) TurboFLASH

lesion with a low signal The scar is hyperintense; in comparison with

image

identified. chyma.

atitis

shows hypervascular lesion signal intensity of the central

of 10#{176}), obtained iO seconds after intravenous injection, shows hypervascular (7/4/400, flip angle of 10#{176}) obtained 2 minutes after intravenous injection. (e) Delayed postcontrast Ti-weighted image (420/20). The lesion is hyperintense High enhancement of the internal scar and the capsule is seen.

FLASH

e.

d.

after bolus injection, lesion with a high

Imaging

1984;

2:3-16.

July

1991

Focal nodular hyperplasia of the liver: assessment with contrast-enhanced TurboFLASH MR imaging.

Twenty-two patients with 25 cases of focal nodular hyperplasia (FNH) proved with pathologic study were imaged with a TurboFLASH (fast low angle shot) ...
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