Peter

Reimer,

Betty

H. Baldwin,

MD

Ralph Weissleder, #{149} Bud C. Tennant,

#{149}

MS

Experimental MR Receptor

MD, PhD DVM

Hepatocellular Imaging’

Relaxation time measurements and magnetic resonance (MR) imaging were performed in three different animal models of hepatocellular carcinoma (HCC). After intravenous administration of asialoglycoproteindirected arabinogalactan-stabilized ultrasmall superparamagnetic iron oxide (10 jmol Fe/kg receptor agent), T2 of normal liver decreased from 41.6 msec ± 1.0 to i9.4 msec ± i.7 (P < .05) in rats. T2 of HCC implanted in normal liver or liver with chronic hepatitis was essentially unchanged. These results were similar to those obtained by administration of a reticuloendothelial cell-directed conventional iron oxide; however, the required dose of receptor agent was lower. MR imaging in a woodchuck model of virally induced HCC confirmed the distribution of the hepatocyte-directed agent to regions of functioning and differentiated hepatocytes but not to malignant tumor tissue. The results suggest that MR receptor imaging may play a role in the differentiation between primary liver tumor and functional liver tissue such as that in normal liver hepatitis or regenerating nodules.

H

is the

malignant has

an

761.1214,

contrast mental, Radiology

terms:

Contrast media, comparative #{149}Liver neoplasms, MR studies, 761.321

enhancement 761.321 1991;

Magnetic

#{149}

-

resonance

Neoplasms,

180:641-645

(MR), experi-

carcinoma (HCC) common primary

most

liver

tumor

worldwide

and

high

prevalence

in

especially

Asia and Africa (1). HCC is frequently associated with hepatitis B virus, and structural abnormalities of the liver are common. As a result, tumor detection is often obscured because of architectural

abnormalities

of hepatic

parenchyma (1-3). Early diagnosis is of paramount importance in improving survival; hepatectomy and liver transplantation required for treatment of large tumors carry a poor prognosis (3). A variety of diagnostic techniques are available for the detection of HCC. a-Fetoprotein

screening

is insensitive

because of the low yield of positive titers (3). Ultrasound (US), computed tomography (CT), and magnetic resonance

accuracy tumors; structurally

(MR)

Amy

E. Yeager,

#{149}

DVM

Carcinoma:

EPATOCELLULAR

imaging

have

a higher

in detecting primary however, small tumors abnormal

reliably

visualized

dothelial

contrast

livers

(4-11). agents

liver in

are

not

Reticuloensuch

of liver

tumor

tissues

have

been

shown

to be devoid

of asialoglycoprotemn (ASG) receptors (14,15); as a result, intravenous administration of ASG-receptor contrast agents increases contrast between metastases and liver tissue (16). The current study was designed to extend previous feasibility studies to primary liver tumors. Hepatocytes are known to lose the ASG receptor when they become pothesized

malignant that

(15,17,18). decreased

the

We hyrecep-

tor activity in malignant tumors could be used to distinguish primary liver tumors from normal liver tissue. To prove our hypothesis, relaxation time measurements and MR imaging experiments were performed with three different animal models of HCC in an attempt

to cover

pathologic in HCC.

abnormalities Measurements

before tration

the

spectrum

of

encountered were obtained

and after intravenous of a hepatocyte-directed

adminisMR

contrast agent, arabmnogalactan-stabilized ultrasmall superparamagnetic iron oxide (AG-USPIO).

as

ethiodol-oil-emulsion-13 (12) for CT and iron oxide for MR imaging have been reported to further improve detectability

Index studies

#{149} Thomas J Brady, MD Jack Wittenberg, MD

#{149}

compared

with techniques that do not involve contrast enhancement. However, uptake of contrast material in structurally abnormal livers reflects only macrophage distribution and does not allow specific differentiation between normally functioning hepatocytes and abnormal, malignant, hepatocytederived cell populations (13). Liver metastases and nonhepatic

MATERIALS Iron

Oxide

AND Preparations

AG-USPIO

(Advanced

Magnetics,

bridge, Mass) is obtained ultrasmall superparamagnetic with an arabinogalactan,

Cam-

by

stabilizing iron oxide a galactose con-

taming polysaccharide (19). Magnetophysical, biologic, and pharmacologic properties of ultrasmall superparamagnetic iron

oxide

and

AG-USPIO

have

been

described

previously (20,21). Particle aggregates of AG-USPIO have a mean size of 12.2 ± 6.5 nm as measured with electron microscopy,

an Ri relaxivity R2 relaxivity blood half-life

of 23.3 mmoVL’ of 48.9 mmoVL’ of 8 minutes

(21). AG-USPIO From the MGH-NMR Center (13th St, Bldg 149, Charlestown, MA 02129), Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston (P.R., R.W., T.J.B., J.W.); and Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY (A.E.Y., B.H.B., B.C.T.). Received February 13, 1991; revision requested March 25; revision received April 9; accepted April 18. Supported in part by a grant from the National Institutes of Health to the MGH-NMR Center and by Public Health Contract NOl Al 82698 to Cornell University. P.R. supported by the Deutsche Forschungsgemeinschaft, Bonn, Germany. Address reprint requests to R.W. © RSNA, 1991

METHODS

tion

of 17 mg/mL

was and

used

. sec’, an sec’, and a (0.47 T, 37#{176}C) -

at a concentra-

administered

at a

1

Abbreviations: AG-USPIO = arabinogalactanstabilized ultrasmall superparamagnetic iron oxide, ASG = asialoglycoprotein, C/N = contrast-to-noise ratio, HCC = hepatocellular carcinoma.

641

dose of 10 p.mol Fe/kg. experiments

(two

In selected

imaging

woodchucks),

an

ul-

dose (2 p.mol Fe/kg) was administered as part of a dose-finding study. Results with the receptor agent were compared with those obtained with conventional, dextran-stabilized iron oxide tralow

aggregates ics). This

(AMI-25;

Advanced

Magnet-

agent was chosen for comparison rather than hepatobiiary (eg, manganese (II) N,N’-dipyridoxylethylenediamineN,N’-diacetate travascular dimeglumine)

5,5’-[bisphosphatej)

or ex-

interstitial (eg, gadopentetate agents because the latter types are neither tumor- nor hepatocytespecific (22,23). AMI-25 has a mean particle size of 50 nm ± 29 as measured with electron microscopy or a 72-nm volume mean diameter as measured with laser light scattering. The pharmacologic characteristics of this agent have been described (24). AMI-25

was

used

mg/mL

and

administered

mol

at a concentration

of 11.2

at a dose

of 10

Animals Three models of HCC were used in the study to cover the spectrum of pathologic abnormalities seen in human HCC. The first model consisted of H-4-II-E hepatoma cells (Peter G. Herman, MD, Brigham and Women’s Hospital, Boston) directly implanted into the liver of 200-300-g male ACI-AXC rats (n = ii) (Harlan Sprague Dawley, Indianapolis); the second model, H-4-ll-E tumors implanted rats with chronic hepatitis

into

ACI-AXC

(n = 10); and the third model, chronic viral hepatitis and spontaneous HCC in woodchucks (n = 7) (2.5-4 kg) (New York State College of Veterinary Medicine, Cornell University, Ithaca, NY) (25,26). A total of 48 ammals were used for either relaxation time measurements (21 rats) or MR imaging (20 seven

woodchucks).

H-4-II-E HCC.-The H-4-II-E cell line is a well characterized, poorly differentiated cell line that resembles a highly malignant human HCC (27). Tumor was propagated as follows. One-cubic-centimeter tumors were removed from tumor-bearing rats, minced in Hanks buffered salt solution (Sigma Chemicals, St Louis), sifted through a 0.3 wire mesh, and resuspended in Hanks buffered salt solution. After host animals were anesthetized with light ether anesthesia,

then

0.1-0.2

injected

after

H-4-II-E

model,

mL of this

solution

tumor HCC

642

tumors

injection

with

needles. In vitro were performed cell inoculation. in chronic

hepatitis-In

of

and

averaged.

Gradient-echo

trates,

were obtained with 120/16, and four signals averaged.

and

hepatitis

#{149} Radiology

moderate

fibrosis

(28).

Once

a

florid chronic hepatitis had been induced, hepatoma cells were implanted into the liver as described above. Woodchuck

regions

woodchuck

HCC.-The

than 90% of those animals develop hepatocellular carcinomas within 3 years (29,30).

The

member

woodchuck

hepatitis

virus,

of the hepadnaviridae,

to hepatitis

hypo-

tios minus vided

mean by the All in vivo

were

performed

in rats,

an

a

tobarbital

was

used

(65

vein)

gual

duration

of the

anesthesia

following

All animals and within

were removed, formaldehyde

for

Milwaukee)

were

ing experiments. was

used

for

The presence

confirmed

with

imag-

of HCC

necropsy

after

USPIO

half-lives).

logic

in all ani-

Time

times

were

ated with an inversion-recovery quence. T2 was measured from

three

separate

pulse se10 data

with a Carr-Purcell-Meisequence with a i of I

value

represents

the

mean

times were measured in tissue before and after ad-

ministration of AG-USPIO and AMI-25. All rats were anesthetized and killed by means of exsanguination. Organs were removed immediately, and relaxation time measurements

within

were

1 hour

after

performed

at 37#{176}C

was Technicare

(GE Medical

performed

with

a 0.6-T

II superconducting

Systems).

multisection images were section thickness of 4 mm

Transverse

obtained with a and a 128 x 256

matrix. With the head coil having a field of view of 16 cm (rats) or 20 cm (woodchucks), pixel dimensions were 0.6 x x 4 mm

and

0.8

x 1.6

x 4 mm,

tively. Spin-echo images were with the following parameters: (repetition six to eight four signals

AGblood

experi-

and their

fixed in buffered 24 hours, and correlative

indi-

histo-

(hematoxylin-eosin the tumors.

or ab-

presence

Analysis in relaxation times and C/Ns study groups were evalu-

Differences among different

ated statistically Wilcoxon signed

with the nonparametric rank test (31).

RESULTS In Vitro

Relaxation and

the H-II-4E administration

marized

tumor model

in Table

Studies relaxation

times

before and of AG-USPIO

1. Normal

respec-

obtained 250/18-20

time msec/echo time msec) and signals averaged, 500/30 and averaged, 1,500/40 and two

in

after are sum-

liver

decrease in T2 relaxation times after intravenous administration of 10 pmol of AG-USPIO (P < .05). The decrease in liver T2 afshows

a significant

ter administration

of AG-USPIO greater than of AMI-25

is

that

after (P < .05).

Liver T2 decreases to a lesser in animals with chronic chemical

MR imaging

1.2

killed

for

to determine of hepatic

significantly administration

death.

Imaging

magnet

three

the MR imaging

examination

Liver of

measurements.

MR relaxation liver and tumor

than

mea-

sured in miffiseconds with an MR spectrometer operating at 0.47 T at 37#{176}C (PC-20 Minispec; IBM, Danbury, Conn). Before each measurement was made, the spectrometer was tuned and calibrated. TI was measured from eight data points gener-

Each

the

under60 mm-

of either

(more

After

Statistical

msec.

pen-

Measurements

Ti and T2 relaxation

points obtained boom-Gill pulse

administration

processed

stain) sence

Relaxation

the

or AMI-25

vidually

mals.

in

of 35 mg/kg

livers 10%

transducer

Systems,

and

employed. Woodchucks on heated pads for the

were

phased-arGE Medical

mg/kg),

administration

the animals

ray

within

woodchucks, a combination of intramuscular administration of 10 mg/kg ketamine hydrochloride and I mg/kg xylazine hydrochloride as well as intravenous (sublin-

ment,

7.5-MHz (Sonochrone;

pixels)

in anesthetized animals; injection of pen-

imaging experiments. went imaging before

in its virus

a

70#{176} flip angle, Homogeneous

intraperitoneal

examinations

with

two

images

signal intensity of liver distandard deviation of noise). MR imaging experiments

utes

(25.1-MHz) this

100

and

livers and tumors were used to tumor-liver contrast-to-noise ra(GINs; mean signal intensity of tumor

structure, genetic organization, and mechanism of replication (29). A total of seven animals with HCC proved by means of US

and in 7-14

(>

of interest

tobarbital was were positioned

is closely

B virus

1,500/80

individual calculate

model with well-differentiated HCC in chronic hepatitis is currently the most widely accepted animal model of human HCC because of similar pathogenesis (hepadnae virus-induced) and similar structural abnormalities (25,26). HCC was induced in woodchucks by inoculation of 100 L of diluted woodchuck serum from a standardized woodchuck hepatitis serum pool. Approximately 30%-60% of these animals become chronic carriers of the woodchuck hepatitis virus, and more

MR

were implanted into livers to simulate the changes in nonneoplastic hepatic tissue frequently encountered in human HCC. Chronic hepatitis was induced in 10 rats with repetitive subcutaneous injections of I mLlkg CC14 diluted in paraffin oil (1:1 voV vol) twice a week (relaxation time measurements) for 6 weeks (28). This longterm administration of CC14 produces with

averaged,

signals

was

into the liver by means

direct percutaneous dermic 25-gauge vivo experiments

days

signals

related

Fe/kg.

rats,

ballooning of liver cells, diffuse necrosis of the parenchyma with mononuclear inifi-

extent hep-

atitis than in healthy animals after administration of AG-USPIO presumably because of reduced activity of the ASG receptor (14). Liver T2 was significantly lower (23.5 msec ± 0.7) after

administration of AG-USPIO than after administration of AMI-25 (31.9 msec ± 1.4; P < .05). Relaxation times of H-II-4-E hepatomas in either normal liver or the chronic hepatitis model did not change after administration of AG-USPIO (Table 1). This finding

indicates

that

the

tumors

September

are

1991

Following administration of either AG-USPIO or AMI-25, contrast between HCC and liver increased because of the selective decrease in liver signal intensity (Fig 1). AG-USPIO increased the tumor-liver C/N significantly (P < .05) more than AMI-25 did (Table 2). Because of the increase in tumor-liver contrast, all 14 tumors could be detected on postenhanced images. Quantitative tumor-liver C/N measurements in woodchucks are summarized in Table 2. The receptor agent (AG-USPIO) increased tumorliver contrast to a greater extent than the RES agent (AMI-25) did for any given pulse sequence studied (P < .05 for all comparisons); this finding was expected, as the receptor agent was shown to reduce liver T2 more effectively than the RES agent did (Table 1). For example, with the spin-echo

“-u’

b.

500/30 pulse sequence, C/N after administration

d.

C.

Figure 1. (T = tumor)

Spin-echo

MR images

(500/30,

four signals averaged) show imaged before (a, c) and after (b, d) intravenous administration of AG-USPIO (a, b) or AMI-25 (c, d). The receptor agent decreases liver greater degree than does the RES agent. As a result, contrast between in b than in d. A hyperintense area (curved arrow in a) was proved to erating nodule. This area decreases homogeneously in signal intensity ministration of the receptor agent (b).

Table 1 Relaxation

Times

of Liver and Tumor

in the H-II-4E

woodchuck hepatoma of 10 mol Fe/kg signal intensity to a liver and HCC is higher correspond to a regenafter intravenous ad-

Model

Relaxation

Time

(msec)

Ti Tissue Time

Type

T2

and

AMI-25

AG-USPIO

AMI-25

AG-USPIO

of Measurement*

Group

Group

Group

Group

Normal liver Before

(n

=

11)

After Chronic

hepatitis

(n

=

263±7.1

263±7.1

234±5.9

223±4.9

41.6±1.0 25.6±1.4

41.6± 1.0 19.4±1.7t

10)

Before

242

±

±

16.3

39.1

±

243

±

16.3 10.9

242

After

192

±

6.8t

31.9

±

655 657

±

13.0

655

±

13.0

63.0

±

±

12.9

657

±

11.2

63.6

±

23.2

656

±

±

21.9

657

±

23.2 23.3

64.2 64.0

±

3.5

±

0.7t

3.5 1.4

39.1 23.5

±

1.4 3.9

63.0 65.6

±

4.6

64.2

±

±

3.8

64.6

±

Tumor in normal liver (n=il) Before

After Tumor in chronic (n = 10)

656 656

Note-Values are presented as mean ± 1 standard deviation. S Before and after administration of AG-USPIO or AMI-25 at 10 p.mol t Significantlylower (P < .05) compared with AMI-25.

devoid of reticuloendothelial cells or functioning ASG

Imaging

180

Number

#{149}

3

Fe/kg (n

=

4.6 5.1

21).

livers

of seven

topsy,

a total

tuseen in the

present in these livers. HCC appeared hypointense (n = 2), isointense (n = 1), or hyperintense (n = 8) relative to liver on Ti-weighted images, which is similar to that observed in patients (32,33). US allowed detection of 10 of the tumors.

Experiments

A total of 11 individual HCC mors (0.7-6-cm diameter) were with nonenhanced MR imaging Volume

1.4 4.4

recep-

tors.

MR

±

hepatitis

Before After

largely (RES)

±

woodchucks; of 14 tumors

at auwere

tumor-liver of AG-

USPIO (10 p.mol Fe/kg) (21.0 ± 2.9) is more than threefold greater than that after administration of AMI-25 (6.4 ± 2.0) (P < .05). Tumor-liver C/N increased significantly (from -3.9 ± 2.7 to 18.9 ± 3.7) even after administration of 2 pmol Fe/kg with a gradient-echo pulse sequence (Fig 2). Regenerating nodules that were not distinguishable from small HCC with US appeared isointense or slightly hyperintense on Ti- and T2weighted precontrast images. It was impossible to differentiate these regenerating nodules from small HCCs on nonenhanced MR images or with US. Although the number of regenerating nodules in this study was too small to carry out a meaningful quantitative analysis, we observed a trend for all nodules to decrease in signal intensity after administration of AGUSPIO. The decrease was similar to that seen in liver parenchyma, potentially allowing the differentiation of regenerating nodules from HCC. DISCUSSION Our results confirm that hepatocyte-directed superparamagnetic iron oxide improves differentiation of HCC from normal liver tissue, thus increasing tumor-liver contrast and lesion detectability. During malignant dedifferentiation, hepatocytes lose many cell-surface receptors, including the ASG receptor system (14,15,17,18). Since ASG-directed MR receptor agents are distributed only to tissue containing intact and differentiated hepatocytes (normal liver, cirrhosis, hepatitis, regenerating nodules), tuRadiology

#{149} 643

mor-liver

contrast

increased.

This

agent

can

targeting

strategies

be specifically

concept

of contrast-

is superior

that

show

to other

a variable

uptake

of contrast agents by tumors (22,23). For example, the interstitial agent gadopentetate dimeglumine reflects differential vascularity and perfusion of tumor parenchyma; hepatobiliary agents

are

all nonspecifically

taken

up

by tumors to a certain degree and are not receptor-specific per se (22-34). Iron oxide preparations can be theoretically targeted to a variety of hepatocyte receptors (eg, asialoglycoprotein, mannose, fucose, and lipoprotein receptors). Targeting to other receptors may provide additional benefit, and these studies are ongoing. The carrier (arabinogalactan) used in this study to deliver iron oxide to ASG receptors can be replaced by other ASG-speciflc carriers (eg, ASG, other arabinogalactans, asialofetuin, orosomucoid, and neoglycoproteins). Likewise, the iron oxide label can be replaced with smaller or monocrystalline

labels,

a.

b.

Figure 2. Gradient-recalled-echo MR images (120/16, 70#{176} flip angle, four signals averaged) show woodchuck HCC before (a) and after (b) administration of 2 pmol Fe/kg of the receptor agent (L = liver). With this low dose, C/N increased from -3.9 ± 2.7 to 18.9 ± 3.7. The tumor (7) is readily detectable after administration of the receptor agent (b).

modifications

that may provide additional benefits for MR imaging. ASG receptors are physiologically abundant on hepatocytes (400,000-500,000 receptors per cell) and are responsible for the clearance of desialylated glycoproteins by the liver (14,18,35-38). ASG receptordirected

iron

oxide

binds

to the

sur-

face membranes of hepatocyte cells as demonstrated with electron microscopy, is subsequently internalized into hepatocytes (21), and is degraded in lysosomes. Iron is then incorporated into the natural iron metabolism existent in each hepatocyte (39). ASG receptor activity has been studied clinically in normal liver, cirrhotic liver, liver metastases, and primary malignant liver tumors (14).

are (i6). This is thought to be due to relatively more of the receptor agent being delivered to the liver; in addition, the different spatial distribution of iron oxide particles to hepatocytes rather than to Kupifer cells may be an additive factor. Another advantage of

rally logic

These

some

imaging may allow differentiation HCC from regenerating nodules. known that regenerating nodules

studies

indicate

that

receptor

activity is always present in normal liver, always absent in extrahepatic tissue including metastases, and reduced in diffuse liver disease such as cirrhosis (14). Only one hepatoma cell line (Hep G2), which originated from a hepatoblastoma and is now cultured in immunodeficient mice, has been reported to have an ASG rest activity of up to 30% (14,40,41). All other primary

malignant

HCCs

demonstrate

ASG rest activities of less than 5%10% (14), significantly less than that present in diffusely diseased, nonmalignant

liver

Receptor vantages agents.

fective times 644

tissue

(i4).

agents

have

over Receptor

reticuloendothelial agents are

in decreasing liver than reticuloendothelial Radiology

#{149}

more

adef-

relaxation agents

receptor

agents

over

large RES agents is their effect on both Ti and T2 relaxation times. Our results show that the smaller receptor agent reduces liver Ti by 15% and liver T2 by 53%, whereas the larger RES agent reduces liver Ti by 11% and liver T2 by 39% (10 pmol Fe/kg). As a result, higher trast can be obtained

tumor-liver conwith receptor

agents by using more Ti-weighted pulse sequences (eg, 500/30), whereas the effects of larger agents are best imaged sequences

The several

smaller

with (eg,

animal

models

study

represent

logic

conditions

tients

with

in woodchucks bles human

more T2-weighted 1,500/40) (Table

used

a spectrum

encountered

HCC.

HCC

The

model

pulse 2).

in this of

patho-

in paof HCC

most closely resemin pathogenesis (vi-

induced chronic characteristics

with cirrhotic or regenerating ing findings Ti-weighted this

tam

model

the

changes such as fibrosis nodules), and imag(tumor hyperintense on images). MR imaging in also

capability

the ASG receptor proximately 50% receptor function promising

hepatitis), histo(chronic hepatitis

results,

suggests

that

of ASG

receptor

uptake

by expressing of the normal (42). Despite more

of It is revia

apASG these

extensive

studies in human tissues are needed to confirm the clinical utility of receptor agents in the differential diagnosis of benign and malignant liver tumors. In summary, our results show that MR receptor imaging improves the detection of HCC in normal and diseased liver biodistribution

because of the of receptor

preferential agents.

The increased tissue relaxivity of receptor-specific agents over conventional iron oxides can be used to either reduce the dose (decreased September

1991

toxicity)

or, at equivalent

achieve

greater

conspicuity agents also mors

doses,

contrast

of small improve

in structurally

(increased

lesions). detection abnormal

Receptor of tu-

13.

livers

and may allow differentiation of regenerating nodules and small HCC on the basis of cell-surface markers. I

14.

2.

Rustgi VK. Epidemiology of hepatocellular carcinoma. Gastroenterol Clin North Am 1987; 16:545-551. Bennett WF, Bova JG. Review of hepatic imaging and a problem-oriented approach to liver masses. Hepatology 1990; 12:761-

17.

775. 3.

4.

5.

6.

7.

8.

9.

10.

11.

Chan CH. Primary carcinoma of the liver. In: Zimmerman H: Diseases of the liver. Philadelphia: Saunders, 1975; 989-994. Nelson RC, ChezmarJL, Sugarbaker PH, Bernardino ME. Hepatic tumors: comparison of CT during arterial portography, delayed CT, and MR imaging for preoperative evaluation. Radiology 1989; 172:27-34. ChezmarJL, Rumancik WM, Megibow AJ, Hulnik DH, Nelson RC, Bernardino ME. Liver and abdominal screening in patients with cancer: CT versus MR imaging. Radiology 1988; 168:43-47. Foley WD, Berland LL, Lawson IL, Smith DF, Thorsen MK. Contrast enhancement technique for dynamic hepatic computed tomographic scanning. Radiology 1983; 147:797-803. Heiken JP, Lee JKT, Glazer HS, Ling D. Hepatic metastases studied with MR and CT. Radiology 1985; 156:423-427. Goldberg BB, Hilpert PL, Burns PN, et al. Hepatic tumors: signal enhancement at Doppler US after intravenous injection of a contrast agent. Radiology 1990; 177:713717. Freeman MP, Vick CW, Taylor KJW, Carithers RL, Brewer WH. Regenerating nodules in cirrhosis: sonographic appearance with anatomic correlation. AJR 1986; 146:533-536. Berland LL, Lawson TL, Foley WD, Melrose BL, Chintapalli KN, Taylor AJ. Cornparison of pre- and postcontrast CT in hepatic masses. AJR 1982; 138:853-858. Takashima T, Matsui 0, Suzuki M, Ida M. Diagnosis and screening of small hepatocellular carcinoma. Radiology 1982; 145:

12.

Thomas JL, Bernardino ME, al. EOE-13 in the detection

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25.

26.

635-638.

180

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3

Verness M, et of hepato-

oxide. Radiology

28.

Sawamura

1990; 174:797-801.

T, Nakada

Y, Tashiro

H, Shiozaki

Y.

Y,

Hyperasialogly-

coproteinemia in patients with chronic liver disease and/or liver cell carcinoma. Gastroenterology 1984; 87:1217-1221. Wu GY, Wu CH, Rubin MI. Acetaminophen hepatotoxicity and targeted rescue: a model for specific chemotherapy of hepatocellular carcinoma. Hepatology 1985;

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References 1.

27.

Sameshima

15.

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