Bernard

A. Bimnbaum,

Edward

Lubat,

MD

MD

Definitive MR Imaging Red Blood

E. Noz,

PhD

Diagnosis of Hepatic versus Tc-99m-labeled Cell SPECT’

Thirty-seven patients with 69 suspected hemangiomas found by means of computed tomography (CT) and/or ultrasound were studied with both 0.5-T magnetic resonance (MR) imaging and single photon emission CT (SPECT) with technetium-99m-labeled red blood cells. Using a criterion of “perfusionblood pool mismatch,” SPECT readems diagnosed 50 of 64 hemangiomas and all five “nonhemangiomas” (sensitivity, 78% [95% confidence interval, 0.664-0.864] accuracy, 80% [0.69-0.877]).

J Megibow,

Jeffrey C. Weinreb, MD #{149}Alec Kanamuller, MD #{149}Marilyn

#{149}

Hildegard

#{149}

Qualitative

analysis

of

lesion signal intensity on T2weighted spin-echo MR images allowed readers to diagnose 58 of 64 hemangiomas and four of five nonhemangiomas (sensitivity, 91% [0.814-0.96]; accuracy, 90% [0.8070.951]). Because of the significantly higher cost of MR imaging and its inability to categorically differentiate hemangiomas from hypervasculam metastases, the authors consider SPECT to be the method of choice for diagnosing hepatic hemangiomas. MR imaging should be meserved for the diagnosis of lesions smaller than 2.0 cm and for those 2.5 cm and smaller adjacent to the heart or major hepatic vessels; in such cases MR imaging was found supenor to SPECT.

H

is the

EMANGIOMA

mon

benign

most

comof the

and 16 had multiple lesions to eight). A total of 70 lesions

liven, with a prevalence of 7.3% of the population, based on autopsy data (1,2). It is the second most cornmon hepatic tumor, exceeded only by metastases. Focal masses highly suggestive of hemangiomas are often discovered

puted

tomographic

sound

(US)

at corn-

(CT)

or ultra-

terms:

761.3194 agnosis, ies,

Angioma,

gastrointestinal CT #{149} Liver neoplasms, #{149} Liver neoplasms, MR

#{149} Emission

761.3194

761.1214

#{149} Liver

neoplasms,

studies, 761.1299 tissue characterization

#{149}

Radiology

176:95-101

I

York

From

1990;

the

University

Magnetic

Department Medical

tract, distud-

radionuclide

resonance

(MR),

Center,

560

New First

Ave.

New York, NY 10016. From the 1989 RSNA annual meeting. Received November 27, 1989; revision requested January 2, 1990; final revision received March 14; accepted March 23. Address reprint requests to B.A.B. c RSNA, 1990

peripherally contrast routinely

Lesions

criteria

were

has

515 was

a high

diagnosis (8-11).

accuracy

for

of hepatic Other

the

definitive

studies

have

high

accuracy

in the

same

plication (12-14). It is not clear the literature which examination most

appropriate

for

a

clinical

the

neoplasms

In 69 lesions proved

from is and

clinical

ate utilization and

of both

MR

labeled-RBC

SPECT

imaging in this

32 patients,

AND

clini-

METHODS

During a 15-month period, 38 patients with suspected hemangioma found at CT and/or US examination were referred for both MR imaging and Tc-99m-labeled

One patient

had incomplete

follow-up and study, allowing the remaining

were

18 men

age was 58.7 The suspected found with 12, and with

Twenty-one

was excluded from the a retrospective analysis of 37 patients’ studies. There and 19 women; their mean years (range, 33-87 years). hemangiomas had been CT in 20 patients, with US in both CT and US in five.

patients

had solitary

cancer

the diagnothe

correlating

with serial

the

were

lesions,

results

results

imaging

of follow-

was

exclud-

occurring

ultimately

character-

ized as hemangiomas. Twenty-eight of these lesions were found in 16 patients without a known history of cancer.

Twelve

lesions

(six patients) in

5),

demonstrat-

size on morphology MR imaging (n

2). Imaging follow-up to 8 months after the initial 4.5 months). 10 patients studies,

MATERIALS

colon

in 37 patients,

and

(n

appropni-

patients

with

by

studies

study

the

the above

Nineteen

including

ed no change nial US (n =

define

meeting

of malignancy,

definitive diagnosis of hemangioma in an individual case. The goal of this is to help

not

prima(n 4), lung cancer (n = 4), breast cancer (n 3), melanoma (n 2), lymphoma (n 1), leukemia (n 1), prostate cancer (n 1), gastric leiomyosancoma (n 1), thyroid cancer (n = 1), and macroglobulinemia (n 1). ry

in

ap-

specific

“reference

up. The one unproved lesion ed from further analysis. Sixty-four reference lesions,

CT has

termed

excluded.

a history

both

shown

that single photon emission (SPECT) with technetium-99m-labeled red blood cells (RBCs)

had

of imaging

hernangiomas

were

two de-

enhanced mass. Initial nonand delayed CT images were not obtained for further character-

ization.

RBC SPECT.

of Radiology,

and these

(range, were

lesions.” Reference lesions were accepted into the study if sonography depicted a well-circumscribed echogenic mass or if sequential dynamic CT with a bolus injection of contrast material demonstrated a

a sus-

Once

cal setting. Index

tected,

pected hernangiorna is detected, furthen imaging may be necessary to specifically characterize this mass, particularly in the oncology patient. The specific CT or US criteria for hemangioma cannot be reliably demonstrated in every case (3-7). Recent studies have claimed that magnetic resonance (MR) imaging

examination.

MD MD

#{149}

Hemangiomas:

neoplasm

serendipitously

#{149}Joseph J. Sanger, Morton A. Bosniak,

MD

Sixteen without but

there

ranged study

lesions follow-up was

no

at se5), or CT

=

from (mean,

occurred imaging

3

in

development

of

clinical signs of hepatic disease or abnormal results of liver function tests in these patients during a 6-19-month period of observation

teen ings itive

(mean,

findings ings

were

were Thirty-six

positive

photon echo

months).

cell,

SE

emission time,

but

negative. reference

Abbreviations: HCC = hepatocellular blood

10.5

Thin-

of these lesions had positive findat labeled-RBC SPECT as well as posMR studies. In three of the 16, MR

TR

=

SPECT

lesions

CSF

were

cerebrospina! carcinoma,

spin

find-

echo,

computed repetition

evalu-

fluid, RBC

SPECT tomography,

red

single TE

time.

95

b.

a.

1. Typical hemangioma. (a) T2-weighted (SE 2,000/100) nal intensity equal to that of CSF. (b) Axial SPECT images reveal flow phase was normal (not shown). Figure

image demonstrates a hypenmntense lesion of the right hepatic delayed uptake of blood pool activity within lesion (arrows).

ated in 16 patients with a known primary tumor ultimately characterized as hemangioma. Twenty-one lesions (eight patients) demonstrated no change in size or morphology with serial MR imaging (n 12), CT (n 6), or US (n 3). Imaging follow-up ranged from 3 to 10 months after the initial study (mean, 6.9 months). Follow-up imaging of 15 lesions was not performed in eight patients without clinical signs of hepatic disease or abnormal results of liver function tests in a 6-17month observation period (mean, 10.6 months). Twelve of these 15 lesions were positive on both labeled-RBC SPECT and MR studies; in two, MR findings were

sions

positive but SPECT findings were negative; and in one, only SPECT findings were positive. Five patients had reference lesions that

from 2 days (n 28) to 2 weeks (n 6) to within 4-10 weeks (n 3). For all MR examinations, spin-echo (SE) pulse sequences were performed with a 0.5-T superconducting magnet (Gyroscan; Philips Medical Systems, Shelton, Conn). After acquisition of a coronal scout image, axial SE images were obtamed through the entire liver at 2,000/ 50-100 (repetition time [TR] msec/echo time [TEJ msec) with a 128 X 128 matrix and two excitations. The section thickness

could not be characterized as hemangiomas. These patients included two with solitary masses of focal nodular hyperplasia (proved by correlation of MR and albumin-colloid liver-spleen SPECT studies), two with solitary hepatic metastases (lymphoma and lung cancer, diagnosed through correlation of imaging studies and clinical follow-up), and one with focal normal liver in the setting of fatty infiltration (established by means of needle biopsy). Patients studied with CT at our institution (n = 22) had scans obtained on a CT/ T 9800 Quick or CT/T 9800 HiLight scanner (GE Medical Systems, Milwaukee). Dy namic incremental scanning was coupled with a bolus infusion of contrast material delivered via power injector (Angiomat CT injector, Liebel-Flarsheim, Cincinnati; or Mark IV injector, Medrad, Pittsburgh). It should be emphasized that

CT was not used 96

Radiology

#{149}

to characterize

the le-

as hemangiomas,

as noncontrast

and delayed single-level contrast-enhanced scans were not obtained to document

fill-in of these lesions. institution (n = 12) were performed with 3.28-MHz transducers (model 128; Acuson, Mountain View, Calif). Outside CT (n 3) and US (n 5) studies were performed with a variety of equipment and without standardized techniques. When appropriate lesions were detected with the above screening modalities, the patients were referred for both MR imaging and SPECT. The interval beUS

isoattenuated

studies

tween

at our

the MR and SPECT

studies

varied

lobe with sigThe dynamic

high-resolution, low-energy collimator (Starcam 400-AC/T camera-computer systern; GE Medical Systems). Once the patient was positioned to optimize visualization of the largest known liver lesion,

a dynamic

flow

phase

was acquired

at a

rate of 3 seconds per frame over a 90-second interval as the patient’s blood was reinjected. Immediately thereafter, without repositioning of the camera or the patient, a 256 X 256-pixel static image was acquired for 2 million counts. Following an

interval

tional by

of 90-120

static

image

acquisition

minutes,

was

an

obtained,

of a SPECT

scan

addi-

followed of the

liv-

er (360#{176} rotation, 64 view angles, 25-30 seconds per projection). After correction for camera nonuniformity and center-ofrotation deviation, the projections were reconstructed with commercially available filtered-back projection and Chang’s

method

of attenuation

correction

into

6-

mm-thick transaxial sections (16). Coronal and sagittal sections were re-sorted from these transaxial sections and ultimately merged as pairs to yield 1.2-cm-thick contiguous axial, coronal, and sagittal sections (64 X 64-pixel matrix). Nuclear im-

was 10 mm, with flow compensation

2-mm gaps. Neither nor motion reduction

age acquisition

techniques

employed.

Hard copy images of the examinations had patient names obscured and were assigned random numbers. Readers of MR images (A.J.M., E.L.) were supplied with only the T2-weighted 2,000/100 images, while SPECT readers (J.J.S., H.K.) were provided with the dynamic-flow and delayed-phase SPECT images. MR and SPECT reader teams consisted of both a junior and senior faculty member. To avoid possible bias due to variable reader ability in interpreting CT and US images, the readers had no access to the referring

weighted

were

(2,000/100)

images

The

T2-

were

specif-

ically obtained at settings with which cerebrospinal fluid (CSF) appeared uniformly and markedly hyperintense. The MR acquisition time was typically about 8.5 minutes, with a total examination time of approximately 25 minutes.

RBC labeling

was performed

according

to the modified in vitro technique, with 30 mCi (1,110 MBq) of Tc-99m pertechnetate (15). A large-field-of-view tomographic gamma camera was fitted with a

50 minutes

time over

typically

a 2.0-2.5-hour

was about interval.

July

1990

a.

b.

Figure 2. patic vein mangioma

C.

SPECT-negative hemangioma. (a) Transverse and inferior vena cava. (b) Axial SPECT scans at confluence of vessels.

CT or US studies. Instead, they were supplied with representative axial diagrams of the liver that demonstrated the size and location of each suspected reference lesion, as well as with the knowledge of whether a history of malignancy was present.

US scan depicts echogenic mass (arrow) at dome fail to show lesion. (C) T2-weighted (SE 2,000/100)

MR analysis confidence

and

are presented

interval

range

with

a 95%

(17). Because

of

the small number of “nonhemangioma” lesions present, analysis of test specificity (number of nonhemangiomas correctly characterized per total number of nonhemangiornas evaluated) was determined to

Readers rated the likelihood that the reference lesion was a hemangiorna on a five-point confidence scale. SPECT readers diagnosed hernangioma when normal or decreased flow to a lesion was associat-

be of uncertain

ed with delayed blood pool activity on the SPECT images. MR readers diagnosed hemangioma when a lesion was found to be either totally or predominantly hyper-

The overall and size-related accuracy and the location-related sensitivity were cornpared by means of a McNemar x2 test for matched pairs with one degree of freedom (18). In addition, a statistical power analysis was performed to evaluate the effects of the study sample size.

intense or isointense nal intensity. Small gions

were

noted

relative to CSF siginhomogeneous rebut

characterization

of

lesions that high signal

did

not

preclude

hemangioma.

appeared intensity

tamed tensity; Strands regions lesions

based

After

and

by size, sensitivity

measurements

were

also

lesion

size.

on reference

in-

and/or stranded. as linear-appearing intensity traversing

of any additional

noted.

five

were

all

correctly

of 78%

(95%

confidence

interval,

0.664-0.864)

and

accuracy

of 80%

(0.69-0.877).

All

hemangiomas

dem-

dence

onstrated normal or decreased activity during the flow phase and pensistent blood pool accumulation cornpared with normal liver on delayed SPECT images (Fig 1). Three lesions

mas

(sizes,

Positive

results

were

characterization

dence

levels

gioma).

based

at the

two

(definite

on lesion highest

confi-

or probable

Indeterminate

lesions

heman-

(confi-

level 3) included those hemangiothat displayed both delayed SPECT blood pool activity and hyperperfusion on the

flow

negative

phase

for data

and

were

analysis,

considered

along

with

those lesions rated at the two lowest confidence levels. Sensitivity (number of hemangiomas correctly characterized per total number of hemangiomas evaluated)

and accuracy sions

number were

Volume

correctly

(number

of reference determined

176

of reference

characterized

per

lesions for overall

Number

#{149}

1

letotal

evaluated) SPECT

and

3.5,

4.0,

and

9.5

cm)

clearly

demonstrated persistent accumulation on delayed-phase SPECT images, but because of increased activity seen on the flow phase images, they were interpreted as indeterminate. The smallest hemangioma identified with SPECT was 1.0 cm and was located at the hepatic periphery. This lesion was located of the right

at the midlatemal aspect lobe and was character-

highest

confidence

to major inferior

hernangiomas were locatto blood vessels on the (1.3-4.0 cm) were adjacent

portal vein branches vena cava; 12 (1.0-6.0

located

the the

at the

to either

hepatic 18 were

was

dome

the

ranged 2). One

identified

on

the

or the cm)

of the

liver

confluence

veins or the not identified

images. These to 2.5 cm (Fig

of

heart. on

Six of SPECT

in size 4.0-cm

from lesion

1.0

SPECT

images

but was ranked as indeterminate because of increased activity observed during giomas

the flow adjacent

Analysis

and

diagnosed by means of labeled-RBC SPECT, yielding an overall sensitivity

Eighteen ed adjacent heart. Six

adjacent cal-

second

(2.0-4.0 cm) with SPECT.

of 64 hemangiomas

nonhemangiomas

at the

to confluence of right heclearly demonstrates he-

level.

were

subcategoriza-

groups

RESULTS Fifty

con-

of low signal

The presence

was

accuracy

culated

nonlinintensity; if they

regions

or (c) septated were defined of low signal

the lesion.

and

three

of predominantly were further classias (a) segmentally in-

inhomogeneous

scattered

not performed.

lion into

significance

Those

fied by appearance homogeneous if they contained ear, focal regions of low signal (b) diffusely

was

statistical

ized

adjacent image

phase. to the

were

Three might

correctly

of the

hemankidney

diagnosed

14 lesions

missed

with

SPECT revealed the following: (a) Three lesions larger than 3.0 cm

were

seen

on

the

SPECT

images

but

called indeterminate on the basis of increased activity in the flow phase; (b) one 2.5-cm hernangioma adjacent to the

middle

identified hemangiomas

hepatic

vein

on SPECT smaller (two

images; than

was

not (c) 10

2.0 cm

were

missed

located

at the dome and adjacent to vessels, two adjacent to vessels, one at the dome near

heart, liver,

three located deep within and two located superficially).

MR imaging correctly enabled agnosis of 58 of 64 hemangiornas four of five nonhemangiomas,

the diand for an

overall sensitivity of 91% (0.814-0.96) and accuracy of 90% (0.807-0.951). Forty-eight (75%) hemangiomas peared as homogeneous masses

apwith

uniformly

on

the

long

high TR/TE

signal (2,000/100)

intensity images

Radiology

97

#{149}

(Fig

1). Nine

(14.1%)

were

ly inhornogeneous,

two

peaned diffusely and five (7.8%)

segmental(3.1%)

ap-

inhomogeneous, contained septations

on strands. Sixty-one hernangiornas (95.3%) were well rnarginated, and three (4.7%) were poorly cincurnscribed. All hernangiornas located at the hepatic dome or adjacent to yessels were correctly diagnosed with MR imaging. A single false-positive finding was a 2.0-cm lesion located at the dome, hyperintense,

greater

appearing with

than

RBC

SPECT

area

in this

that

homogeneously signal intensity

of CSF.

showed

Labeled-

a photopenic

region.

The

patient

had

abnormal liven function tests and died of metastatic lung cancer. Of the six false-negative MR findings, three lesions were superficially located (1.5-2.0 cm) and three were located

deep within (1.0-1.2 cm). MR imaging

the

hepatic

parenchyma

CD

z

demonstrated an addi27 lesions not identified previ(nonrefemence lesions). Twentywere homogeneously hypeninand were thought to represent

tional ously three tense

either

cysts

or hemangiomas,

interpreted

three

as possible

were

metastasis,

indeterminate.

was made to nemeview ies to correlate these

readers

one

of MR

studies that cant motion not interfere

images

U,

was

UJ C)

‘I,

and

LU

-J

the entry studlesions. The

LU

C CD

z

‘C w =

three

by

signifithis did lesion

was

accurate

than

SPECT

found

to be more

in characteriz-

ing the total number of lesions (P = .047) and in characterizing lesions smaller than 2.0 cm (P .044) when tested for significance with a x2 test

matched

pairs.

significant were noted

differences between

O#{149}U

UUSUSU 1.2

I-. 3.

1.4

cc

ci

#{149}s

so

#{149}

#{149}EIU

#{149}US

S

UU#{149} U U

U

U U

1.8

2.2

1.6

1.0-1.9cm

Reference

the

cally significant differences evaluations were found tients with and without

0 0

lesion

SPECT

in the between paa history of a

3, where

the

nef-

2f

3

5

4

6

7

8

S S

) 9

10

U

11

12

13

I

3.0-13cm

Circles

findings

tive

means

has gained popuas a cost-effec-

of imaging

number

the

of incidentally

hernangiomas

has

cally, hernangiomas scnibed, homogeneous,

diagnostic.

The

liven,

the

discovered

increased. are

Classi-

well-cincumdensely echo-

this appearit is not

differential

of

negative;

(5,6,23,24). shown that

varying

Radiology

MR

DISCUSSION As abdominal US larity and acceptance

in accuracy two modal-

enence lesions have been categorized into three groups based on size (1-1.9 cm, 2-2.9 cm, and greater than 3.0

#{149}

2.6

2.O-2.9cm.....

analysis.

and

Table

98

2.4

U U

no history of neoplasm; squares = history #{149} #{149}SPECT and MR findings positive; C 13 = SPECT findings positive, MR findings negative; 0 II = MR findings positive, SPECT findings negative; X nonhemangioma. neoplasm;

genic masses. Although ance is frequently seen,

cm).

i-

-

primary neoplasm. When lesions were analyzed by location, 18 hemangiornas were adjacent to major vessels or the heart. When these lesions were directly compared, MR imaging proved more effective than SPECT in their diagnosis (P = .044). The results of the SPECT and MR examinations are summarized in the in Figure

2.0

#{149}#{149}U S UUU#{149} SU .UUUU

No statistically

in characterizing lesions larger 2.0 cm. Furthermore, no statisti-

and

0

0

#{149}ci

0 0

1.0

Figure

imaging

IJ II El

z

LU

identified

Z

z z

No attempt

were degraded artifact, although with reference

MR

ities than

C

w

characterization.

for

0 z

diagnosis

Preliminary work has pulsed Doppler US may

help in differentiation ma from HCC; however, enable guished

hemangiomas from metastases

been extensively benign hepatic Early

hepatic cifically teristic

reports

of hemangioit does not to be distinand has

evaluated masses (25). suggested

not

for other that

most

hemangiomas could be spediagnosed with CT if characfeatures were identified

of echogenic hepatic masses includes metastases, hepatocellular carcinoma (HCC), hepatic adenoma, and focal

(3,26-29). These findings were enthusiastically received, because prior to this, the only way to definitively

nodular

diagnose

hyperplasia

(3,4,19-22).

The

sonographic features of hemangioma are variable, as these lesions may also appear hypoechoic, demonstrate enhancement, complexity

degrees

of posterior

acoustic

or display varying depending on the degree

of degeneration, fibrosis, hemomrhage, on calcification present

hemangiomas

had

been

by

means

of angiography.

on the ployed, shown

strictness of CT criteria emmore recent studies have that the CT findings of he-

mangiorna can only 55%-89%

When present,

the

Depending

be demonstrated of patients (7,30).

classic findings are theme is an 86% chance

in

that July

1990

the lesion is actually a hemangioma (31). Most clinical studies of the abdomen are performed with a dynamic-bolus incremental technique, a method

directed

Specific

lesion

at lesion detection. characterization may mequime a second CT examination to evaluate a given lesion’s response to a bolus injection of contrast material over time. Because it is not clean that

the

second

CT study

will

be able

to

document the classic features in every case, alternative modalities have been advocated when the clinical sit-

uation

requires

terization.

exact

lesion

chamac-

in lesions

Furthermore,

smaller than 3 cm, misnegistration problems caused by variable respimatory excursion may make these featunes impossible to demonstrate in individual cases (28). CT may also be limited in evaluating patients with multiple lesions suspected to be hemangiomas. Prior studies have shown that labeled-RBC method mangioma, technique

scanning is an accurate of diagnosing hepatic heand the sensitivity of this is significantly improved

by the addition of SPECT (12-14,3235). The specificity and positive predictive value of this test approach 100% (14), with only four documented false-positive cases in the litera-

ture one

(three cases of HCC case of hemangiosarcoma

In a recent

ranging played

study,

in size delayed

(14).

[33,36]

none

from blood

similar

and [37]).

of 45 HCCs

is morpho-

to hemangioma;

therefore, it is understandable that delayed blood pool activity could be seen. This neoplasm is mare and is not

generally a differential consideration unless ry of hemochnomatosis

ported

SPECT

diagnostic theme is a histoor of chronic

series

larger;

the

sensitivity

cated

along

sions

of this

detection. Because

the

oth-

neoplasm or HCC, we attempted to identify “perfusion-blood pool mismatch,” that is, observed perfusion within the lesion equal to or less than that of surrounding normal liven, associated

pool

uptake.

will ficity

maintain at the

because

with

The

expense hemangiomas

large

lesions

study

population. 176

degree

to liver seen in three in the

If the Number

#{149}

criteria of speci-

of sensitivity, may display

relative This was encountered

(12,14,32,33).

blood

of such

a high

hyperpenfusion

Volume

delayed

use

flow-phase 1

margin,

more

lo-

but

often

labeled-RBC

le-

escaped

activity

per-

hepatic

veins

(Fig

2). Five

of

these lesions were between 1 .0 and 1.9 cm; the sixth was a 2.5-cm lesion located at the dome adjacent to the middle hepatic vein. Although a sirnilar difficulty may occur in the megion of the night kidney (14), this situation was not a problem in our series. SPECT correctly demonstrated all three hemangiomas (all larger than 2 cm) in this location. It is known that false-negative mesults when

at labeled-RBC hemangiomas

by thrombosis situation was

fective

from

accuracy

sists in the heart and major intrahepatic blood vessels on delayed SPECT blood pool images, it may be problematic to discriminate activity within small hemangiomas (which are also accumulating activity) when they are adjacent to these structures. Delayed SPECT scanning did not permit identification of six of 18 hemangiomas adjacent to major intrahepatic vessels, or at the hepatic dome near the heart and/or the confluence

fementiating

(12-14,32a vascular

and

liven

size

study population. MR imaging

hemangiomas

SPECT

was similar for both techniques. SPECT identified one 1-cm lesion

exposure to vinyl chloride, thorium dioxide, arsenicals, or radium (14,38). The importance of the dynamic flow phase of RBC scanning in difem lesions is controversial 34). In order to exclude

(14).

compared favorably with MR imaging for detection of lesions 2.0 cm on

of the

1.4 to 5.0 cm dispool activity

Hemangiosarcoma

logically

findings were ignored, these three hemangiomas would have been interpreted as true-positive on the SPECT studies, resulting in equal SPECT and MR sensitivity and accuracy for lesions larger than 3 cm. Our results with the labeled-RBC SPECT technique are comparable to those of the largest previously me-

modality mangiomas

SPECT can occur are complicated

or fibrosis (33,34). This not encountered in our is the

means

of distinguishing

attempted

them

hepatic Previous

neostudies

to characterize

he-

mangiomas on the em contrast-to-noise

basis of lesion-livratios, lesion-liv-

en signal

ratios,

intensity

mean

T2 of hemangiomas

may

calculated

T2 relaxation times, and morphologic inspection (8-1 1,39-42). New mesearch suggests a potential role for gadolinium-enhanced studies (43). A comparison of the signal intensity of a mass relative to that of the liven may be inaccurate in cases with fatty infiltration, cirrhosis, hemosidemosis, on other infiltrating hepatic diseases. Quantitative analysis based on T2 me-

differ

significantly from that of other focal liven lesions, many investigators believe that the large standard deviations in these relaxation times predude their use in characterizing a lesion in the individual patient (810,39-42). Our MR analysis was based on visual inspection of hardcopy

images,

a qualitative

assessment

that simulates the most commonly used interpretive clinical approach and has proved as reliable as available quantitative techniques (11,41). Hemangiomas classically appear as homogeneous masses of high signal intensity on T2-weighted images (Fig 1) (11). Inhomogeneous areas may be present, particularly in large lesions, reflecting regions of fibrosis, thrombosis, hemorrhage, liquefaction, and calcification (44,45). Sixteen (25%) of the 64 hemangiomas in our series displayed variable amounts of lowsignal-intensity foci. These observations agree with those of Ros et al, who found hemangiomas frequently inhomogeneous on gross anatomic sections as well as T2-weighted MR images (44). Despite these regions of low

signal

intensity,

no equivocation

the

readers

had

in characterizing

the

given lesions as hemangiomas, because the predominant signal intensity was equal to on greaten than that

of an internal (CSF). tance

dand the

reference

standard

This underscores of interpreting

settings,

the images

as it is easy

appearance

manipulation

greaten

lesions

by

of operator-selected

sensitivity

labeled-RBC

impomat stan-

to change

of these

window levels and widths. We found MR imaging

sensitive

for detecting hepatic heand is known to be an ef-

from most malignant plasms (8-11,39-42). have

most

laxation times may not be neproducible in different imaging systems, and inherent inaccuracies exist in commonly used two-point fit measurements. Furthermore, while some series have shown that the calculated

and

to have

accuracy

than

SPECT scanning, to two important

pri-

marily due advantages. First, MR imaging proved more accurate in the diagnosis of small

hernangiomas

(smaller

than

on

equal to 2.5 cm) adjacent and major intrahepatic

to the heart vessels (Fig

2). Second,

effective

it was

more

in

both detection hernangiomas Nevertheless,

and diagnosis of small (smaller than 2.0 cm). analysis of our test me-

sults study

by size,

is limited sample

only 69 reference en level” for our 95%

confidence

power analysis that, theoretically,

the relatively which included

small

lesions. test was

The “pow0.42 at the level. A statistical of our data revealed 289 reference leRadiology

99

#{149}

sions

would

have

been

required

the study to have a “power 0.95 at the 95% confidence degree The

of freedom). specificity

of MR

for

level” of level (one imaging

was

less than that of SPECT, reflecting a single false-positive finding, metastatic adenocarcinoma from the lung that appeared as a homogeneous, hypenintense lesion. Previous reports have

described

a homogeneous,

high-signal-intensity

appearance

ondary to metastatic chromocytoma, islet

creatic

and

and

uterine

various

sec-

carcinoid, cell tumor,

pheopan-

(unspecified)

(11,41). Thus, even with strict criteria of a homogeneous hypenintense lesion, MR imaging is seen to lack the nean-100% positive predictive value of positive labeled-RBC SPECT scanfling

(14).

It has been suggested previously that hemangioma-metastasis discrimination may be improved by using SE pulse sequences with TEs ranging up to 120-180 rnsec (9,1 1). However, such techniques may still not ensure that be differentiated

on necrotic

all

hernangiornas from hypervascular

neoplasms.

We chose

can

to

use a TE of 100 msec for practical reasons, as this setting allowed us to study the entire liver in a reasonable

amount

of time,

signal

to noise

provided on

our

optimal system,

and

enabled confident There confidence tenization

sufficient T2 weighting for characterization. was no difference in the of hemangioma characbetween patients with and

without lignancy.

a history Only

had

a history

been 22%

predicted of patients

tumors

that

(particularly

of concurrent ma19 of the 37 patients

of malignancy. that with

approximately known primary

metastasize colon,

It has

to the

liver

and

breast

lung,

cancer as seen in our study) will ultimately be found to have hepatic cancen (31). Thus, these statistics are lirnited by the small number of nonhemangioma lesions present. Our study evaluated only lesions initially suspected to be hemangiomas and excluded all other hepatic masses. Thus, there was an inherent case selection bias. However, we attempted to simulate the common clinical situation, wherein lesions that are clearly not hemangiomas (eg, cysts and defiflute

malignant

US scans to further Because features

suggestive

Radiology

#{149}

on

CT

and/or

are generally not subjected imaging characterization. we studied lesions with

on CT and/or ing selection 100

tumors)

of hemangioma

US studies, the resultbias may have artificial-

the

accuracies

ied, the evaluation is limited. Had

of MR

irn-

of test specificity more necrotic on hy-

pervascular metastases been included, our results may have been significantly different. This study has demonstrated that the sonographic finding of a well-

manginated, or the

adenocarcinoma,

sarcomas

ly increased

aging and SPECT by eliminating those hemangiomas with atypical features, which may be difficult to diagnose. Furthermore, as only five nonhemangiorna lesions were stud-

CT

echogenic

mass

finding

of a peripherally

hepatic a strong

mass may be comepretest probabili-

enhanced lated with

ty of hernangioma

lation focal

hepatic

without hepatic

in a patient

history disease.

settings where nign hemangioma

the

popu-

of neoplasia or In those clinical

likelihood is high,

serial

of a beim-

aging accompanied by clinical follow-up may be all that is necessary for diagnostic evaluation, with no corroborative testing necessary. However,

when

a hepatic

mass

is de-

tected in a symptomatic patient on in an oncology patient, further noninvasive imaging is often necessary to characterize the lesion(s) specifically. Because it has been demonstrated that peripheral ment may occur hancing hepatic

contrast enhancein up to 54.5% of enneoplasms studied

with the dynamic-bolus incremental technique, there is overlap in the CT appearance of hepatic hemangiomas and malignant neoplasms when this technique is used (31). Despite the fact that CT is highly accurate when findings are positive (when penformed as a characterization study) it does not consistently yield characteristic enhancement patterns, limiting its clinical usefulness. As a result, both MR imaging and/on labeledRBC SPECT have been advocated as additional methods for diagnosing

these

lesions

specifically

and

defini-

when

hemangiomas

The

decision

should

be based

smaller

than

cm and

smaller

and/or

MR

major

imaging

is slightly

greater

tivity in the mas smaller

detection than 2.0

of hemangiocm, as well

(smaller

tivity

than 2.0 in detection

cm), and was not

the

cm

and

size

for

and

those

to the

intrahepatic

primary

hypervascular

2.5

heart

blood

tumors

yes-

may

The authors

knowledge the cheerful Lopez for her assistance manuscript

that

pro-

rnetastases.

Acknowledgment:

U

wish

contribution with data

to ac-

of Jennie entry and

preparation.

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#{149}