Irwin

Richard William Joseph

Feuerstein, MD #{149}Douglas L. Jicha, MD #{149} Harvey I. Pass, MD #{149}Catherine K. Chow, Chang, MD #{149} Alexander Ling, MD #{149}Suvimol C. Hill, MD #{149} Andrew J. Dwyer D. Travis, MD #{149} Marc E. Horowitz, MD #{149}Seth M. Steinberg, PhD A. Frank, MD #{149} John L. Doppman, MD

Pulmonary Surgical

Metastases: Correlation

The sensitivity of magnetic resonance (MR) imaging for detection of pulmonary metastases in 11 patients scheduled for thoracotomy and curative resection of metastases was evaluated with a prospective, controlled study. MR imaging performed at 0.5 T was compared with chest radiography, computed tomography (CT), and thoracotomy in 12 cases. (One patient had two separate occurrences of pulmonary metastases.) All images were interpreted in blinded fashion. When all MR sequences were interpreted together, MR imaging enabled correct identification of all patients with pulmonary nodules (100%). CT enabled detection of at least one nodule in all 12 cases (100%) by design; the sensitivity of chest radiography was only 64%. For individual nodules, MR imaging was at beast as sensitive as CT (P2 < .25 [two-sided value]) and significantly more sensitive than chest radiography (P2 < .01). Among all MR sequences, short inversion time inversion-recovery sequences had the highest sensitivity for detection of individual nodules (82%). Index terms: Lung neoplasms, CT, 60.1211 Lung neoplasms, diagnosis, 60.332, 60.333 Lung neoplasms, MR. 60.1214 . Lung neoplasms, secondary. 60.332, 60.333 #{149} Lung, nodule, 60.332, 60.333 #{149} Magnetic resonance (MR), comparative studies Radiology

1992;

182:123-129

MR Imaging A Prospective

P

ULMONARY

lungs

are

with Study’

metastases are a frequent cause of morbidity and death in cancer patients, and the by

far

the

most

common

site

for metastatic disease in certain mabignancies such as muscuboskebetab samcomas (1, 2). Several variably effective therapies exist, including surgical mesection of metastases, which can be performed as soon as pulmonary metastatic disease has been detected (1, 2). Considerable amounts of diagnostic

radiation

are

delivered

to pa-

tients in an attempt to detect pulmonary metastases early (3), usually by means of computed tomography (CT), which is considered the current standard of reference for detection of lung nodules (4-9). A sensitive screening modality that does not require use of ionizing radiation would be of value, especially in young persons. Many young patients never develop metastases and undergo screening for many years with a substantial cumubative

dose

Magnetic has

made

of radiation.

resonance considerable

(MR)

imaging

diagnostic

progress in the thorax; many studies have addressed the use of MR imaging in cardiac and pericandial disease, lung cancer, adenopathy, aontic dissection, and soft-tissue lesions (10-13). MR imaging techniques continue to improve, opening new venues for study. focused

However, on lung

few studies metastases,

have and,

detection of pulmonary nodules, but their study lacked surgical confirmation, pathologic correlation, and a prospective design (14). Barakos et ab included only a few metastases in their retrospective review of chest lesions

and

did

to

tivity

provide

details

of MR

imaging

for

detection

of

pulmonary metastases and compared these results with the results of CT, chest radiography, and thomacotomy in all cases. PATIENTS

Surgical was

AND

METHODS

Groups

Study

resection

initiated

group-A

pilot with

in collaboration

study the Na-

tional Cancer Institute. Twelve MR examinations were prospectively performed in 11 patients with pulmonary nodules be-

lieved

to be metastases.

two separate metastases; 7-74

years

were

eligible

One

occurrences these

patient

metastases

were were

The patients

(mean

had

of pulmonary

age,

30 years).

for the protocol

evalu-

aged

They if they had

an extrapulmonic malignancy, had one more lung nodules that had been diagnosed with CT, were scheduled to un-

or

dergo thoracotomy with surgical resection of metastases, and were willing to undengo MR imaging. Histologic findings in the primary neoplasms were as follows: musculoskeletal sarcomas in 10 patients (osteogenic sarcoma in three patients, osseous Ewing or soft-tissue sarcoma in seven patients) and colon carcinoma in two patients. Control group-MR images from six control patients were blended into the patient data. From the MR image log, a nonsconing

From the Department of Diagnostic Radiology, Bldg 10, Rm 1C660, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892 (I.M.F., R.C., AL., S.C.H., A.J.D.,J.A.F., J.L.D.); Surgery Branch (D.L.J., HIP.), Laboratory of Pathology (W.D.T.), Pediatric Branch (M.E.H.), and Biostatistics and Data Management Section (S.M.S.), National Cancer Institute, National Institutes of Health, Bethesda, Md; and Departments of Radiology (I.M.F., C.K.C., R.C., AL., S.C.H.,J.A.F.,J.L.D.) and Internal Medicine OAF.), Georgetown University Medical Center, Washington, DC. From the 1990 RSNA scientific assembly. Received March 14, 1991; revision requested May 13; revision received August 1; accepted August 9. Address reprint requests to I.M.F. c--RSNA, 1992 See also the editorial by Panicek (pp 10-11) in this issue.

not

about these lesions (15). We performed a controlled, prospective study to ascertain the sensi-

ated separately.

our knowledge, none has prospectively dealt with surgically proved pulmonary metastases. MUller et ab compared MR imaging and CT for

I

MD

M.

radiologist

images

(I.M.F.)

of six patients

ing criteria: (a) Their T2-weighted images, time inversion-recovery

Abbreviations: inversion

time

SE inversion

selected

who

met

Ti-weighted and short

(STIR)

= spin

echo, recovery.

control

the followimages, inversion

images

STIR

= short

123

were

similar to those obtained in the study (although a gadolinium-enhanced Ti image was not mandatory); (b) no lung metastases had been identified on their official MR imaging reports, and, on review, they had no disease on the MR image that would have made it obvious they were controls; and (c) a CT scan obtamed at the time of MR imaging showed no lung metastases. The control patients were aged 26-29 years (mean age, 27 years). The indications for MR imaging and CT were screening for ectopic sources patients

of adrenocorticotropic

hormone

of muscuboskeletal

or study

tumors.

CT of the chest tients by

at the use

9800

onds),

scanner

(scan duration was obtained

administered

soon

as the

gery

and

days

before

patient

were

and

to ii

days

chest

radiographs

chest

obtained

images

between ing

was

used

for

chest 0-10 scanner

of the

study.

(Vista

The

itself and for injection

MR imagI day).

with

HPQ;

0-40

interval

interval,

a 0.5-T

Picker

Heights, consent

Inter-

Ohio). All pafor the ex-

separate of contrast

informed material.

The following pulse sequences were used: STIR (repetition time msec/echo time msec/inversion time msec = 1,800-3,000/ 30/100, with four signal averages and 128 views),

T2-weighted

spin-echo

3,000/80, two to four 128 views), performed artifact

signal with

suppression

(SE)

SE (300-700/10-12,

averages,

and

weighted

images

128-192

and

signal

could

obtained

without

be performed

in every

case. The following sequences were formed: STIR, 12 patients; T2-weighted SE,

10 patients;

and

unenhanced

weighted, 10 patients. hanced Ti-weighted tamed in eight adults; receive

injections.

tamed apices

All

Ti-

were

ob-

in the axial plane from the through the upper abdomen.

sections

were

10 mm

per-

Gadolinium-enimages were obchildren did not images

thick.

Most

lung All images

were obtained without intersection gaps. In three tall patients, intersection gaps not exceeding 3 mm were inserted to cover the entire lungs in a single series of T2weighted SE or STIR sections on two series of Ti-weighted

quences ing

were

images.

respiratory

and

not

performed

during

ing.

124

Breathholding

and

#{149} Radiobotrv

for

lateral

radio-

our

study.

was

performed

in all

stennotomies

resections

thoracotomy

in one in four

case; cases.

se-

cardiac

gat-

MR

imag-

cases.

bilateral

gardless

without

cases;

sternotomy,

ule.

or both

Control

in each

patients

individual

did

dimeglu100 (8) disease was defined as a one nodule. Numbers in panumber of patients. could tolerate all MR Sevaries from 12 in several inchest radiograph could not be

not

nod-

undergo

tho-

of whether

the

Any

nodule but not

in retrospect. radiobogic gery ing.

thoracotomies, was resected

and separately submitted for histologic examination. The pathologist recorded the location, size, histologic findings, and the presence of calcification, grossly visible necrosis,

60 (10) with gad-

Me-

wedge

in seven

and unilateral Each nodule

study

was considered Statistical analysis

individual and the gonies greater formed

of size: 1-9, 10-14, and in diameter. Analyses by use of two-by-two

tables

to identify

other and

Each

R.C.,

the

degree

agreed

was

each blinded

examinations, to the results

The

CT

reader

sequences, of surgery.

was

given

the

entire scan, including lung windows, diastinal windows, and scout views.

meThe

assignments

pa-

were

rotated

after

each

tient. One of the radiologists evaluated the MR image with all sequences viewed simubtaneously, and hereafter the term MR imaging refers to this interpretation with all the MR images viewed together. Conversely, when an MR image is specified, that image was interpreted in isolation from the rest of the images. Because the MR images were separated in this manner, they were reviewed in blinded fashion several months after both MR imaging and

surgery

Each

were

examination

or negative

for

performed.

was pulmonary

scored nodules,

as positive with

positive meaning that at least one nodule was detected. Each image was then scored on a nodule-by-nodule basis. All results

given from

The the

hereafter

findfor

15 mm or were percontingency to which

McNemar significance

are

pairs

identifi-

are

denoted

test of twoby P2.

RESULTS

pato the

Each interpreter scored one of the four MR images, the CT scan, or the chest madiograph.

and

on a at sur-

nodules, three cate-

in enabling

All P values

discordance.

visible

AL.,

evaluated

radiologist

radiologic data, and

the sided

(C.K.C.,

J.L.D.)

Data

was

diagnosed confirmed

a false-positive was performed

cation of metastases. was used to establish

and

lesion

patients, individual nodules stratified into

of modalities

racotomy.

Image Interpretation Analysis

90 (10)

nodule

12 study

performed

SE without

and

palpable

with

were

bilateral

tissue

of any

100 (12) 100 (12)

palpation

parenchymab

resection

dian

thorough

together

Note.-Metastatic finding of at least rentheses are the * Not all patients quences; hence n stances. Also, one found.

Techniques with

(%)*

64(11) 100 (12)

opentetate mine

In all pa-

and

Thoracotomy

tient.

Ti-

enhancement by intravenously administered contrast material and then after intravenous injection of 0.1 mmol/kg of gadopentetate dimeglumine (Magnevist; Berlex Imaging, Wayne, NJ). Because of the claustrophobia of some patients, not

all sequences

examination.

be retrieved

Six radiologists S.C.H., A.J.D.,

Ti-

eight

views).

were

(2,000-

averages, and the motion

technique,

weighted

not

wedge

inter-

was

performed

in a room

of the chest were obtained with patient erect. One chest radiograph

of pulmonary

MR

The

and

(mean

was

to chest

CT, of

Sensitivity

Chest radiography CT MR imaging All sequences STIR T2-weighted Ti-weighted gadopentetate dimeglumine Ti-weighted

scan by use

material.

done

posteroanterior

Surgical

The

to the

radiography

national, Highland tients gave informed amination consent

scans

the

1

3 days).

20 days).

days

could

between

MR imaging

interval,

sun-

from

CT

Modality

a few

ranged

in time

CT and

the

interval

interval,

closest

MR imaging clinical

The

as for

performed

and

were (mean

accepted

surgery

(mean

val between days

was

scheduled

generally

surgery.

MR imaging day

tients, graphs

were

of Chest Radiography, and MR Imaging in Classification Patients with Metastatic Disease

scanner

contrast was

1

2 sec-

8800

= 9.3 seconds). One at another institution

radiography

dedicated

MR examinations

duration, the

Table Sensitivity

(GE

of a different scanner (1200SX, Picker International) (scan duration, 2 seconds). Contiguous sections 10 mm thick were obtained from the lung apices through the upper abdomen without use of intravenously

Techniques

with

pa-

Systems, Mibwauwere obtained with

(scan

two,

in ii of Health

scanners

GE Medical of the scans

and

Chest

Radiologic

performed Institutes

of third-generation

9800/8800; kee). Nine the

was

National

in Tables 1-3 and Figures 1-6 are the prospective, blinded review, re-

Thoracotomy cases of suspected five lesions were

were

resected

was

performed in 12 metastases. Fortyfound. Forty-two

initially,

one

was

me-

sected at follow-up thonacotomy, and two were not nesected for surgical reasons, even though, during the same operation, the surgeon resected other nodules that were similar in

appearance

to-and

to have the istics as-these

same

three

malignant

were

presumed

histologic two lesions.

lesions

characterThirty-

were

found:

32 metastases (Figs 1-6) and a small (10-mm-diameter) primary adenocarcinoma of the lung that was included with the others for the purpose of our study. All lesions were 1-40 mm in

diameter

(mean

diameter,

11 mm).

Only mm

two nodules were bess than 5 in diameter. None of the metastases was calcified at microscopic examination. Twelve of the mesected tissues (listed later in this section) were benign. January

1992

Table

of Chest Nodules,

Sensitivity

Malignant

Radiography, CT, and MR Imaging Stratified by Diameter

in Detection Diameter

Chest radiography CT MR imaging All sequences STIR

together

T2-weighted TI-weighted

SE without

opentetate mine

1-9

10-14

48 (31) 70 (33)

44 (9) 56 (9)

40 (10) 75 (12)

8(12)

85 (33) 82 (33)

67 (9) 56 (9)

92 (12) 92 (12)

92 (12) 92 (12)

71 (28)

57 (7)

80 (10)

73(11)

33(27)

20(5)

36(11)

36(11)

52(23)

20(5)

80(10)

38(8)

15

75(12)

dimeglu-

Table 3 False-Positive Detection

Findings

of Chest

Radiography,

Chest radiography CT MR imaging All sequences

CT, and MR Imaging

FalsePositive Findings

Modality

together

STIR T2-weighted

SE

Ti-weighted opentetate mine Ti-weighted opentetate

without gaddimeglu-

radiograph of nodules

Diameter

could not be (the cumulative

for Nodule

retrospect, was probably

Mean Diameter (mm)

(mm)

mm;

the mean

adjacent to the misinterpreted

artifact.

The

was

identified

not

other,

10 mm on

the

aorta

and as flow

in diameter, MR

images

0

0

2 1 3

4, 5 5 5, 6, 15

5 5 9

only one nodule 4 mm in diameter was missed. (It was missed on CT scans, too.)

at MR imaging diameter,

radio-

5,12,20

12

8,20

5 of 13 findings

chest

3 0

2

total

the

even in retrospect. In the three tall patients in whom gaps were used for the STIR and T2-weighted SE images,

14

with gaddimeglu-

mine

with

graph in the 10-14-mm mange. Use of CT caused the readers to miss all three nodules (mange, 10-30 mm; mean diameter, 22 mm) adjacent to the left ventricle, which were easily detected with the STIR image (Fig 3). These blended in with the paracardiac fat and were also false-negative on T2-weighted SE images (n = 3) and gadolinium-enhanced Tiweighted images (n = 2). Two metastases were less than 5 mm in diameter (one was 1 mm, and one, 4 mm in diameter), and these were missed with all modalities. MR imaging enabled correct identification of all but two lesions larger than 9 mm in diameter. One nodule 25 mm in diameter was clearly obvious, in

gad-

Note-Not all patients could tolerate all MR sequences, and one chest found. Numbers are percentages; numbers in parentheses are the number number in the patients who underwent the specified examination).

was 4-30

SE sequences

with gad-

opentetate mine

ules

(mm)

dimegbu-

TI-weighted

*Note_A

of Individual

All

Modality

-

than CT or chest radiography, although the only difference approaching significance (P2 < .10) was in a comparison of STIR or T2-weighted

2

10, 10, 10, 20, 30 were

false-positive.

The

16

range

of diameters

of all nod-

11 mm.

Intravenous injection of gadopentetate dimeglumine improved detection of 35% of lung nodules (n = 8; range of diameters, 6-40 mm; mean diameter, 16 mm) over detection on baseline, unenhanced Ti-weighted images. contrast

Six nodules were material-enhanced

seen

on images

the

only. Two other nodules were easier to see after injection. Enhancement Table

1 shows

radiography, classification

the

accuracy

CT, and of patients

MR

of chest

imaging as positive

in or

negative for metastatic disease. The combination of all MR sequences enabled connect categorization of all six control

examinations

(100%)

as nega-

tive for metastasis. After separation, the STIR and T2-weighted images were also always considered negative. In one control patient, unenhanced Ti-weighted images revealed two nodules,

which

were

sensitive

at beast

one

CT

enabled

lung

nodule

of suspected

imaging, sequence,

nodules negative

detection

metastases

and

in all 12 cases

vs MR sensitive

(100%).

diameters

in particular

also

enabled

findings.

of MR

the STIR detection

in all 12 cases,

with

of

no false-

False-negative

overall categorizations occurred with chest nadiographs and the isolated Tiand T2-weighted MR images, abVolume

182

#{149} Number

1

imaging). STIR MR sequence

followed by imaging) (48%, P2 < .01 was the most (82%). The

in Table

measured

CT (70%, and chest

considered

false-positive. By design,

though no significant differences could be found among the modalities, probably because our sample size (all 11 patients) and the number of discordant interpretations were small. An analysis of each of the surgically proved malignant nodules was then performed. Table 2 shows the sensitivity of each imaging modality. With a radiologist reading all sequences together, MR imaging was the most

by

the

radiography

pathologist

ubes (27%) 12 nodules

eter;

modality (85%), P2 < .25 vs MR

and

were (36%),

2 were

10-14

homogeneous

except ripherab hancing sent

in every

instance

one. This nodule showed peenhancement with a nonencenter that proved to nepre-

grossly

visible

central

necrosis

at

pathologic examination (Fig 1). In another patient who had previously undergone surgery and in whom it was difficult to differentiate a pleural mecunnence from a postoperative fluid collection, uniform enhancement conrectby suggested that it was neoplasm. Twelve benign lesions (range of diameters, 1-5 mm; mean diameter, 2 mm) were nesected: metaplastic bone (n

=

2), bronchial

cartilage

(n

=

1),

in diameter;

calcified granubomata (n = 2), fibmocabcific nodule (n = 1), intrapulmonic lymph node (n = 1), focal fibrosis

mm

(n

(W.D.T).

1-9 mm

was

Nine

nod-

in diam-

12 nodules (36%), 15 mm or greater in diameter. In all size manges, MR imaging and the STIR sequence revealed a few more lung nodules

=

2), and

pieces

of lung

tissue

with

no pathologic diagnosis (n = 3). Both calcified granubomas were seen with CT. All of the other benign lesions were missed with all modalities. Radiology

#{149} 125

a.

b.

Figure

1.

MR

of pulmonary metastasis SE (2,977/80) (a) and STIR

(a, b) T2-weighted (straight tive

c.

images

arrow).

of necrosis.

Heterogeneity

of signal

(c) Ti-weighted

(300/iO)

from

Ewing

(2,938/30/100) intensity, shown image

sarcoma,

an

image

enhanced

with

(b) images through the right lung base show best in a as more marked central hyperintensity

obtained

before

same area, which, though detectable, is not conspicuous. row) is much more conspicuous on this image (300/10) pseudocapsule. The lesion itself enhances peripherally;

d.

including

injection

of gadopentetate

dimegbumine

gadopentetate

dimeglumine.

a hyperintense metastatic lesion (curved arrow, a and b), is suggesreveals

vague

signal

intensity

from

(d) After intravenous injection of gadopentetate dimeglumine, the lesion (curved than in c. A thin, hypenntense rim (straight arrow) may be compressed lung tissue this appearance correlated with central necrosis proved at histologic examination.

aror

Data from suspected individual nodules not confirmed at surgery in the operative group (false-positive findings) are given in Table 3. Overall, the diameters of the false-positive nodules, measured from the MR images themselves, ranged from 4 to 30 mm (mean diameter, 11 mm). Gadolinium-enhanced Ti-weighted images generated the most false-positive findings

(n

=

5). CT,

MR

imaging,

and

STIR

generated, respectively, no falsepositive findings, two false-positive findings, and one false-positive finding. These differences were not statistically significant because the number of discordant interpretations was very small. The Ti-weighted sequences also generated larger false-positive findings (larger false-positive lesions) than the other MR sequences. Falsepositive diagnoses were more common in the bower lobes (n = 8) than in the upper lobes (n = 4) on right middbe lobe (n = 1). No preference existed for the right (n = 6) on left (n

=

ages,

7) side.

the

nodules

In antenoposterior

( 46%)

majority of the false-positive were in the middle (n = 6) on

were

near

of the

lung.

or in the

vascular

DISCUSSION The results of this study indicate that MR imaging has great potential for detection of pulmonary metastatic disease. In this group of prethoracotomy patients and control patients, MR imaging was just as effective as CT in classification of patients as positive on negative for metastatic disease. For detection of individual pubmonary metastases, MR imaging enabled 126

#{149} Radiology

Figure nodule (arrow)

2.

Pulmonary

metastasis

from

osteogenic

(arrow) in the right middle lobe. with excellent lesion conspicuity.

sarcoma.

(a) CT scan

shows

a noncabcified

(b) STIR image (2,067/30/100) also shows the nodule At surgery, this was a metastatic lesion 15 mm in

diameter.

im-

posterior (n = 5) third of the lungs. Six of the 13 false-positive nodules core

b.

a.

detection although

of more nodules than CT, the difference was not statisticabby significant (Figs 1-6). MR imaging compared quite favorably in spite of the entrance requirement of an abnormal CT scan, which could have

biased imaging.

the

study toward CT oven MR MR imaging may be some-

what better for detection of small panacardiac metastases, which may be a blind spot for CT (Fig 3). MR images were significantly better than the plain chest radiographs for detection of individual Some MR cantly better

nodules. sequences were signifithan others. In particu-

lam, the

sequence

est

STIR

sensitivity

(82%)

had and

the

high-

a bow

false-

positive

rate

detection

of

(8%) more

and

enabled

nodules

CT,

than

although this difference was not significant (P, > .25). STIR was particularly useful in the panacardiac zone (Fig 3). The STIR sequence was statisticabby equivalent to MR imaging with all sequences taken together, a result that raises questions about the need

to use

a full set of sequences.

T2-

weighting did not enable detection of as many metastases as STIR but was still essentially equivalent to CT and not statistically different than STIR. Unenhanced Ti-weighted images were the least sensitive (P, < .01 vs MR imaging or STIR). Gadoliniumenhanced Ti-weighted images had a January

1992

study,

were

probably

enab factors. these studies less

caused

sensitive

to motion

susceptibility

sev-

artifacts

artifacts

tissue-air

by

The imagers used for operate at 0.5 T and are from

interfaces

and

the

than

soft

those

open-

ating at higher field strengths. Technicab improvements and upgrades continue to improve image quality. Motion suppression is used for T2weighted sequences. Additionally, a major operative factor is the use of the STIR sequence (17,18). This pulse sequence has additive Ti and T2 charactemistics,

eased lesion

very

high

tissues, and conspicuity.

contrast

allows easy discrimination tissues from paracamdiac, or penidiaphragmatic

a.

for

dis-

produces profound Fat suppression of diseased mediastinal, fat.

MR imaging has several other practical and theoretical advantages. A key benefit is the lack of ionizing radiation. Screening the lungs for metas-

b.

involves

significant

diation

tases

with

doses

CT

(0.5-2.0

mad [5-20

mGyl),

which

are

especially

ma-

impor-

tant because of the need for frequent examinations repeated over years (3). In patients with high-grade sarcomas, who are at great risk for pulmonary metastases

and

whose

tumors

may

have doubling times measured in weeks, screening the lungs with CT is often performed several times a year. At that rate, total radiation exposure accumulates

Figure 3. Paracardiac pulmonary metastases that were prospectively missed on CT scans but were seen with STIR images. Images from two patients show nodules in the left paracardiac zone (arrow, b and d) that blended into the cardiac contours and were not identified on CT scans (a, c) but were ules were metastatic

well seen on STIR images (b [2,067/30/100], lesions proved with surgery.

d [1,867/30/1001).

Both

nod-

quickly

intermediate of unenhanced

weighted

images

and

between Ti-

that

images but had the highest tive rate. Although it was barby helpful for detection static disease, enhancement

gadopentetate vide

potentially

patients

with

imaging detection

should be more sensitive for of small nodules near the

of the youth sarcoma.

branching vascular the center of the this was suggested

proved

in two

(14,16).

Too

were

few

in the

data

in two

was shown homogeneous

fabse-posinot panticuof metawith

cases.

did

in one lesion enhancement

essary ficity lesions

to study the utility and speciof enhancement of pulmonary in MR imaging. It is unclear #{149} Number

1

spatial

detection

1), and in an-

lesion suggested tumor a complicated postoperative collection. Further work

182

the

necrosis (Fig

with

detection MR

imaging

readily achievable. vides high contrast

pro-

other than fluid

Volume

In theory, ules

morphologic

Central

capacity tection

this time whether having more sequences available for correlation might reduce the number of falsepositive interpretations.

of STIR

dimeglumine useful

the

of lung

nod-

should

be

resolution

is adequate

of structures

several

for

milli-

meters in diameter. Doppman (16) reported excellent sensitivity

MR imaging

rather

bronchial

is nec-

for surgically carcinoid

though

tumors;

proved of

these tumors were 1 cm or smaller in diameter (J.L.D., personal communication). The excellent results of Doppat

man

et al, as well

as those

of our

previous

near lobes; statistically

studies

nodules

in our

study

perivascubam

statistical impressive

or beating cardiac

MR

and

come

analysis was

of the

to enable the moving

heart,

de-

even

respiratory

gating

were not used. Even without gating, these nodules were readily visualized. Motion of nodules during quiet breathing at MR imaging need not be deleterious;

it may

of a nodule

over

allow

several

visualization

images

and

may be preferable to the potential mismegistration of uneven breathhobds during CT (19) (Fig 4). Helical CT, during which many sections can be

et al of

several

structures pulmonary but not

central,

of many

In theory,

of MR imaging of nodules near

diaphragm

MR imaging proof soft tissues, and

is of special

because

of the lung for this issue. More sensitivity sensitivity

and

concern

obtained

during

a single

breathhold,

has the potential to improve detection of lung nodules. This study has several limitations. Because most MR images were ob-

Radiology

#{149} 127

b.

a.

nodule. (a) CT scan shows two nodules (arrows) in the right lung. No convincing evidence of a nodule is seen in the lingula on this or either adjacent section, presumably because of uneven breath holding. (b) STIR image (2,267/30/100) enables conclusive detection of the lingubar nodule missed with CT (arrow). Other lesions are clearly shown. The lesion near the left hilum was shown on an adjacent CT section. At surgery, all these lesions, including the 10-mm metastasis from the bingula, were resected. Figure

4.

Pulmonary

metastases

from

colon

cancer,

including

a lingular

tamed after the corresponding CT scans were obtained, a bias that may favor MR imaging was introduced. However, such a bias should play a small role in this study. Virtually all of the lesions missed with CT and detected with MR imaging were missed

because

they were in difficult

boca-

tions, had poor contrast with sunrounding structures, on both, not because of interval growth. An unresolved question is the sensitivity of MR imaging for depiction of nodules less

than

5 mm

in diameter.

The

pau-

city of nodules in this size range was unexpected; the reason for that is unclear. Further work, perhaps in a different population of patients, is needed to address this question. Even if MR imaging is proved less sensitive for these smallest nodules, one will have to weigh the significant radiation dose of CT against the lack of evidence that detection of these tiniest metastases influences patient sunvival. Fortunately, the heterogeneity in nodule size frequently ensures that several

nodules

will

be easily

detect-

abbe with MR imaging, enabling conrect diagnosis and facilitating management of the patient. In these cases, CT can be reserved for further chanactenization or problem solving. Issues of intenobserven variation and the effects of increased interpreter experience await further studies. Another issue

is the

false-positive

rate.

Because

they appeared normal, the control images were selected to provide a frame of reference for the readers. Therefore, further study is necessary to enable prediction of the actual false-positive rate that might result 128

#{149} Radiobostv

a. Figure 5. Pulmonary metastasis from osteogenic (arrow), which had developed since the previous (b) T2-weighted SE image (2,533/80) also shows mm in diameter was found in this location.

sarcoma.

scan was the nodule

(a) CT scan

obtained, clearly.

a tiny

nodule

in the left lower

reveals

lobe.

At surgery,

a metastasis

10

from screening with MR imaging. In the typical clinical setting with a bower prevalence of metastases, it is possible that less favorable sensitivi-

tivity in smaller nodules remains to be established. CT is an excellent modality, has been studied extensively, and is firmly entrenched as the radiobogic

ties

standard

and

specificities

will

result.

In summary, this study suggests that MR imaging has a high sensitivity for detection of pulmonary metastases

in patients

who

undergo

cura-

five resection of these lesions and has the potential to perform well in othens. MR imaging performed at beast as well as CT for nodules greater than 5 mm

in diameter.

Furthermore,

of lung

nod-

References 1.

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STIR

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(arin

Muller NL, Gamsu G, Webb WR. Pulmonary nodules: detection using magnetic resonance and computed tomography. Radiology 1985; 155:687-690. Barakos JA, Brown JJ, Brescia RJ, Higgins CB. High signal intensity lesions of the chest in MR imaging. J Comput Assist Tomogr 1989; 13:797-802. Doppman JL, Pass HI, Nieman LK, et al. Detection of ACTH-producing bronchial carcinoid tumors: MR imaging vs CT. AIR 1991; 156:39-44. Dwyer AJ, Frank JA, Sank VJ, Reinig JW, Hickey AM. Doppman JL. Short-TI inversion-recovery pulse sequence: analysis and initial experience in cancer imaging. Radiology 1988; 168:827-836. Bydder GM, Young IR. MR imaging: dinical use of the inversion recovery sequence. J Comput Assist Tomogr 1985; 9:659-675. Krudy AG, Doppman JL, Herdt JR. Failure to detect a 1.5 centimeter lung nodule by chest computed tomography. J Comput Assist Tomogr 1982; 6:1178-1180.

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ie,i,

Pulmonary metastases: MR imaging with surgical correlation--a prospective study.

The sensitivity of magnetic resonance (MR) imaging for detection of pulmonary metastases in 11 patients scheduled for thoracotomy and curative resecti...
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