Radiology

Thoracic Junpei Stephen

Ikezoe, MD2 L. Done, MD

#{149} Sadayuki #{149} Johny

Murayama, A. Verschakelen,

Bronchopulmonary CT Assessment’

sequestration.

David

Godwin,

MD

MD

Sequestration:

Computed tomographic (CT) scans of 24 bronchopulmonary sequestrations in 23 patients were reviewed. Seventeen sequestrations were diagnosed at surgery, three at angiography, and four on the basis of radiographic or CT findings combined with appropriate history. Sixteen sequestrations were intralobar, and eight were extralobar; 21 were posterobasal. Seventeen occurred on the left side and seven on the right. Anomalous systemic arterial supply was demonstrated by CT in 16 sequestrations. In the others, a systemic artery was not shown, presumably because of unfavorable onentation or small size of the vessel. The lung abnormalities shown by CT were classified into three types: A = cysts containing air or fluid (n = 8), or soft-tissue masses (n 2); B = emphysematous lung surrounding cysts, and/or soft-tissue nodules (n = 13); and C lung hypervasculanity (n = 2). In only three cases did the chest radiograph show the emphysematous lung tissue. Such emphysematous lung has rarely before been reported as a CT finding, and lung hypervascularity has not, to the authors’ knowledge, been reported. The authors conclude that CT can be helpful in the diagnosis and evaluation of bronchopulmonary

#{149} J.

MD3

Characteristic

B

from

newborn

tion is an uncommon congenital anomaly consisting of maldeveboped lung tissue that typically lacks a nor-

were more

less than 20 years old, than 20 years old.

mal connection (1-3). Theme

surgically, four on

RONCHOPULMONARY

sequestra-

to the bronchial intrabobar and

are

tree extra-

lobam forms, the intraboban form embedded in normal lung and the extrabobar form separated from adjacent lung by its own visceral pleural investment (4-7). The arterial supply is systemic,

and

venous

but

computed

features

have

small focus

tomogmaphic

been

described

series (9-18). Further, of these reports was

the the

main dem-

onstration of the systemic arterial supply, and there was little descniption of the parenchymal abnonmalities

in the

sequestered

PATIENTS

AND

in 23 patients

gathered reviewed had

METHODS

pulmonary (16

seven

bilateral

Ages

I

From

the

University

(J.I., SM., gy,

Department

J.D.G.);

Children’s

(S.L.D.);

the

(J.A.V.). requested

March 26; accepted requests to J.D.G. 2 Current address: Osaka

Department

University

Seattle

of Radiology,

K. U.

Leuven,

Leuven,

Received

January

February

14; revision

April

98195

Center,

9, 1990;

16. Address

Medical

School,

re-

received

reprint

of Radiology, Osaka,

Ja-

pan.

Index 94.15

terms:

Lung,

#{149} Lung,

CT,

abnormalities,

60.1211

60.145,

3 Current address: Kyushu University

oka,

Radiology

1990;

176:375-379

C

Japan. RSNA,

pain

and

1),

As

diagnosis,

further

CT on

confin-

three

of the

systemic

four

arterial

and

patients symptoms.

had

was

had

1),

no For not

sympproduction

were

fever

bruit (n = 1), and respiratory

tients

presenting sputum

symptoms

fatigue

tomatology

hemoptysis

(n shortness distress

1), chest of breath (n 1).

chest or constitutwo patients, sympavailable.

recurrent

Eight

on persistent

pa-

pneu-

monia.

Radiographs and CT scans were analyzed SM., J.D.G.), to the

(available in 22 patients) (available in all 23 patients) by three observers (J.I., with special attention given presence

arterial

of anomalous

supply

abnormalities

sys-

and to the parenchywithin

panenchymal

the

sequestna-

Department of Radiology, Faculty of Medicine, Fuku-

abnormalities

pulmonary at CT

types: A soft-tissue rounding

were

of the

sequestration classified

into

cysts containing air masses; B emphysema cysts and/or soft-tissue

=

three or fluid, sunnodules

or

on masses; and C hypervascularity of a region of lung (ie, dilatation of or an excess number of lung vessels connecting to a systemic artery). We defined a cyst as a complete on nearly complete ring contaming air on fluid on both. A nodule on mass was defined as a well-defined round water

having

and

represent that a cyst

aceous tissue

1990

diagnosis

stability

follow-up.

7). Other

opacity Department

the

of characteristic

radiographic

of the

The

of Radiolo-

Medical

and

intraloban

SB-05, WA

Department

Hospitals,

Belgium vision

the

Hospital

and

University

Seattle,

patients

tion.

ranged

of Radiology,

of Washington,

two

on the basis

(n (n

shown

manifestations are (a) a complex lesion containing solid or fluid components combined with emphysematous lung or (b) any basal lesion supplied by a systemic artery.

or

to have no normal cornwith the bronchial tree. In

The most common toms were cough and

mal

female),

his-

supply.

temic

institutions, were One patient

sequestrations.

with

remaining

both

sequestrations

male,

from several retrospectively.

the

Nine tional

We reviewed the CT findings in 24 patients with pulmonary sequestration and evaluated both vascular and parenchymal abnormalities.

Twenty-four

bronchognaphy

shown,

bronchoscopy, munication

(n

lung.

and and CT

were

had CT-demonstrated in

proved

with appropriate four sequestrations

mation

only

were

angiographically, of radiographic

findings combined tory. Two of these

long-term

(CT)

12 patients and 1 1 were

sequestrations

three the basis

findings

by a pulmonary vein (in the bar form) or by a systemic vein (in the extrabobar form) (4,5). Radiographic features are well known (4,8),

Seventeen

was made

is either intrabo-

return

to 71 years;

defined

higher

therefore

attenuation

not

a fluid-filled containing

fluid mass

could on

CT

as a region

cyst. highly

be mistaken scans.)

than

considered

to

(It is possible protein-

for a soft-

was

Emphysema

of abnormally

low-at-

375

Summary

of Clinical

Features

and Imaging

Findings CT Findings

Patient/Age

Clinical Findings

(y)/Sex

1/20/M 2/58/M 3/5/F 4/12/F 5/29/M 6138/M 7/71/M

Pneumonia Cysts Cysts Cysts Mass Mass Postinflammatory

Cough, sputum Cough, sputum Cough, sputum Cough, sputum Fever, fatigue Asymptomatic Asymptomatic

Diagnosis

+ +

Surgery, Clinical

AG, BG follow-up

Intra Intra

-

Surgery

+ + +

AG Surgery,

-

BG, MRI Surgery

Mass Mass Mass Abnormal vessels Cysts (left) Normal (right) Mass Cysts

B B (calc) C C

+ (calc) + + +

Surgery AG BFS Surgery

Intra Intra Intra Intra

B B A A

+ + + +

AG

Intra Intra Intna Intra Intra Extra, bronchogenic cyst, emphysema

!ntna

Intra Intra Intra

AG

Intra

emphysema

12/20/M 13/42/M 14/l9/M

Shortness Cough,

15/newborn/F

Asymptomatic

Cysts

A

-

16/44/F

Asymptomatic

Mass

B

+

Surgery, Surgery Clinical Surgery,

B

-

Surgery

Extra,

Surgery

cysts Extra, emphysema

of breath sputum

. .

18/3

wk/M

. .

22/2

wk/M

Respiratory distress Asymptomatic

23/1

1 mo/M

Cough

Note-A cysts (with or without angiography, BC bronchography, MRI = magnetic resonance imaging, 2 courtesy

of Julie

patient

Takasugi,

18 courtesy

tenuation indicate

tissue

(A that

a bulla

MD,

of Arvin

lung wall.

.

. .

Mass,

Asymptomatic ureter stone Cough, sputum

19/3/F 20/28/M 2l/newborn/M

was

Other Supporting Diagnostic Studies

Asymptomatic Asymptomatic Hemoptysis Chest pain, murmur Asymptomatic

17/14/F

fined

Anomalous Artery

A A A A A B B

change, 8/56/M 9/48/M 10/17/F 1 1/l6/M

Parenchymal Change

Radiographic Findings

B A

mass, B emphysema surrounding caic calcification, Intra intralobar + present, absent. Patients

6 courtesy

Orleans;

of David

patient

Tamas,

MD,

13 courtesy

Surgery, Surgery,

AG, AG

-

Surgery,

-

Surgery,

+

Surgery

Little

of Bruce

1,

Rock,

S. Grover,

BC

Extra, Extra,

emphysema emphysema

US

Extra,

emphysema

US

Extra,

emphysema

Extra

cysts and/or nodules, C = multiple dilated vessels, AG pulmonary sequestration, Extra = extralobar sequestration, 10 courtesy of Charles Mueller, MD, Columbus, Ohio; patient Ark; patient 9 courtesy of Robert Tarver, MD, Indianapolis; MD, Madigan Army Medical Center, Tacoma, Wash.

=

cases,

of scan-

medium was administered. In four dynamic scanning was used. Most were obtained with 10-mm collima-

were

Mass, emphysema, situs inversus Mass vs pneumonia

+

-

cyst.)

on a variety

trast cases, scans

vals

B B B

would

In

at 10-mm collimation

Mass Cysts Mass

-

pulmonary

attenuation

ners.

tion mm

all

New

B

follow-up AG

a well-de-

of low

on air-filled

patient

MD,

wall

area

CT was performed almost

Seattle;

lacking

emphysema

fluid) or soft-tissue BFS bronchoscopy, US ultrasonography,

Robinson,

well-defined the

.

.

AG

intravenous

con-

intervals, but 5-mm or 7and 5-mm or 7-mm inter-

used

in seven

children.

RESULTS Seventeen sequestrations were on the left side, and seven were on the right. Sixteen were intralobar, and eight were extrabobar (Table). Intralobar sequestration the posterobasal

was portion

confined of the

to lower

a. Figure ic scans

b. 1.

CT

show

scans

of 16-year-old

boy

systemic

artery

anomalous

ing through the chymal abnormality

pulmonary ligament. is hypervasculanity

formed.

sequestrations

with

intralobar

(arrow)

(b)

sequestration

arising

Lung window (type C-dilatation

from

the

(patient descending

demonstrates of vessels

11). aorta

that the only within lung).

(a) Dynamand

pass-

panen-

lobe, and extrabobar sequestration was located just beneath the lower lobe in four patients, in the posterior mediastinum tenor

in three,

mediastinum

in

and in the the remaining

an-

patient.

In 15 of the demonstrated systemic

other,

artery

#{149} Radiology

CT

a single anomalous (Fig 1), and in one

CT demonstrated

In 13 of these gery and/or

376

24 sequestrations,

two

16 sequestrations, angiography was

arteries. sumper-

maining

eight

shown to have one anomalous systemic artery, and one had two arteries, corresponding to those shown by

Nine

strated

systemic

In three Table), two

tions, type

CT.

cases

or more ies were demonstrated phy and/or surgery,

showed

only

one

(patients

were

5, 13, 20;

anomalous arterat angiogmaalthough CT

(Fig

2). In the

me-

detected

with

cases, arterial

surgery

demon-

supply

not

CT.

the 16 intrabobar sequestraCT demonstrated eight with A parenchymal abnormality (cysts [n = 7] [Fig 3] or soft-tissue masses [n = 1]), six with type B (emphysema surrounding cysts [n = 4] Among

August

1990

#{149}

:‘

.

,. -----

--‘-

.‘

.

TLa,fk

a.

b.

Figure

2.

shows

only

Images a single

of 29-year-old man with systemic artery (arrow).

intralobar sequestration (b) Angiogram shows

(patient 5). (a) CT scan two systemic arteries

(arrows).

Figure 5. CT scan of 14-year-old girl extralobar sequestration and multiple monany cysts (patient 17). The sequestration, actually below the lung, appears soft-tissue mass within the lung, with fluid

level.

The

with pulas a a

area of low attenuation

in

the right lung base, interpreted as emphysema, was actually composed of numerous small, aerated pulmonary cysts in the lung,

adjacent

to the extraloban

sequestration.

._

41

4.

3.

Figures 3, 4. (3) CT scan of 58-year-old man with tiple cysts with air-fluid levels (type A) are visible Takasugi, MD, Seattle.) (4) CT scan of 38-year-old

6). Sequestration David Tamas,

MD,

is demonstrated Little Rock,

as emphysema Ark.)

intralobar

sequestration

in the left lower man

with

surrounding

intralobar

nodules

(patient

lobe.

(Courtesy

2). Mul-

of Julie

sequestration (patient (type B). (Courtesy of

Figure with Dense

temic

6. CT scan of 56-year-old man intralobar sequestration (patient 8). calcification in the anomalous sys-

artery

probably

or soft-tissue nodules [n 2] [Fig 4]), and two with type C (hypervasculanity) (Fig 1). Among the eight extrabobar sequestrations,

CT

showed

only

one

with type A pamenchymal abnormality (soft-tissue mass). The remaining seven had type B abnormalities (softtissue

masses

combined

with

emphy-

sema) (Fig 5). In one of the seven (patient 17) (Fig 5), numerous small, airfilled cysts were demonstrated at pathologic examination of the right lower lobe, immediately adjacent to the extrabobar pulmonary sequestration. On CT scans, the thin walls of these cysts were not discernible, so the lung abnormality was thought to represent emphysema. In a second case (patient 16), a small extrabobar sequestration and a small fluid-filled bronchogenic cyst were found at opVolume

176

#{149} Number

2

enation within the left pulmonary ligament, accompanied by emphysema in the adjacent lower lobe. In a third case (patient ing air and fluid

20), cysts and adjacent

containem-

physematous lung were seen. Because of the adjacent emphysema, these three cases were thought to be intrabobar rather than extrabobar sequestrations before surgery. In the remaining four cases of emphysema (patients 18, 19, 21, 22), cystic masses filled with necrotic material were found in the mediastinum, accompanied by emphysema in the adjacent portion of the lung. These abnormalities were diagnosed as extraloban sequestrations or mediastinal masses preoperatively. CT findings showed no difference between the children and the younger on older adults.

arising

reflects

Radiognaphs in all malities

nia (n and

descending

showed

22 patients

available. (n

from

The were

aorta

atherosclerosis.

for

most

abnormalities whom

they

common

masses

(n

7). Less common (n = 1), dilated

=

8)

were

were

abnomor cysts pneumo-

shadows atelectasis 1), and mediastinal masses (n = 4), which were accompanied by emphysema of the adjacent lung in two. In the case of bilateral sequestrations (patient 12), the left-side anomaly manifested as cysts, but

vascular

1), postinflammatory emphysema (n

the

night-side

lesion

was

not

visi-

ble. Calcification two patients,

was detected in one within

anomalous

systemic

(Fig 6) and tered lung

in the other itself (patient

artery

at CT in the (patient

in the 9). Radiology

8)

seques-

#{149} 377

three

DISCUSSION Even though previous cases had been described, bronchopulmonary sequestration was first defined by Pryce (1,2). It is generally thought to be congenital, although some authors have argued that intmabobar sequestrations may be acquired (19). Some consider sequestration to be part of the spectrum of bronchopulmonary fomegut malformations (20), but others disagree (4). Intralobar sequestration is almost always located posterobasally in the bower lobe, with a left-side preponderance (58%)

(5);

upper-lobe

cases

are

mare.

Ex-

trabobar sequestration is typically in the lower hemithomax (3), under the lung. It has an even greater left-side preponderance (over 80%) (5). Symptoms and signs are uncommon in the extmabobam type. Even the intralobar type is often asymptomatic, and the lesion is detected as an incidental finding on radiographs (3). However, symptoms can develop at any time of life, although usually in the first 2 or 3 decades (3). Infection, hemoptysis, hemothoma.x,

and

congestive

heart

failure

resulting from left-to-left shunt may occur. A murmur is sometimes heard over the aberrant artery. Nine of our patients had no chest symptoms. The usual radiographic finding is a cystic or solid mass in the base of the lung. Other findings include normalappearing lung, hyperlucent areas, a combination of solid and cystic masses, and pneumonia (8). Most descriptions of CT findings in pulmonary sequestration have relied on single-or at most a few-cases

(9-18).

The

radiographic

ab-

normalities we observed were similar to those already described, indicating that our cases are representative of sequestration in general. Radiogmaphs in our cases showed solid masses (n = 8), cysts (n = 7), pneumonia (n 1), prominent vessels (n = 1), postinflammatory atebectasis combined with emphysema (n 1), and mediastinal masses (n = 4) (of which two were combined with adjacent lung emphysema). Systemic

Arterial

Because

identifying

Supply systemic

arterial

supply is the critical aspect of radiographic diagnosis, aomtogmaphy has been considered essential (3,4,21,22); however, CT and, more recently, MR imaging have been able to demonstrate systemic arteries in most cases (91 1,13,18,23,24). The anomalous artery (or arteries in 15% of cases) typically arise from the thoracic aorta (less often from the abdominal aorta [21]) and enter the lung via the pulmonary ligament. In our patients, one or two systemic arteries were demonstrated by CT in 16 of the 24 sequestrations. In 378

#{149} Radiology

of these

cases

(patients

5, 13, 20),

ment

of veins.

Patient

20

was

unusual

two or more arteries were found at sumgery and/or angiography (Fig 2). In a case (patient 3) in which CT did not show anomalous arteries, numerous

in that even though the lesion was tralobar, it was shown by angiography to be drained by a pulmonary vein.

small

Parenchymal

arteries

arising

from

intercostal

arteries were found at surgery. There is no clear explanation for why CT did not demonstrate anomalous vessels in the

other

seven

Likely

cases.

explana-

tions are small size of the arteries and unfavorable orientation with respect to the scanning plane. Other authors have also found that CT may fail to demonstrate arteries shown at angiography on surgery (13). Systemic arterial supply is not pathognomonic it can also occur

of sequestrationin other congenital

conditions

as arteniovenous

formation

such

or interrupted

pulmonary

artery, or as an isolated quired conditions such fection or inflammation pleura; or in the case of ated shunt (25). MR imaging has clear over CT in identifying but

the

accumulated

anomaly; in acas chronic inof the lung or a surgically creadvantages blood vessels,

experience

is still

too limited to determine whether MR imaging will ultimately prove sensitive enough to obviate angiography. Therefore, in evaluating suspected sequestration, if CT fails to show a systemic amtery, first MR imaging and then angiography might be used if needed. In a patient being considered for surgical resection, angiography is probably still essential because of the potentially senious consequences of inadvertent 5evering of a thomacic or abdominal feeding

artery

(3,22).

Many reports have documented that the systemic artery supplying a sequestration is prone to partial or complete thrombosis

and

to

premature

athero-

sclerosis (1-3,22). Such atherosclerosis can occur even in a young patient and manifest as calcification (Fig 6). Sometimes calcium is deposited in a thrombus in the systemic artery (17). Calcification can also occur in sequestration in hamartomatous

elements,

Pathologic

studies

most

or because

of dystrophic changes or secondary hyperpamathyroidism, or for unknown reasons (4,14-17). In our series, calcifications were found in two patients, in one within the anomalous artery (patient 8, Fig 6), and in the other in the sequestered lung itself (patient 9). In the latter patient, three small punctate calcifications were found along the periphery of the lesion, probably in the visceral pleura and presumably dystrophic. (The lesion was not resected, and no pathologic specimen was available.) In no case did CT demonstrate the venous drainage of the sequestration. However, even in the four cases in which dynamic scanning was used, the examination was not tailored for assess-

have

pamenchymab sequestration

common

of

air, mucus, cysts

tions

(types

A and

lined

with

respiratory

have

various

1 1 intralobar B).

amounts

(6,8).

They

vary

(round, lobulated, branching), and

cysts

and

of cartilage

and

glands

in

in

shape

size,

forming bronchi.

of a normal airway, the anthracotic

ever,

some

their

recognizable

Because

of

communication sequestration

lacks

are

epithelium

elongated, and even degree of differentia-

tion-sometimes ectatic

contain

sequestraThe

of bronchial

walls

presence

that

(3). We observed

such

but

is the

cysts

on pus in

documented

abnormalities (4,6), the

which

or multiple

numbers

mal-

Abnormalities

extensive in intralobar of single

ex-

the

the

pigmentation.

cases

lack

with typically

How-

do have

a communica-

tion with the airway that is more likely congenital than acquired (2,26). Besides the cysts, connective tissue, inflammatory cells, and alveoli may be present. The alveoli vary in degree of

differentiation

(4,6,8,13).

ten hypeninflated (6), accounting

or emphysematous for the findings

physema

in

six

questrations. festation

Emphysema of sequestration

knowledge,

been

one previous sema typically of the lesion and its cause

the

ventilation

sequestra-

can take

of

place

during

a patient

mechaniundergoing

of a sequestration

that

enters

the

of

a sequestration

portions

with of

easily leave the sebecause a direct is lacking. Such and trapping of

observed

been

resection air

in only

lung tissue merges collateral ventilation

(6,8,26). Air cannot questration, however, bronchial connection collateral ventilation has

se-

as a CT manihas, to our

emphasized

the sequestration

cal

of em-

16 intrabobar

in intrabobar

tion abnormal normal tissue,

air

are of-

report (13). This emphyinvolves at least the part bordering normal lung, is probably trapping of air

Because

(27).

of

They

(27).

more

The

central,

cystic

usually

comes from a congenital connection to a bronchus,

or acquired although

Felson (4) believes that air in cysts can also come from collateral ventilation. Although hypervascularity in the lung our

has

been

as a sign diographs gorgement is the

it has

of perfusion The

hypervasculanity

evidence

circulation two

not,

described

of sequestration or CT scans. and profusion lung

pressures.

tional

been

result

sistance ing

illustrated,

knowledge,

The

to

before

on plain ravascular enwe observed

of

the

low-re-

at systemic patients

manifest-

(type C) had addiof sequestration in that

August

1990

bronchi

were

seen

to be displaced

around the abnormality py or bronchography.

Compared

at bronchoscoFurther, CT

they

were

warrant

not

extensive

classifying had or parenchymab lesions would

chial these

to the type I lesion (1), that is, systemic

enough

described arterial

to

by Pryce supply to

normal lung tissue. Some, but not all, authors consider systemic antemialization of normal lung as distinct from true sequestration, but related (25,28). Surprisingly, all but one extralobar sequestration had pulmonary cysts (n 1) or emphysema (n 6) in the lung tissue immediately adjacent to the sequestration. Therefore, the lung pamenchymal

abnormalities

were

classi-

fied as type B. According to the study of Stocker and Kagan-Hallet (7), three of 15 cases of extrabobar sequestration involved a bronchogenic cyst adjacent to the

sequestered

lung.

The

presence

of pulmonary cysts or emphysema in our patients may be unrelated to the extrabobar sequestration; however, it cannot be neglected because of the high

association

tration

with

of extrabobar

seques-

congenital

anoma-

other

lies, including diaphragmatic cystic adenomatoid malformation, plications of the gastrointestinal

tracheoesophageal pulmonary venous emphysema

fistula, return,

(3,7,29).

hernia, dutract,

anomalous and bobar

Further,

in some

patients, features of intrabobar and extrabobar sequestration may coexist (5). Because of the associated cystic abnormality with adjacent emphysematous lung, three of the eight extrabobar sequestrations

in

tinguishable

from

tion. The

our

principal

respect

in

the

normally

indis-

of CT with

obscured

aphragm.

of

attenuation

by the

Further,

in showing

lung

areas

of ab-

in lung

mediastinum

CT is more

that

#{149} Number

supply

to the

sematous

to

a sequestra-

left

atrium

(30).

Not

components

(23)

sia,

cystic

adenomatoid

or show

malformation,

bronchiectasis,

scess,

arteniovenous

ic arterial

fistula,

supply

lung. Identifying arterial supply limit

the

system-

diagnosis,

shown

by CT.

abnor-

Even

and

surgery

can

be

and

that

this

show

either

obviated

in

information

temic

a cystic

or

associated with lesion supplied

artery.

2

11.

12.

13.

14.

17.

18.

20.

an

can

help establish the diagnosis. Sequestration should be considered when CT lung lesion or any basal

10.

19.

asymptomatic patient. We conclude that CT provides a unique view of the variable pathologic anatomy of bronchopulmonary sequestration

AJ.

though

some cases will undoubtedly still require angiography or resection and pathologic examination for definitive diagnosis, CT may permit a sufficiently confident diagnosis so that angiognaphy

Chest

as does

to the parenchymal

mabities

Miller

16.

anomalous systemic to the abnormality helps

differential

attention

and

21.

22.

23.

24.

complex

emphysema by a sys-

2.

3.

.

58:457-467. Pryce DM, Sellors TH, Blair LC. Intralobar sequestration of lung associated with abnorma! pulmonary artery. Br J Surg 1947; 35:1829. Savic B, Birtel FJ, Tholen W, Funke HD,

28.

Knoche

R.

30.

en

and

Thorax 4.

5.

cases, it in

of 540

report published

of sevcases.

Minor

CR,

Buschi

visualization

DR, Kane

in “intralobar

29.

PE, Free

pulmonary

EA, Taybi

H.

sequestration.”

Sys-

Dis

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or di-

effective

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demonstrating it in both our whereas radiography showed only

CT, MR imaging at demonstrating

is its supe-

indicate emphysema. In only three of the 13 sequestrations in which emphysema was present was it recognized on radiographs. CT is also better than radiogmaphy in depicting the lung bases, where most sequestrations occur, since on cross-sectional images the lung is not

tration

scans

sequestra-

radiography detection

low

were

advantage

to plain

mionity

series

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tion (23,24). even showed

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