Imaging of the Chest

1594 Pages·2008·97.484 MB·English

by  Nestor Luiz Muller, C. Isabela S. Silva

Imaging of the Chest
Volume I
E d i t o r s
Nestor L. Müller, MD, PhD
Professor and Chairman
Department of Radiology
University of British Columbia
Head and Medical Director
Department of Radiology
Vancouver General Hospital
Vancouver, British Columbia
Canada
C. Isabela S. Silva, MD, PhD
Research Associate
Department of Radiology
University of British Columbia and Vancouver General Hospital
Vancouver, British Columbia
Canada
Associate Editor
David M. Hansell, MD
Professor of Thoracic Imaging, Department of
Radiology, Royal Brompton Hospital, London,
England
Assistant Editors
Kyung Soo Lee, MD
Professor, Department of Radiology, Sungkyunkwan
University School of Medicine; Director of Thoracic
Imaging, Department of Radiology, Samsung
Medical Center, Seoul, Korea
Martine Remy-Jardin, MD
Professor of Radiology, Department of Radiology,
University Center of Lille; Head of Department,
Department of Radiology, University Center of
Lille, Hospital Calmette, Lille, France
FM-X4048.indd iii 1/10/2008 4:26:45 PM
1600 John F. Kennedy Boulevard
Suite 1800
Philadelphia, PA 19103-2899
IMAGING OF THE CHEST ISBN: 978-1-4160-4048-4
Copyright © 2008 by Saunders, an imprint of Elsevier Inc.
All rights reserved. No part of this book may be produced or transmitted in any form or by any
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Notice
Knowledge and best practice in this fi eld are constantly changing. As new research and experience
broaden our knowledge, changes in practice, treatment, and drug therapy may become necessary
or appropriate. Readers are advised to check the most current information provided (i) on
procedures featured or (ii) by the manufacturer of each product to be administered, to verify the
recommended dose or formula, the method and duration of administration, and contraindications.
It is the responsibility of the practitioner, relying on his or her own experience and knowledge of
the patient, to make diagnoses, to determine dosages and the best treatment for each individual
patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the
Publisher nor the Authors assume any liability for any injury and/or damage to persons or property
arising out of or related to any use of the material contained in this book.
The Publisher
Library of Congress Cataloging-in-Publication Data
Imaging of the chest / [edited by] Nestor L. Müller, C. Isabela S. Silva.—1st ed.
p. ; cm.
Includes bibliographical references and index.
ISBN 978-1-4160-4048-4 (alk. paper)
1. Chest—Imaging. 2. Chest—Diseases—Diagnosis. I. Müller, Nestor Luiz.
II. Silva, C. Isabela S.
[DNLM: 1. Diagnostic Imaging—methods. 2. Thoracic Diseases—diagnosis. WF 975 I318 2008]
RC941.I42 2008
617.5′407572—dc22 2007048871
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Developmental Editor: Kristina Oberle
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FM-X4048.indd iv 1/10/2008 4:26:46 PM
11
NNoorrmmaall CChheesstt RRaaddiiooggrraapphh
Nestor L. Müller and C. Isabela S. Silva
TECHNIQUE Patient Respiration
Projections Respiration must be suspended, preferably at full inspira-
tion. On radiographs performed at low lung volumes,
The standard radiographic views for evaluation of the
the mediastinum appears widened, the cardiopericardial
chest are the posteroanterior and lateral projections with
silhouette appears enlarged, and the pulmonary vessels
the patient standing; such projections provide the essen-
appear crowded and prominent.
tial requirement for proper three-dimensional assessment
(Fig. 1-1). In patients who are too ill to stand, anteropos-
Exposure
terior upright or supine projections offer alternative, but
considerably less satisfactory views. The anteroposterior Exposure factors should be such that there is faint visual-
projection is of inferior quality because of the shorter ization of the thoracic spine and the intervertebral discs
focal-fi lm distance, the greater magnifi cation of the heart, on the posteroanterior radiograph so that lung markings
and the restricted ability of many such patients to suspend behind the heart are clearly visible. Exposure should be
respiration or achieve full inspiration. as short as possible, consistent with the production of
adequate contrast. Exposure time should be less than
40 ms, and the maximum mean skin entrance radiation
Basic Radiographic Techniques
dose should be 0.3 mGy.1
Diagnostic accuracy in chest disease is related partly to
the quality of the radiographic images themselves. Careful Kilovoltage
attention to several variables is necessary to ensure such
A high-kilovoltage technique (115 to 150 kVp) should be
quality.
used for posteroanterior and lateral chest radiographs.1
The abbreviation kVp is the peak voltage applied across
Patient Positioning
the x-ray tube. The high kVp allows better penetration
Positioning must be such that the x-ray beam is centered of the mediastinum and shorter exposure times, thus mini-
properly, the patient’s body is not rotated, and the scapu- mizing cardiac motion artifacts and providing sharper
las are rotated suffi ciently anteriorly that they are pro- outline of the pulmonary and mediastinal structures.
jected away from the lungs. The easiest method to Because high kVp results in increased scatter radiation,
determine whether the patient is properly positioned is grids (10 : 1 or 12 : 1) are required to reduce image degra-
to assess the distance between the medial ends of the dation. Use of a grid increases contrast by removal of
clavicles (anterior structures) and the spinous processes scatter and improves the signal-to-noise ratio, particularly
of the thoracic vertebrae (posterior structures). In a prop- in the mediastinum.1
erly centered radiograph, the medial ends of the right and
left clavicles are equidistant from the spinous processes
Conventional Film-Screen Radiography
(Fig. 1-2). The American College of Radiology standards
for performance of standard chest radiography in adults Conventional chest radiography uses fi lm to capture,
specify the use of at least a 72-inch (1.8 m) tube-fi lm display, and store the images. Film has several advantages,
distance.1 including easy handling, high sensitivity, and good
3
Ch001-X4048.indd 3 1/7/2008 2:38:15 PM
4 PART ONE ● Normal Chest
A B
■ FIGURE 1-1 Normal chest radiograph. A, Posteroanterior projection. B, Lateral projection.
technique incorporates a feedback system that modulates
the intensity of the x-ray beam according to the patient’s
body habitus. Despite these developments, conventional
fi lm-screen radiography has a number of limitations and
therefore has been replaced by computed radiography
(CR) and digital radiography in many centers.
Computed Radiography and
Digital Radiography
■ FIGURE 1-2 Properly centered chest radiograph. A view from a The process of acquisition, transmission, display, and
frontal radiograph shows that the medial ends of the right and left storage of digital images has many advantages over con-
clavicles (highlighted in black) are equidistant to the spinous process ventional screen-fi lm systems.4,5 One of the most impor-
(arrow) of the vertebra at the same level, thus indicating that the
tant is its wide exposure latitude, which is 10 to 100 times
radiograph is properly centered.
greater than the widest dynamic range of screen-fi lm
systems. During digital image processing, the systems
automatically determine the range of clinically appropri-
uniformity; however, it is limited by the small exposure ate gray levels and produce an image within that range.
range over which it provides diagnostic information. The As a result, the fi nal image is virtually independent of
thorax ranges from the nearly radiotransparent lung to the absolute x-ray exposure levels. A potential disadvantage is
highly attenuating mediastinum, rib cage, and spine. Ade- that patients may receive unnecessarily high radiation
quate visualization of these various structures on conven- doses, which may not be detected because they do not
tional fi lm requires wide-latitude fi lm. Other techniques result in perceivable alterations in image quality.
that have been used include customized patient-specifi c The wider latitude of digital systems allows them to be
fi lters2 and scanning equalization radiography.3 The latter used under a much broader range of exposure conditions
Ch001-X4048.indd 4 1/7/2008 2:38:16 PM
CHAPTER 1 ● Normal Chest Radiograph 5
than possible with conventional systems and makes out the detector. The detectors in digital radiography are
them an ideal choice for applications in which exposure selenium based and provide the additional advantage
is highly variable or diffi cult to control, such as bedside of having considerably greater quantum effi ciency than
radiography. Another major advantage of digital radiogra- conventional screen-fi lm systems and photostimulable
phy is that it produces what are essentially electronic phosphor detectors do.11,12 This high detection effi ciency
images; as a result, an image may be transmitted to any allows image quality superior to that of screen-fi lm
location, displayed at multiple sites simultaneously, and systems and existing storage phosphor detectors at a com-
effi ciently archived for later reference. The images can be parable or lower radiation dose.10 The main disadvantage
distributed widely by using picture archiving and com- of digital radiography at the current time is its relatively
munications systems (PACS), displayed on video monitors high cost.
(soft copy), or printed onto fi lm or paper (hard copy).
Two main types of digital systems are available commer-
cially: systems based on photostimulable storage phos-
NORMAL ANATOMY OF THE CHEST
phor image receptors, known as CR, and systems based
on fl at-panel x-ray detectors or array of detectors that Airways
directly capture the radiographic image, known as digital
Trachea and Bronchi
radiography.
CR (storage phosphor radiography) involves the use The trachea is a midline structure, and the tracheal walls
of a reusable photostimulable phosphor plate rather than are parallel except on the left side just above the bifurca-
fi lm to record the image. Plates coated with the phosphor tion, where the aorta commonly causes a smooth indenta-
are loaded into special cassettes that are outwardly similar tion (Fig. 1-3). In older individuals, unfolding and ectasia
to screen-fi lm cassettes. During exposure, the receptor of the aorta lead to deviation of the lower part of the
stores the x-ray energy and is then scanned by a laser trachea to the right. The trachea measures 10 to 12 cm in
beam, which results in the creation of visible or infrared length and has 16 to 20 U-shaped cartilage rings on its
radiation, the intensity of which corresponds to the lateral and anterior aspects and a fi bromuscular posterior
absorbed x-ray energy. The resultant luminescence is mea- margin. Calcifi cation of the cartilage rings is a common
sured and recorded digitally.6 CR has been used mainly for normal fi nding in patients older than 40 years, particularly
bedside chest radiography because its wide dynamic range women, but it is seldom evident on radiographs (Fig. 1-4).
allows it to achieve consistent images over a wide range The upper limits of normal for coronal and sagittal diam-
of x-ray exposure.7 Storage phosphor systems have a eters of the trachea in men are 25 and 27 mm, respec-
dynamic range of approximately 1 : 10,000, as opposed to tively; in women, they are 21 and 23 mm.13 The lower
1 : 100 for standard fi lms8; that is, they are capable of pro- limit of normal for both dimensions is 13 mm in men and
ducing diagnostic images over a much broader range of 10 mm in women.13
exposure, which results in a considerable decrease in the The trachea divides into the left and right main bronchi
repeat rate for bedside chest radiographs.9 at the carina, at approximately the level of the fi fth
Other advantages of CR over the conventional fi lm- thoracic vertebra. The subcarinal angle ranges from 35 to
based system are its greater contrast resolution and suit- 90 degrees (mean, 61 degrees).14 Because of the wide
ability for computer image processing. Images have a range, measurement of the subcarinal angle is seldom
more reproducible quality, thereby resulting in a reduc- helpful in the detection of abnormalities.
tion in the retake rate. However, photostimulable phos- The right main bronchus measures approximately
phors have lower spatial resolution than conventional fi lm 2 cm in length and has a more vertical course than the left
systems do and greater sensitivity to the lower energy main bronchus does (see Fig. 1-3). It divides into the
components of the x-ray spectrum and are therefore more right upper lobe bronchus and the bronchus intermedius.
susceptible to degradation by scatter.10 Consequently, it is The bronchus intermedius continues distally for 3 to
important to use an antiscatter grid for adult portable 4 cm from the takeoff of the right upper lobe bronchus
chest radiography to adequately visualize the parenchyma and then bifurcates into bronchi to the middle and lower
and the mediastinum and to assess the location of cathe- lobes. The left main bronchus is approximately 5 cm in
ters and other devices in the mediastinum.10 length and divides into the left upper and lower lobe
A major limitation of CR is the need for separately bronchi.
reading the phosphor plate after exposure, which is time The lobar bronchi branch into segmental bronchi. Seg-
consuming not only because of the process itself but also mental bronchi are visible on chest radiographs only when
because of the necessity to bring the cassette to CR plate they are seen end-on as ring shadows or when they are
readers. Despite these limitations, CR is currently the most abnormally thickened. The most commonly seen segmen-
practical option for portable radiography.10 In most other tal bronchi on a chest radiograph are the anterior segmen-
areas of radiography, however, CR is rapidly being replaced tal bronchi of the upper lobes. These bronchi are seen as
by digital radiography.10 ring shadows adjacent to the accompanying segmental
pulmonary artery (Fig. 1-5). On an upright chest radio-
graph the diameter of the anterior segmental bronchus of
Digital Radiography
the upper lobe (approximately 5 mm) is slightly larger
Digital radiography uses a fl at-panel x-ray detector or than that of the adjacent segmental pulmonary artery. The
array of detectors to directly capture the radiographic anatomy of the segmental bronchi and smaller airways is
image numerically, thus eliminating the step of reading illustrated in Chapter 2.
Ch001-X4048.indd 5 1/7/2008 2:38:17 PM
6 PART ONE ● Normal Chest
A B
■ FIGURE 1-3 Normal trachea and main bronchi. A, View from a frontal radiograph showing that the tracheal air column is fairly straight and
located in the midline except at the level of the aortic arch (AA), where the trachea is indented and may be slightly deviated to the right. The trachea
divides into a short right main bronchus and a longer and more horizontal left main bronchus. B, Coronal reformatted image from a CT scan
demonstrating the normal anatomy of the trachea, the slight indentation at the level of the aortic arch (AA), and the main bronchi. Approximately
2 cm after its origin the right main bronchus branches into the right upper lobe bronchus and the bronchus intermedius.
(Fig. 1-6). Though variable, the common pattern is for the
KEY POINTS: TRACHEA ascending artery to subdivide into segmental branches
that supply the right upper lobe and for the descending
■ Normal diameter in men: 13 to 27 mm branch to contribute segmental arteries to the middle and
■ Normal diameter in women: 10 to 23 mm right lower lobes.
■ Normal subcarinal angle: 35 to 90 degrees
The fi rst portion of the right interlobar artery is hori-
zontal and interposed between the SVC in front and the
intermediate bronchus behind (Fig. 1-6). It then turns
sharply downward and backward and assumes a vertical
Pulmonary Arterial and
orientation within the major fi ssure (thus its name) antero-
Venous Circulation lateral to the intermediate and right lower lobe bronchi
before giving off segmental branches, one or two to the
Pulmonary Arteries
middle lobe and usually single branches to each of the fi ve
The main pulmonary artery originates in the mediastinum bronchopulmonary segments of the lower lobe.
at the pulmonary valve and extends cranially and slightly Although the course of the most proximal pulmonary
to the left for 4 to 5 cm before bifurcating within the arteries is fairly constant, the origin and branching pattern
pericardium into the shorter left and longer right arteries of the lobar and segmental arteries show considerable
(Fig. 1-6). The left pulmonary artery continues in more or variation. Despite this variation, the pulmonary arterial
less the same line as the pulmonary trunk until it reaches system is invariably intimately related to the airways and
the hilum, where it arches over the left main bronchus. divides with them, and a branch always accompanying the
Subsequently, the artery sometimes gives off a short adjacent airway down to the level of the distal respiratory
ascending branch that divides into segmental branches to bronchioles.
the upper lobe; more commonly, it continues directly into Measurements of pulmonary arterial diameter can be
the vertically oriented left interlobar artery, from which helpful in the assessment of pulmonary vascular disease.
segmental arteries to the upper and lower lobes arise Because the more proximal vessels are not well seen on
directly. The left interlobar artery lies posterolateral to the radiographs, measurement of large pulmonary arteries is
upper lobe bronchus. usually limited to the right interlobar artery. The upper
The right pulmonary artery courses behind the ascend- limit of normal of the transverse diameter of the interlobar
ing aorta before dividing behind the superior vena cava artery (measured from its lateral aspect to the air column
(SVC) and in front of the right main bronchus into ascend- of the intermediate bronchus) is 16 mm in men and 15 mm
ing (truncus anterior) and descending (interlobar) branches in women (Fig. 1-7).15 Dilation of the interlobar pulmonary
Ch001-X4048.indd 6 1/7/2008 2:38:17 PM
CHAPTER 1 ● Normal Chest Radiograph 7
A B
■ FIGURE 1-4 Tracheal and bronchial wall calcifi cation. A magnifi ed
view from a posteroanterior chest radiograph (A) in an elderly patient
shows calcifi cation of the tracheal and bronchial walls. Coronal (B) and
sagittal (C) reformatted images from a multidetector CT scan show the
extent of tracheal and bronchial calcifi cation. Airway wall calcifi cation is a
C normal fi nding in elderly patients. The patient was an 84-year-old
woman.
Ch001-X4048.indd 7 1/7/2008 2:38:18 PM
8 PART ONE ● Normal Chest
Pulmonary Veins
The pulmonary veins arise from venules that drain the
alveolar capillaries and the capillary network of the pleura.
In contrast to the pulmonary arteries, they are not associ-
ated with the airways. Although their fi nal course is vari-
able, there are usually two main superior and two main
inferior vessels, the former draining the middle and upper
lobes on the right side and the upper lobe on the left and
the latter draining the lower lobes (Fig. 1-9). The right-
sided veins course beneath the main pulmonary artery
posterior to the SVC and enter the left atrium separately.
The left-sided veins pass anterior to the descending aorta
and enter the atrium separately as on the right or join
within the pericardial cavity to enter the atrium as a
common channel. As in the pulmonary arterial system,
numerous supernumerary vessels join the veins as they
course through the lung.
Pulmonary Hila
■ FIGURE 1-5 Anterior segmental bronchus of the right upper lobe The pulmonary hila are areas in the center of the thorax
seen end-on. A view from a frontal radiograph shows a ring shadow that connect the mediastinum to the lungs. The anatomic
(curved arrow) corresponding to the anterior segmental bronchus of structures rendering the hila visible on radiographs are
the right upper lobe seen end-on and the adjacent anterior segmental
primarily the pulmonary arteries and veins, with lesser
pulmonary artery (straight arrow). The outer diameter of the bronchus on
contributions from the bronchial walls, surrounding con-
the upright chest radiograph is slightly larger than that of the adjacent
artery. nective tissue, and lymph nodes (Fig. 1-10).
On a posteroanterior radiograph the main shadow of
artery may result from increased pressure (e.g., pulmonary the right hilum is formed by the vertically oriented inter-
arterial hypertension), increased fl ow (e.g., left-to-right lobar artery. Right hilar structures immediately cephalad
shunts), or aneurysm formation (e.g., Behçet’s disease) to the interlobar artery include the ascending pulmonary
(Fig. 1-8). artery and superior pulmonary vein (Fig. 1-11). The end-on
Another measurement that can be useful is the pulmo- opacity and radiolucency of the contiguous anterior (and
nary artery–to-bronchus diameter ratio. In a study of 30 occasionally posterior) segmental artery and bronchus can
healthy individuals, the ratio on frontal radiographs was be identifi ed in approximately 80% of normal individu-
0.85 ± 0.15 (mean ± standard deviation) above and 1.34 ± als.17 On an upright chest radiograph the anterior segmen-
0.25 below the right hilar angle in the erect position (see tal bronchus normally measures approximately 5 mm in
Fig. 1-5) and 1.01 ± 0.13 above and 1.05 ± 0.13 below diameter and has a wall thickness of 1 mm or less and a
the right hilar angle in the supine position.16 Calculation diameter slightly greater than that of the adjacent artery
of these ratios is particularly helpful in the assessment of (see Fig. 1-5).
volume overload and congestive heart failure. For example, The right superior pulmonary vein can often be seen
in a study of 30 patients with volume overload complicat- as it crosses the junction of the horizontal and vertical
ing chronic renal failure, the mean artery-to-bronchus ratio limbs of the interlobar artery and the respective branches
in the erect position was 1.62 ± 0.31 above the right hilar of these vessels. The horizontally oriented inferior pulmo-
angle and 1.56 ± 0.28 below it; in patients who had conges- nary vein lies more inferiorly. The radiolucent lumen of
tive heart failure, the ratio was 1.50 ± 0.25 above and 0.87 the intermediate bronchus can be invariably identifi ed
± 0.20 below in the erect position and 1.49 ± 0.31 above medial to the interlobar artery. Occasionally, segmental
and 0.96 ± 0.31 below in the supine position.16 bronchi and arteries in the middle and lower lobes can be
seen in profi le or end-on.
On the left, the upper hilar opacity is formed by the
KEY POINTS: PULMONARY distal left pulmonary artery, the proximal portion of the
ARTERIES left interlobar artery and its segmental arterial branches,
and the left superior pulmonary vein and its major tributar-
■ Normal diameter of the right interlobar pulmonary artery: ies. Because the left pulmonary artery arches over the left
<16 mm
main and left upper lobe bronchi, the left hilum is typi-
■ Normal pulmonary artery–to-bronchus diameter ratio:
cally 1 to 2 cm higher than the highest point of the right
● Upright chest radiograph: above the right hilum, 0.85
± 0.15 hilum (right interlobar artery) (see Fig. 1-10).
Surrounding the hilar vessels and bronchi are small
● Upright chest radiograph: below the right hilum, 1.34
± 0.25 amounts of fat and small lymph nodes. They cannot nor-
● Supine chest radiograph: 1.04 ± 0.13 mally be distinguished from other structures on the radio-
graph. Enlargement of the hilar lymph nodes leads to
Ch001-X4048.indd 8 1/7/2008 2:38:19 PM
CHAPTER 1 ● Normal Chest Radiograph 9
A B
■ FIGURE 1-6 Normal anatomy of the central pulmonary arteries.
A, A maximum intensity projection image obtained from a CT scan
demonstrates that the main pulmonary artery (MPA) courses posteriorly
and branches into the right (RPA) and left (LPA) pulmonary arteries. The
right pulmonary artery branches shortly after its origin into the truncus
anterior, which courses cephalad to supply most of the right upper lobe,
and a larger right interlobar pulmonary artery (RI), which courses just
anterior and then lateral to the bronchus intermedius (BI). B, Coronal
image from a CT scan demonstrating the orientation of the right (RPA)
and left pulmonary arteries (LPA) in the same projection as the frontal
radiograph. The right pulmonary artery and the central portion of the left
pulmonary artery are in the mediastinum and therefore cannot be
identifi ed on the chest radiograph. The right pulmonary artery branches
into the truncus anterior (TA) and right interlobar pulmonary artery (RI).
C, Sagittal image demonstrating the orientation of the right and left
pulmonary arteries that corresponds to the lateral chest radiograph. The
main pulmonary artery (MPA) originates from the right ventricle (RV) and
C courses cephalad and posteriorly. AA, aortic arch; asterisk,
aortopulmonary window.
increased size and opacity of the hilum, a lobulated left pulmonary artery. The air column of the normally
contour, and obscuration of the interlobar artery (Fig. more cephalic right upper lobe bronchus can be identifi ed
1-12). Masses situated in front of or behind the hilum end-on as a rounded radiolucency in 50% of subjects,
result in increased opacity of the hilar shadow but do not whereas that of the more caudal left upper lobe bronchus
obscure the margins of the interlobar artery. This fi nding is seen in about 75%.19 The orifi ce of the right upper lobe
is known as the hilum overlay sign. bronchus is seldom as well circumscribed as that of the
The radiographic anatomy of the hila on a lateral pro- left because the latter is completely surrounded by vessels
jection is complex because the right and left hilar compo- (the left pulmonary artery above, the descending artery
nents are to a large degree superimposed (Fig. 1-13).18,19 behind, and the mediastinal component of the left supe-
The trachea is usually well seen down to the level of the rior pulmonary vein in front) whereas the former is devoid
carina. The level of the carina can be identifi ed because of vascular envelopment on its posterior aspect such that
it is the level where the air column can be seen to taper aerated upper or lower lobe parenchyma normally abuts
(Fig. 1-13). At the level of the carina the left pulmonary its wall. Consequently, clear identifi cation of the right
artery can be seen as a curved structure as it courses above upper lobe bronchial lumen en face constitutes highly
the left main bronchus and continues as the descending suggestive evidence that the airway is completely
Ch001-X4048.indd 9 1/7/2008 2:38:19 PM