Thoracic Imaging

211 Pages·2014·23.48 MB·English

by  Copley

SECOND EDITION

illustrated

clinical
cases
Thoracic Imaging
SECOND EDITION
S J COPLEY
MD FRCP FRCR
Consultant Radiologist and Reader in Thoracic Imaging
Imperial College Healthcare Trust, Hammersmith Hospital, London, UK
J P KANNE
MD
Chief of Thoracic Imaging, University of Wisconsin School of Medicine, Madison, WI, USA
D M HANSELL
MD FRCP FRCR
Professor of Thoracic Imaging, Royal Brompton Hospital, London, UK
CRC Press
Taylor & Francis Group
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CONTENTS
Preface iv
List of Abbreviations v
Glossary vi
Clinical Cases 1
Further Reading & Useful Websites 201
Index 202
PREFACE
Thoracic imaging plays a part in the assessment of patients in a wide variety of
disciplines, not just respiratory medicine. The chest radiograph is a ubiquitous first-
line investigation in many acutely ill patients, and the accurate interpretation of such
a relatively humble technique still remains a challenge. The radiographic findings may
guide further more sophisticated imaging techniques such as computed tomography
(CT). Advances in CT technique, such as high-resolution CT (HRCT), have led to
increased sensitivity for the detection of pulmonary disease and increased specificity for
diagnosis. Multidetector CT (MDCT) allows for much faster scanning times, multiplanar
reconstructions and optimisation of intravenous contrast enhancement.
Radiation dose is always a consideration in CT, particularly in children and young
adults; however, recent and future advances should make this less of an issue. Dual source
CT (DSCT) was initially designed to decrease gantry rotation time by utilizing two
orthogonal x-ray beams and detectors simultaneously rotating around the patient. A spin
off from this technology was the use of x-ray beams of different energy, so called dual
energy CT (DECT). DECT uses the different absorption characteristics of photons of
different energy (keV) to improve differentiation of various tissues, particularly following
intravenous contrast enhancement, and clinical applications include the assessment of
lung perfusion, particularly in the context of thromboembolic disease.
Advances in nuclear medicine, such as positron emission tomography (PET) and CT/
PET, have had a large impact on the assessment and staging of many cancers, especially
lung cancer. The role of magnetic resonance imaging (MRI) is expanding, and MR
pulmonary venography, assessment of the heart and aorta, staging of some thoracic
neoplasms and assessment of pulmonary ventilation with radiolabelled helium are
increasingly common.
This book is primarily aimed at medical students and physicians and surgeons with an
interest in thoracic imaging, and the cases included in this book vary from very simple
to more demanding and esoteric cases that will challenge even experienced radiologists.
Thus in some cases the diagnosis is straightforward, while others are more complicated
and designed to demonstrate the intricacies of the more sophisticated techniques, such
as CT, MRI and CT/PET, and hopefully encourage further reading. Radiologists in
training will also find the book useful as a self-assessment exercise before their specialist
examinations.
iv
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LIST OF ABBREVIATIONS
AAT alpha-1-antitrypsin HIV human immunodeficiency virus
ABPA allergic bronchopulmonary HPOA hypertrophic osteoarthropathy
aspergillosis HRCT high-resolution computed
AIDS acquired immunodeficiency tomography
syndrome Ig immunoglobulin
AP antero–posterior projection IPAH idiopathic pulmonary arterial
(chest radiography) hypertension
ARDS acute respiratory distress IPF idiopathic pulmonary fibrosis
syndrome JVP jugular venous pressure
AVM arteriovenous malformation Kco gas transfer coefficient adjusted
c-ANCA cytoplasmic antineutrophil for accessible alveolar volume
cytoplasmic autoantibodies KS Kaposi’s sarcoma
CD4 surface antigen on helper T LAD left anterior descending artery
lymphocytes LAM lymphangioleiomyomatosis
CF cystic fibrosis MAC Mycobacterium avium complex
CLE congenital lobar emphysema MDCT multidetector computed
COP cryptogenic organising tomography
pneumonia MRI magnetic resonance imaging
CPAM congenital pulmonary airway NTM nontuberculous mycobacteria
malformation PA postero–anterior projection
CRP C-reactive protein (chest radiography)
CT computed tomography PAH pulmonary arterial hypertension
CTPA computed tomography pCO partial pressure of carbon
2
pulmonary angiography dioxide
DAD diffuse alveolar damage PE pulmonary embolus
DECT dual energy computed PET positron emission tomography
tomography PLCH pulmonary Langerhans cell
DLco histiocytosis
(or TLco) total diffusion coefficient for PMF progressive massive fibrosis
carbon monoxide pO partial pressure of oxygen
2
DNA deoxyribonucleic acid PR3 proteinase 3
DSCT dual source computed RDS respiratory distress syndrome
tomography RV residual volume
ECG electrocardiogram SVC superior vena cava
ESR erythrocyte sedimentation rate TB tuberculosis (Mycobacterium
FDG fluorodeoxyglucose tuberculosis)
FEV forced expiratory volume in 1 TLC total lung capacity
1
second UIP usual interstitial pneumonia
FVC forced vital capacity V–Q ventilation–perfusion
GM-CSF granulocyte–macrophage colony (scintigraphy)
stimulating factor WHO World Health Organization
Hb haemoglobin
v
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GLOSSARY
Air trapping Cyst
Abnormal retention of air within the A thin-walled (<3 mm thick), well-
lung on expiration. Seen on expiratory defined air- or fluid-containing lesion.
CT as areas showing less than normal Normally refers to an air-filled lesion
increase in attenuation and little or no on HRCT.
decrease in size.
Emphysema
Architectural distortion Permanent, abnormal enlargement
Abnormal displacement of pulmonary of airspaces distal to the terminal
structures (bronchi, vessels, fissures) bronchiole, with destruction of alveolar
resulting in a distorted appearance of walls (pathology definition). Seen on
lung anatomy. Most frequently seen in HRCT as decreased attenuation areas
fibrotic lung disease. of destruction, usually without visible
walls.
Bronchiectasis
Irreversible bronchial dilation which Expiratory CT
is localised or diffuse. Bronchial wall HRCT scans performed during end-
thickening and mucus impaction are expiration to demonstrate air trapping.
often seen in both large and small
airways. Ground-glass opacity/opacification
A hazy increase in lung density on
Centrilobular HRCT which does not obscure the
A structure (bronchiole or artery) or margins of bronchovascular structures. A
disease process which involves the nonspecific finding which can represent
centre of the secondary pulmonary interstitial thickening or fibrosis,
lobule. airspace filling or a combination of
both.
Consolidation
An increase in lung opacity,
demonstrated on radiographs or CT, HRCT
that results in obscuration of underlying The principle of high-resolution
vessels or bronchial margins. Represents computed tomography involves the
replacement of alveolar air by fluid, use of very thin (1 mm) sections and
cells or other material. Should be a high spatial frequency algorithm
differentiated from ground-glass opacity to produce highly detailed images of
(which is grey, rather than white) the lung parenchyma. Most modern
in which there is no obscuration of multidetector scanners acquire a
bronchovascular margins. volumetric data set, from which very
thin reconstructions can be routinely
obtained.
vi
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Honeycombing Multidetector CT (MDCT)
Multiple, often adjacent, cystic The principle of helical or spiral CT
airspaces ranging in size from a few involves continuous rotation of x-ray
millimetres to several centimetres in beam and detectors around the patient
diameter, bounded by clearly-defined while the table moves through the
walls (which are often thick, reflecting x-ray gantry to produce a volumetric
the fibrous nature of the walls). data set. Any scan acquired on this type
Honeycombing usually results from, and of scanner will be ‘helical’ or ‘spiral’.
is associated with, pulmonary fibrosis. Multidetector CT involves multiple
rows of detectors which allow larger
Interlobular septum and interlobular septal anatomical areas to be covered in
thickening shorter time frames.
A connective tissue structure which
marginates the pulmonary lobule Nodule
and contains veins and lymphatics. A small focal opacity of varying size –
These septa measure about 0.1 mm may be well defined or have indistinct
in thickness and are not usually seen margins.
in healthy subjects. The septa can
be abnormally thickened by fibrosis, Opacification
oedema or cells, allowing them to be Indicates an increase in attenuation
visualised (most conspicuous in the or density of the lung parenchyma
periphery of the lung). This sign is the (normal lung is near black) and includes
equivalent of the radiographic Kerley consolidation (white lung) and ground-
‘B’ line. glass opacity (grey lung).
Interstitium Peribronchovascular interstitium
The fibrous supporting structure of the The connective tissue which encloses
lung parenchyma. the bronchi and hilar vessels and
extends from the pulmonary hila into
Intralobular interstitium and intralobular the lung periphery.
interstitial thickening
The fine interstitial network within the Peribronchovascular thickening
secondary pulmonary lobule (excluding Thickening of the peribronchovascular
the interlobular septa). Not normally interstitium resulting in apparent
visible on HRCT but when thickened thickening of the bronchial wall and
results in a very fine reticular or ‘net- increase in size of the pulmonary
like’ appearance. arteries. The thickening can be smooth
or nodular.
Mosaic attenuation
Inhomogeneity of lung attenuation.
Most frequently encountered in
airways disease, but may reflect vascular
obstruction or patchy infiltrative lung
disease.
vii
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Pulmonary lobule Window level and window width
Smallest unit of lung marginated by Each CT section is a matrix of
connective tissue septa. The pulmonary three-dimensional elements (voxels)
lobules are usually bounded by containing a measurement of x-ray
interlobular septa containing veins and attenuation, arbitrarily expressed
lymphatics and supplied by bronchioles as Hounsfield units (HU): water
and arteries which are within the measures 0 HU, air -1000 (so that
centre of the structure. A single lobule lung parenchyma is approximately
is made up of a variable number of -600), fat -80 HU, soft tissue 40–80
acini, is roughly polyhedral in shape and HU, and bone 800 HU. In order to
measures 1–2.5 cm in diameter. display images of such varying densities,
appropriate window settings need to
Terminal bronchiole be used, depending on the density of
The last purely conducting airway that interest. The window width determines
does not participate in gas exchange. the number of HU to be displayed,
with any densities greater than the
Traction bronchiectasis upper limit displayed as white and any
Bronchial dilation and irregularity below the limit as black. Between these
caused by surrounding retractile two limits, the densities are displayed
pulmonary fibrosis. as different shades of grey. The median
density is the window centre or level.
Tree-in-bud
Filling of bronchioles by fluid, pus or
mucus, resembling a branching tree
about to bud. Usually seen in the lung
periphery.
For further explanation of these and other terms used in thoracic imaging, see:
Hansell DM et al. (2008). Fleischner Society: Glossary of Terms for Thoracic Imaging.
Radiology 246:697–722.
viii
QUESTION 1
1 A 21-year-old female from Zambia presented with a fever, night sweats and
malaise. She had developed the symptoms several weeks before presentation. On
examination she was not clubbed and had a slight pyrexia (37.5°C). She was not
immunocompromised (CD4 count normal) and had a mild leucocytosis. Her chest
radiograph is shown (1).
1
i. What are the possible diagnoses?
1
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