Chest Radiology

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CHEST RADIOLOGY: Primary function of the airways: To conduct air to the alveolar surface, where gas transfer takes place between inspired air and blood of the alveolar capillaries Lungs are subdivided into 3 zones: 1. CONDUCTING ZONE - composed of airways whose walls do not contain alveoli - walls are thick enough that gas cannot diffuse into the adjacent lung parenchyma - it includes the trachea, bronchi and membranous (non-alveolated) bronchioles 2. TRANSITIONAL ZONE - carries out both conductive and respiratory functions - it consists of the respiratory bronchioles and alveolar ducts - alveolar ducts conduct air to the most peripheral portion of the lung. - Alveoli that arise from the walls of these airways also serve in gas exchange 3. RESPIRATORY ZONE - consists of the alveoli whose primary function is the exchange of gases between air and blood

The respiratory zone together with the transitional zone constitutes the LUNG PARENCHYMA The cornerstone of radiologic diagnosis is the CHEST RADIOGRAPH The most satisfactory basic or routine radiographic views for evaluation of the chest are: 1. posteroanterior and 2. left lateral projections The optimal chest radiograph is obtained  in the postero-anterior (PA) view  at a target-to-film distance of 72 inches  with the patient in the upright position  at maximum inspiration ADEQUATE PENETRATION BY RADIATION • Thoracic spine shld be barely seen thru the heart • bronchovascular structures can usually be seen thru the heart • spine appears to be darker caudally. This is due to more air in lung in the lower lobes and less chest wall. • Sternum shld be seen edge on • Posteriorly there should be two sets of ribs

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2nd indication = when pneumothorax is suspected and the visceral pleural line is not visible 2. Valsalva and Muller maneuvers - may aid in determining thevsacukar or solid nature of intrathoracic mass 3. Bedside radiography -In patients who are too ill to stand, anteroposterior (AP) upright or supine projections offer an alternative -

Non-standard chest radiography LORDOTIC PROJECTION: It is advocated in 3 situations: 1. for improving visibility of the lung apices, superior mediastinum and thoracic inlet 2. for locating a lesion by parallax 3. for identifying the minor fissure in these suspected cases of atelectasis of the right middle lobe LATERAL DECUBITUS - it is particularly helpful for the identification of small pleural effusions - it is also useful to demonstrate a change in position of an air fluid level in a cavity - to ascertain whether a structure that forms part of a cavity represents a freely mowing intracavitary loose body(fungus ball)

OBLIQUE PROJECTION - useful in locating a disease process ( pleural plaque) SPECIAL RADIOGRAPHIC TECHNIQUES: 1. Inspiratory-Expiratory radiography - main indication is the investigation of air trapping either general or local i. General air trapping = exemplified by asthma or emphysema ii. Local air trapping = there is bronchial obstruction, or lobar emphysema

COMPUTED TOMOGRAPHY Most common indication for the used of CT scan 1. Evaluation of suspected mediastinal abnormalities identified on standard chest radiograph 2. Search for occult thymic lesions 3. determination of the presence and extent of neoplastic 4. search for diffuse or central calcification in a pulmonary nodule Miscellaneous indications: 1. assisting in the percutaneous biopsy of a lesion such as mediastinal, pleural or pulmonary masses 2. localization of loculated collections of fluid within the pleural space 3. assessment of the size and configuration of the thoracic aorta Main indication for the use of HRCT 1. diagnosis of bronchiectasis

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2. detection of parenchymal lung disease MAGNETIC RESONANCE IMAGING: - plays an important role in the evaluation of the abnormalities of the great vessels, mediastinum, hila and chest wall. ULTRASONOGRAPHY - assessment of pleural effusion and distinction of effusions from solid pleural lesions - assessment of the diaphragm - guide to needle biopsy and catheter placement ANATOMY: Please review the chest anatomy

ATELECTASIS - state of incomplete expansion of a lung or any portion of it - loss of lung volume (collapse) CAUSES OF COLLAPSE • Intrinsic mass: primary or metastatic neoplasms or eroding lymph nodes • Intrinsic stenosis: TB, inflammatory processes, fracture of a bronchus • Extrinsic pressure:

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enlarged lymph nodes, mediastinal tumor, aortic aneurysm, cardiac enlargement Bronchial plugging: FB or mucus accumulation

DIRECT SIGNS OF COLLAPSE • Displaced septa à most reliable sign • Loss of aeration • Vascular & bronchial signs à crowding INDIRECT SIGNS OF COLLAPSE • Elevation of a leaf of diaphragm • Shift of the mediastinal structures toward the side of the affected lobe • Ipsilateral decrease in size of the thoracic cage • Compensatory hyperaeration of the uninvolved lobes • Hilar displacement -most important indirect sign of collapse LUNG HERNIATION • More common in left side collapse • 3 main locations: 1. anterior to the ascending aorta – most common 2. lower thorax behind the heart 3. under the arch of aorta TYPES 1. Resorption / obstructive atelectasis

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- occurs when communication between the trachea and alveoli is obstructed- may be intrinsic, caused by a tumor, foreign body, inflammatory disease, heavy secretions - extrinsic pressure on bronchi caused by tumor or enlarged nodes or bronchial constriction secondary to inflammatory disease 2. Passive atelectasis - intrapleural abnormalities - caused by space occupying process that can compress the lung - pneumothorax, pleural fluid, diaphragmatic elevation, herniation of the abdominal viscera into the thorax, large intrathoracic tumors 3. Compressive atelectasis - intrapulmonary abnormalities - is a secondary effect of compression of normal lung by a primary, space-occupying abnormality - bullous emphysema, lobar emphysema 4. Adhesive atelectasis - occurs when the luminal surfaces of the alveolar walls stick together - hyaline membrane disease, pulmonary embolism, acute radiation pneumonitis, uremia 5. Cicatrization atelectasis - is primarily the result of fibrosis and scar tissue formation in the interalveolar and interstitial space - classic cause of cicatrizing atelectasis - TB - histoplasmosis PNEUMONIA:

Classification: 1. Lobar pneumonia 2. Lobular pneumonia 3. Interstitial pneumonia

Complication of Pneumonia: 1. Cavitation - organisms Staph aureus Streptococci Gr(-) bacilli Anaerobes - types a. Lung abscess – single well defined mass often with air fluid levels. b. Necrotizing pneumonia - small lucencies or cavities c. Pulmonary gangrene - sloughed lung 2. Pneumatoceles - subpleural collections of air which result from alveolar rupture - thin walled - seen in children - organisms Staph aureus

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3. Hilar and mediastinal adenopathy - TB and fungi 4. Pleural effusion and empyema 5. Other complications ARDS Bronchiectasis Recurrent pneumonitis Summary of clinical clues to the etiology of pneumonia 1. Previously well community acquired - 50-70% Strep pneumoniae - Mycoplasma pneumoniae - virus or legionella pneumophila 2. Hospital acquired - gr(-) Pseudomonas aeruginosa Klebsiella pneumoniae Escherichia coli Enterobacter species 3. Alcoholism - Most common - Pneumococcus - Frequent - Gram (-), anaerobes, S. aureus 4. Diabetes mellitus - gram (-), S. aureus 5. Altered consciousness and coma - gram(-), anaerobes 6. Postinfluenza - Staphyloccus aureus 7. Chronic bronchitis with exacerbation - Haemophilus influenzae Summary of radiographic clues to the etiology of pneumonia

1. “Round” pneumonia Streptococcus pneumoniae 2. Complete lobar consolidation Streptococcus pneumoniae, pneumoniae Other gram (-) bacilli

Klebsiella

3. Lobar enlargement Klebsiella pneumoniae, Staphylococcus aureus Haemophilus influenzae 4. Bilateral pneumonia (bronchopneumonia)\ Pneumococcus –still common Staphylococcus aureus 5. Interstitial pneumonia Virus, Mycoplasma pneumoniae 6. Septic emboli S. aureus 7. Empyema or bronchopleural fistula S. aureus, Gr(-)bacilli, anaerobes 8. Cavitation S. aureus, gr(-) bacilli, anaerobic bacteria Streptococcus 9. pulmonary gangrene Klebsiella pneumoniae, Escherichia coli Haemophilus influenzae, M. tuberculosis 10. pneumatoceles S. aureus, gr(-) bacilli, H. influenzae, M. tuberculosis, measles 11. lymphadenopathy

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M. tuberculosis, pneumoniae

fungi,

virus,

Mycoplasma

PNEUMONIAS CAUSED BY GRAM (+) BACTERIA 1. Streptococcus pneumoniae Most common community acquired pneumonia More common in adults Radiograhic features Lower lobes Consolidation Lobar or sublobar Round pneumonia in children 2. Staphylococcus aureus More common in infants and children Radiograhic features in children Consolidation Lower lobes Pneumatoceles Radiograhic features in adults Bilateral Cavitation Empyema 3. Streptococcus pyogenes Radiograhic features Consolidation Segmental Lower lobes

Effusion

PNEUMONIAS CAUSED BY GRAM (-) AEROBIC ORGANISMS 1. Klebsiella pneumoniae Middle age, elderly patients Chronic lung disease and alcoholic patients Radiologic features Lobar consolidation Bulging fissures Cavitation Pulmonary gangrene 2. Escherichia coli Direct extension from GI / GU tract Secondary to bacteremia Radiologic features Necrosis, multiple cavities Lower lobes 3. Pseudomonas aeurginosa Hospitalized, debilitated patients Tracheostomy tubes and suction devices Radiologic features Lower lobes, consolidation Rapid spread to both lungs Multiple irregular nodules Cavitation 4. Haemophilus influenzae

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COPD Bronchopneumonia Radiographic features Homogeneous segmental Lower lobes

Lobar and right sided atelectasis (children) Anterior segment of the upper lobes (adult) Pleural involvement Pleural effusion is more common in adult Slow resolution may occur in 3-9 months

TUBERCULOSIS  Usually deposited in the middle and lower lobes  Primary TB remains clinically silent  Development of delayed hypersensitivity occurs 1- 3 weeks after inoculation  PPD is positive By 3weeks PRIMARY TB Ghon focus Initial focus of parenchymal disease Ranke complex Combination of Ghon focus and affected lymph nodes Radiologic manifestations Parenchymal involvement air-space consolidation Rt upper lobe – most common (adult) Right middle lobe – least common Lymph node involvement Hilar and mediastinal –right paratracheal region (children) Airway involvement

POST PRIMARY TB  Pulmonary involvement increases  Often cavitation occus  Bronchogenic spread  Pleural involvement and / or empyema  With bronchopleural fistula  Tendency to localized in the apical and posterior segment of the upper lobes  Focal areas of consolidation  Cavities occurs  Apical and posterior segments of upper lobes  Superior segments of the lower lobes  Tuberculoma  Upper lobe, right more often than the left DISSEMINATED TB 1. BRONCHOGENIC - Occurs when exudate from a cavity or small area of caseation drains into a bronchus - Aspirated into previously unaffected areas, On the same side On the opposite side

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2. HEMATOGENEOUS - Leads to miliary TB Extrapulmonary lesions thru out the body - Acute massive hematogeneous Spread causes miliary TB - Chronic spread in smaller amount Results in the chronic extrapulmonary foci 3. LYMPHATIC - Common in primary TB Responsible for involvement with subsequent enlargement of hilar and mediastinal node ( children) - In adults, hilar and mediastinal nodes Primary infection Reactivation Pulmonary neoplasms I. Benign tumors 1. Hamartomas Characteristics Acquired Tissues normal to organ Disorganized growth 5%-8% solitary pulmonary nodules Clinical 30-70 years Asymptomatic Pathology Cartillage Fat Fibrous tissue

Radiologic features Solitary well-defined pulmonary nodules CA++ 10 % to 15% CT- fat and calcium (25%)

II. Malignant tumors 1. Adenocarcinoma - Most common of the bronchogenic tumors - Most common type found in women - non-smokers Clinical features Occasionally asymptomatic Pathologic features Slow growing Metastasize early Association with fibrosis Peripheral, subpleural Radiographic features Peripheral with lobulated or irregular margins Solitary nodule or mass Spiculated border Pleural retraction or tethering Hilar or perihilar mass Parenchymal mass with hilar or mediastinal lymphadenopathy

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One third of all lung cancers Ectopic parathormone production Pathologic features Central, endobronchial Local mestastases to lymph nodes Central necrosis 2. Bronchioloalveolar carcinoma Subtype of adenocarcinoma Clinical features Severe bronchorrhea Radiographic features Solitary nodule Most common Hazy, ill-defined “ground-glass” on CT Air bronchogram Consolidation Multiple nodules 3. Squamous-Cell Carcinoma - 2nd most common - Predominantly in men - Peak incidence at the age of 60 yrs - Strong association with cigarette smoking - Most common cause of Pancoast tumor - Most common type of lung CA to hypercalcemia Clinical Features Best prognosis

Radiologic features Two thirds central Endobronchial lesion best seen on CT Atelectasis of lung or lobe Postobstructive pneumonitis One third peripheral Thick-walled, cavitary mass Solidary nodule

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Superior Sulcus Carcinoma (Pancoast tumor) Clinical features Pain Horner’s syndrome Bone destruction Atrophy of hand muscles Pathologic features Most common squamous cell Invasion Chest wall Base of neck Brachial plexus Vertebral bodies and spinal canal

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Sympathetic ganglion Subclavian artery Radiologic features Apical mass or asymmetric thickening Bone destruction MRI Multiplanar imaging Local extension 4. Small Cell Carcinoma - Most common lung CA to cause superior vena cava obstruction - Most common lung CA to cause Cushing’s syndrome and secretion of inappropriate antidiuretic hormone (SIADH) Clinical features Most aggressive Strongest association with smoking Poorest survival 15% to 20% of cancers Treated with chemotherapy Pathologic features Large central mass Tumor necrosis Radiographic features Arises in association with proximal airways Lobar and main bronchi Centrally located tumor Hilar or perihilar mass Massive adenopathy, often bilateral Lobar collapse Rare-peripheral nodule

5. Large-Cell Undifferentiated Carcinoma Characteristics 2%-5% of lung cancers Strong association with cigarette smoking Rapid growth Early metastases Poor prognosis Pathologic features Peripheral Large, > 4 cm Radiologic features Large bulky peripheral mass Necrosis Pleural involvement with effusion More aggressive and spread early Peripheral > 4 cm Paraneoplastic syndromes associated with bronchogenic carcinoma Hypercalcemia Ectopic adrenocorticotropic hormone production Syndrome of inappropriate secretion of antidiuretic hormone Eaton-Lambert syndrome (peripheral neuropathy with myasthenia-like symptoms) Acanthosis nigricans Hypertrophic osteoarthropathy

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Lobar, segmental, subsegmental bronchi Obstructive pneumonia and atelectasis Peripheral 20% of cases Slow growth if typical Large and faster growth if atypical Calcification seen on CT OTHER MALIGNANT TUMOR 1. Carcinoid Tumors Characteristics Arise from neuroendocrine cells Type 1, typical carcinoid Type 2, atypical carcinoid Low-grade malignancy in type 1 Good prognosis Clinical features Medium age -50 Males and females equally affected Cough, hemotysis Rarely Cushing’s syndrome Pathologic features Small cells Neuroscretory granules Atypical carcinoids Peripheral 10% of cases Metastasize in 40% to 50% of cases Radiographic features Central 80% of cases

2. Hodgkin’s disease Clinical features Bimodal age-distribution Young adults Elderly men Mass in neck or groin Systemic symptoms – ‘B’ classification Survival of 75% - stage 1 and II radiotherapy alone Radiographic features CT for staging 85% - thoracic involvement Multiple lymph-node groups Anterior mediastinum most common Lung involvement Primary-lung hdogkin’s rare Nodules,masses Perihilar Cavitation Air bronchograms Follow-up Recurrence adjacent to radiation portal Pericardial nodes

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MRI Differentiates residual from recurrent tumor from fibrosis T2 weighed Fibrosis – low SI Tumor – bright SI Eggshell calcification in nodes 3. Non-Hodgkin’s lymphoma Clinical features Low grade Older patients Generalized lymphadenopathy Asymptomatic Intermediate and high grade Younger patients Treatment with aggressive chemotherapy Immunocompromised hosts AIDS Transplant recipients <50% intrathoracic involvement Radiologic features Similar to Hodgkin’s disease Chest-wall involvement More common Direct extension or primary site Pleura Direct extension Localized plaque-like seeding Pleural effusions-lymphatic obstruction Lung parenchyma

Primary extranodal site Mass with air bronchogram Multiple masses or consolidation Follow up Localized recurrence Within 2 years Radiation pneumonitis and fibrosis 6 to 8 weeks posttreatment Conforms to portal Consolidation with air bronchograms Fibrosis Loss of volume Linear opacities Traction bronchiectasis 4. Metastatic disease – hematogenous spread CT High sensitivity, low specificity, false positives owing to intraparenchymal lymph nodes, granulomas Both lungs, lower lobes Periphery Round, well marginated Variable doubling times Ca++ Primary bone and cartilage tumors Mucinous adenocarcimonas Cavitation Metastatic squamous cell Solitary pulmonary nodule <10% of cases

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If squamous cell, likely a lung primary

Thyriod Breast Colon Radiographic features Atelectasis Hilar Mass

5. Metastatic disease- lymphangitic spread Characteristics May result from hematogenous spread Primary sites Lung Breast Upper-abdominal malignancy More commonly bilateral Radiographic features Chest radiograph Reticulonadar pattern Kerley B lines Pleural effusion (60%) Adenopathy (25%) High resolution CT Nodular thickening of bronchovascular bundles Polygonal arcades Beaded septal thickening

7. Metastatic disease – intrathoracic adenopathy Sites of primary malignancy Genitourinary Head and neck Breast Skin (melanoma) Radiographic features Adenopathy ± parenchymal metastases

6. Metastatic Disease – endobronchial metastases Site of primary malignancy Kidney Melanoma

3. Ideal position of the chest tube - chest tube placed to evacuate a pneumothorax should ideally be placed with its tip in the non-dependent part of the pleural space

Location of ICU tubes: 1. Tip of the endotracheal tube - tip should be about 4 cm the tracheal carina 2. Tip of the nasogastric tube - tip and sideport of the NGT should be positioned distal to the esophagogastric junction and proximal to the gastric pylorus

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- chest tube placed to evacuate a pleural fluid should be positioned in a dependent portion of the pleural space

- a balloon on the catheter inflates during diastole, improving myocardial perfusion by increasing blood flow through the coronary arteries; the balloon deflates during systole. - tip of IABP should be seen at the junction of the aortic arch and descending thoracic aorta, just distal to the origin of the left subclavian artery

4. Best position of the central venous catheter - used primarily to administer fluid and medication - to provide vascular access for hemodialysis - if pressure measurements are going to be obtained tip of the catheter must be proximal to the venous valves - a well positioned central venous catheter projects over the silhouette of the superior vena cava, in zone demarcated superiorly by the anterior 1st rib and clavicle and inferiorly by the top of the right atrium

Chronic Obstructive Pulmonary Disease 1. Emphysema Pathology Centrilobular (central lobule) Panlobular (entire lobular) Paraseptial (distal lobule, subpeural) Paracicatricial (around scars)

5. Tip of the Swan-Ganz catheter - used to monitor pulmonary capillary wedge pressure - to measure cardiac output in patients suspected of having left ventricular dysfunction -tip should be positioned within the right or left main pulmonary arteries or in one of their large lobar branches 6. Intraaortic ballon pump - cardiac assist device positioned in the descending thoracic aorta via a femoral arterial approach

Clinical features Cigarette smoking Dyspnea Chronic airflow obstruction (↓ FEV1, ↑ TLC, ↑ RV, ↓ DLCO) Radiologic features Overinflation Low, flat diaphragm Increased retrosternal clear space Emphysema as Seen on HRCT Centrilobular Multiple small areas of low attenuation No walls

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Upper lobes Panlobular Fewer and smaller vessels Lower lobes Paraseptal Subpleural and along fissures Thin walls Single row Paracicatricial Usually focal Associated with scars 2. Chronic Bronchitis Clinical and pathologic features Clinical definition Pathology-mucous-gland hyperplasia Radiographic features Normal Thickened bronchial walls End-on ring shadows Tram lines (in profile) Overinflation 3. Asthma Clinical pathologic features Reversible bronchospasm Two thirds atopic Active inflammation of the airways Radiographic features Uncomplicated

Normal in majority Signs of hyperinflation Bronchial-wall thickening HRCT Broncial-wall thickening and mild dilation of bronchi

Complicated Pneumonia Lobar or segmental atelectasis Allergic bronchopulmonary aspergillosis (ABPA) Mucoid impaction Pneumomediastinum Pneumothorax BRONCHIECTASIS

Causes of Bronchiectasis Infection Viral (RSV, adenovirus, mycoplasma) Tuberculosis Chronic or recurrent bacterial infections Recurrent aspiration pneumonia Deficiency in host defense Agammaglobulinemia Granulomatous disease of childhood Abnormalities of cartilaginous structure Williams-Campbell syndrome Abnormal mucus production Cystic fibrosis

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Abnormal ciliary clearance Dyskinetic cilia syndrome Kartegener’s syndrome Bronchial obstruction Allergic bronchopulmonary aspergillosis (ABPA) Noxioux fume inhalation Pulmonary fibrosis Traction bronchiectasis Radiation fibrosis Sarcoidosis Idiopathic pulmonary fibrosis Classification of broncheictasis 1. Cylindrical - Bronchi are minimally dilated, have straight regular outlines and end squarely and abruptly - Average number of bronchial divisions is 16 microscopically (17-20 bronchial divisions normally) 2. Varicose - Dilation of bronchus with sites of relative construction, bulbous appearance - Average number of bronchial divisions: 8 3. Cystic or saccular - Ballooned appearance, air/fluid levels - Average number of bronchial divisions: 4 Radiographic features of bronchiectasis

- Thick-walled bronchus larger in diameter than accompanying pulmonary artery - Dilated and thick walled bronchi in the periphery of the lung Cylindrical broncheictasis Smooth dilation of bronchus with lack of tapering “Tram-lines” when seen on plane of scan “Signet ring” when seen in cross section Varicose bronchiectasis Bulbous appearance of bronchus May mimic cylindrical broncheictasis in crosssection Cystic broncheictasis String or cluster of cysts with discernable walls Air/fluid levels within cysts HRCT Air trapping • refers to the abnormal retention of gas within the lung following expiration. • On HRCT, the lung parencyhma remains lucent on expiration, while normal lung areas show increased attenuation. Inspiration scans can be completely normal in air trapping. • Air trapping therefore cannot be diagnosed on inspiration scans; lung inhomogeneity during inspiration scans can be interpreted as mosaic perfusion. Traction bronchiectasis

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• • • •

refers to bronchial dilation that occurs in patients with lung fibrosis or distorted lung architecture. Traction on the bronchial walls due to fibrous tissue reults in irregular bronchial dilation (bronchiectasis). Usually segmental and subsegmental bronchi are involved, but small periperhal bronchi or bronchioles may also be affected. Commonly associated with honeycombing

Centrilobular nodules • Nodules as small as 1-2 mm in diameter can be detected by HRCT. • Nodules can be classified according to their appearance such as well-defined (likely interstitial) or ill-defined (likely air-space) or classified according to their distribution in relation to other lung structures (i.e. perilymphatic, random, or centrilobular). Randomly distributed nodules • Random nodules are usually well-defined and appear diffuse, but uniform in distribution.

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Exudative pleural effusions occur when pleural membranes or vasculature are damaged or disrupted therefore leading to increased capillary permeability or decreased lymphatic drainage.

Ground-glass opacity • is a non-specific term that refers to the presence of increased hazy opacity within the lungs that is not associated with obscured underlying vessels (obscured underlying vessels is known as consolidation). • It can reflect minimal thickening of the septal or alveolar interstitium, thickening of alveolar walls, or the presense of cells or fluid filling the alveolar spaces. • In an acute setting, it can represent active disease such as pulmonary edema, pneumonia, or diffuse alveolar damage.

Perilymphatic nodules • Perilymphatic nodules are usually well-defined and occur in relation to the lymphatics. They often affect the pleural surfaces and the peribronchovascular, interlobular septa, and centrilobular interstitial components.

Honeycombing • suggests extensive lung fibrosis with alveolar destruction and can result in a cystic appearance on gross pathology. • can be diagnosed via HRCT by the presence of thichwalled, air-filled cysts, usually between the size of 3mm to 1cm in diameter.

Pleural effusions • Transudative pleural effusions are formed when normal hydrostatic and oncotic pressures are disrupted.

Lymphadenopathy • Enlargement of hilar or mediastinal lymph nodes can be symmetric or asymmetric.

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It can represent hematogenous metastasis, a primary carcinoma, or other pathology.

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• Mosaic perfusion / attenuation • refers to areas of decreased attenuation which results from regional differences in lung perfusion secondary to airway disease or pulmonary vascular disease. • Distribution is often patch, hence the designation "mosaic." • Often with mosaic perfusion, the pulmonary arteries will be reduced in size in the lucent lung fields thus allowing mosaic perfusion to be distinguished from ground-glass opacity Interlobular septal thickening • is commonly seen in patients with interstitial lung disease. • On HRCT, numerous clearly visible septal lines usually indicates the presence of some interstitial abnormality. • Septal thickening can be defined as being either smooth, nodular or irregular and each likely represents a different pathologic process. Tree-in-bud

appearance represents dilated and fluid-filled (i.e. pus, mucus, or inflammatory exudate) centrilobular bronchioles. Abnormal "tree-in-bud" bronchioles can be distinguished from normal centrilobular bronchioles by their more irregular appearance, lack of tapering or knobby/bulbous appearance at the tip of their branches. The "tree-in-bud" distribution is often patch throughout the lung.

Patterns of Opacities in Infiltrative Lung Disease Nodular or reticular nodular pattern (Small Rounded Opacities) Silicosis Coal worker’s pneumoconiosis Hypersensitivity pneumonitis Histiocystosis X Lymphangitic carcinomatosis Sarciodosis Pulmonary alveolar microlithiasis Linear Pattern (Small Irregular, Reticular Opacities) Idiopathic pulmonary fibrosis (UIP) (IPF) Chronic interstitial pneumonias (DIP, LIP, BIP) Sarciodosis Radiotion fibrosis Fibrosis associated with collagen vascular disease Asbestosis Drug reactions

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Lymphangitic carcinomatosis Cystic Pattern IPF (honeycombing) Lymphangioleiomyomatosis Histiocytosis X

Ground-Glass Attenuation Hypersensitivity pneumonitis DIP, IPF Alveolar proteinosis Parenchymal consolidation (air-space or alveolar disease) Bronchiolitis obliterans organizing pneumonia Chronic eosinophilic pneumonia Bronchioloalveolar carcinoma Lymphoma Alveolar proteinosis Vasculitis Pulmonary hemorrhage Septal Lines Lymphangitic carcinomatosis CHF – interstitial edema Zonal Preference Upper Zones

Silicosis Coal worker’s pneumoconiosis Sarcoidosis Ankylosing spondylitis Histiocytosis X Lower Zones Chronic interstitial pneumonias IPF Asbestosis Fibrosis due to collagen vascular disease Central Pulmonary edema Pulmonary alveolar proteinosis Some lymphangitic tumors (Kaposi’s) Peripheral Chronic interstitial pneumonias, IPF Bronchiolitis obliterans-organizing pneumonia Chronic eosinophilic pneumonia Pleural Disease Pneumothorax Histiocytosis X End-stage honeycombing Pleural Effusion Lymphangioleiomyomatosis Collagen vascular disease Lymphangitic carcinomatosis Pulmonary edema Pleural Thickening

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Asbestosis (plaques or diffuse) Collagen vascular disease Lung Volumes Reduced Idiopathic pulmonary fibrosis Chronic interstitial pneumonias Asbestosis Collagen vascular disease Normal Sarcoidosis Histiocytosis Increased lymphangioleoiomyomatosis High-resolution CT-Linear Opacities Thickening of bronchovascular bundles (axial) Interlobular septal thickening (septal lines) Intralobular interstitial thickening Honeycombing Subpleural lines Centrilobular abnormalities MEDIASTINUM: 1. Anterior Mediastinum Boundaries - anteriorly by the sternum - posteriorly by the anterior margins of the pericardium, aorta, and brachiocephalic vessels Normal structures - Thymus gland - Lymph nodes

- Fat - Internal mammary vessel Differential diagnosis of anterior mediastinal masses - Thymoma - Lymphoma - Germ cell neoplasms - Thyroid abnormalities

2. Middle Mediastinum Boundaries - By posterior margin of anterior division and anterior margin of posterior division Normal structures Heart and pericardium Ascending and transverse aorta Brachiocephalic vessels SVC and IVC Main pulmonary vessel Trachea and main bronchi Lymph nodes Fat Differential diagnosis of middle mediastinal masses Lymphanedopathy Bronchogenic cyst Vascular abnormalities Pericardial cyst

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Tracheal tumor

3. Posterior Mediastinum Boundaries Bounded anteriorly by the posterior margins of the pericardium and great vessels and posteriorly by the thoracic vertebral bodies Normal structures Descending thoracic aorta Esophagus Thoracic duct Azygous/hemiazygous Autonomic nerves Lymph nodes Fat Differential diagnosis of posterior mediastinal masses Neurogenic tumors Paravertebral abnormalities Vascular abnormalities Esophageal abnormalities Lymphadenopathy

Neurenteric cyst Bochdalek hernia Extramedullary hematopoeisis Thymoma Demographics Age Usually 40-60; unusal in patients less than 30 Gender Male and females equally Associations Myasthenia gravis, hypogammaglobulinemia, red cell aplasia Descriptive features Thymoma (noninvasive) Well-defined, round, soft tissue, density mass, usually located anterior to the junction of the heart and great vessels Curvilinear calcification in 20% Invasive thymoma Additional findings of invasion of adjacent mediastinal structures, chest wall invasion, or contiguous spread along pleural surfaces (usually unilaterally) Hodgkin’s lymphoma Demographics Age Bimodal distribution, with initial peak in young adults and second peak after age 50 Gender

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Male predominance, especially among youngest patients Descriptive features Variable appearance, ranging from a single spherical soft tissue mass to a large lobulated mass Margins may be well-defined or irregular The mass may be homogenous or heterogenous soft tissue attenuation Calcification is rare in untreated cases

Thyroid Masses Demographics Age – usually >30 years of age Gender- female predominance Descriptive features CXR features - Well-defined mass that extends from above the thoracic inlet - Displacement and/or compression of the trachea - Foci of calcification may occasionally be visible

Germ-cell neoplasms Demographics Age Young patients, usually third decade Gender Malignant germ cell neoplasms –male predominance Descriptive features Benign GCN (Teratoma, Dermoid Cyst) Heterogenous, predominantly cystic mass with solid components Well-defined margins Calcification common Presence of fat is suggestive; identification of a tooth, while rare, is diagnostic Malignant GCN(seminoma, choriocarcinoma, Embryonal cell carcinoma, Yolk sac tumor) Heterogenous solid mass Irregular margins Calcification uncommon

CT features - Continuity with the cervical thyroid gland - Foci of high attenuation on noncontrast images - Intense enhancement following intravenous contrast administration - Cystic areas and foci of calcification are common Bronchogenic Cyst Demographics Age – often seen on younger patients but may be detected at any age Gender – males and females equally Descriptive features - Subcarinal or right paratracheal location - Well-defined homogenous mass with imperceptible walls - Fluid or soft-tissue attenuation on CT - Variable appearance on MRI, depending on cyst contents low signal on T1 and bright on T2 or

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bright signal or T1 and bright on T2 (if cyst contains mucin, protein or hemorrhage

MR characteristics similar to those of nerve sheath tumor PLEURA

Neurogenic tumors Demographics Age- usually occur in younger patients first 4 decades of life Gender- males and females equally affected Descriptive features Nerve sheath tumors Round, homogenous, paraspinal mass May be associated with widening of the neural foramen MRI: slightly brighter than muscle on T1 and very bright on T2 homoegenous enhancement following gadolinium administration Sympathetic chain tumors Fusiforms, homogenous parspinal mass May be associated with vertebral body erosion

Radiologic featuers of pneumothorax Standard radiographs Visceral pleural line separated from chest wall by gas space devoid of vessels Apex when upright Lung opaque only with complete collapse Tension Mediastinal shift Depression of hemidiaphragm Supine Medial recess-juxtacardiac Deep sulcus sign Subpulmonic Retrocardiac lucent triangle medially Ancillary views Expiratory Decubitus Pitfalls Skinfolds Clothing Tubing artifacts Bullae CT

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More sensitive in detection of small pneunothoraces More accurate in determining size Malignant Mesothelioma Clinical features Rare – 2000 to 3000 cases per year 80% - history of asbestos exposure 30 to 40 year latency 6th to 8th decades of life Men more than women – 4:1 Symptoms Chest pain Dyspnea; weight loss Pathologic features Types Epithelial (50%) Sarcomatous Mixed Gross fetures Encasement of lung Growth of tumor into lung, chest wall, mediastinum, diaphragm Radiologic features Standard radiographs Diffuse pleural thickening Nodular Encases lung Pleural effusion Pleural mass

Decrease in size of hemithorax, shift of mediastinum to affected side Plaques CT Staging Extent Chest wall, mediastinal diaphragmatic invasion MR Improved staging

Pleural metastases Origins Lung Breast Ovary Stomach Lymphoma Manifestation Maligant effusion Diffuse thickening Focal seeding BENIGN VS MALIGNANT NODULE Benign Malignant Shape Round irregular Size < 3 cm > 3 cm Spiculation absent present Margins well defined ill defined

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Calcification present Cavitation absent Doubling time < 1 mo or > 2 yrs

absent present > 1 mo or < 2 yrs

MEDIASTINAL VS PULMONARY MASS MEDIASTINAL MASS PULMONARY MASS Epicenter in the mediastinum Epicenter in lung Obtuse angle w/ the lung Acute angle w/ the lung (-) air bronchogram (+) air brochogram Smooth and sharp margins Irregular margins Movement w/ swallowing Movement w/ respiration Bilateral unilateral Radiologic signs

1. air bronchogram—indicates a parenchymal process, including nonobstructive atelectasis, as distinguished from pleural or mediastinal processes 2. deep sulcus sign on a supine radiograph—indicates pneumothorax 3. Golden S sign -indicates lobar collapse caused by a central mass, suggesting an obstructing bronchogenic carcinoma in an adult 4. Hampton’s hump—pleural-based, wedge-shaped opacity indicating a pulmonary infarct

5. silhouette sign—loss of the contour of the heart, aorta or diaphragm allowing localization of a parenchymal process (eg, a process involving the medial segment of the right middle lobe obscures the right heart border, a lingular process obscures the left heart border, a basilar segmental lower lobe process obscures the diaphragm)