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 exchange3. RESPIRATORY ZONE

- consists of the alveoliwhose 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 and2. 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 RADIATIONThoracic spine shld be barely seen thru the heartbronchovascular structures can usually be seen thru the heartspine 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 onPosteriorly there should be two sets of ribs

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Non-standard chest radiographyLORDOTIC 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 parallax3. 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

- 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

COMPUTED TOMOGRAPHYMost common indication for the used of CT scan

1. Evaluation of suspected mediastinal abnormalities identified on standard chest radiograph

2. Search for occult thymic lesions3. determination of the presence and extent of

neoplastic4. 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 masses2. localization of loculated collections of fluid within

the pleural space3. assessment of the size and configuration of the

thoracic aorta

Main indication for the use of HRCT1. diagnosis of bronchiectasis2. detection of parenchymal lung disease

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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 : enlarged lymph nodes, mediastinal tumor, aortic aneurysm, cardiac enlargement

Bronchial plugging : FB or mucus accumulation

DIRECT SIGNS OF COLLAPSEDisplaced septa à most reliable signLoss of aerationVascular & bronchial signs à crowding

INDIRECT SIGNS OF COLLAPSEElevation of a leaf of diaphragmShift of the mediastinal structures toward the side of the affected lobeIpsilateral decrease in size of the thoracic cageCompensatory hyperaeration of the uninvolved lobesHilar displacement -most important indirect sign of collapse

LUNG HERNIATIONMore common in left side collapse3 main locations:1. anterior to the ascending aorta – most common2. lower thorax behind the heart3. under the arch of aorta

TYPES 1. Resorption / obstructive atelectasis - 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

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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 tumors3. 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, uremia5. 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 pneumonia2. Lobular pneumonia3. Interstitial pneumonia

Complication of Pneumonia:1. Cavitation - organisms

Staph aureusStreptococciGr(-) bacilliAnaerobes

- typesa. Lung abscess – single well defined mass often with air fluid levels.b. Necrotizing pneumonia- small lucencies or cavitiesc. Pulmonary gangrene- sloughed lung

2. Pneumatoceles- subpleural collections of air which result from alveolar rupture- thin walled- seen in children

- organismsStaph aureus

3. Hilar and mediastinal adenopathy- TB and fungi

4. Pleural effusion and empyema5. Other complications

ARDSBronchiectasisRecurrent pneumonitis

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Summary of clinical clues to the etiology of pneumonia1. Previously well community acquired

- 50-70% Strep pneumoniae- Mycoplasma pneumoniae- virus or legionella pneumophila

2. Hospital acquired- gr(-) Pseudomonas aeruginosa

Klebsiella pneumoniaeEscherichia coliEnterobacter 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 pneumonia1. “Round” pneumonia

Streptococcus pneumoniae 2. Complete lobar consolidation

Streptococcus pneumoniae, Klebsiella pneumoniae

Other gram (-) bacilli

3. Lobar enlargementKlebsiella pneumoniae, Staphylococcus aureusHaemophilus influenzae

4. Bilateral pneumonia (bronchopneumonia)\Pneumococcus –still commonStaphylococcus aureus

5. Interstitial pneumoniaVirus, Mycoplasma pneumoniae

6. Septic emboliS. aureus

7. Empyema or bronchopleural fistulaS. aureus, Gr(-)bacilli, anaerobes

8. CavitationS. aureus, gr(-) bacilli, anaerobic bacteriaStreptococcus

9. pulmonary gangreneKlebsiella pneumoniae, Escherichia coliHaemophilus influenzae, M. tuberculosis

10. pneumatocelesS. aureus, gr(-) bacilli, H. influenzae, M.

tuberculosis,measles

11. lymphadenopathyM. tuberculosis, fungi, virus, Mycoplasma

pneumoniae

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PNEUMONIAS CAUSED BY GRAM (+) BACTERIA1. Streptococcus pneumoniaeMost common community acquired pneumoniaMore common in adults

Radiograhic featuresLower lobesConsolidationLobar or sublobarRound pneumonia in children

2. Staphylococcus aureusMore common in infants and children

Radiograhic features in children ConsolidationLower lobesPneumatoceles

Radiograhic features in adults BilateralCavitationEmpyema

3. Streptococcus pyogenes Radiograhic features

ConsolidationSegmental Lower lobesEffusion

PNEUMONIAS CAUSED BY GRAM (-) AEROBIC ORGANISMS1. Klebsiella pneumoniaeMiddle age, elderly patientsChronic lung disease and alcoholic patients

Radiologic featuresLobar consolidationBulging fissuresCavitationPulmonary gangrene

2. Escherichia coliDirect extension from GI / GU tractSecondary to bacteremia

Radiologic featuresNecrosis, multiple cavitiesLower lobes

3. Pseudomonas aeurginosaHospitalized, debilitated patientsTracheostomy tubes and suction devices

Radiologic featuresLower lobes, consolidationRapid spread to both lungsMultiple irregular nodulesCavitation

4. Haemophilus influenzaeCOPDBronchopneumonia

Radiographic featuresHomogeneous segmental Lower lobes

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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 TBGhon focus

Initial focus of parenchymal diseaseRanke complex

Combination of Ghon focus and affected lymph nodes

Radiologic manifestationsParenchymal involvement

air-space consolidationRt upper lobe – most common (adult)Right middle lobe – least common

Lymph node involvementHilar and mediastinal –right paratracheal region

(children)Airway involvement

Lobar and right sided atelectasis (children)Anterior segment of the upper lobes (adult)

Pleural involvementPleural effusion is more common in adult

Slow resolution may occur in 3-9 months

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 TB1. BRONCHOGENIC - Occurs when exudate from a cavity or small area of caseation drains into a bronchus - Aspirated into previously unaffected areas,

On the same sideOn the opposite side

2. HEMATOGENEOUS - Leads to

miliary TBExtrapulmonary lesions thru out the body

- Acute massive hematogeneousSpread causes miliary TB

- Chronic spread in smaller amountResults in the chronic extrapulmonary foci

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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 infectionReactivation

Pulmonary neoplasmsI. Benign tumors1. HamartomasCharacteristics

AcquiredTissues normal to organDisorganized growth5%-8% solitary pulmonary nodules

Clinical30-70 yearsAsymptomatic

PathologyCartillageFatFibrous tissue

Radiologic featuresSolitary well-defined pulmonary nodulesCA++ 10 % to 15%CT- fat and calcium (25%)

II. Malignant tumors1. Adenocarcinoma

- Most common of the bronchogenic tumors- Most common type found in women - non-smokers

Clinical featuresOccasionally asymptomatic

Pathologic featuresSlow growingMetastasize earlyAssociation with fibrosisPeripheral, subpleural

Radiographic featuresPeripheral with lobulated or irregular marginsSolitary nodule or massSpiculated borderPleural retraction or tetheringHilar or perihilar massParenchymal mass with hilar or mediastinal lymphadenopathy

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2. Bronchioloalveolar carcinomaSubtype of adenocarcinomaClinical features

Severe bronchorrheaRadiographic featuresSolitary nodule

Most commonHazy, ill-defined“ground-glass” on CTAir bronchogram

ConsolidationMultiple 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 cause hypercalcemia

Clinical FeaturesBest prognosisOne third of all lung cancersEctopic parathormone production

Pathologic featuresCentral, endobronchialLocal mestastases to lymph nodesCentral necrosis

Radiologic featuresTwo thirds central

Endobronchial lesion best seen on CT Atelectasis of lung or lobe

Postobstructive pneumonitisOne third peripheral

Thick-walled, cavitary massSolidary nodule

Superior Sulcus Carcinoma(Pancoast tumor)Clinical features

PainHorner’s syndromeBone destructionAtrophy of hand muscles

Pathologic featuresMost common squamous cellInvasion

Chest wallBase of neckBrachial plexusVertebral bodies and spinal canal

Sympathetic ganglionSubclavian artery

Radiologic featuresApical mass or asymmetric thickeningBone destruction

MRI Multiplanar imaging Local extension

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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 featuresMost aggressiveStrongest association with smokingPoorest survival15% to 20% of cancersTreated with chemotherapy

Pathologic featuresLarge central massTumor necrosis

Radiographic featuresArises in association with proximal airways

Lobar and main bronchi Centrally located tumor Hilar or perihilar massMassive adenopathy, often bilateralLobar collapseRare-peripheral nodule

5. Large-Cell Undifferentiated CarcinomaCharacteristics

2%-5% of lung cancersStrong association with cigarette smokingRapid growthEarly metastasesPoor prognosis

Pathologic featuresPeripheralLarge, > 4 cm

Radiologic featuresLarge bulky peripheral massNecrosisPleural 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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OTHER MALIGNANT TUMOR1. Carcinoid TumorsCharacteristics

Arise from neuroendocrine cellsType 1, typical carcinoidType 2, atypical carcinoidLow-grade malignancy in type 1Good prognosis

Clinical featuresMedium age -50Males and females equally affectedCough, hemotysisRarely Cushing’s syndrome

Pathologic featuresSmall cellsNeuroscretory granulesAtypical carcinoids

Peripheral 10% of cases Metastasize in 40% to 50% of casesRadiographic featuresCentral

80% of casesLobar, segmental, subsegmental bronchiObstructive pneumonia and atelectasis

Peripheral20% of casesSlow growth if typicalLarge and faster growth if atypical Calcification seen on CT

2. Hodgkin’s diseaseClinical featuresBimodal age-distribution

Young adults Elderly menMass in neck or groinSystemic symptoms – ‘B’ classificationSurvival of 75% - stage 1 and II radiotherapy aloneRadiographic featuresCT for staging85% - thoracic involvementMultiple lymph-node groupsAnterior mediastinum most commonLung involvement

Primary-lung hdogkin’s rare Nodules,masses Perihilar Cavitation Air bronchogramsFollow-up Recurrence adjacent to radiation portal Pericardial nodesMRIDifferentiates residual from recurrent tumor from fibrosisT2 weighed

Fibrosis – low SI Tumor – bright SI

Eggshell calcification in nodes

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3. Non-Hodgkin’s lymphomaClinical featuresLow grade Older patients Generalized lymphadenopathy

AsymptomaticIntermediate and high grade

Younger patients Treatment with aggressive chemotherapyImmunocompromised hosts AIDS Transplant recipients <50% intrathoracic involvementRadiologic featuresSimilar to Hodgkin’s diseaseChest-wall involvement More common Direct extension or primary sitePleura Direct extension Localized plaque-like seeding Pleural effusions-lymphatic obstructionLung parenchyma Primary extranodal site Mass with air bronchogram Multiple masses or consolidationFollow up Localized recurrence Within 2 yearsRadiation pneumonitis and fibrosis

6 to 8 weeks posttreatment

Conforms to portalConsolidation with air bronchogramsFibrosis

Loss of volume Linear opacities Traction bronchiectasis

4. Metastatic disease – hematogenous spreadCT

High sensitivity, low specificity, false positives owing to intraparenchymal lymph nodes, granulomas

Both lungs, lower lobesPeripheryRound, well marginatedVariable doubling timesCa++

Primary bone and cartilage tumors Mucinous adenocarcimonas

Cavitation Metastatic squamous cell

Solitary pulmonary nodule <10% of cases If squamous cell, likely a lung primary

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5. Metastatic disease- lymphangitic spreadCharacteristics May result from hematogenous spread Primary sites Lung Breast Upper-abdominal malignancy More commonly bilateralRadiographic featuresChest radiograph

Reticulonadar patternKerley B linesPleural effusion (60%)Adenopathy (25%)

High resolution CT Nodular thickening of bronchovascular bundles Polygonal arcades Beaded septal thickening

6. Metastatic Disease – endobronchial metastasesSite of primary malignancy

KidneyMelanomaThyriodBreastColon

Radiographic featuresAtelectasisHilar Mass

7. Metastatic disease – intrathoracic adenopathySites of primary malignancy

GenitourinaryHead and neckBreastSkin (melanoma)

Radiographic featuresAdenopathy± parenchymal metastases

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

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

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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 obtainedtip 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

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- 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

Chronic Obstructive Pulmonary Disease1. EmphysemaPathologyCentrilobular (central lobule)Panlobular (entire lobular)Paraseptial (distal lobule, subpeural)Paracicatricial (around scars)

Clinical featuresCigarette smokingDyspneaChronic airflow obstruction (↓ FEV1, ↑ TLC, ↑ RV, ↓ DLCO)Radiologic featuresOverinflationLow, flat diaphragmIncreased retrosternal clear space

Emphysema as Seen on HRCTCentrilobular

Multiple small areas of low attenuationNo wallsUpper lobes

PanlobularFewer and smaller vesselsLower lobes

ParaseptalSubpleural and along fissuresThin wallsSingle row

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ParacicatricialUsually focalAssociated with scars

2. Chronic BronchitisClinical and pathologic features

Clinical definitionPathology-mucous-gland hyperplasia

Radiographic featuresNormalThickened bronchial walls

End-on ring shadowsTram lines (in profile)

Overinflation

3. AsthmaClinical pathologic featuresReversible bronchospasmTwo thirds atopicActive inflammation of the airwaysRadiographic featuresUncomplicated

Normal in majoritySigns of hyperinflationBronchial-wall thickeningHRCT Broncial-wall thickening and mild dilation of

bronchi

ComplicatedPneumoniaLobar or segmental atelectasisAllergic bronchopulmonary aspergillosis (ABPA)

Mucoid impactionPneumomediastinumPneumothorax

BRONCHIECTASISCauses of BronchiectasisInfection

Viral (RSV, adenovirus, mycoplasma)TuberculosisChronic or recurrent bacterial infections

Recurrent aspiration pneumoniaDeficiency in host defense

AgammaglobulinemiaGranulomatous disease of childhood

Abnormalities of cartilaginous structureWilliams-Campbell syndrome

Abnormal mucus productionCystic fibrosis

Abnormal ciliary clearanceDyskinetic cilia syndrome

Kartegener’s syndromeBronchial obstructionAllergic bronchopulmonary aspergillosis (ABPA)Noxioux fume inhalationPulmonary fibrosisTraction bronchiectasisRadiation fibrosis

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SarcoidosisIdiopathic pulmonary fibrosis

Classification of broncheictasis1. 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 lungCylindrical 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 bronchiectasisBulbous appearance of bronchusMay mimic cylindrical broncheictasis in cross-section

Cystic broncheictasisString or cluster of cysts with discernable wallsAir/fluid levels within cysts

HRCTAir 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• 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

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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.

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.

Pleural effusions• Transudative pleural effusions are formed when normal

hydrostatic and oncotic pressures are disrupted. • 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.

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 thich-walled, air-filled cysts, usually between the size of 3mm to 1cm in diameter.

Lymphadenopathy• Enlargement of hilar or mediastinal lymph nodes can

be symmetric or asymmetric. • 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 DiseaseNodular or reticular nodular pattern (Small Rounded Opacities)SilicosisCoal worker’s pneumoconiosisHypersensitivity pneumonitisHistiocystosis XLymphangitic carcinomatosisSarciodosisPulmonary alveolar microlithiasis

Linear Pattern (Small Irregular, Reticular Opacities)Idiopathic pulmonary fibrosis (UIP) (IPF)Chronic interstitial pneumonias (DIP, LIP, BIP)SarciodosisRadiotion fibrosisFibrosis associated with collagen vascular diseaseAsbestosisDrug reactionsLymphangitic carcinomatosis

Cystic PatternIPF (honeycombing)LymphangioleiomyomatosisHistiocytosis X

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Ground-Glass AttenuationHypersensitivity pneumonitisDIP, IPFAlveolar proteinosisParenchymal consolidation (air-space or alveolar disease)Bronchiolitis obliterans organizing pneumoniaChronic eosinophilic pneumoniaBronchioloalveolar carcinomaLymphomaAlveolar proteinosisVasculitisPulmonary hemorrhage

Septal LinesLymphangitic carcinomatosisCHF – interstitial edema

Zonal PreferenceUpper ZonesSilicosisCoal worker’s pneumoconiosisSarcoidosisAnkylosing spondylitisHistiocytosis XLower ZonesChronic interstitial pneumoniasIPFAsbestosisFibrosis due to collagen vascular disease

CentralPulmonary edemaPulmonary alveolar proteinosisSome lymphangitic tumors (Kaposi’s)

PeripheralChronic interstitial pneumonias, IPFBronchiolitis obliterans-organizing pneumoniaChronic eosinophilic pneumonia

Pleural DiseasePneumothoraxHistiocytosis XEnd-stage honeycombingPleural EffusionLymphangioleiomyomatosisCollagen vascular diseaseLymphangitic carcinomatosisPulmonary edemaPleural ThickeningAsbestosis (plaques or diffuse)Collagen vascular disease

Lung Volumes ReducedIdiopathic pulmonary fibrosisChronic interstitial pneumoniasAsbestosisCollagen vascular diseaseNormalSarcoidosisHistiocytosis

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Increasedlymphangioleoiomyomatosis

High-resolution CT-Linear OpacitiesThickening of bronchovascular bundles (axial)Interlobular septal thickening (septal lines)Intralobular interstitial thickeningHoneycombingSubpleural linesCentrilobular abnormalities

MEDIASTINUM:1. Anterior MediastinumBoundaries- anteriorly by the sternum - posteriorly by the anterior margins of the pericardium, aorta, and brachiocephalic vesselsNormal structures- Thymus gland- Lymph nodes- Fat- Internal mammary vesselDifferential diagnosis of anterior mediastinal masses- Thymoma- Lymphoma- Germ cell neoplasms- Thyroid abnormalities

2. Middle MediastinumBoundaries - By posterior margin of anterior division and anterior margin of posterior division

Normal structuresHeart and pericardiumAscending and transverse aortaBrachiocephalic vesselsSVC and IVCMain pulmonary vesselTrachea and main bronchiLymph nodes FatDifferential diagnosis of middle mediastinal massesLymphanedopathyBronchogenic cystVascular abnormalitiesPericardial cystTracheal tumor

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3. Posterior MediastinumBoundariesBounded anteriorly by the posterior margins of the pericardium and great vessels and posteriorly by the thoracic vertebral bodiesNormal structuresDescending thoracic aortaEsophagusThoracic ductAzygous/hemiazygousAutonomic nervesLymph nodesFatDifferential diagnosis of posterior mediastinal massesNeurogenic tumorsParavertebral abnormalitiesVascular abnormalitiesEsophageal abnormalitiesLymphadenopathyNeurenteric cystBochdalek herniaExtramedullary hematopoeisis

ThymomaDemographicsAge Usually 40-60; unusal in patients less than 30Gender Male and females equallyAssociations

Myasthenia gravis, hypogammaglobulinemia, red cell aplasia

Descriptive featuresThymoma (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 lymphomaDemographicsAge Bimodal distribution, with initial peak in young adults and second peak after age 50Gender Male predominance, especially among youngest patientsDescriptive features

Variable appearance, ranging from a single spherical soft tissue mass to a large lobulated mass

Margins may be well-defined or irregularThe mass may be homogenous or heterogenous

soft tissue attenuationCalcification is rare in untreated cases

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Germ-cell neoplasmsDemographicsAge Young patients, usually third decadeGender Malignant germ cell neoplasms –male predominanceDescriptive featuresBenign GCN (Teratoma, Dermoid Cyst)

Heterogenous, predominantly cystic mass with solid components

Well-defined marginsCalcification commonPresence of fat is suggestive; identification of a

tooth, while rare, is diagnosticMalignant GCN(seminoma, choriocarcinoma, Embryonal cell carcinoma, Yolk sac tumor) Heterogenous solid mass Irregular margins Calcification uncommon

Thyroid MassesDemographicsAge – usually >30 years of ageGender- female predominanceDescriptive featuresCXR 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

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 CystDemographicsAge – often seen on younger patients but may be detected at any ageGender – males and females equallyDescriptive 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 bright signal or T1 and bright on T2 (if cyst contains mucin, protein or hemorrhage

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Neurogenic tumorsDemographicsAge- usually occur in younger patients first 4 decades of lifeGender- males and females equally affectedDescriptive featuresNerve sheath tumors Round, homogenous, paraspinal mass

May be associated with widening of the neural foramenMRI: slightly brighter than muscle on T1 and very bright on T2 homoegenous enhancement following gadolinium administration

Sympathetic chain tumorsFusiforms, homogenous parspinal massMay be associated with vertebral body erosionMR characteristics similar to those of nerve sheath tumor

PLEURA

Radiologic featuers of pneumothoraxStandard radiographsVisceral pleural line separated from chest wall by gas space devoid of vesselsApex when uprightLung opaque only with complete collapseTension Mediastinal shift

Depression of hemidiaphragmSupine Medial recess-juxtacardiac Deep sulcus sign Subpulmonic Retrocardiac lucent triangle medially

Ancillary views Expiratory Decubitus

Pitfalls Skinfolds Clothing Tubing artifacts Bullae

CT More sensitive in detection of small pneunothoraces More accurate in determining size

Malignant MesotheliomaClinical featuresRare – 2000 to 3000 cases per year80% - history of asbestos exposure30 to 40 year latency6th to 8th decades of lifeMen more than women – 4:1Symptoms Chest pain Dyspnea; weight loss

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Pathologic featuresTypes Epithelial (50%) Sarcomatous MixedGross fetures Encasement of lung Growth of tumor into lung, chest wall, mediastinum, diaphragm

Radiologic featuresStandard radiographs Diffuse pleural thickening Nodular Encases lung Pleural effusion Pleural mass Decrease in size of hemithorax, shift of mediastinum to affected side PlaquesCT Staging Extent Chest wall, mediastinal diaphragmatic invasionMR Improved staging

Pleural metastasesOrigins Lung Breast Ovary Stomach LymphomaManifestation Maligant effusion Diffuse thickening Focal seeding

BENIGN VS MALIGNANT NODULEBenign Malignant

Shape Round irregularSize < 3 cm > 3 cmSpiculation absent presentMargins well defined ill definedCalcification present absentCavitation absent presentDoubling time < 1 mo or > 2 yrs > 1 mo or < 2 yrs

MEDIASTINAL VS PULMONARY MASSMEDIASTINAL MASS PULMONARY MASSEpicenter in the mediastinum Epicenter in lungObtuse angle w/ the lung Acute angle w/ the lung(-) air bronchogram (+) air brochogramSmooth and sharp margins Irregular marginsMovement w/ swallowing Movement w/ respirationBilateral unilateral

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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)

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