Chest Radiology
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Transcript of Chest Radiology
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 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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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 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 :
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 common2. lower thorax behind the heart3. 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 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
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3. Hilar and mediastinal adenopathy- TB and fungi
4. Pleural effusion and empyema5. Other complications
ARDSBronchiectasisRecurrent pneumonitis
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 pneumonia
1. “Round” pneumoniaStreptococcus pneumoniae
2. Complete lobar consolidationStreptococcus pneumoniae, Klebsiella
pneumoniaeOther 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. lymphadenopathy
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M. tuberculosis, fungi, virus, Mycoplasma pneumoniae
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 lobes
Effusion
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 influenzae
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COPDBronchopneumonia
Radiographic featuresHomogeneous segmental Lower lobes
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
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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
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 prognosis
One 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
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Sympathetic ganglionSubclavian artery
Radiologic featuresApical mass or asymmetric thickeningBone destruction
MRI Multiplanar imaging Local extension4. 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 cases
Lobar, 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 nodes
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MRIDifferentiates residual from recurrent tumor from fibrosisT2 weighed
Fibrosis – low SI Tumor – bright SI
Eggshell calcification in nodes
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 posttreatmentConforms 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
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If squamous cell, likely a lung primary
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
KidneyMelanoma
ThyriodBreastColon
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
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- chest tube placed to evacuate a pleural fluid should be positioned in a dependent portion of the pleural space
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 walls
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Upper lobesPanlobular
Fewer and smaller vesselsLower lobes
ParaseptalSubpleural and along fissuresThin wallsSingle row
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
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Abnormal ciliary clearanceDyskinetic cilia syndrome
Kartegener’s syndromeBronchial obstructionAllergic bronchopulmonary aspergillosis (ABPA)Noxioux fume inhalationPulmonary fibrosisTraction bronchiectasisRadiation fibrosisSarcoidosisIdiopathic 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
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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.
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.
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• It can represent hematogenous metastasis, a primary carcinoma, or other pathology.
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 reactions
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Lymphangitic carcinomatosis
Cystic PatternIPF (honeycombing)LymphangioleiomyomatosisHistiocytosis X
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 Zones
SilicosisCoal 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 Thickening
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Asbestosis (plaques or diffuse)Collagen vascular disease
Lung Volumes ReducedIdiopathic pulmonary fibrosisChronic interstitial pneumoniasAsbestosisCollagen vascular diseaseNormalSarcoidosisHistiocytosisIncreasedlymphangioleoiomyomatosis
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 cyst
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Tracheal tumor
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 abnormalitiesLymphadenopathy
Neurenteric 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
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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
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
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bright signal or T1 and bright on T2 (if cyst contains mucin, protein or hemorrhage
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 erosion
MR 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
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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
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 defined
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Calcification 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
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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