Thoracic imaging Flashcards
What are the mechanisms of atelactasis?
- Obstructive atelactasis
- Relaxation atelactasis caused by relation of lung adjacent to an intrathoracic lesion causing mass effect, such as pleural effusion, pneumothorax or pulmonary mass
- Adhesive atelactasis due to surfactant deficiency: neonatal respiratory distress syndrome, but also seen in ARDS
- Cicatricial atelactasis is volume loss from architectural distortion of lung parenchyma by fibrosis
Frontal and lateral schematic of lung
- The luftsichel (air-sickle in German) sign is a crescent of air seen on the frontal radiograph, which represents the interface between the aorta and the hyperexpanded superior segment of the left lower lobe. However, this sign is not always present.
- It is important to recognize left upper lobe collapse and not mistake the left lung opacity for pneumonia or pleural effusion, since a mass obstructing the airway may be the cause of the lobar atelectasis.
- Collapse of both right middle and lower lobes occurs from obstruction of the bronchus intermedius, and it causes obscuration of both the right heart border and right hemidiaphragm, with a linear superior margin directed towards the hilum.
Round atelactasis is most common in the posterior lower lobes
All five of the following findings must be present to diagnose round atelectasis:
1) Adjacent pleura must be abnormal.
2) Opacity must be peripheral and in contact with the pleura.
3) Opacity must be round or elliptical.
4) Volume loss must be present in the affected lobe.
5) Pulmonary vessels and bronchi leading into the opacity must be curved — this is the comet tail sign.
What is the secondary pulmonary lobule comprised of?
Each SPL contains a central artery (centrilobular artery) and a central bronchus, each branching many times to produce acinar arteries and respiratory bronchioles
Connective tissue, called interlobular septa, encases each SPL. Thickening of the interlobular septa can be seen on CT.
What is the ddx fora cute consolidation?
- Pneumonia (most common cause)
- Aspiration: consolidation may appear heterogenous from mucus plugging
- Pulmonary hemorrhage (primary pulmonary hemorrhage or aspiration of hemorrhage)
- Adult respiratory distress synrome (ARDS), which is non cardiogenic pulmonary edema seen in critically ill patients
- Pulmonary edema may cause consolidation if severe
What is ddx for chronic consolidation?
- Adenocarcinoma
- Lymphoma
- Organizing pneumonia
- Chronic eosinophilic pneumonia
What can be the chronic causes of below image?
- Lung adenocarcinoma
- Organizing pneumonia
- Chronic eosinophilic pneumonia
- Interstitial lung disease
- Hypersensitivity pneumonitis (HP) is a type 3 hypersensitivity reaction to inhaled organic antigens.
What is dx and ddx?
Smooth interlobular septal thickening: CT demonstrates thickening of the interlobular septa (arrows) in pulmonary edema. Conditions that dilate the pulmonary veins cause smooth interlobular septal thickening.
Ddx: pulmonary edema, lymhangitis carcinomatosis
Axial CT shows diffuse nodular septal thickening (yellow arrows). This was a case of lymphangitic carcinomatosis.
Nodular, irregular or asymmetric septal thickening tends to be caused by processes that infiltrate the peripheral lymphatics, most commonly by lymphangitic carcinomatosis and sarcoidosis (rarely has septal thickening).
What is the approach to multiple micronodules: centrilobular, tree in bed, perilymphatic, random?
- Perilymphatic nodules follow the anatomic locations of pulmonary lymphatics, which can be seen in three locations in the lung:
1. Subpleural.
2. Peribronchovascular.
3. Septal (within the interlobular septa separating the secondary pulmonary lobules). - Sarcoidosis is the most common cause of perilymphatic nodules, typically with an upper- lobe distribution.
What is dx and ddx?
Pulmonary sarcoidosis with galaxy sign: Axial and coronal CT images demonstrate extensive upper-lobe predominant confluent perilymphatic nodules. The galaxy sign is most apparent on the axial image, where the confluent nodules appear like the confluence of stars forming a galaxy.
ddx for perilymphatic nodules: sarcoidosis, pneumoconioses, lymphangitic carcinomatosis
What is the ddx for this distribution of lesion?
Randomy distributed nodules usually occur via haematogenous spread.
Haematogenous metastases
Disseminated mycobacteria
Disseminated fungal bacteria
Miliary TB
ddx for distribution of lesion
Mycobacterium tuberculosis and atypical mycobacteria
Viral pneumonia
Aspiration pneumonia
Rarely, lymphangitic carcinomatosis and vascular abnormalities
Solitary cavaitory lesion that is spiculated and irregular margin –> lung SCC
Maximum wall thickness of <4mm is usually benign and a wall thickness >15mm is usually malignant
What is the ddx for solitary cavitary lesion?
- Primary bronchogenic carcinoma. While both SCC and adenocarcinoma can cavitate, SCC cavitates more frequently. SCLC never known to cavitate.
- TB (upper lobe cavitary consolidation)
- Fungal pneumonia
- Cavitary bacterial pneumonia
Whats ddx?
Multiple cavitary lesions
* Septic emboli
* Vasculitis, including granulomatosis with polyangiitis (GPA)
* Metastases, classically SCC but any metastatic lesion can cavitate
What is the ddx for multiple lung cysts?
Lymphangioleiomyomatosis: diffuse cystic lung disease due to smooth muscle proliferation of the distal airways
Pulmonary Langerhans cell histiocytes
Lymphoid interstitial pneumonia: rare associated with sjogren
Amyloid
Pneumocystis jirovecii pneumonia which features cysts in late stage disease
ddx>
Usual interstitial pneumonia pattern
Other causes of UIP pattern, including RA and asbestosis
Non specific interstitial pneumonia
What are the 3 stages of empyema?
What sign is seen?
1) Free-flowing exudative effusion: Can be treated with needle aspiration or simple drain. 2) Development of fibrous strands: Requires large-bore chest tube and fibrinolytic therapy. 3) Fluid becomes solid and jelly-like: Usually requires surgery.
Reactivation TB: Frontal chest radiograph (left image) shows a cavitary lesion in the left upper lobe (arrow), confirmed by CT (arrow). There was no significant mediastinal adenopathy. The differential diagnosis of this appearance would include cavitary primary lung cancer, which would be expected to feature a thicker wall.
- Healed TB is evident on radiography as apical scarring, usually with upper lobe volume loss and superior hilar retraction.
- Calcified granulomas may be present as well, which indicate containment of the initial infection by a delayed hypersensitivity response.
Atypical mycobacteria infection
3 types?
(1) “Classic” or nodular cavitary form that simulates TB; typically seen in patients with chronic lung disease.
(2) Non-classic or bronchiectatic form (more common).
(3) Disseminated form, typically lymphadenopathy in immunocompromised patients (usually AIDS).
Bronchiectatic atypical mycobacteria is an elderly with cough, low grade fever and weight loss, called Lady Windermere syndrome.
Mycobacterium intracellulare and M.kanasii are the 2 most common organisms.
- Chest radiograph findings can be normal but a classic finding of Pneumocystis pneumonia is bilateral perihilar (central) airspace opacities with peripheral sparing.
- The classic CT appearance is ground glass opacification, sometimes with crazy paving (ground glass and thickening of the interlobular septa).
What are the 5 categories of aspergillus pulmonary disease?
Finger-in-glove sign of ABPA: Chest radiograph shows upper-lobe predominant bronchiectasis with branching perihilar opacities. CT shows dense bronchial mucoid impaction representing the finger-in-glove sign (arrow).
Patients present clinically with recurrent wheezing, low-grade fever, cough, and sputum production containing fragments of aspergillus hyphae. The diagnosis may be made using serum testing for aspergillus IgE.
Aspergilloma and Monod sign: CT shows an irregular opacity (arrows) resting dependent within a left upper lobe cavity, representing an aspergilloma (arrows). The Monod sign is the curvilinear air surrounding the aspergilloma. This patient has prior TB with biapical scarring and left apical cavity.
Aspergilloma: conglomeration of intertwined aspergillus fungal hyphae
The most common cause of preexisting cavity are prior TB and sarcoidosis.
If symptomatic = haemoptysis most common symptom. Treatment is embolization or resection rather than antifungal medication
The air crescent sign is reserved for angioinvasive aspergillus –> monod sign
Halo sign: CT shows a left upper lobe mass with peripheral ground glass (yellow arrow), representing pulmonary hemorrhage.
dx: angioinvasive aspergillosis
ddx: viral infection, granulomatosis with polyangiitis (GPA), Kaposi sarcoma, hemorragic metastasis and others
The air crescent sign represents a crescent of air from retraction of infarcted lung and occurs with recovery of neutrophil counts. It a good prognostic sign as it indicates that the patient is in the recovery phase.
Radiograph demonstrates moderate enlargement of the cardiac silhouette and sternotomy wires. There are increased interstitial markings with Kerley B lines (arrows). Chest CT shows smooth interlobular septal thickening (arrows), corresponding to the Kerley B lines seen on radiography.
A complication of aggressive thoracentesis is reexpansion pulmonary edema, caused by rapid reexpansion of a lung in a state of collapse for more than 3 days.
Right mainstem bronchus intubation: Chest radiograph shows the endotracheal tube terminating in the right mainstem bronchus (yellow arrow), a few centimeters distal to the carina (red arrow).
Direct intubation of either the right or left mainstem bronchus (right mainstem bronchus far more common) is an emergent finding that can cause complete atelectasis of the un-intubated lung.
Swan Ganz pulmonary artery catheter
Chest radiograph with a sharpening filter applied shows a left internal jugular pulmonary artery catheter that takes a normal course through the SVC, right atrium, tricuspid valve, right ventricle, pulmonic valve, and finally the right pulmonary artery (arrow).
If the tip is distal to the proximal interlobar pulmonary artery, there is a risk of pulmonary artery rupture or pseudoaneurysm. Other complications of pulmonary artery catheter placement include intracardiac catheter knot and arrhythmia
Axial CT shows a solid nodule with air bronchograms (yellow arrow) and a more peripheral ground glass nodule (red arrow), both shown to be adenocarcinoma subtypes on pathology.
Axial contrast-enhanced CT shows a right lower lobe consolidative opacity with air bronchograms (arrow). Adenocarcinoma is an important differential consideration for chronic ground glass or consolidation.
Post transplant what is dx?
PTLD (post transplant lymphoproliferative disorer) presents as new pulmonary nodules in patient after solid organ transplantation
Lung cancer presenting as a hilar mass: Frontal radiograph (left image) shows a right paramediastinal opacity (arrow), which does not silhouette the right heart border. CT shows a large right infrahilar mass (arrows).
Superior sulcus tumor: Chest radiograph shows nearly imperceptible increased opacity in the right apex (arrow). A superior sulcus mass is clearly evident on CT (arrows), with encasement of the vasculature and effacement of the superior mediastinal fat.
- A Pancoast tumor is a type of superior sulcus tumor with involvement of the sympathetic ganglia causing a Horner syndrome, with ipsilateral ptosis, miosis, and anhidrosis.
- A superior sulcus tumor is a stage T3 tumor. The staging of lung cancer is subsequently discussed.
Lymphangitic carcinomatosis: Axial (left image) and coronal CT shows asymmetric, nodular septal thickening of the right lung in a patient with metastatic uterine sarcoma. Aside from a trace effusion, the left lung is clear.
- On imaging, carcinomatosis manifests as smooth or nodular interlobular septal thickening, which is often asymmetric.
What is the staging of lung cancer?
Stage IIIA lung cancer: Axial CT in lung windows (left image) shows a right upper lobe peripheral mass (arrow) that abuts the pleura. There is diffuse centrilobular emphysema. Soft-tissue window CT shows ipsilateral right paratracheal adenopathy (arrow). The T staging is T2 (for size >3 cm) and the N staging is N2 for ipsilateral mediastinal nodes. The overall stage is therefore IIIA and this tumor is resectable.
Stage IV lung cancer: Axial CT (left image) shows a dominant, spiculated right upper lobe T2 mass. More inferiorly (right image), a small contralateral nodule (arrow) is present. This nodule was determined to be malignant on follow-up, for an M staging of M1a and stage IVA disease.
Stage IV lung cancer: Axial CT (left image) shows a left upper lobe mass with ipsilateral hilar adenopathy (arrows). Coronal CT through the upper abdomen shows bilateral adrenal masses (arrows), which were confirmed to be metastases (M1c), representing stage IVB disease.
What is management of low/intermediate/high risk pulmonary embolism?
What sign to observe for in CXR pulmonary embolism?
Fleischer sign: widening of the pulmonary arteries
Westermark sign: regional oligemia in the lung distal to the pulmonary artery thrombus
Chest radiograph shows an abnormal convex mediastinal bulge representing an enlarged main pulmonary artery (red arrow). Pulmonary hypertension
Noncontrast CT (bottom left image) and gated contrast-enhanced cardiac CT (bottom right image) show that the pulmonary arterial atherosclerotic plaque has both calcified (arrow in noncontrast image) and noncalcified (arrow in contrast-enhanced image) components. The diameter of the main pulmonary artery (PA) is clearly larger than that of the aortic root.
Pulmonary hypertension
Pulmonary artery wall calcifications are pathognomonic for chronic pulmonary artery hypertension typically seen due to shunts.
The hilum convergence sign describes the appearance of hilar pulmonary artery branches converging into an enlarged pulmonary artery.
HP (hypersensitivity pneumonitis): Diffuse ground glass opacities affecting both lungs with mosaic attenuation. There are diffuse small centrilobular nodules (arrow). This was a case of acute/subacute HP.
Silicosis complicated with progressive massive fibrosis: CT demonstrates upper lobe predominant fibrotic changes. There are perilymphatic nodules (yellow arrows) and a developing left upper lobe conglomerative mass (red arrow).
Egg-shell calcified lymph nodes are present in the mediastinum (blue arrows).
Caplan syndrome is seen in patients with RA and either CWP or silicosis (more common in CWP) and represents necrobiotic rheumatoid nodules superimposed on the smaller centrilobular and subpleural nodules of the pneumoconiosis.
Chronic eosinophilic pneumonia: Chest radiograph demonstrates upper lobe and peripheral consolidation. Axial CT shows bilateral patchy peripheral consolidative opacities.
Reverse batwing configuration. Consolidation may cross fissures, distinguishing it from COP.
Alveolar hemorrhage due to ANCA-associated microscopic polyangiitis: Axial CT shows basal predominant central ground glass with associated mild interlobular septal thickening. This patient had renal insufficiency and had a P-ANCA positive vasculitis with alveolar hemorrhage.
Pulmonary vasculitis
* Pulmonary vasculitis includes a group of inflammatory conditions involving small vessels, large vessels, and granulomatous disease.
* Imaging manifestations include 1) alveolar hemorrhage and 2) nodular foci with cavitation.
GPA, what is the clinical triad?
What is seen?
- Granulomatosis with polyangiitis (GPA) is a systemic small-vessel vasculitis with a classic clinical triad of sinusitis, lung involvement, and renal insufficiency. C-ANCA is positive.
Chest radiograph shows numerous cavitary lesions bilaterally (arrows).
Coronal and axial CT confirms multiple thick-walled cavitary lesions (arrows). The primary differential consideration would be septic emboli; however, this patient was C-ANCA positive.
What is located in the anterior, middle and posterior mediastinum?
Where is the lesion and why?
Anterior mediastinal mass: Frontal radiograph shows a right mediastinal mass with silhouetting of the right heart border. The right pulmonary artery is visible through the mass (arrows), representing the hilum overlay sign and indicating that the mass is not in the middle mediastinum. Lateral radiograph shows the mass in the retrosternal clear space, confirming its anterior mediastinal location. This was a teratoma.
Obliteration of the retrosternal clear space on the lateral radiograph is direct sign of prevascular mediastinal location.
Displacement of the descending aortic stripe: Frontal chest radiograph (left) shows lateral displacement and bowing of the left para-aortic interface (arrows). Axial contrast-enhanced CT shows a nonenhancing homogeneous mass (arrow) effacing the esophagus. Although extremely rare, this was a liposarcoma.
What is dx?
What is associated condition?
Invasive thymoma with drop metastasis: Contrast-enhanced CT shows a slightly heterogeneous mass with calcifications (yellow arrow) anterior to the aorta and SVC, with two pleural metastases (red arrows).
Thymoma associated with MG.
Also associated with red cell aplasia, hypogammaglobulinemia and other paraneoplastic syndromes.
Teratoma: Chest radiograph shows an extra mediastinal contour (yellow arrow) lateral to the aortic arch (red arrow). Because the mass does not silhouette the aorta it cannot be in the middle mediastinum. On CT there is a mediastinal mass containing a large focus of fat (yellow arrow) likely representing a benign teratoma.
Inferior extension of a goiter into the mediastinum:
Chest radiograph demonstrates a right superior mediastinal mass (arrow) with obscuration of the superior border of the mass, representing the cervicothoracic sign, which implies that the mass is in continuity with the soft tissues of the neck.
Noncontrast CT shows a large heterogeneous mass (arrows) with coarse calcifications replacing the thyroid gland.
Although the thyroid is anterior, the goiter extends inferiorly into the middle mediastinum due to an embryologic fascial plane created by the inferior thyroidal artery.
Hiatal hernia: Frontal radiograph shows a retrocardiac lucency (arrows), which was confirmed to be a moderate-sized hiatal hernia on CT (arrows).
Contrast enhanced axial CT shows a hypervascular mediastinal mass (yellow arrow) with central areas of necrosis (red arrow) directly abutting the borders of the ascending and descending thoracic aorta just above the level of the pulmonary veins, consistent with a parasympathetic paraganglioma.
A paraganglioma or extra-adrenal pheochromocytoma is a highly vascular neuroendocrine tumor that originates from embryonic neural crest cells of the peripheral nervous system. It can be sympathetic or parasympathetic. A visceral compartment mediastinal paraganglioma tends to be parasympathetic in origin.
Cardiac or aortopulmonary paragangliomas can present as a visceral compartment mediastinal mass, arising from phrenic, vagus, and recurrent laryngeal nerves.
What tumor could this be in adults?
What could it be in children/young adults?
Peripheral nerve tumors: Adults (schwannoma (most common), neurofibroma and malignant peripheral nerve sheath tumor)
Schwannoma: Frontal radiograph shows a round opacity overlying the right hilum with the hilum overlay sign
(arrow) corresponding to a paravertebral abnormality on lateral radiograph. CT shows a low density lesion without significant enhancement. MRI shows heterogeneous T2 hyperintense signal within the cystic lesion in keeping with a schwannoma.
Sympathetic ganglion tumors (more common in children):
ganglioneuroma (most common), neuroblastoma (early childhood), ganglioneuroblastoma
Osteomyelitis and paraspinal phlegmon: Radiograph shows displacement of the bilateral paraspinal lines (arrows). Sagittal T1- (middle image) and T2-weighted MRI (right image) shows loss of Disc space height and marrow edema in two adjacent lower thoracic vertebral bodies. There is associated paraspinal phlegmonous change (arrows), which caused the paraspinal line displacement on radiography.
Bronchiectasis from chronic aspiration: Axial and coronal CT show bronchial wall thickening in the bilateral lower lobes due to dependent aspiration (arrows).
Bronchiectasis of the right middle lobe and lingula (arrows) due to Mycobacterium avium intracellulare infection.
Bronchocentric infections, such as tuberculosis and atypical mycobacteria.
Endotracheal squamous cell carcinoma: Radiograph shows a tracheal luminal narrowing (arrow) at the level of the thoracic inlet. On CT there is an eccentric enhancing mass invading the left tracheal wall and markedly narrowing the tracheal lumen (arrow)
SCC as higher up: associated with smoking
Adenocarcinoma would be located at lower 1/3 (gastroesophageal junction)
Centrilobular and paraseptal emphysema: Coronal (left image) and axial CT demonstrates both centrilobular and paraseptal emphysema. Centrilobular emphysema is predominant in the upper lobes (yellow arrows) and paraseptal emphysema is seen anteromedially (blue arrows).
Panacinar emphysema due to alpha-1-antitrypsin deficiency: Frontal radiograph and coronal CT show diffuse emphysematous changes most severely affecting the lower lobes, with flattening of the diaphragms (arrows).
Mesothelioma: Contrast-enhanced CT through the thorax (left image) shows extensive nodular pleural thickening of the left hemithorax (arrows). Images through the upper abdomen show extensive soft tissue abnormality with invasion of the chest wall (arrows).
Mesothelium lines the pleural, cardiac, peritoneal cavity. Most cases are due to prior asbestos exposure, with a latency of >20 years
