Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

123 results found
Article

Air bronchogram

Air bronchogram refers to the phenomenon of air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white). It is almost always caused by a pathologic airspace/alveolar process, in which something other than air fills the alveoli. Air bronchograms will not ...
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Air crescent sign

An air crescent sign describes the crescent of air that can be seen in invasive aspergillosis, semi-invasive aspergillosis or other processes that cause pulmonary necrosis. It usually heralds recovery and is the result of increased granulocyte activity. In angioinvasive fungal infection, the no...
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Air trapping

Air trapping in chest imaging refers to retention of excess gas (“air”) in all or part of the lung, especially during expiration, either as a result of complete or partial airway obstruction or as a result of local abnormalities in pulmonary compliance. It may also sometimes be observed in norma...
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Anterior bronchus sign

The anterior bronchus sign refers to the appearance of the anterior segmental bronchus of the upper lobes as seen on a frontal chest radiograph. Normal anatomy The anterior segment bronchus of the upper lobes courses anteriorly and laterally. When the orientation is predominantly anteriorly t...
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Bat wing pulmonary opacities

Bat's wing or butterfly pulmonary opacities refer to a pattern of bilateral perihilar shadowing. It is classically described on a frontal chest radiograph but can also refer to appearances on chest CT 3-4. Differential diagnosis Bat's wing pulmonary opacities can be caused by: pulmonary oedem...
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Big rib sign

The big rib sign is a sign to differentiate right and left ribs on lateral chest radiographs.  It exploits a technique of magnification differences on lateral projections between right and left ribs. For example, on right lateral projections the left ribs appear larger than right ribs.  This s...
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Box-shaped heart

A 'box-shaped' heart is a radiographic description given to the cardiac silhouette in some cases of Ebstein anomaly. The classic appearance of this finding is caused by the combination of the following features: huge right atrium that may fill the entire right hemithorax shelved appearance of ...
Article

Bronchial cut off sign

The bronchial cut off sign refers to the abrupt truncation of a bronchus from obstruction, which may be due to cancer, mucous plugging, trauma or foreign bodies. Typically, there is associated distal lobar collapse. 
Article

Bronchorrhoea

Bronchorrhoea is the expectoration of copious amounts of mucus from the lungs. It has been defined as production of more than 100ml of mucus in 24 hours, which is more than is usually seen in chronic lung disease (e.g. chronic bronchitis typically produces 25ml/24hrs) 2. It may be a feature of: ...
Article

Bubbly consolidation

Bubbly consolidation describes internal or central lucencies which represent normal aerated lung lobule within infrarcted, consolidated, lung parenchyma. It is one of the unique imaging appearances of focal pulmonary haemorrhage or possibly pulmonary infarct secondary to pulmonary embolism.  Ra...
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Bulging fissure sign

The bulging fissure sign refers to lobar consolidation where the affected portion of the lung is expanded. It is now rarely seen due to the widespread use of antibiotics. The most common infective causative agents are 1: Klebsiella pneumoniae: Klebsiella pneumonia Streptococcus pneumoniae Ps...
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Cannonball metastases

Cannonball metastases refer to large, well circumscribed, round pulmonary metastases that appear, well, like cannonballs. The French term "envolée de ballons" which translates to "balloons release" is also used to describe this same appearance. Metastases with such an appear...
Article

Cervicothoracic sign

The cervicothoracic sign, a variant of the silhouette sign, is believed to have been coined by Benjamin Felson. It helps to discern the anterior or posterior location of a mass in the superior mediastinum on frontal chest radiographs.  As the anterior mediastinum ends at the level of the clavic...
Article

Chang sign

The Chang sign refers to the dilatation and abrupt change in calibre of the main pulmonary artery due to pulmonary embolism 1.  See also knuckle sign in pulmonary embolism
Article

Cheerio sign - pulmonary nodule

Cheerio sign in thoracic imaging relates to pulmonary nodules with a central lucent cavity as seen on CT. It is due to proliferation of (malignant or non-malignant) cells around an airway. They are so named because of their resemblance to the breakfast cereal, Cheerios 1-2.  The Cheerio sign pu...
Article

Coin lesion

Coin lesion refers to a round or oval, well-circumscribed solitary pulmonary lesion. It is usually 1-5 cm in diameter and calcification may or may not be present 1,3. Typically but not always the patient is asymptomatic 1.  Differential diagnosis The differential diagnosis for such lesions is ...
Article

Comet tail sign - chest

The comet tail sign is a finding that can be seen on computed tomographic scans of the chest. It consists of a curvilinear opacity that extends from a subpleural "mass" toward the ipsilateral hilum. The comet tail sign is produced by the distortion of vessels and bronchi that lead to a...
Article

Continuous diaphragm sign

The continuous diaphragm sign is a chest radiograph sign of pneumomediastinum or pneumopericardium if lucency is above the diaphragm, or of pneumoperitoneum if lucency is below the diaphragm.  Normally the central portion of the diaphragm is not discretely visualised on chest radiographs as it ...
Article

Crazy paving

Crazy paving refers to the appearance of ground-glass opacity with superimposed interlobular septal thickening and intralobular reticular thickening, seen on chest HRCT. It is a nonspecific finding that can be seen in a number of conditions.  Pathology Aetiology Common causes: acute respirat...
Article

Crow feet sign

Crow feet sign is a characteristic but uncommon feature seen in round atelectasis. On CT, this is seen as linear bands radiating from mass into adjacent lung tissue which resembles the feet of the crow. This sign should not be confused with fibrotic changes occurring in the lung.
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CT angiogram sign

The CT angiogram sign refers to vessels appearing prominent during a contrast enhanced CT as they traverse an airless low attenuation portion of consolidated lung. Although initially thought to be specific for bronchoalveolar carcinoma, it has now been recognised as a generic appearance provided...
Article

Dark bronchus sign

Dark bronchus sign is the appearance of relatively darker bronchus to the adjacent ground glass opacity. If the ground glass opacity progress to consolidation, air bronchograms will be visualised.  This sign is useful to identify diffuse ground glass opacity on HRCT in cases of Pneumocystis jir...
Article

Deep sulcus sign

The deep sulcus sign on a supine chest radiograph is an indication of a pneumothorax. In a supine film (common in the ICU), it may be the only indication of a pneumothorax because air collects anteriorly and basally, within the nondependent portions of the pleural space, as opposed to the apex ...
Article

Dense hilum sign

The dense hilum sign suggests a pathological process at the hilum - hilar malignancy or bronchogenic carcinoma should be suspected. On a well-centred chest PA radiograph the density of the hilum is comparable on both sides. In absence of calcification or adenopathy, the hila should appear of eq...
Article

Dependent viscera sign

The dependent viscera sign is one of the signs of diaphragmatic rupture on axial CT or MR images, where herniated viscera lies against the posterior thoracic wall in a dependent position, as it is no longer supported by the diaphragm. See also  collar sign (or hour glass sign)
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Double diaphragm sign

The double diaphragm sign is one of several radiological signs seen with a pneumothorax in a supine patient. Supine films are commonly performed in unwell patients, particularly in the ICU. In a supine patient with a pneumothorax, air may outline the anterior portions of the hemidiaphragm and c...
Article

Eggshell calcification

Eggshell calcification refers to fine calcification seen at the periphery of a mass, and usually relates to lymph node calcification. In 1967 Jacobsen and Felson published criteria to help "avoid over-reading of the incidental circumferential concentrations of calcium and to eliminate conf...
Article

Extrapleural air sign

The extrapleural air sign is one of the many signs of pneumomediastinum, and was first described by Lillard and Allen in 1965. It is defined as the presence the air between the parietal pleura and the diaphragm. On a lateral projection the air forms a radiolucent pocket of air posterior to the d...
Article

Extrapleural fat sign

The extrapleural fat sign is an imaging feature which can be seen on CT under certain circumstances. It occurs from the inward displacement of an extrapleural fat stripe by an extrapleural fluid collection, extrapleural haematoma or extra pleural mass. The presence of the extrapleural fat sign i...
Article

Extrapleural sign

The extrapleural sign, described by Felson in 1973 1, refers to the appearance of a pulmonary opacity with oblique margins that taper slowly to the chest wall when the lesion is viewed tangentially to the x-ray beam. This appearance suggests that the lesion is extrapleural in nature, as opposed ...
Article

Fallen lung sign

The fallen lung sign (also known as CT fallen lung sign) describes the appearance of collapsed lung away from the mediastinum encountered with tracheobronchial injury (in particular those > 2 cm away from the carina). It is helpful to look for this rare but specific sign, in cases of unexplai...
Article

Feeding vessel sign

Feeding vessel sign consists of a distinct vessel leading directly to a nodule or a mass. This sign indicates either that the lesion has a hematogenous origin or that the disease process occurs near small pulmonary vessels.  A number of vessel-related non-neoplastic disorders of the lung produc...
Article

Feline oesophagus

Feline oesophagus also known as oesophageal shiver, refers to the transient transverse bands seen in the mid and lower oesophagus on a double contrast barium swallow. The appearance is almost always associated with active gastro-oesophageal reflux 2,3 and is thought to be due to contraction of ...
Article

Figure 3 sign

The figure 3 sign is seen in aortic coarctation and is formed by prestenotic dilatation of the aortic arch and left subclavian artery, indentation at the coarctation site (also known as the "tuck"), and poststenotic dilatation of the descending aorta. On barium studies of the oesopha...
Article

Finger in glove sign

The finger in glove sign can be seen on either chest radiograph or CT chest and refers to the characteristic sign of a bronchocoele. The same appearance has also been referred to as: rabbit ear appearance mickey mouse appearance toothpaste shaped opacities Y-shaped opacities V-shaped opacit...
Article

Flat waist sign

The flat waist sign refers to flattening of the contours of the aortic arch and adjacent main pulmonary artery. It is seen in severe left lower lobe collapse and is caused by leftward displacement and rotation of the heart.
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Fleischner sign

Fleischner sign is a prominent central artery that can be caused either by pulmonary hypertension that develops or by distension of the vessel by a large pulmonary embolus. It can be seen on chest radiographs and CT pulmonary angiography. It is seen most commonly in the setting of massive pulmo...
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Fluid colour sign

The fluid colour sign is a diagnostic sign to differentiate a pleural effusion from pleural thickening by means of colour Doppler ultrasound. In the case of pleural effusion a colour signal is seen in the pleural fluid during respiratory and cardiac movement, whereas this colour signal is not se...
Article

Funnel trachea

Funnel trachea is a colloquialism for congenital long-segment intrathoracic tracheal stenosis.  The diameter of the trachea immediately below the cricoid is normal, and becomes becomes progressively more stenotic caudally. The posterior, membranous portion of the trachea may be partially or com...
Article

Galaxy sign

The so-called galaxy sign, initially described as the sarcoid galaxy, represents a coalescent granuloma seen in a minority of patients with pulmonary sarcoidosis 1. The same appearance can be seen in tuberculosis 2,3. In other words, it represents a mass-like region composed of numerous smaller ...
Article

Garland triad

Garland triad, also known as the 1-2-3 sign or Pawnbrokers sign, is a lymph node enlargement pattern which has been described in sarcoidosis: right paratracheal nodes right hilar nodes left hilar nodes Hilar lymphadenopathy is symmetrical and usually massive. These so-called potato nodes don...
Article

Ghon lesion

A Ghon lesion (sometimes called Ghon focus) represents a calcified tuberculous caseating granuloma (tuberculoma) and represents the sequelae of primary pulmonary tuberculosis infection. When associated with a calcified ipsilateral hilar node it is known as a Ranke complex.
Article

Ginkgo leaf sign - chest x-ray

The ginkgo leaf sign of the chest, also referred as the ginkgo leaf sign of subcutaneous emphysema, is a radiograph appearance which is seen at extensive subcutaneous emphysema of the chest wall. Air outlines the fibers of the pectoralis major muscle and creates a branching pattern that resemble...
Article

Golden S-sign

The Golden S-sign is seen on both PA chest radiographs and on CT scans. It is named because this sign resembles a reverse S shape, and is therefore sometimes referred to as the reverse S-sign of Golden.  Although typically seen with right upper lobe collapse, the S-sign can also be seen with th...
Article

Hairy pleural plaques

The so-called hairy pleural plaque, are a manifestation of asbestos related disease. They arises from the visceral pleura, typically from an interlobar fissure. The hairiness stems from short radially oriented linear regions of fibrosis extending from the plaque into the adjacent lung parenchyma...
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Halo sign (chest)

The halo sign (HS) in chest imaging is a feature seen on lung window settings (typically HRCT), ground glass opacity surrounding a pulmonary nodule or mass and represents haemorrhage. It is typically seen in angioinvasive aspergillosis. Pathology Histopathologically, it represents a focus of p...
Article

Hampton hump

Hampton hump refers to a dome-shaped, pleural-based opacification in the lung most commonly due to pulmonary embolism and lung infarction (it can also result from other causes of pulmonary infarction (e.g. vascular occlusion due to angioinvasive aspergillosis). While a pulmonary artery embolism ...
Article

Haystack sign

The haystack sign on chest x-rays in paediatric patients is indicative of pneumomediastinum. The paediatric heart is surrounded above and below with air and giving it an appearance of a haystack from Monet's paintings. 
Article

Head cheese sign

Head cheese, believe it or not, is not a cheese and is often not made of head. It is in fact a type of terrine, with bits of meat scavenged from various parts of various animals (including the head) usually from a calf or pig. It has a heterogeneous mosaic pattern, ranging from light to dark. T...
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Hemithorax white-out

Complete white-out of a hemithorax on the chest x-ray has a limited number of causes. The differential diagnosis can be shortened further with one simple observation - the position of the trachea. Is it central, pulled or pushed from the side of opacification? Trachea pulled toward the opacifie...
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Hilum convergence sign

The hilum convergence sign is a useful chest radiograph sign to help distinguish a bulky hilum due to pulmonary artery dilatation from a mass/nodal enlargement. In the former, pulmonary vessels can be seen to converge and join a dilated pulmonary artery.  The sign was first described by Benjami...
Article

Hilum overlay sign

The hilum overlay sign refers to an appearance on frontal chest radiographs of patients with a mass projected at the level of the hilum which is in fact either anterior or posterior to the hilum. When a mass arises from the hilum, the pulmonary vessels are in contact with the mass and as such t...
Article

Hoffman-Rigler sign

The Hoffman-Rigler sign is a sign of left ventricular enlargement where an approximation of the distance between the inferior vena cava (IVC) and left ventricle is used.​ Radiographic features On a lateral chest radiograph, if the distance between the left ventricular border and the posterior ...
Article

Holly leaf sign

The holly leaf sign refers to the appearance of pleural plaques on chest x-rays. Their irregular thickened nodular edges are likened to the appearance of a holly leaf. 
Article

Honeycombing

Honeycombing refers to the computed tomographic (CT) manifestation of diffuse pulmonary fibrosis (usual interstitial pneumonia). The Fleischner Society definition is clustered cystic air spaces (between 3-10mm in diameter but occasionally as large as 2.5 cm) which are usually subpleural and basa...
Article

Hydatid cyst signs

There are several signs in hydatid cyst are seen in associated with hydatid disease: cumbo sign: air is seen between the pericyst  and the laminated membrane of the cyst  serpent sign: internal rupture of the cyst with collapse of membranes of parasite into the cyst spin sign/whirl sign: deta...
Article

Hypercontracting (nutcracker) oesophagus

Hypercontracting (nutcracker) oesophagus is a motility disorder of the oesophagus. This condition is primarily diagnosed with manometry with high intra-oesopahgeal pressure and normal peristalsis. Most patients will have a normal barium swallow.  Hypercontracting oesophagus ("nutcracker oe...
Article

Incidental lung nodules

Incidental lung nodules are encountered commonly in routine cross sectional imaging. The risk of developing cancer in very small nodules (<5mm) is very low. However, clear-cut recommendations are still not in place with high variation in practice amongst reporting radiologists 1. As a result,...
Article

Incomplete border sign

The incomplete border sign is useful to depict an extrapulmonary mass on chest radiograph. An extrapulmonary mass will often have a inner well defined border and an ill-defined outer margin 1-3. This can be attributed to the inner margin being tangential to the x-ray beam and has good inherent ...
Article

Interface sign - HRCT chest

The interface sign is a feature seen on HRCT chest imaging and refers to the presence of irregular interfaces at the margins of pulmonary parenchymal structures or the pleural surface of lung. It suggest interstitial thickening.
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Juxtaphrenic peak sign

The juxtaphrenic peak sign or diaphragmatic tenting refers to the peaked or tented appearance of a hemidiaphragm which can occur in the setting of lobar collapse. It is caused by retraction of the lower end of diaphragm at an inferior accessory fissure (most common 1), major fissure or inferior ...
Article

Kirklin sign

The Kirklin sign refers to a deformity of the normal gastric air bubble on an upright chest radiograph due to a mass lesion of the gastric cardia or fundus. The differential for a Kirklin sign includes gastric tumour gastric carcinoma oesophageal carcinoma gastrointestinal stromal tumour (G...
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Knuckle sign

Knuckle sign refers to the abrupt tapering or cutoff of a pulmonary artery secondary to embolus. It is better visualised on CT pulmonary angiography scan than chest x-ray. This is an important ancillary finding in pulmonary embolism (PE), and often associated with the Fleischner sign of dilated ...
Article

Lambda sign

There are a number of lambda signs: lambda sign of twin pregnancy lambda sign of sarcoidosis
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Lambda sign of sarcoidosis

The lambda sign is seen on gallium-67 scans in the setting of thoracic sarcoidosis. Bilateral hilar and right paratracheal lymph nodes are typically involved which can resemble the lambda symbol (λ). See also lambda sign of twin pregnancy
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Low attenuation lymphadenopathy

Low attenuation lymphadenopathy suggests underlying necrosis and can be seen in: metastatic carcinoma (or lymphoma) infections (tuberculous or fungal) Whipple disease coeliac sprue See also lymphadenopathy low attenuating lymphadenopathy high attenuating lymphadenoapthy
Article

Luftsichel sign

The Luftsichel sign is seen in some cases of left upper lobe collapse and refers to the frontal chest radiographic appearance due to hyperinflation of the superior segment of the left lower lobe interposing itself between the mediastinum and the collapsed left upper lobe.   Radiographic feature...
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Medial stripe sign

Medial stripe sign refers to an area of increased lucency at the interface of the medial lung and the mediastinum in case of medial pneumothorax. A small volume of pneumothorax generally accumulates anteriorly or medially which can be difficult to detect hence this sign holds a certain significa...
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Melting sign

The melting ice cube sign describes the resolution of pulmonary haemorrhage following pulmonary embolism (PE).  When there is pulmonary haemorrhage without infarction following PE, the typical wedge-shaped, pleural-based opacification (Hampton's hump) resolves within a week while preserving its...
Article

Monod sign

Monod sign (often spelt Monad sign) simply describes air that surrounds a mycetoma (most commonly an aspergilloma) in a pre existing pulmonary cavity 1-3. It should not be confused with the air crescent sign which is seen in recovering angioinvasive aspergillosis 4. The air crescent sign herald...
Article

More black sign

The more black sign is a normal finding in lateral chest x-ray, and refers to the gradual increased apparent radiolucency (blackness) of the vertebral bodies, when proceeding from upper to lower chest. This is due to the increased proportion of the chest comprised of air containing lungs over di...
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Mosaic attenuation pattern in lung

Mosaic attenuation is the description given to the appearance at CT where there is a patchwork of regions of differing attenuation.  It is a non-specific finding, which may be seen in any of the following: obstructive small airways disease: low attenuation regions are abnormal and reflect decre...
Article

Naclerio V sign

The Naclerio V sign is a sign described on the plain film in patients with a pneumomediastinum occurring often secondary to an oesophageal rupture.  It is seen as a V-shaped air collection. One limb of the V is produced by mediastinal air outlining the left lower lateral mediastinal border. The...
Article

Obliteration of the retrosternal airspace

Obliteration of the retrosternal airspace is seen in any cause of an anterior mediastinal mass. 
Article

Onion peel sign

The onion peel sign (also called the cumbo sign) is a feature seen with complicated pulmonary hydatid cyst in which air lining between the endocyst and pericyst has the appearance of an onion peel. 
Article

Oreo cookie sign

The oreo cookie sign refers to the appearance of a pericardial effusion on lateral radiographs of the chest. A vertical opaque line (pericardial fluid) separating a vertical lucent line directly behind sternum (epicardial fat) anteriorly from a similar lucent vertical lucent line (pericardial fa...
Article

Panda sign

The humble panda has a few signs to its name: panda sign of the midbrain panda sign of sarcoidosis See also animal and animal produce inspired signs
Article

Panda sign of sarcoidosis

The panda sign of sarcoidosis is a gallium-67 citrate scan finding. It is due to bilateral involvement of parotid and lacrimal glands in sarcoidosis, superimposed on the normal uptake in the nasopharyngeal mucosa. The presence of perihilar adenopathy adds the lambda distribution of increased up...
Article

Peri-bronchial cuffing

Peri-bronchial cuffing refers to a radiographic (usually plain film but sometimes CT) descriptive term to describe hazyness around a bronchus or large bronchiole seen end on (plain film). When viewed tangentially this can give the appearance of a tram line 3. It is sometimes described as a "...
Article

Pericardial calcification

Pericardial calcification (PC) usually occurs in patients with a history of pericarditis.  Pathology Causes uraemia previous trauma or prior pericarditis later sequelae of rheumatic heart disease malignant pericardial involvement (e.g. mediastinal teratoma) On chest radiography, location ...
Article

Pleural mouse

A pleural mouse (also known as a fibrin body), is a 1-2 cm mobile rounded clump of fibrin left over after resolution of a pleural effusion.
Article

Pneumothorax in supine projection

A pneumothorax does not display classical signs when a patient is positioned supine for a chest radiograph. Instead, the pneumothorax may be demonstrated by looking for the following signs: relative lucency of the involved hemithorax deep, sometimes tongue-like, costophrenic sulcus: deep sulcu...
Article

Pneumothorax: ultrasound

Pneumothorax is a serious potential consequence of blunt thoracic trauma and, if misdiagnosed, it may quickly become life-threatening. For a discussion on epidemiology, clinical presentation, pathology, and treatment and prognosis please see the main pneumothorax article.  Radiographic feature...
Article

Polo mint sign

The polo mint sign is a description given to a venous thrombosis on contrast enhanced CT imaging.  When viewed in the axial plane, a thin rim of contrast persists around a central filling defect due to thrombus. This gives an appearance like that of the popular mint sweet, the polo, also referre...
Article

Popcorn calcification

Popcorn calcification refers to amorphous calcifications often with rings and arcs that resemble popped corn kernels. This type of calcification may be seen in many radiological settings including 1: chondroid lesions (e.g enchondroma, chondrosarcoma) fibrous dysplasia pulmonary hamartomas d...
Article

Pseudocavitation of a lung lesion

Pseudocavitation has been described as a well recognised feature of  adenocarcinoma in situ / minimally invasive adenocarcinoma - (bronchoalveolar carcinoma) of lung. It refers to the central bubble-like low density region seen within a pulmonary nodule on CT.
Article

Pseudopneumomediastinum

Pseudopneumomediastinum is the false impression, usually on a chest X-ray, of pneumomediastinum. Correctly identifying pneumomediastinum is important, but making the diagnosis in error may lead to further unnecessary investigation and possible treatment. Causes include: Mach bands superimpose...
Article

Pulmonary plethora

Pulmonary plethora is a term used to describe the appearances of increased pulmonary perfusion on chest radiographs. It is commonly used in paediatric radiology.  Pathology Usually a left-to-right shunt of 2:1 is required for pulmonary plethora to occur 2,3. Increased pulmonary perfusion occur...
Article

Quad sign

The quad sign is a static sonographic sign observed in pleural effusion. It consists of four lines representing the pleural, rib, fluid and lung. Similar to the sinusoid sign, this sign has a high sensitivity and specificity for pleural effusion, which is anechoic in itself.
Article

Ranke complex

Ranke complex is seen in 'healed' primary pulmonary tuberculosis comprised of two parts: Ghon lesion: calcified parenchymal tuberculoma ipsilateral calcified hilar node
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Reverse bat wing pulmonary opacities

Reverse bat wing pulmonary opacities refer to peripheral opacities of the lungs, sparing the perihilar region. It is a relatively unusual appearance with a relatively narrow differential. chronic eosinophilic pneumonia cryptogenic organising pneumonia, formerly bronchiolitis obliterans with or...
Article

Reverse figure 3 sign

The reverse figure 3 sign (also known as the E sign) is seen on barium swallows in patients with a coarctation of the aorta and is the medial equivalent of the figure 3 sign seen on CXR. It is formed by prestenotic dilatation of the ascending aorta, indentation of the coarctation site (or "...
Article

Reversed halo sign

Reversed halo sign (RHS), also known as the atoll sign, is defined as central ground-glass opacity (GGO) surrounded by denser consolidation of crescentic (forming more than three fourths of a circle) or ring (forming a complete circle) shape of at least 2 mm in thickness. It was initially descri...

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