The mediastinum is a space in the thorax that contains a group of non-delineated organs and their surrounding connective tissue. It lies in the midline of the chest between the pleura of each lung and extends from the sternum to the vertebral column.
The mediastinum contains all...
The International Thymic Malignancy Interest Group (ITMIG) classification of mediastinal compartments was developed to reflect a division of the mediastinum based on cross-sectional imaging. It was in part an effort to consolidate prior discrepant classification systems in use by different medic...
Medical devices in the thorax are regularly observed by radiologists when reviewing radiographs and CTs.
tubing, clamps, syringes lying on or under the patient
rubber sheets, foam mattresses, clothing, hair braids, nipple piercings etc. may also be visible
Mega oesophagus or diffuse oesophageal dilatation can be caused by a variety of conditions.
Some of the more common causes are given below 1-3:
malignant stricture, e.g. oesophageal canc...
Melioidosis is an infectious disease caused by Burkholderia pseudomallei (previously known as Pseudomonas pseudomallei) and is a multisystem disorder which may affect the lungs, brain, visceral organs, or musculoskeletal system.
Melioidosis is a disease of the monsoon season in th...
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...
Mendelson syndrome or peptic pneumonia refers to acute chemical pneumonitis caused by the aspiration of stomach contents in patients under general anesthesia.
The etiologic agents is believed to be aspiration of acidic stomach contents, other compounds, e.g. bile, may also play a rol...
A mesenchymal hamartoma of the chest wall is a very rare benign chest wall tumour. It is sometimes classified as a non-neoplastic developmental anomaly rather than a tumour.
They typically present in neonates or infants 1-3.
Many present with a chest wall m...
Mesothelioma, in general, is an aggressive malignant tumour of the mesothelium. The overwhelming majority arise from the pleura, pleural mesothelioma, which this article will focus on.
Given the presence of the mesothelium in different parts of the body, mesothelioma can arise in various locati...
This is a basic article for medical students and other non-radiologists.
Pleural mesotheliomas are malignant tumours of the lining of the lungs. There is a strong association with asbestos exposure.
This is a summary article; read more in our article on mesothelioma.
Metastases to the thymus are rare, although they are probably under reported due to lack of symptoms.
Varied primary tumours have been reported to metastasise to the thymus 1,2:
Metastatic axillary lymphadenopathy of unknown primary can be a very chellanging situation.
Usual potential sites include:
occult breast cancer: the incidence of an axillary lymph node manifestation from an occult primary breast cancer is low, ranging from 0.3-0.8% of all patients ...
Metastatic pulmonary calcification (MPC) is a form of pulmonary calcification where there is calcium deposition in normal lung pulmonary parenchyma.
It can occur in a variety of benign and malignant disorders such as:
chronic renal failure: considered commonest cause 5
Methotrexate lung disease is the specific aetiological type of drug-induced lung disease. It can occur due to the administration of methotrexate which is an antimetabolite, which is given for various reasons but commonly to treat rheumatoid arthritis. It is also given alone or in combination wit...
In medical imaging literature, a Mickey Mouse appearance has been given to imaging features that depict that of Mickey Mouse when viewed from the front. It has been described in the following:
progressive supranuclear palsy 1
synonymously with a finger in glove sign
the flared ...
Microcystic honeycombing is an imaging descriptor on thoracic HRCT/CT which is typically given to denote extremely small cysts typically occurring in a subpleural location on a background of interstitial lung disease. It is typically described in association with non-specific interstitial pneum...
Microlithiasis merely means very small stones and may refer to:
Microscopic polyangiitis (MPA) is small vessel non-granulomatous necrotising vasculitis. It most often affects venules, capillaries, arterioles, and small arteries, although it occasionally involves medium-sized arteries 9.
It typically affects middle aged individuals.
Middle East Respiratory Syndrome coronavirus (MERS-CoV) infection is an uncommon viral infection (<1000 cases) with the first case reported in Saudi Arabia in 2012. It most commonly causes pneumonia and acute renal failure with a mortality rate of ~40%. MERS-CoV raises concern because of its sim...
Distribution of bronchiectasis can help in narrowing the differential diagnosis.
Middle lobe bronchiectasis is typically seen in:
non tuberculous mycobacterial infections
middle lobe syndrome in children
upper lobe bronchiectasis
The differential diagnosis for a middle mediastinal mass includes 1-3:
aneurysm, e.g. aortic, pulmonary artery, bronchial artery
foregut duplications cyst (e.g. oesophageal, bronchial)
primary/secondary cardiac tumour
The middle mediastinum is an artificial space of the mediastinum divided from the remainder of the extra-pleural intrathoracic cavity by arbitrary lines. It forms the largest component of the inferior mediastinum.
superiorly: superior mediastinum, divided by the thora...
The mid (or middle) zone is one of the four chest radiograph zones.
on frontal chest radiographs, extends between the superior and inferior aspects of the hilum
Migrating pericardial cysts or wandering pericardial cysts are an unusual form of pericardial cysts. They are usually pedunculated and change in position on serial imaging but have all other imaging characteristics supportive of a pericardial or pleuro-pericardial cyst.
Getting a film with miliary nodules in the exam is one of the many exam set-pieces that can be prepared for.
The film goes up and after a couple of seconds pause, you need to start talking:
There are multiple tiny soft-tissue density nodules present throughout both lungs with...
The term miliary opacities refers to innumerable, small 1-4 mm pulmonary nodules scattered throughout the lungs. It is useful to divide these patients into those who are febrile and those who are not.
Additionally, some miliary opacities are very dense, narrowing the differential - see multiple...
Miliary sarcoidosis is a rare thoracic manifesation of sarcoidosis where there are numerous miliary-like nodules scattered throughout the lungs. It is thought to represent less than 1% of cases.
From the limited case reports available, there is some suggestion that this form may ...
Miliary tuberculosis is an uncommon pulmonary manifestation of tuberculosis. It represents haematogeneous dissemination of uncontrolled tuberculous infection and carries a relatively poor prognosis.
It is seen both in primary and post-primary tuberculosis and may be associated with tuberculous ...
Minimal aortic injuries are traumatic aortic lesions that usually involve the intima and are recognised more frequently due to the use of high-resolution imaging.
Minimal aortic injuries account for 10-28% of all blunt traumatic aortic injuries 1,6,7. The proportion of this type o...
Minimally invasive adenocarcinoma of the lung is a relatively new category in the classification for adenocarcinoma of the lung. Lesions that fall into this category refer to small solitary adenocarcinomas < 3 cm with either pure lepidic growth or predominant lepidic growth with ≤ 5 mm of stroma...
Minimum intensity projection (MinIP) is a data visualization method that enables detection of low-density structures in a given volume. The algorithm uses all the data in a volume of interest to generate a single bidimensional image, in other words, its consists of projecting the voxel with the ...
A misplaced or malpositioned endotracheal tube is a relatively common complication that is detected on post-intubation radiographs.
if the ETT is too high it can rub against the vocal cords and cause cord trauma
if the ETT is too low it can selectively intubate the right or left...
Mitral annular calcification (MAC) refers to deposition of calcium (along with lipid) in the annular fibrosa of the mitral valve.
Annular calcification is seen in up to 35% of elderly patients. It is common in females over 65 years, in those with myxtomatous degeneration of the mi...
Mixed connective tissue disease (MCTD) is a type of connective tissue disease. With regards to clinical and imaging features, it can have significant overlap with other connective tissue disease such as systemic lupus erythematosus and scleroderma 1. It therefore classified as a type of overlap ...
Pulmonary manifestations of mixed connective tissue disease can be seen in a wide range (20-85%) of those of mixed connective tissue disease. It can have multiple manifestations.
More commonly described features include:
an interstitial pneumonitis: 20-65%
pulmonary fibrosis: 20-65%
Mixed dust pneumoconiosis (MDP) is classified as a type of pneumoconiosis. It is sometimes classified pathologically as a pneumoconiosis showing dust macules or mixed-dust fibrotic nodules, with or without silicotic nodules, in an individual with a history of exposure to mixed dust 2.
The modified PIOPED criteria for the diagnosis of pulmonary embolus (PE) determine the probability of pulmonary emboli following a VQ scan.
two or more large mismatched segmental defects or equivalent moderate/large defects with a normal x-ray
any perfusion de...
The 'moguls of the heart' refer to the bulges of the cardiomediastinal contour on frontal chest radiographs. The cardiomediastinal bulges are likened to skiing moguls (bumps of packed snow on a mountainside sculptured by turning skis). Awareness of their usual locations and aetiologies is helpfu...
Monod sign (often misspelt Monad sign) simply describes gas 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 her...
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...
Mosaic attenuation is a descriptive term used in describing a patchwork of regions of differing pulmonary attenuation on CT imaging. It is a non-specific finding, although is associated with the following:
obstructive small airways disease: low attenuation regions are abnormal and reflect decr...
Mounier-Kuhn syndrome is a somewhat controversial entity and used synonymously with tracheobronchomegaly by most authors 7,8,9.
Mounier-Kuhn syndrome is most frequently seen in middle age men before the age of 50 1,6.
The anatomical and physiological chang...
Mucoepidermoid carcinoma (MEC) of the lung is a type of non small cell lung cancer (NSCLC). It is classified under the group of lung carcinomas of the salivary gland type.
Mucoepidermoid carcinoma (MEC) is the most common of the SGTTLs 9. The tumour is thought to account for ~ 0.2...
Mucoid impaction, also referred to as mucus plugging or bronchocele, airway filling by mucoid secretions and can be obstructive or non-obstructive. It is a common pathological finding in chest imaging.
Mucoid impaction may result from either obstructive or non-obstructive ...
Multifocal micronodular pneumocyte hyperplasia (MMPH) is a rare benign hamartomatous proliferation of type II pneumocytes and is seen in association with tuberous sclerosis (TS). It can occur with or without concurrent lymphangiomyomatosis.
HRCT / Contrast CT Chest
Multilobar pneumonia, as the name suggests, is a lobar pneumonia affecting multiple lobes. Patients with community acquired multilobar pneumonia have a worse prognosis with longer admissions, more need for ventilatory support and more frequent treatment failure 1.
Multinodular goitre (MNG) is defined as an enlarged thyroid gland (i.e. goitre) due to multiple nodules which may have normal, decreased or increased function.
When increased activity and hyperthyroidism are present then the condition is referred to a toxic multinodular goitre or ...
The musculophrenic artery is one of two terminal branches of the internal thoracic artery.
The musculophrenic artery runs along the costal slips of the diaphragm. It supplies the 7th, 8th and 9th intercostal spaces with paired anterior intercostal arteries, as well as fine branch...
Myasthenia gravis (MG) is the most common neuromuscular junction disease and presents with increasing fatigue brought on by exertion.
Incidence is estimated at 15-20 per 100,000 1,2. Females are more affected (3:1) under the age of 40, but males are more affected by the age of 50...
Mycetoma refers to a chronic and progressively destructive granulomatous disease. The defining clinical triad comprises:
localised mass-like soft tissue injury with
draining sinuses, that
discharge grains of contagious material
It is one of the 17 neglected tropical diseases defined by WHO...
Mycoplasma pneumonia is a type of community-acquired pneumonia caused by the organism Mycoplasma pneumoniae. It is usually grouped under an atypical pneumonia.
It is relatively common in the paediatric population where it is considered the most common community-acquired pneumonia ...
Mycosis fungoides (MF), also known as cutaneous T-cell lymphoma, is a type of malignant T-cell lymphoma that primarily involves the skin.
In the United States, it is more common in males and African Americans. In Europe, it accounts for ~6% of all non-Hodgkin lymphomas. It is rar...
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 gas outlining the left lower lateral mediastinal border. The...
This is a basic article for medical students and other non-radiologists
Nasogastric (NG) tube position on chest x-ray should be assessed following initial placement and on subsequent radiographs.
This is a summary article; we have a more in-depth reference article NGT.
Near drowning pulmonary oedema is considered an aetiological subtype of non cardiogenic pulmonary oedema. It can occur with both salt water and fresh water near-drowning.
It is thought to result from the inhalation of either fresh water or sea water resulting in lung damage and a ven...
Necrobiotic pulmonary nodules are sterile cavitating lung nodules associated with inflammatory bowel disease (more often with ulcerative colitis than Crohn disease) and rheumatoid arthritis.
Histologically, necrobiotic nodules consist of a core of fibrinoid necrosis and sterile aggr...
Necrotising pneumonia refers to pneumonia characterised by the development of the necrosis within infected lung tissue.
While the term has sometimes been used synonymously with cavitating pneumonia in some publications 2, not all necrotising pulmonary infections may be complicated ...
Necrotising sarcoid granulomatosis (NSG) is a rare systemic disease, characterised by sarcoid-like granuloma formation, vasculitis and variable degrees of necrosis. It is sometimes classified under the group of pulmonary angiitis and granulomatois.
It typically affects middle-aged...
The neonatal chest radiograph in the exam setting may strike fear into the heart of many radiology registrars, but it need not!
There are only a limited number of diagnoses that will be presented on such films and they are often highlighted by the history.
First of all, have a look ...
Neonatal lines and tubes are widely used in the NICU (neonatal intensive care unit) in the management of critically ill neonates. Examples include:
nasogastric (NG) tube
endotracheal (ET) tube
central venous line
umbilical artery catheter
umbilical vein catheter
The NG tu...
Neonatal pneumonia refers to inflammatory changes of the respiratory system caused by neonatal infection.
It is one of the leading causes of significant morbidity and mortality in developing countries. Neonatal pneumonia accounts for 10% of global child mortality. At the time of w...
Neonatal pneumothorax describes pneumothoraces occurring in neonates. It is a life threatening condition, associated with high morbidity and mortality. The diagnosis is a challenge especially when the amount of air is small and may accumulate along the anterior or medial pleural space.
Causes of neonatal distress can be broadly split into intrathoracic, extrathoracic and systemic:
respiratory distress syndrome (RDS)
transient tachypnoea of the newborn (TTN)
meconium aspiration syndrome
bronchopulmonary dysplasia (BPD)
patent ductus arteriosus (PDA)...
Thoracic manifestations of neurofibromatosis type 1 (NF1), or von Recklinghausen disease, are related to pulmonary and mediastinal features of this multisystem neurocutaneous disorder, which is the most common phakomatosis.
For other thoracic manifestations as focal thoracic scoliosis, enlarged...
Neurogenic pulmonary oedema is an aetiological subtype of non-cardiogenic pulmonary oedema.
The diagnosis of neurogenic pulmonary oedema is based on the occurrence of oedema after a neurologic event/insult and the exclusion of other plausible causes.
It characteristically presents w...
Neurogenic tumours are the cause of approximately 90% of posterior mediastinal masses. They can be subdivided into three groups by their location and involvement of peripheral nerves or sympathetic chain 1-3.
peripheral nerve sheath tumours
sympathetic ganglia tumours
NEXUS Chest is a clinical decision rule that supports the appropriate use of thoracic imaging in trauma. There are seven criteria 1,2:
>60 years old
rapid deceleration defined as fall > 6 metres or motor vehicle crash >64 km/hour
abnormal alertness or mental status
Niemann-Pick disease (NPD) is actually a collection of a number of distinct autosomal recessive lysosomal storage diseases.
deficiency of acid sphingomyelinase 1
Niemann-Pick disease type A (NPA)
severe hepatosplenomegaly in infancy
severe central nervous system involvement, with atrophy or...
Niemann-Pick type B disease (NPD-B), along with Niemann-Pick type A (NPD-A) disease, is one of the more common forms of this group of autosomal recessive disorders that share the feature of abnormal storage of sphingomyelin. Common manifestation includes splenomegaly and variable neurologic defi...
Nipple markers can be a useful technique in the evaluation of densities overlying the expected position of the nipple on a chest radiograph. Not uncommonly a small round opacity projects over the lower thorax on a chest radiograph (see: solitary pulmonary nodule).
Often, especially in women, th...
Nipple shadows refer to the silhouettes of the nipples on frontal chest radiographs.
Nipple shadows are apparent on ~7.5% (range 3.5-11%) of frontal chest x-rays 1.
It has been proposed by Miller et al. that solitary pulmonary nodules that reach some or all of the foll...
Nodular bronchiectatic mycobacterium avium complex pulmonary disease is a morphological from of pulmonary mycobacterium avium complex infection although it is worthwhile understanding that there can be spectrum of the disease with mixed forms.
This form may have greater predilect...
Nodular opacification is one of the broad patterns of pulmonary opacification that can be described on a chest radiograph or chest CT. The others, linear opacification and airway opacification are discussed separately.
Nodular opacification in the lung may be a
Nodular pleural thickening is a form of pleural thickening.
Essentially all common causes of nodular pleural thickening are malignant and include:
metastatic pleural disease, particularly from adenocarcinomas, e.g.
Nodular pulmonary amyloidosis is a subtype of pulmonary amyloidosis. It is considered a limited form of amyloidosis polarised by one or more intrapulmonary nodules or masses (amyloidomas).
Albeit rare in general it is commoner than the diffuse parenchymal form. The incidence is th...
Nodular pulmonary sarcoidosis is a very rare manifestation of thoracic sarcoidosis, varying from 1.6% to 4% of patients with sarcoidosis.
They are thought to typically consist of coalescent granulomas.
There may be distinct nodules measuring from 1 t...
Non-calcified hyperdense pulmonary nodules are predominantly the result of inhalational exposure to substances, although embolisation of material may cause dense nodular opacification within the lung.
inhalation disease, e.g. pneumoconioses
pulmonary baritosis (barium dust)
The causes of non-cardiogenic pulmonary oedema can be recalled with the following mnemonic:
N: near drowning
O: O2 therapy/post-intubation pulmonary oedema
T: trauma/transfusion (TRALI: transfusion-related acute lung injury)
C: CNS: neurogenic pulmonary o...
There are several non lymphomatous lymphoid disorders that can affect the lung. This implies that they comprise of lymphoid tissue but may not have progressed as far as an overt lymphoma. They include:
lymphocytic interstitial pneumonia
Non small-cell lung cancer represents a heterogeneous group of lung cancers that do not have small-cells on histology. They are thus separated, as small cell carcinoma of the lung has distinctive management implications. The major histological types include:
adenocarcinoma of lung
Non-specific interstitial pneumonia (NSIP) is the second most common morphological and pathological pattern of the interstitial lung diseases. NSIP has two main subtypes:
fibrotic type: most common, having a more dismal outcome
cellular type: less common, but carries a much better prognosis du...
This article lists examples of normal imaging of the chest and surrounding structures, divided by modality.
PA adult male
example 2: with inverted windows
PA adult female
example 3: with labels
A detailed understanding of the structures that make up the normal contours of the heart and mediastinum (cardiomediastinal contour) on chest radiography is essential if abnormalities are to be detected.
Frontal view (PA/AP)
Right cardiomediastinal contour
From superior to inferior:
As a result of the heart and sub-diaphragmatic organs, the hemidiaphragms are not at the same level on frontal erect inspiratory chest radiographs, but are usually within one rib intercostal space height (~2 cm) of each other. The left hemidiaphragm is usually lower than the right.
If the left...
The Nuss procedure (also termed MIRPE - minimally invasive repair of pectus excavatum) is one of the operative treatments employed in patients with pectus excavatum.
It involves inserting of one (or more) concave metal bars beneath the sternum in the anterior chest wall. It is significantly les...
The oblique fissures (also called the major fissures or greater fissures) are bilateral structures in both lungs separating the lung lobes.
Right oblique fissure
The superior part of the right oblique fissure separates the right upper lobe from the right lower lobe and the infe...
Obliteration of the retrosternal airspace is seen in any cause of an anterior mediastinal mass.
Obliterative bronchiolitis (OB), also known as bronchiolitis obliterans or constrictive bronchiolitis, is a type of bronchiolitis and refers to bronchiolar inflammation with submucosal peribronchial fibrosis associated with luminal stenosis and occlusions. OB should not be confused with bronchio...
A mnemonic to remember the causes of obliterative bronchiolitis is:
C: cryptogenic organising pneumonia (COP)/BOOP
R: rheumatoid arthritis
I: infectious: post-viral/post-atypical infection (e.g. Mycoplasma pneumonia)
T: transplant: heart/lung/haematopoetic stem cell transpl...
Obstructive bronchopulmonary aspergillosis is an uncommon manifestation of non-invasive aspergillosis seen in patients with AIDS. It is typically caused by Aspergillus fumigatus and represents marked overgrowth of intraluminal of the fungus.
Octreotide scintigraphy uses 111In-labelled octreotide which is a somatostatin analog; it is also known as an OctreoscanTM, a brand name for 111In-labelled pentetreotide; pentetreotide is a DTPA-conjugated form of octreotide, originally manufactured by Mallinckrodt Nuclear Medicine LLC, which no...
Oesophageal atresia is closely related to tracheo-oesophageal fistula and can be divided into1:
type A: isolated oesophageal atresia (8%)
type B: proximal fistula with distal atresia (1%)
type C: proximal atresia with distal fistula (85%)
type D: double fistula with intervening atresia (1%)
Oesophageal bronchus refers to the rare occurrence where a bronchus arises directly from the oesophagus.
It is more common in females with a M:F of 1:2 2.
Oesophageal bronchi may be the main bronchus, which gives rise to oesophageal lung, or may be a lobar bronchu...