The subclavian arteries are asymmetric paired arteries that supply blood to the posterior cerebral circulation, cerebellum, posterior neck, upper limbs and the superior and anterior chest wall.
Right and left subclavian arteries classically have different origins:
The subclavian vein (SCV) is the major venous channel that drains the upper limb.
Origin and course
The subclavian vein starts at the crossing of the lateral border of the 1st rib. It then arches cephalad, posterior to the medial clavicle before curving caudally and receiving it...
The subcostal muscle has variable anatomy and forms part of the intercostal muscle group. It lies on the deep surface of the innermost intercostal muscle in the posterior chest, near the angles of the ribs, usually running over 2-3 intercostal spaces. It is most common in the upper (1-4) and low...
The subcostal nerve can also be considered as the twelfth intercostal nerve. Some authors describe it as the first branch of the lumbar plexus.
The anterior division of the twelfth thoracic nerve, called the subcostal nerve, is larger than the other intercostal nerves. It runs al...
Subcutaneous or surgical emphysema, strictly speaking, refers to air in the subcutaneous tissues. But the term is generally used to describe any soft tissue emphysema of the body wall or limbs since the air often dissects into the deeper soft tissues and musculature along fascial planes.
Subpleural line refers to a thin curvilinear opacity, 1-3 mm in thickness, lying less than 1 cm from and parallel to the pleural surface. It corresponds to:
atelectasis of normal lung if seen in the dependent posteroinferior portion of lung of a patient in the supine position (disappears if pro...
Subpleural pulmonary bullae are a location specific descriptive term to describe pulmonary bullae occuring in subpleural locations. Many are considered to represent regions of paraseptal emphysema where the emphysematous spaces are greater than 1cm in diameter 1. They may or may not contain sept...
Subpleural sparing in thoracic radiology is a imaging descriptor usually used on cross sectional imaging (mainly CT) where the pathology that affects the lungs spares the extreme peripheral lung margin abutting the pleura - chest wall.
It can be seen in a number of situations
non specific inte...
Subpulmonic effusions are a pleural effusion that can be seen only on an erect projection. Rather than layering laterally and blunting the costophrenic angle, the pleural fluid lies almost exclusively between the lung base and the diaphragm.
The fluid ca...
The superior accessory fissure is present in around 5% of individuals examined with CT 4.
The superior accessory fissure of the right lobe of the lung is located in the same plane and posterior to the right minor fissure. It separates the right lower lobe into superior and basal...
Superior mediastinum is an artificially divided wedge-shaped compartment of the mediastinum located between the thoracic plane inferiorly and the thoracic inlet superiorly. The inferior mediastinum, comprising of the anterior, middle and posterior parts, lies inferiorly.
The superior pulmonary sulcus (or just the superior sulcus) refers to an apical pleuro-pulmonary groove formed by the subclavian artery as it curves in front of the pleura runs upward and lateral immediately below the apex. It is a typical location for Pancoast tumours (also known as superior su...
The superior thoracic aperture, also known as the thoracic inlet or outlet, connects the root of the neck with the thorax.
The superior thoracic aperture is kidney-shaped and lies in an oblique transverse plane, tilted anteroinferiorly to posterosuperiorly.
The superior vena cava (SVC) is a large valveless venous channel formed by the union of the brachiocephalic veins. It receives blood from the upper half of the body (except the heart) and returns it to the right atrium.
The SVC begins behind the lower border of the first right co...
Superior vena cava (SVC) obstruction can occur from extrinsic compression, intrinsic stenosis or thrombosis. Malignancies are the main cause and are considered an oncologic emergency. Superior vena cava syndrome (SVCS) refers to the clinical syndrome with symptoms that results from this obstruct...
Superior vena caval duplication is the most common form of a left sided SVC, where the normal right sided SVC remains. The right SVC however can be smaller in ~2/3rds of such cases 3.
Results from failure of the embryonic left anterior cardiac vein to regress. Drainage is variable an...
The suprascapular artery is 1 of the 4 branches of the thyrocervical trunk (off the first part of the subclavian artery).
It traverses inferiorly and laterally in the lower anterior neck superficial to the anterior scalene muscle and phrenic nerve before crossing the third part of the subclavia...
The supreme intercostal arteries, or superior intercostal arteries, are formed as a direct result of the embryological development of the intersegmental arteries. These arteries are paired structures of the upper thorax which normally form to provide blood flow to the first and second intercosta...
Surgical emphysema (or subcutaneous emphysema) occurs when air/gas is located in the subcutaneous tissues (the layer under the skin). This usually occurs in the chest, face or neck.
This is a summary article; read more in our article on surgical emphysema.
The Swiss cheese sign has been attributed to the appearances on CT of fluid containing pneumatoceles, that typically occur following pulmonary lacerations.1
The pneumatoceles appear as 'holes' in the lung parenchyma and hence the description with respect to Swiss style cheeses (e.g. emmental), ...
Swyer-James syndrome (SJS), also known as Swyer-James-MacLeod syndrome and Bret syndrome, is a rare lung condition that manifests as unilateral hemithorax lucency as a result of postinfectious obliterative bronchiolitis.
The condition typically follows a viral respiratory infecti...
Pneumothoraces (singular: pneumothorax) are collections of gas within the pleural space. If the pneumothorax is under pressure, it is called a tension pneumothorax.
This is a summary article; read more in our article on pneumothorax.
a wide range of pa...
Synchronous primary lung carcinoma (SPLC) is a term given to occurrence of two or more primary lung carcinomas within different portions of the lung in the same time period.
They are thought to the carry the same pathophysiological mechanism as metachronous lung carcinoma (i.e. two or more prim...
Systemic lupus erythematosus (SLE) is a complex autoimmune disease with multisystem involvement. It is also sometimes classified as a vasculitis.
There is an overall increased female predilection. In adults, women are affected 9-13 times more than males. In children, this ratio i...
Thoracic manifestations of systemic lupus erythematosus can be variable.
For a general discussion, and for links to other system specific manifestations, please refer to the article on systemic lupus erythematosus.
pleuritis: considered one of the c...
Takayasu arteritis (TA), also known as idiopathic medial aortopathy or pulseless disease, is a granulomatous large vessel vasculitis that predominantly affects the aorta and its major branches. It may also affect the pulmonary arteries. The exact cause is not well known but the pathology is thou...
The Takeuchi procedure refers to a direct anastomosis of the anomalous left coronary artery from the pulmonary artery directly to the aorta was described in the 1970s and currently remains the procedure of choice.
An intrapulmonary aortocoronary tunnel or baffle was performed by Takeuchi prior ...
Talc induced lung disease comprises of a group of pathologies that can occur related to talc (Magnesium silicate)
Four types of pulmonary disease secondary to talc exposure have been defined these include:
talco-silicosis - associated with occupational exposure
talco-asbestosis - associated w...
Talc (magnesium trisilicate) pulmonary embolism is a rare cause of non thrombotic pulmonary embolism. It tends to be more prevalent in patients with narcotic abuse.
Most patients are asymptomatic although dyspnea and persistent cough occur with severe talc exposure. Clini...
Talcosis is a type of pneumoconiosis and can be prevalent in intravenous drug users. It is one of the four recognised types talc induced lung disease.
Talc (magnesium silicate) is used in the preparation of tablets intended for oral use, where it acts as a 'filler' and lubricant. Whe...
Tc-99m DTPA (diethylenetriamine-pentaacetic acid) (aerosol) is one of the technetium agents and is used in VQ imaging.
photon energy: 140 KeV
physical half life: 6 hours
biological half life: 1 hour
normal distribution: lungs
aerosol deposited in bronhoal...
Tc-99m MAA (microaggregated albumin) is one of the technetium radiopharmaceuticals used in lung perfusion imaging.
photon energy: 140 KeV
physical half life: 6 hours
biological half life: 2-3 hours
normal distribution: lungs, liver, spleen, kidneys
Tension gastrothorax describes a rare life-threatening condition caused by mediastinal shift due to a distended stomach herniating into the thorax through a diaphragmatic defect.
Presentation is generally with acute and severe respiratory failure, with clinical features ...
Tension pneumothoraces occur when intrapleural air accumulates progressively in such a way as to exert positive pressure on mediastinal and intrathoracic structures. It is a life-threatening occurrence requiring rapid recognition and treatment is required if a cardiorespiratory arrest is to be a...
This is a basic article for medical students and other non-radiologists
Tension pneumothoraces are pneumothoraces under pressure. If the pressure gets high enough, the pneumothorax can compress the heart and great vessels, and even cause cardiac arrest.
Presentation is u...
The terminal bronchioles are a continuation of the bronchi and are the last divisions of the conducting airways.
Terminal bronchioles, are confusingly named, as they not the final branches but rather the distal bronchioles that do not bear alveoli. The first 19 divisions from ...
Thalassaemia is an autosomal recessive haemoglobinopathy that originated in the Mediterranean region. The genetic defect causes a reduction in the rate of globin chain synthesis which causes the formation of abnormal haemoglobin molecules. The resultant microcytic anaemia is the characteristic p...
The Macklin effect describes one of the pathophysiological processes of pneumomediastinum in blunt chest trauma. The Macklin effect accounts for ~40% of severe blunt traumatic pneumomediastinum. Exclusion of tracheobronchial and oesophageal causes of pneumomediastinum is mandatory to exclude con...
Thickening of bronchovascular bundles is a chest CT imaging feature that can be observed in a number of entities.
Conditions that can result in bronchovascular bundle thickening include:
sarcoidosis - see pulmonary manifestations of sarcoidosis 1
classical condition to giv...
The third mogul sign can be seen on frontal chest radiograph in the presence of left atrial enlargement. It refers to an extra mogul or bump along the upper left cardiac silhouette just below the left main bronchus.
The third mogul sign commonly represents the enlarged left atrial appendage, pa...
Thoracentesis, commonly known as a pleural or chest tap, is a procedure where excess pleural fluid is drained from the pleural space for diagnostic and/or therapeutic reasons. Ultrasound-guided thoracentesis performed by radiologists has been shown to have fewer complications than blind thoracen...
Thoracic actinomycosis refers to an uncommon indolent infection caused principally by the genus Actinomyces (higher prokaryotic bacteria belonging to the family Actinomyceataceae).
While it is rare in general, the thoracic form actinomycosis may constitutes ∼15% of the total burde...
Thoracic air leak syndrome (TALS) is an uncommon late complication in haematopoetic stem cell transplant recipients with chronic graft verses host disease. These patient led to develop features of thoracic air-leakage (i.e. spontaneous pneumomediastinum, spontaneous pneumothorax, pneumopericardi...
Thoracic aortic aneurysms are relatively uncommon compared to abdominal aortic aneurysms. There is a wide range of causes, and the ascending aorta is most commonly affected. CTA and MRA are the modalities of choice to image this condition.
The term aneurysm is used when the axial d...
There are a number of causes and mimics of thoracic aortic dilatation.
post-stenotic dilatation, e.g. bicuspid aortic valve
thoracic aortic aneurysm
atherosclerosis (usually descending thoracic aorta)
Thoracic aortic injury is the most common type of traumatic aortic injury and is a critical life-threatening, and often life ending event. It can result from either blunt or penetrating trauma:
blunt trauma (more common)
rapid deceleration (eg. motor vehicle accident, fall from great height)
The differential for thoracic aortic stenosis includes:
aortitis (especially Takayasu arteritis)
Williams syndrome: supravalvular aortic stenosis
congenital rubella syndrome: supravalvular aortic stenosis
The thoracic cage refers to the skeleton of the thorax:
thoracic vertebral column
12 pairs of ribs
The thoracic duct is the main lymphatic channel for the return of chyle to the venous system. It drains lymph from both lower limbs, abdomen (except the convex area of the liver), left hemithorax, left upper limb and left face and neck.
The thoracic duct is the superior continua...
Pleural-thoracic empyema (commonly referred simply as an empyema) or pyothorax refers to an infected purulent and often loculated pleural effusion, and is a cause of a large unilateral pleural collection. It is a potentially life-threatening condition requiring prompt diagnosis and treatment.
Thoracic endometriosis is an uncommon location for endometriosis and the main cause of catamenial pneumothorax.
Most often occurs in the third and fourth decades of life 3.
Symptoms may include:
catamenial pleuritic chest pain
catamenial haemoptysis: whe...
Thoracic (or pulmonary) histoplasmosis refers to pulmonary manifestations from infection with the organism Histoplasma capsulatum which is an organism endemic to El Salvador but can be found widely in other parts of North, Central and South America. It can have variable clinical and radiographic...
High resolution CT (HRCT) of the lungs has specific terminology relating to pulmonary anatomy with which one needs to be comfortable.
secondary pulmonary lobule
interlobular septal thickening
Thoracic lymph nodes are divided into 14 stations as proposed by the International Association for the Study of Lung Cancer (IASLC) 1, principally in the context of oncologic staging.
highest mediastinal nodes: low cervical, supraclavicular, and sternal notch nodes
Thoracic myelolipomas are extremely rare entities; only ~3% of myelolipomas are thought to occur in the thorax. When do occur in the thorax they can manifest as
mediastinal myelolipoma: most occur in the posterior mediastinum
intrapulmonary myelolipoma (much less common)
As with my...
Thoracic outlet syndrome (TOS) refers to a group of clinical syndromes caused by congenital or acquired compression of the brachial plexus or subclavian vessels as they pass through the superior thoracic aperture.
Clinical presentation will depend on the structure compre...
The thoracic plane, also known as the transthoracic plane or the plane of Ludwig is an artificial horizontal plane used to divide the mediastinum into the superior mediastinum and the inferior mediastinum.
It is defined as a horizontal line that runs from the manubriosternal joint (sternal angl...
A handy mnemonic to remember the structures found at the level of the thoracic plane (also known as the plane of Ludwig) is:
C: cardiac plexus
L: ligamentum arteriosum
A: aortic arch (inner concavity)
P: pulmonary trunk
T: tracheal bifurcation (carin...
The thoracic spine sign on lung ultrasound is an indirect indicator of the presence of a pleural effusion or haemothorax. It represents the visualisation of the vertebral bodies in the thoracic cavity above the diaphragm which are usually not seen unless there is a fluid collection.
Thoracic splenosis refers to autotransplantation of splenic tissue into the pleural space which typically occurs after trauma. It may occur in approximately 18% of patients with combined diaphragmatic and splenic injuries and is more common after penetrating injuries.
Splenic tissue ...
Thoracoabdominal sign, a variation of the silhouette sign, is a frontal chest radiograph sign which helps to localize a thoracic lesion.
Since the posterior costophrenic sulcus is more caudal than the anterior lung, a thoracic lesion must be posterior if its caudal end is visible below the dome...
Thoracoliths are rare, calcified pleural-based nodules that are almost always incidental findings. They are usually considered mobile, and more common on the left.
The exact aetiology is unknown and theories include 1,2:
calcified fibrin body
degenerated pleural lipoma
Thoracoplasty is a surgical procedure that was originally designed to permanently collapse the cavities of pulmonary tuberculosis by removing the ribs from the chest wall 1-3 . The resection of multiple ribs, allows the apposition of parietal to the visceral or mediastinal pleura. Until supplant...
Thymic carcinoid tumour refers to a carcinoid tumour arising in the thymus. It is the most common histologic type for a neuroendocrine tumour of the thymus.
Affected patients are typically in the fourth or fifth decades of life. There is a recognised male predominance with M:F ra...
Thymic carcinoma is part of the malignant end of thymic epithelial tumours.
Patients are typically 50 to 70 years of age at presentation 9.
The incidence of paraneoplastic syndromes are thought to be low. At least 10 different histologic variants have been described 4....
Thymic cysts are cysts that occur within, or arise from, the thymus.
Thymic cysts are uncommon lesions and are estimated to account for approximately 1-3% of all anterior mediastinal masses 4. Approximately 50% of congenital thymic cysts are incidentally discovered during the firs...
Thymic epithelial tumours are rare tumours arising from thymus in anterior mediastinum of middle age patients. However, they are still the most common primary neoplasm of the thymus and of the anterosuperior mediastinum. This article discusses thymomas, invasive thymomas and thymic carcinoma.
Thymic hyperplasia is a disorder whereby there is hyperplasia of the thymus gland.
Thymus hyperplasia can be subdivided into two forms:
true thymic hyperplasia
Both true thymic hyperplasia and lymphoid hyperplasia manifest as diffuse symmetric enlargement of...
The thymic notch sign represents normal thymus in newborn on a frontal chest radiograph. Interruption of the cardiac silhouette forms a notch, which may be seen on either side, but more frequently seen on left side.
The thymic sail sign represents a triangular-shaped inferior margin of the normal thymus seen on neonatal frontal chest radiograph. It is more commonly seen on the right side, and can also be bilateral. It is seen in 3-15% of all cases. This sign should not be confused with the spinnaker sail si...
Thymolipoma is a rare, benign anterior mediastinal mass of thymic origin, containing both thymic and mature adipose tissue.
Thymolipomas comprise ~5% (range 2-9%) of all thymic neoplasms, but are less common than a mediastinal lipoma of non-thymic origin. There is no recognised s...
The thymus is a T-cell producing lymphoid organ in the anterior mediastinum that plays a role in the development of the immune system.
It is relatively large in infancy (weighing 25 g at birth) reaching a maximal weight in adolescence between 12 and 19 years (35 g), and graduall...
Tietze syndrome refers a benign costochondritis accompanied by hypertrophy of the costal cartilages.
The exact incidence of occurrence is not known. It is seen most commonly in the 2nd to 5th decades of life. Both sexes are affected equally.
It is characterised as a te...
Tissue tropism is a phenomenon by which certain host tissues preferentially support the growth and proliferation of pathogens. This concept is central to the radiological evaluation of infectious disease.
As infections that display tissue tropism will thrive in certain tissue locati...
Total repair of tetralogy of Fallot is a corrective surgical procedure that involves closure of the ventricular septal defect (VSD) and relief of right ventricular outflow tract (RVOT) obstruction.
Most patients with tetralogy of Fallot (TOF) undergo elective surgical repair between ...
The trachea, known colloquially as the windpipe, connects the upper respiratory tract to the lungs via the tracheobronchial tree, enabling gas exchange.
The trachea is a tube-shaped structure consisting of 15-to-20 D-shaped cartilage rings anterolaterally bridged by annular ligam...
Primary tracheal and endobronchial lesions are generally rare and can be either malignant or benign. The majority of these lesions are malignant.
primary malignant endobronchial lesions
squamous cell carcinoma: commonest malignant lesion in tr...
Tracheal atresia (TA) is an extremely rare anomaly and refers to a congenital absence of the trachea.
There may be a greater male predilection 5.
Tracheal atresia falls under the spectrum of laryngeal-tracheo-bronchial atresia which in turn results either from an obstr...
A tracheal bronchus (with some variations also known as a pig bronchus) is an anatomical variant where an accessory bronchus originates directly from the supracarinal trachea. The latter term (pig bronchus or bronchus suis) is often given when the entire upper lobe (usually right side) is suppli...
Tracheal buckling is a normal finding in young infants when it is more flexible. There is typically deviation of the trachea anteriorly and to the right (up to 90 degrees) and any other configuration (i.e. to the left or posteriorly) should raise the possibility of underlying pathology.
Tracheal calcification is a benign radiological finding of the middle aged and elderly and is usually of no clinical significance.
The appearance is often striking as individual tracheal rings become radio-opaque and stand out from the soft tissue mediastinum.
A tracheal diverticulum is usually an incidental finding. Occasionally it may mimic pneumomediastinum, so called pseudopneumomediastinum.
It may be congenital or acquired. The acquired form is thought to be due to prolonged increased intraluminal pressure, e.g. due to a chronic cough...
The differential for tracheal masses can be rather wide.
For a single mass consider:
direct invasion from adjacent organ (lung, thryoid,esophagus)
distant metastsis ( such as melanoma)
squamous cell carcinoma: commonest primary tracheal malignancy 2 ~50 %
Tracheal stenosis is usually acquired and is caused by intubation or tracheostomy. Inflammation and pressure necrosis of the tracheal mucosa most commonly occur at either the tracheostomy stoma or at the level of the tube balloon. Acute post-intubation stenosis results from mucosal oedema or gra...
Tracheal webs occur as a thin layer of tissue that narrows the tracheal lumen. They do not completely obstruct the trachea.
The incidence of congenital tracheal is 1:10,000 births.
Some patients will be asymptomatic. Symptomatic patients can present with co...
Tracheo-oesophageal fistula is a pathological communication between the trachea and oesophagus.
It can be broadly classified into two types:
congenital tracheo-oesophageal fistula
acquired tracheo-oesophageal fistula: from malignancy/tuberculosis
Tracheo-bronchial amyloidosis (TBA) refers to tracheal and/or bronchial involvement in amyloidosis. It is sometimes classified as a sub type of pulmonary amyloidosis 4.
It is a rare manifestation with some reports suggesting less than 100 published cases around the time of writing...
Tracheobronchial branching anomalies can be seen as an isolated finding or accompanying heterotaxy syndromes, pulmonary sling, and conditions associated with pulmonary underdevelopment (agenesis and aplasia), including the scimitar syndrome.
Abnormal branching patterns include:
right sided iso...
Traumatic tracheobronchial injury is a serious but uncommon manifestation of chest trauma. It is usually a fatal injury with only a small percentage of patients making it to hospital. Given the magnitude of force required to injure the major airways, there are often multiple chest injuries and o...
Trecheobronchial papillomatosis refers to the occurrence of multiple squamous cell papillomas involving trachea and bronchi. It is the most common benign tumour in laryngo-tracheal region.
Multiple papillomas can occur at other sites which have distinctive terms. Examples include:
A tracheo-bronchial stent is a device used in the treatment of symptomatic airway compression.
This device is inserted under bronchoscopic guidance in patients with external compression from mediastinal based malignancy, for example lung or oesophageal cancers. It may also be used in the treat...
The tracheobronchial tree is the branching tree of airways beginning at the larynx and extending inferiorly and peripherally into the lungs as bronchioles. The luminal diameter decreases as the branching increases more peripherally into the lungs. The walls of the airway down to the level of the...
Tracheobronchopathia osteochondroplastica (TO) is a very rare idiopathic non neoplastic tracheo-bronchial abnormality.
The estimated prevalence on routine bronchoscopy can be upto 0.7% . It typically affects those in the 5th to 6th decades and there may be a male predilection 4.