Thyroid transcription factor 1 (TTF1) refers to a homeodomain-containing nuclear transcription factor which belongs to the Nkx2 gene family encoded by a gene located on chromosome 14q13.
It is expressed in the forebrain, thyroid and lung tissues. The presence of TTF-1 protein on a tissue sample...
Thyroid transcription factor 1 deficiency is a situation characterised by mutations in the gene encoding thyroid transcription factor, NKX2-1.
It can result in neurological, thyroid, and pulmonary dysfunction (including neonatal respiratory distress). Children can have a range of mil...
Tietze syndrome refers to 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...
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...
The tracheal bifurcation angle can have a wide range of normal values in patients and can vary significantly in serial radiographs. It is of poor diagnostic value due to the lack of sensitivity and specificity in identifying the underlying pathology.
The interbronchial angle is th...
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°) and any other configuration (i.e. to the left or posteriorly) should raise the possibility of underlying pathology.
Tracheal calcification, or tracheobronchial calcification, is a benign radiological finding of the middle aged and elderly and is usually of no clinical significance.
Patients are generally asymptomatic.
Long-term warfarin therapy may be associated with trache...
Tracheal diverticula, also known as tracheoceles, are usually an incidental finding. Occasionally it may mimic pneumomediastinum, so-called pseudopneumomediastinum.
There is overlap in the use and description of the terms paratracheal air cyst and tracheal diverticulum in the liter...
The differential for tracheal masses can be rather wide.
For a single mass consider:
direct invasion from adjacent organ (lung, thyroid, oesophagus and larynx)
distant metastasis (e.g. melanoma, breast, renal and colon cancer)
squamous cell carcinoma: common...
Tracheal stenosis is usually acquired following intubation or tracheostomy. It can also arise as part of the spectrum of tracheobronchial stenosis.
Inflammation and pressure necrosis of the tracheal mucosa most commonly occur at either the tracheostomy stoma or at the level of the tube balloon....
Tracheal wall thickening may have several causes. For diagnostic purposes, tracheal thickening may be categorised by length of airway involvement in order to narrow the differential diagnoses. Note that some aetiologies may be associated with either focal or diffuse pattern of involvement.
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 a ...
Tracheobronchial amyloidosis refers to tracheal and/or bronchial involvement in amyloidosis. It is sometimes classified as a subtype of pulmonary amyloidosis.
It is a rare manifestation with some reports suggesting less than 100 published cases around the time of writing 5.
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...
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 other body ...
A tracheobronchial 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 treatm...
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 tracheobronchial abnormality.
The estimated prevalence on routine bronchoscopy can be up to 0.7%. It typically affects those in the 5th to 6th decades and there may be a male predilection 4.
Tracheomalacia, or sometimes described as tracheobronchomalacia, is a common incidental finding on imaging of the chest of older patients and manifests as an increase in tracheal diameter as well as a tendency to collapse on expiration.
Tracheomalacia can be broadly considered as being congenit...
A dilated trachea has numerous causes, and in almost all cases represents tracheomalacia (increased size and increased compliance).
As is almost always the case, various diameters have been used. Typical figures include >26 mm in men, >23 mm in women or >3 cm for both genders.
Although many of...
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
Traction bronchiectasis refers to an aetiological subtype of bronchiectasis where there is irreversible dilatation of bronchi and bronchioles within areas of pulmonary fibrosis or distorted lung parenchymal architecture.
It can arise from a number of underlying causes which result in...
Tram-track sign may be used in chest radiography or CT to denote the thickened non-tapering (parallel) walls of cylindrical bronchiectasis.
It should not be confused with other tram-track signs elsewhere in the body.
Transfusion-related acute lung injury (TRALI) is defined as non-cardiogenic pulmonary oedema temporally-related to transfusion therapy.
It tends to occur within 6 hours after a blood transfusion and requires exclusion of other alternative diagnoses such as sepsis or volume overload.
Transient tachypnoea of the newborn, also known as retained fetal fluid or wet lung disease, presents in the neonate as tachypnoea for the first few hours of life, lasting up to one day. The tachypnoea usually resolves within 48 hours.
Transient tachypnoea is one of the commonest...
A transudate is a collection of fluid that has a relatively low specific gravity and protein concentration. They occur secondary to increased hydrostatic pressure or reduced colloid oncotic pressure:
left ventricular failure (increased hydrostatic pressure)
hypoalbuminaemia (decreased colloid ...
The transverse cervical artery, also known as the cervicodorsal trunk, is 1 of the 4 branches of the thyrocervical trunk (off the first part of the subclavian artery).
It is a short artery that bifurcates into the superficial and deep branches, both which course superficially and laterally acro...
The transversus thoracis muscle is the innermost muscle of the anterior thoracic wall (deep to external intercostal and internal intercostal muscles).
The transversus thoracis is a thin band of muscle and tendon arising from the lower posterior surface of the sternum, posterior...
Trapped lung, also known as unexpandable/unexpanded lung, is a term used where there is non-expandable lung after fluid removal, often thoracentesis. It is similar to but not entirely synonymous with the term lung entrapment, which is a similar condition caused by active pleural disease rather t...
Trauma CT thorax review areas are useful to reduce the potential for error, which is higher than usual given the larger number of images requiring review, and the often present time pressures and the potential presence of numerous concurrent injuries (see CT polytrauma).
Using some standard re...
Tree-in-bud sign or pattern describes the CT appearance of multiple areas of centrilobular nodules with a linear branching pattern. Although initially described in patients with endobronchial tuberculosis, it is now recognised in a large number of conditions.
The triangle of safety is an anatomical region in the axilla that forms a guide as to the safe position for intercostal catheter (ICC) placement. With the arm abducted, the apex is the axilla, and the triangle is formed by the:
lateral border of the pectoralis major anteriorly
lateral border o...
Triple-rule-out CT (TRO CT) angiography may be ordered in the setting of acute chest pain to examine the thoracic aorta and the coronary and pulmonary arteries. The protocol helps exclude life-threatening causes of acute chest pain, especially if atypical, or if alternative causes to acute coron...
Tuberculomas or tuberculous granulomas are well defined focal masses that result from Mycobacterium tuberculosis infection and are one of the more severe morphological forms of tuberculosis. Tuberculomas most commonly occur in the brain (see: CNS tuberculosis) and the lung (see: pulmonary tuberc...
Tuberculosis encompasses an enormously wide disease spectrum affecting multiple organs and body systems predominantly caused by the organism Mycobacterium tuberculosis. A small proportion can also be caused Mycobacterium bovis.
Although tuberculosis continues to be very common in...
Pulmonary manifestations of tuberculosis are varied and depend in part whether the infection is primary or post-primary. The lungs are the most common site of primary infection by tuberculosis and are a major source of spread of the disease and of individual morbidity and mortality.
A general d...
This is a basic article for medical students and other non-radiologists
Tuberculosis (TB) is a non-bacterial multisystem infection that often affects the lungs. It may be a primary tuberculous infection, secondary infection or appear as chronic scarring. TB may also be seen on a chest x-ray as ...
Tuberculous empyema is a chronic, active infection of the pleural space characterised by a thick rind of pleura with dense and irregular calcification of both the parietal and visceral pleura usually surrounding a loculated pleural fluid which contains a large number of tubercle bacilli 1. This ...
Tuberous sclerosis, also known as tuberous sclerosis complex or Bourneville disease, is a neurocutaneous disorder (phakomatosis) characterised by the development of multiple benign tumours of the embryonic ectoderm (e.g. skin, eyes, and nervous system).
Tuberous sclerosis has an i...
Tulip bulb sign refers to the characteristic appearance of annuloaortic ectasia as seen on CT angiography.
There is symmetric dilatation of the three sinuses of Valsalva, with extension into the ascending aorta and effacement of the sinotubular junction.
It is seen especially in Marfan syndro...
There are many tumour-like conditions of the pleura. These are non-malignant entities that on imaging may mimic a pleural tumour.
Tumours of the chest wall are varied, some of which are found most often in this region. They can be divided into benign and malignant tumours and into those which arise in the ribcage and those of soft tissue density.
Benign tumours include 1,3,4:
Tumour spread through air spaces (STAS) is a relatively recently recognised pattern of invasion in lung adenocarcinoma. According to the 2015 WHO classification, STAS is defined as “micropapillary clusters, solid nests, or single cells spreading within air spaces beyond the edge of the main tumo...
A tumour-to-tumour metastasis, also known as a collision tumour, is a rare metastatic process in which a primary malignant tumour ('donor') metastasises to another tumour ('recipient'), most commonly a benign tumour such as a meningioma.
Tumour-to-tumour metastasis is considered v...
The twelfth rib is an atypical rib. It is the shortest rib, and one of two floating ribs.
The 12th rib has a single facet on its head for articulation with the T12 vertebra. It has a short neck and no tubercle. It also lacks a costal groove and angle. internal surface ...
Type IV endoleaks are a type of endoleak which usually occurs secondary to graft porosity and are typically seen in the immediate post operative angiogram following an endovascular aneurysm repair.
Type IV endoleaks are extremely rare and studies report a prevalence of 0.3%. This ...
Typical pulmonary carcinoid tumours are considered the more common and more benign low grade form of peripheral pulmonary carcinoid tumours. There is little or no known association between typical carcinoid tumours and tobacco use or exposure to other carcinogens which contrasts to atypical carc...
Typical ribs are those numbered 2 to 10 with ribs 1, 11 and 12 considered atypical.
A typical rib is long and flat. They contain a:
Ribs have a rounded, smooth superior border. The inferior border is thin and sharp.
The term unfolded aorta refers to the widened and 'opened up' appearance of the aortic arch on a frontal chest radiograph. It is one of the more common causes for apparent mediastinal widening and is seen with increasing age.
It occurs due to the discrepancy in the growth of the ascending aorta...
A unifocalisation procedure is a corrective surgical technique used in patients with complete pulmonary artery atresia with major aortopulmonary collateral arteries (MAPCAs). In this technique, the collateral vessels supplying blood from the aorta directly to the lungs are brought into continuit...
Mnemonics for a unilateral hyperlucent hemithorax include:
C: contralateral lung increased density, e.g. supine pleural effusion
A: air, e.g. pneumothorax
W: wall, e.g. chest wall mass, mastectomy, polio, Poland syndrome, surgical re...
Unilateral hypertranslucent hemithorax has many potential causes. It may be the result of rotation away from an optimal position or because of pathology.
A unilateral hypertranslucent hemithorax may be caused by the positioning of the patient. Rotation away from the radiation beam alt...
Unilateral pulmonary artery atresia (UPAA), also known as unilateral absence of the pulmonary artery (UAPA) or proximal interruption of the pulmonary artery, is a variant of pulmonary artery atresia.
The term interruption is preferred by some to absence or atresia because the anom...
Unilateral pulmonary oedema represents only 2% of cardiogenic pulmonary oedema with predilection for the right upper lobe and is strongly associated with severe mitral regurgitation 1, 2. It is hypothesised that the regurgitation jet is directed towards the right superior pulmonary vein thus pre...
Unilateral pulmonary vein atresia is a type of pulmonary vein atresia.
The condition usually present in infancy or childhood with recurrent episodes of pneumonia and/or haemoptysis. Presentation in adulthood does occur but is uncommon.
It results from failure ...
The upper and lower lobe distribution of certain bilateral pulmonary pathologies can be recalled using the following mnemonics:
upper lobe or apical predominance: CASSET HPP or SET CAP
lower lobe or bibasilar predominance: BAD RASH
C: cystic fibrosis
A: ankylosing spo...
Distribution of bronchiectasis can help in narrowing the differential diagnosis. Upper lobe bronchiectasis is typically seen in:
Rarely it may be seen with non tuberculous mycobacterial infection (e.g. MAC infection 2). Traction bronchiectasis in the upper lobes c...
Upper lobe predominant pulmonary fibrosis can be associated with a number of pathologies. These include
cystic fibrosis: see pulmonary manifestations of cystic fibrosis
Langerhans cell histiocytosis
Upper lobe pulmonary venous diversion (cephalisation) reflects elevation of left atrial pressure and can occur with pulmonary oedema. It produces stag-antler's sign on a frontal chest x-ray.
The normal left atrial pressure is 5-10 mmHg. An elevation of left atrial pressure to 10-15 mmHg will re...
The upper zone is one of the four chest radiograph zones. Sometimes the upper zone includes the apical zone.
on frontal chest radiographs, the upper zone extends from the inferior margin of the clavicles to the superior aspect of the hilum
Urinothorax (plural: urinothoraces), also known as urothorax, is a rare cause of pleural effusion due to the accumulation of urine within the pleural space.
Patients present with varying degrees of respiratory distress depending on the amount of fluid that has accumulated...
The ubiquitous USB flash drive (or USB stick) may be an odd article on a radiology website, but those who report a lot of chest radiographs will be aware that it can be often be confused for an implantable loop recorder device or leadless pacemaker.
Whilst USB drives com...
Usual interstitial pneumonia (UIP) is a histopathologic and radiologic pattern of interstitial lung disease, which is the hallmark pattern for idiopathic pulmonary fibrosis (IPF).
On imaging, UIP usually presents with a lung volume loss and a craniocaudal gradient of peripheral septal thickeni...
American Thoracic Society (ATS) criteria for the histopathological diagnosis of usual interstitial pneumonia (UIP) are as follows:
advanced subpleural or paraseptal fibrosis +/- honeycombing
patchy temporally heterogeneous fibrosis
the absence of features against UIP
The Valsalva manoeuvre is the forced expiration of air against a closed airway, resulting in increased intra-abdominal, intrathoracic and pharyngeal pressure. It can be performed against a closed glottis or by one closing the mouth and pinching the nose while forcibly exhaling.
It is commonly u...
Vaping associated lung disease, or EVALI (e-cigarette or vaping product use-associated lung injury), consists of patterns of inhalational pulmonary injury induced by electronic cigarettes (also known as e-cigarettes, e-vaporisers, e-hookahs, vapes, vape pens). These products heat up a liquid con...
Varicella pneumonia is a type of viral pneumonia. It is a common cause of multiple small round calcific lung lesions. Varicella-zoster virus most commonly causes self-limited benign disease (chickenpox) in children. However, in adults it tends to cause significant complications including varicel...
Varicose bronchiectasis refers to an uncommon morphological sub type of bronchiectasis. According to one study, this type as a pure form accounted for ~10% of all bronchiectasis 1.
For a general discussion, please refer to the article on bronchiectasis.
There are intermi...
Vascular invasion in lung cancer is one of the invasive patterns that can occur in lung cancer. Dependant on the publication, this could mean:
intratumoural vascular invasion (IVI)
microscopic vascular invasion (MVI)
lymphovascular invasion (LVI)
Vascular pedicle is bordered on the right by venous structures (right brachiocephalic vein above and superior vena cava) and on the left by an arterial structure (the left subclavian artery origin). The azygos vein (black oval) is seen en face above the right main bronchus.
The vascular pedicle...
Vascular rings and slings refer to the congenital vascular encirclement of the oesophagus and/or trachea by anomalous/aberrant vessels.
Vascular rings are rare, occurring in <1% of patients 1. No gender or ethnic predispositions have been identified 3.
The vena caval foramen is one of the three major apertures in the diaphragm. It is the highest of the three and situated at the level of T8-9. It is quadrilateral and placed at the junction of the right and middle leaflets of the central tendon.
It transmits several structures between the thora...
The venous drainage of the thoracic wall drains deoxygenated venous blood from the peripheries of the thoracic cage back into systemic circulation.
Anterior thoracic wall
Anterior intercostal veins
The anterior intercostal veins originate from the intercostal space just inferio...
Ventilator-associated pneumonia (VAP) is a form of hospital acquired pneumonia (considered the commonest form 3).
It is sometimes defined as a pneumonia occurring more than 48 hours after patients have been intubated and received mechanical ventilation 5.
It is usually suspected when the patie...
Ventriculopleural shunting is an alternative option for the diversion of CSF and relief of hydrocephalus. In this technique, the distal catheter is placed in the pleural space. It is an alternative to a ventriculoperitoneal shunt (often considered a next most used alternative).
The vertical fissure line commences in or near the costodiaphragmatic recess and heads superomedially towards the hilum and terminates before or at the horizontal fissure. More commonly occurs on the right and may indicate partial volume loss of the lower lobe 1.
Viral bronchiolitis refers to a bronchiolitis secondary to viral aetiology.
Viral infection of airways resulting in inflammation and peribronchial oedema. Can then result in small airways occlusion which is the basis of hyperinflation and subsegmental atelectasis. Children more susce...
Viral respiratory tract infection is a broad term given to pulmonary infection caused by viruses.
They can be caused by any of a large number of viral agents, including but not limited to:
H1N1 pneumonia (swine influenza)
Visceral pleural invasion is a feature that can be seen in lung cancers. It is defined as tumour extension beyond the elastic layer of the visceral pleura. It is considered an aggressive sign and one of the most important adverse prognostic factors in non-small cell lung cancers 1.
Vital capacity (commonly termed VC) is a spirometric parameter giving maximum amount of air that can be expelled from the lungs after a maximum inhalation. It is equal to the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume.
Vital capacity increases with
V/Q (ventilation/perfusion) scan is a scintigraphic examination of the lung that evaluates pulmonary vasculature perfusion and segmental bronchoalveolar tree ventilation.
diagnosis of suspected pulmonary embolism
monitor pulmonary function following lung transplant
The water bottle sign or configuration refers to the shape of the cardiac silhouette on erect frontal chest x-rays in patients who have a very large pericardial effusion. Typically the effusion has accumulated over many weeks to months (e.g. in patients with malignancy) and the pericardium has g...
The water-lily sign is seen in hydatid infections when there is detachment of the endocyst membrane which results in floating membranes within the pericyst that mimic the appearance of a water lily.
It is classically described on plain radiographs (mainly chest X-ray) when the collapsed membran...
A well-differentiated fetal adenocarcinoma (WDFA) of lung is a rare low grade lung tumour. Some consider this as a variant of adenocarcinoma with others considering this under the group of pulmonary blastomas 5.
According to classification by the World Health Organisation in 1999, it was remov...
The Wells criteria for pulmonary embolism is a risk stratification score and clinical decision rule to estimate the probability for acute pulmonary embolism (PE) in patients in which history and examination suggests acute PE is a diagnostic possibility. It provides a pre-test probability which, ...
Westermark sign is a sign of pulmonary embolus seen on chest radiographs. It is one of several described signs of pulmonary embolus on chest radiographs.
The theory behind the sign is either obstruction of the pulmonary artery or distal vasoconstriction in hypoxic lung 3.
In one stu...
Thoraco-pulmonary manifestations of Whipple disease are uncommon and present in the late stages of the disease.
Lung involvement is seen in 35-60% of patients with gastrointestinal whipple disease.
Majority of patients present with non-specific pulmonary an...
The WHO classification scheme for thymic epithelial tumours is one of many classifications systems for thymoma and related tumours, and classifies them according to histology:
spindle cell thymoma
type ab: mixed thymoma
type b1: lymphocyte rich