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.

38 results found
Article

Dacryoadenitis

Dacryoadenitis is infection of the lacrimal gland results in diffuse homogeneous enlargement, which can sometimes compress the globe. Most common organisms are Staphylococcus aureus, mumps, infectious mononucleosis, and influenza virus.
Article

Dacryocystitis

Dacryocystitis is the inflammation of the nasolacrimal sac and needs to be distinguished from conjunctivitis and pre-septal orbital cellulits (both of which often co-exist).  Epidemiology Dacryocystitis has a bimodal distribution: neonates and individuals older than 40 years of age.  Most cas...
Article

Dacryocystocele

Dacryocystoceles are caused by obstruction of both the proximal and distal ends of the nasolacrimal duct. An imperforate Hasner membrane causes the distal blockage, but the cause of proximal obstruction is less clearly understood. Epidemiology Dacryocystoceles, although rare, are the second mo...
Article

Dacryocystography

Dacryocystography is fluoroscopic contrast examination of the nasolacrimal apparatus. The duct is cannulated enabling contrast to be instilled into the nasolacrimal system. Indications The most frequent indication is epiphoria: tearing or watering of the eyes. Technique Equipment is similar ...
Article

Danger space

The danger space is a potential space located behind the true retropharyngeal space, which connects the deep cervical spaces to the mediastinum.  Gross anatomy Boundaries anteriorly: alar fascia posteriorly: prevertebral layer of the deep cervical fascia superiorly: clivus inferiorly: post...
Article

De Quervain thyroiditis

De Quervain thyroiditis, or subacute granulomatous thyroiditis, is a form of self-limited subacute thyroiditis usually preceded by upper respiratory tract viral infection such as mumps, measles, coxsackie virus, adenovirus, and influenza viruses. Epidemiology It usually affects middle age fema...
Article

Deep brain ultrasound therapy

Deep brain ultrasound (DBUS) therapy is a form of precision medicine using a technique based on the principle of high-intensity focused ultrasound (HIFU), also referred to as focused ultrasound surgery (FUS). Technique The method combines two main components 1: guidance component MRI of the ...
Article

Deep cervical fascia

The deep cervical fascia consists of 3 separate but related fascial layers that encircle structures in the neck and allow anatomic compartmentalisation. These layers cannot be visualized directly by cross sectional imaging. All 3 layers meet to form the carotid sheath. From superficial to deep, ...
Article

Deep spaces of the head and neck

Head and neck anatomy is described in slightly different terms in the radiology literature reflecting the importance of fascia lined spaces in confining various pathologies. As such the neck has been divided into a number of 'deep spaces' which overlap with traditional anatomical description. A...
Article

Deep temporal branches

The deep temporal arteries (anterior and posterior) are branches from the second part of the maxillary artery. They ascend between the temporalis muscle and the pericranium supplying the overlying muscle. The anterior branch communicates with the lacrimal artery by means of small branches which...
Article

Deep temporal nerves

The deep temporal nerves are a pair of motor branches of the anterior division of the mandibular division of the trigeminal nerve. It should not be confused with the temporal branch of the facial nerve. Gross anatomy The two deep temporal nerves divide off the anterior division and course abov...
Article

Dehiscence

Dehiscence is a general term referring to 'splitting open' and is used in a variety of contexts in medicine generally and radiology more specifically.  The two most common usages are: splitting open of a wound (e.g. sternal dehiscence) loss of bone separating one structure from another (e.g. ...
Article

Dehiscent jugular bulb

Dehiscent jugular bulbs are present when the sigmoid plate between a high riding jugular bulb and the middle ear is absent, allowing the wall of the jugular bulb to bulge into the middle ear cavity. Epidemiology The estimated incidence may be around 3.5-7 % of the symptomatic population (e.g. ...
Article

Delphian node

The Delphian node (prelaryngeal) along with paratracheal nodes, pretracheal nodes, perithyroidal nodes make up level VI cervical lymph nodes, and is not routinely excised in radical neck dissections. It receives lymph from the thyroid and larynx.  History and etymology The Delphian node gains ...
Article

Dental abscess

Dental (periapical) abscess is an acute infection of the periapical tissue around the root of the tooth. Clinical presentation Patients may present with pain, oedema, and purulent discharge localised to the site of pathology with or without fever and tender cervical lymphadenopathy 1. Patholo...
Article

Dental caries

Dental caries are very common but can lead to serious morbidity.  Pathology Dental caries are areas of focal enamel and dentin deminerlisation. There are multiple theories in their pathogenesis but contributing factors include a combination of diet, anatomy, oral cavity microbiome and time 1,2...
Article

Dentigerous cyst

Dentigerous cysts, also called follicular cysts, are slow growing benign and non-inflammatory odontogenic cysts that are thought to be developmental in origin. On imaging, they usually present as a well-defined and unilocular radiolucency surrounding the crown of an unerupted or impacted tooth ...
Article

Denver criteria for blunt cerebrovascular injury

The Denver criteria are a set of screening criteria for blunt cerebrovascular injury (BCVI) in trauma used to reduce the need for CT angiography and its associated radiation exposure.  Screening criteria The screening protocol criteria 1,3 for BCVI are divided into signs and symptoms of BCVI a...
Article

Depressed skull fracture

Depressed skull fractures result in the bone of the skull vault being folded (depressed) inward into the cerebral parenchyma. It is usually the result of a high energy impact to the skull. Pathology These mostly (~75%) occur in the frontoparietal region 3. Associations There are number of as...
Article

Depressor anguli oris

The depressor anguli oris (triangularis) muscle is one of the muscles of facial expression. Summary origin: oblique line of the mandible insertion:  ​angle of the mouth superficial fibres from both sides merge to form the transversus menti innervation: facial nerve action:  depresses the...
Article

Dermolipoma

The dermolipoma is one of the fat-containing epibulbar mass lesions of lateral canthal area beneath the temporal or superotemporal bulbar conjunctivae. Epidemiology  Dermolipomas are congenital and more commonly seen in young patients with mean age of 30 years old. There is no gender predilect...
Article

Developmental orbital cysts

Developmental orbital cysts correspond to a heterogeneous group of congenital orbital developmental anomalies with cystic component, ranging from closed sacs lined by an ectodermal epithelium, such as epidermoid and dermoid, to neoplasms as teratoma 1.    choristoma: it is formed by heterotopic...
Article

Deviated nasal septum

A deviated nasal septum is a common incidental finding seen on brain and paranasal sinus CT studies. Pathology Aetiology It can be congenital or acquired. The most common acquired cause is trauma from motor vehicle collisions, sports-related injuries, and altercations. Associations Deviated...
Article

Diabetes insipidus

Diabetes insipidus (DI) is the deficiency or resistance to the hormone vasopressin (antidiuretic hormone), which results in polyuria and polydipsia.  Epidemiology DI occurs in 3 per 100,000 people 2.  Pathology DI may be described as 1-3: central/neurogenic/hypothalamic: vasopressin deficie...
Article

Differential diagnosis for calcified masses in the mandible

Differential diagnosis for calcified masses in the mandible includes: calcifying odontogenic cyst (Gorlin cyst) calcifying epithelial odontogenic tumour (Pindborg tumour) fibrous dysplasia foreign body odontoma cemento-ossifying fibroma osteoma synovial osteochondromatosis focal sclero...
Article

Digastric line

The digastric (or biventer) line has been described and used to evaluate basilar invagination on frontal skull plain film and coronal recontructed CT image.  The digastric line is drawn between right and left digastric grooves. The tip of the odontoid process and atlanto-occipital joint normall...
Article

Digastric muscle

The digastric muscle is composed of two bellies, anterior and posterior, connected by an intermediate round tendon. The two bellies of the muscle have different embryonic origins and hence are supplied by different cranial nerves. Summary origin anterior belly: digastric fossa on the deep sur...
Article

Digastric triangle

The digastric triangle is one of the paired triangles in the anterior triangle of the neck. The triangles of the neck are surgically focussed, first described from early dissection-based anatomical studies which predated cross-sectional anatomical description based on imaging (see deep spaces of...
Article

Disc herniation

Disc herniation refers to the displacement of intervertebral disc material beyond the normal confines of the disc but involving less than 25% of the circumference (to distinguish it from a disc bulge. A herniation may contain nucleus pulposus, vertebral endplate cartilage, apophyseal bone/osteop...
Article

Dolan's lines

Dolan's lines are the collective name given to three lines described by Dolan and Jacoby 1 that aid in evaluating for maxillofacial fractures on an occipitomental skull radiograph. They are usually used as an adjunct to McGrigor-Campbell lines. orbital line traces the inner margins of the later...
Article

Dolichoectasia

The term dolichoectasia means dilated and elongated. It is used to characterise arteries that have shown a significant deterioration of their tunica intima (and occasionally the tunica media), weakening the vessel walls and causing the artery to elongate and distend. Epidemiology Dolichoectasi...
Article

Dorello canal

Dorello canal channels the abducens nerve (CN VI) from the pontine cistern to the cavernous sinus.  Gross anatomy Dorello canal is found at the medial most end of the petrous ridge at the confluence of the inferior petrosal, basal, and cavernous sinuses. Boundaries superiorly: petrosphenoida...
Article

Dorsal nasal artery

The dorsal nasal artery, also known as the dorsonasal artery, is a terminal branch of the ophthalmic artery. Gross anatomy Arising as a terminal branch of the ophthalmic artery, the dorsal nasal artery exits the orbit after piercing the orbital septum above the medial canthal tendon (medial pa...
Article

Dorsum sellae

The dorsum sellae is the square shaped process of the sphenoid bone. It ascends superiorly from the posterior part of the sphenoid body to form the posterior wall of the sella turcica. Gross anatomy Relations The dorsum sellae forms the posterior wall of the sella turcica, which houses the pi...
Article

Double disc sign

Thickening of the insertion of the lateral pterygoid muscle can mimic an anterior displaced temporomandibular disc. When both thickening of the inferior belly insertion and an anteriorly displaced disc are present, the two structures parallel each other; the so-called "double disc" sign.
Article

Duct of Rivinus

The duct of Rivinus connects the sublingual gland to the floor of the mouth. Despite its name, it is not a single duct, but numerous small ducts all of which open into the floor of the mouth and are collectively termed the duct of Rivinus. The largest of these little ductules is the major duct...
Article

Ducts of the salivary glands

The ducts of the salivary glands allow the passage of salivary juice from the glands to the oral cavity: parotid duct (Stenson duct): connects the parotid gland to the buccal mucosa, adjacent to maxillary second molar submandibular duct (Wharton duct): connects the submandibular gland to the f...
Article

Dysphagia

Dysphagia refers to subjective awareness of difficulty or obstruction during swallowing. It is a relatively common and increasingly prevalent clinical problem.  Fluoroscopy is the mainstay of imaging assessment but manometry can help evaluate the esophageal motor pattern and lower esophageal sp...

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