D-SPECT represents the next step in the evolution of SPECT technology and is based on a unique acquisition geometry. It has nine arrays of cadmium zinc telluride (CZT) detectors, each of which rotates around its central axis with programmable angular rotation 1. The detectors are very compact al...
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.
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).
Dacryocystitis has a bimodal distribution: neonates and individuals older than 40 years of age.
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.
Dacryocystoceles, although rare, are the second mo...
The dagger sign is a radiographic feature seen in ankylosing spondylitis as a single central radiodense line on frontal radiographs related to ossification of supraspinous and interspinous ligaments.
Dameron-Lawrence-Bofte classification of proximal 5th metatarsal fractures divides fractures into three zones based on anatomy:
zone 1: tuberosity of 5th metatarsal
avulsion fracture of tuberosity or pseudo-jones fractures
zone 2: meta-diaphyseal junction
zone 3: proximal di...
Dandy-Walker continuum, also referred as Dandy-Walker spectrum or Dandy-Walker complex, corresponds to a group of disorders believed to represent a continuum spectrum of posterior fossa malformations, characterised by a combined posterior fossa cyst communicating with the fourth ventricle as wel...
Dandy-Walker malformation (DWM) is the most common posterior fossa malformation, characterised by the triad of:
hypoplasia of the vermis and cephalad rotation of the vermian remnant
cystic dilatation of the fourth ventricle extending posteriorly
enlarged posterior fossa with torcular-lambdoi...
Dandy-Walker variant (DWv) is a less severe posterior fossa anomaly than the classic Dandy-Walker malformation (DWM) and is considered being on the lesser end of the disease spectrum in the Dandy-Walker continuum.
This term was created to include those malformations that do not mee...
The danger space is a potential space located behind the true retropharyngeal space, which connects the deep cervical spaces to the mediastinum.
anteriorly: alar fascia
posteriorly: prevertebral layer of the deep cervical fascia
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...
Dashes and hyphens are used all over Radiopaedia.org and should be used in a particular way to ensure cohesive use across the site.
Dashes and hyphens
In publishing, there are distinct differences between the following which usually are of different lengths:
minus sign: used exclusively to ...
Dawson fingers are a radiographic feature depicting demyelinating plaques through the corpus callosum, arranged at right angles along medullary veins (callososeptal location). They are a relatively specific sign for multiple sclerosis (MS), which presents as T2 hyperintensities.
History and ety...
De Garengeot hernia is defined as a femoral hernia containing the appendix. It is a rare phenomenon, with only 1% of all femoral hernias containing the appendix (and usually found incidentally at surgery), and only 0.08-0.13% containing an incarcerated acute appendicitis (sometimes detected on p...
De Quervain tenosynovitis, also known as washerwoman's sprain/strain, is a painful stenosing tenosynovitis involving the first extensor (dorsal) tendon compartment of the wrist (typically at the radial styloid). This compartment contains the abductor pollicis longus (APL) and extensor pollicis b...
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.
It usually affects middle age fema...
The Deauville five-point scale (Deauville 5ps) is an internationally recommended scale for clinical routine and clinical trials using FDG-PET/CT in the initial staging and assessment of treatment response in Hodgkin lymphoma (HL) and certain types of non-Hodgkin lymphomas (NHL).
Along with the Stanford classification, the DeBakey classification is used to separate aortic dissections into those that need surgical repair, and those that usually require only medical management.
The DeBakey classification divides dissections into 1-5:
type I: involves asce...
There are a number of debated spellings in our world. We are well aware that there are accepted differences between UK and US English. We tend towards British spelling on the site, but realise that with an international audience, we will have British and American spelling on the site.
The decibel (dB) is a unit that measures the relative difference between two sound intensities. The relationship is logarithmic:
dB = 10 log (I2 / I1)
dB = relative intensity of the sounds
I1 = intensity of sound 1
I2 = intensity of sound 2
Informally, we use decibel as a unit of "loudness,...
Decidual cast refers to the presence of an amount of relatively echogenic material in the uterine cavity in the context of an ectopic pregnancy.
A decidual reaction is feature seen in very early pregnancy where there is a thickening of the endometrium around the gestational sac. A thin decidual reaction of less than 2 mm is considered one of the features suggestive of an anembryonic pregnancy 2. A decidual reaction in some situations can...
A dedifferentiated chondrosarcoma is a combined tumour made up to two components which are often sharply demarcated from one another (thus raising the possibility of it representing a collision tumour).
conventional chondrosarcoma (low grade)
dedifferentiated high grade areas
Deductive echocardiography is a step-by-step approach in diagnosing and differentiating congenital heart disease.
position of heart
Deep brain stimulation is used in a variety of clinical settings, predominantly in patients with poorly controlled movement disorders. Although effective, its exact mode of function continues to be poorly understood 2.
Careful patient selection and target selection are essential if the proced...
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).
The method combines two main components 1:
MRI of the ...
Deep cerebral vein thrombosis is a subset of cerebral venous thrombosis involving the internal cerebral veins, often coexisting with cortical vein thrombosis or dural venous sinus thrombosis, and with different clinical presentations relying on which segment is involved.
As such please refer to...
The deep cervical fascia consists of 3 separate but related fascial layers that encircle structures in the neck and allow anatomic compartmentalisation. All 3 layers meet to form the carotid sheath. From superficial to deep, the 3 layers are:
1. Investing layer of the deep cervical fascia is th...
The deep circumflex iliac artery arises from the external iliac artery.
origin: lateral aspect of the external iliac artery above the inguinal ligament, almost opposite to the inferior epigastric artery
course: travels superiorly parallel to the inguinal ligament towards the ant...
The deep femoral vein or the profunda femoris vein lies anterior to its artery, and receives tributaries corresponding to the branches of the artery. Through these tributaries it connects distally with the popliteal and proximally with the inferior gluteal veins. It sometimes drains the medial a...
Deep inferior epigastric perforator flap (DIEP) reconstruction is a type of breast reconstruction surgery. It essentially involves the transfer of the patient's own skin and subcutaneous tissues from the lower abdominal wall to the chest to form the breast mound.
The operation spare...
The deep inguinal nodes lie medially to the femoral vein. There are around three in number and receive lymphatic channels that run with the deep femoral vessels and from the glans penis / clitoris from the perineum. There are common channels with the superficial inguinal nodes, and they drain in...
The deep perineal pouch is an anatomic space above the perineal membrane in the urogenital triangle of the perineum, posterior to the transverse line between the ischial tuberosities.
The deep perineal pouch is above (deep to) the perineal membrane in the urogenital triangle.
The deep peroneal (fibular) nerve is one of two terminal branches of the common peroneal nerve.
origin: the terminal branch of common peroneal nerve in the lateral compartment of the leg
course: passes into the anterior compartment of the leg, where it courses inferiorly into the dors...
The deep posterior compartment of the leg is one of the four compartments in the leg between the knee and foot. Muscles within this compartment primarily produce ankle plantarflexion and toe flexion, with exception of the popliteus which acts on the knee. Of the two posterior compartments, the d...
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.
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 ...
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
branch communicates with the lacrimal artery by means of small branches w...
The term deep vein thrombosis (DVT) is practically a synonym for those that occur in the lower limbs. However, it can also be used for those that occur in the upper limbs and neck veins. Other types of venous thrombosis, such as intra-abdominal and intracranial, are discussed in specific section...
The deepest (maximal) vertical pocket (DVP) depth is considered a reliable method for assessing amniotic fluid volume on ultrasound 1-2. It is performed by assessing a pocket of maximal depth of amniotic fluid which is free of umbilical cord and fetal parts.
The usually accepted values are:
Degenerative disc disease (DDD) is an exceedingly common entity in the spine, encountered with increasing frequency throughout life and becoming almost universal in late adulthood to a varying degree. It is related to a combination biomechanical stresses and genetic predisposition which alter th...
Degloving bowel injuries are a rare type of bowel and mesenteric injury only being described a handful of times in the literature 1-5. In these injuries the bowel is stripped of its mesentery and muscle, leaving a "mucosal tube" 2,3. Perforation may or may not be present.
Degloving injuries can refer to a number of conditions:
degloving soft tissue injury
Morel-Lavallee lesion (closed degloving soft tissue injury)
intramuscular degloving injury
degloving bowel injury
Degloving soft tissue injuries can be extensive and quite severe conditions. These may be open or, less commonly, closed injuries, which are known as Morel-Lavallee lesions. This article focuses on open injuries with closed injuries discussed in the Morel-Lavallee lesion article.
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. ...
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.
It is one of the causes of pulsatile tinnitus and is a common cause of a ...
Dejerine-Sottas disease (also sometimes known as hereditary motor and sensory neuropathy type III or hypertrophic interstitial polyneuritis) is a rare hereditary motor and sensory neuropathy (HMSN).
The disease is characterised by an early-onset demyelinating neuropathy, ...
A generalised retardation in skeletal maturation has different causative or aetiological factors, these can be classified as follows:
chronic ill health
congenital heart disease (especially cyanotic)
chronic renal disease
inflammatory bowel disease
malnutrition: failure to thrive (FTT)
Delayed myocardial enhancement, as seen on cardiac MRI, occurs when gadolinium contrast material seeps into fibrotic or necrotic myocardial tissue. It is due to a number of aetiologies, and has variable appearances.
subendocardial enhancement indicates an ischaemic aetiology
Delayed myocardial enhancement can occur in cardiac MR assessment due to a number of causes.
myocardial ischaemia: typically subendocardial and follows a vascular territory 1
nonischaemic dilated cardiomyopathy
Delayed nephrogram, commonly described on plain film urography, but also visible on CT urography, is when there is absence or reduction of normal renal parenchymal enhancement on nephrographic phase images.
A delayed nephrogram is characteristically unilateral and is usually distinguished from ...
Delayed onset muscle soreness (DOMS) refers to the muscular pain and swelling that follows unaccustomed exertion.
Patients may have an ache in affected muscles with reduced strength 4.
DOMS is thought to occur from reversible microstructural muscle injury that...
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 ...
The delta resistive index (delta RI or Δ RI) is a measurement that can be made when performing Doppler ultrasound.
In preterm babies who have hydrocephalus secondary to intraventricular haemorrhage, the delta RI can be used to determine whether decompression of the ventricular system with a...
Deltoid ligament injuries involve the deltoid ligament that forms the medial part of the ankle joint. It attaches the medial malleolus to multiple tarsal bones.
Mechanism of injury
It occurs due to eversion and/or pronation injury, or can be associated with lateral ankle fractures.
The deltoid ligament or medial collateral ligament of the ankle forms the medial part of the ankle joint. It attaches the medial malleolus to multiple tarsal bones.
The ligament is composed of two layers. The superficial layer has variable attachments and crosses two joints whil...
The deltoid muscle is the largest of the shoulder muscles. The muscle is composed of three heads (clavicular, acromial and spinous), although electromyography suggests that there are at least seven control regions that could act independently 1.
origin: lateral 1/3 of the clavicle, acr...
Dementia with Lewy bodies (DLB), also known as Lewy body disease, is a neurodegenerative disease (a synucleinopathy to be specific) related to Parkinson disease (PD). It is reported as the second most common form of dementia following Alzheimer disease (AD), accounting for 15-20% of cases at aut...
Demise of a twin is a complication that can occur in a twin pregnancy (particularly monochorionic pregnancies) and may be due to a wide range of conditions. Once the twin dies, most of the dead twin tends to be absorbed leaving behind a small flattened remnant known as the fetus papyraceus.
Demyelinating disorders are a subgroup of white matter disorders characterized by the destruction or damage of normally myelinated structures. These disorders may be inflammatory, infective, ischaemic or toxic in origin and include 1-7:
multiple sclerosis (MS)
Demyelination is incorrectly often equated to multiple sclerosis, whereas in reality it is a generic pathological term simply describing, as the word suggests, the loss of normal myelin around axons in the central nervous system. This should be distinguished from dysmyelination where the formati...
MRI protocol for demyelinating diseases is a group of MRI sequences put together to best approach these white matter disorders characterized by the destruction or damage of normally myelinated structures. These disorders may be inflammatory, infective, ischaemic or toxic in origin.
Note: This ...
Denervation changes in muscles can be observed in a number of settings.
in the very early stage, muscle signal may be normal
earliest change is increased T2 signal (best seen on a fat saturated T2WI such as STIR)
chronic changes are marked by muscle atrophy and fat...
The dense hilum sign suggests a pathological process at the hilum or in the lung anterior to posterior to the hilum. Malignancy, especially lung cancer, should be suspected.
On a well-centred chest PA radiograph the density of the hilum is comparable on both sides. In the...
The differential diagnosis of dense metaphyseal bands is wide.
chronic anaemia, e.g. sickle cell disease, thalassemia
chemotherapy, e.g. methotrexate
growth acceleration lines following growth arrest due to systemic illness or stress in infancy or childhood, e....
Dental (periapical) abscess is an acute infection of the periapical tissue around the root of the tooth.
Patients may present with pain, oedema and purulent discharged localised to the site of pathology with or without fever and tender cervical lymphadenopathy 1.
The dentate gyrus is located in the mesial temporal lobe and forms part of the hippocampal formation, along with the hippocampus proper and subiculum.
The dentate gyrus receives fibres from the entorhinal cortex via the perforant path and projects fibres to the CA3 portion of the hippocampus. ...
The dentate nucleus is the largest and most lateral of the cerebellar nuclei, located medially within each cerebellar hemisphere, just posterolateral to the fourth ventricle 1. It is part of the triangle of Guillain and Mollaret, connected to the contralateral red nucleus via the superior cerebe...
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 ...
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.
The screening protocol criteria 1,3 for BCVI are divided into signs and symptoms of BCVI a...
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.
collar sign (or hour glass sign)
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.
These mostly (~75%) occur in the frontoparietal region 3.
There are number of as...
Dermatofibrosarcoma protuberans (DFSP) is an uncommon exophytic, slow growing, low grade, spindle cell tumour arising in the dermal and subcutaneous tissues, particularly of the trunk region with excellent outcome after complete surgical resection.
The tumour occurs in patients of...
Dermatomyositis is an autoimmune inflammatory myositis.
There is a recognised female predilection. It has a bimodal age of presentation depending on the variant:
juvenile dermatomyositis (JDM): affects children and tends to be more severe
adult dermatomyositis (ADM): typically a...
The dermolipoma is one of the fat-containing epibulbar mass lesions of lateral canthal area beneath the temporal or superotemporal bulbar conjunctivae.
Dermolipomas are congenital and more commonly seen in young patients with mean age of 30 years old. There is no gender predilect...
A derotational screw is an orthopaedic device used for internal fixation of fractures to, unsurprisingly, limit rotation of the fracture.
They are applied across fractures at risk of rotation and hence avascular necrosis.
The descending aorta is the continuation of the aortic arch in the posterior mediastinum.
The descending aorta commences at the level of the fourth thoracic vertebra body in the plane of Ludwig as the continuation of the aortic arch. It continues as the abdominal aorta at the aor...
The descending branch of the lateral circumflex femoral artery descends from the lateral aspect of the femoral neck and extends as far as the knee where it provides blood to the patellar network (the complex arterial anastomosis around the knee).
origin: lateral circumflex femoral arte...
The descending colon is the continuation of the transverse colon after the left colic flexure, where the colon loses its mesentery.
The descending colon measures up to 25 cm length and is secondarily retroperitoneal. It descends down and is attached to the left posterior abdomin...
The descending geniculate artery arises from the distal portion of the superficial femoral artery before it becomes the popliteal artery. Along with other arterial branches, it provides blood to the patella network and the knee.
origin: superficial femoral artery
supply: patella netwo...
Describing a fracture is a basic requirement when making an assessment of a plain radiograph. There are many ways to approach the assessment of the radiograph; this is just one approach.
I: Describe the film
What film (or films) are you looking at? Check the who, what, why, when and where.
Desmoid tumours are benign, non-inflammatory fibroblastic tumours (see WHO 2002 classification of soft tissue tumours) with a tendency for local invasion and recurrence but without metastasis.
The terms desmoid tumour and aggressive fibromatosis are occasionally used synonymously b...
Desmoplastic fibromas (DF) are extremely rare bone tumours that do not metastasize, but may be locally aggressive. They are considered to be a bony counterpart of soft tissue desmoid tumours and are histologically identical.
Incidence is ~0.3%. The most common areas of i...
Desmoplastic infantile gangliogliomas are a form of desmoplastic infantile tumours, and despite their aggressive appearances tend to have a good prognosis.
The vast majority occur in children with less than one year of age, and males are more commonly affected with a M:F ratio of...
Desmoplastic infantile tumours are rare benign lesions that has aggressive radiological and pathological features. Patients usually present in first two years of life.
increasing head circumference
Desmoplastic small round cell tumour (DSRCT) is a rare and highly aggressive primary peritoneal malignancy. It is seen usually in young adoloscent and has male predominance with a mean survival of 2-3 years.
It usually presents with a palpable abdominal mass and abdominal...
Desquamative interstitial pneumonia (DIP) is an interstitial pneumonia closely related to, and thought to represent the end stage of respiratory bronchiolitis interstitial lung disease (RB-ILD) 1. It is associated with heavy smoking.
It is considered one of the rarest of idiopathi...
Detective quantum efficiency (DQE) is one of the fundamental physical variables related to image quality in radiography and refers to the efficiency of a detector in converting incident x-ray energy into an image signal.
The words "quantum efficiency" have a precise meaning, because the DQE me...
Atrial situs refers to the relative position of cardiac atria in relation to abdominal viscera and the midline.
Identification of atrial situs is an important initial step in the antenatal and postnatal diagnosis of cardiac structural and situs anomalies.
Deterministic effects describe a cause and effect relationship between radiation and some side-effects. They are also called non-stochastic effects to contrast their relationship with the chance-like stochastic effects, e.g. of cancer induction.
Deterministic effects have a threshold below whic...
Developer solution is used in dark room for developing (i.e. converting latent image to visible image) X-ray films used in conventional (screen film) radiography.
developer: hydroquinone (for high contrast) + metal/phenidone (for low contrast)
the developer itself gets oxidised and...
Developmental anomalies of the kidneys and ureters are numerous and not only potentially render image interpretation confusing but also, in many instances, make the kidneys more prone to pathology:
horseshoe kidney - most common
Developmental dysplasia of the hip (DDH) denotes aberrant development of the hip joint and results from an abnormal relationship of the femoral head to the acetabulum. There is a clear female predominance, and it usually occurs from ligamentous laxity and abnormal position in utero. Therefore, i...