The commonly used abbreviations e.g. (for example) and i.e. (that is) are sometimes used incorrectly. E.g. is used to give one or more examples, while i.e. is meant to clarify and elaborate a bit on the preceding text.
e.g. (Latin abbreviation of "exempli gratia") means "for exam...
Eagle syndrome refers to symptomatic elongation of the styloid process or calcified stylohyoid ligament 1-2. It is often bilateral. In most cases the cause is not known however the condition is sometimes associated with disorders causing heterotopic calcification such as abnormal Calcium-Phospho...
Early DWI reversal in ischaemic stroke (also referred to as diffusion lesion reversal) is encountered early in the course of ischaemic infarction, most frequently in the setting of reperfusion within 3 to 6 hours of onset 1. In the vast majority of cases it is transient and does not represent tr...
Early pregnancy roughly spans the first ten weeks of the first trimester.
0-4.3 weeks: no ultrasound findings
possible small gestational sac
possible double decidual sac sign (DDSS)
possible intradecidual sac sign (IDSS)
The earth-heart sign is a newly recognised sign of cardiac compromise that may be seen on chest radiographs of patients with tension pneumomediastinum.
The substantial pressure exerted on the heart by the air trapped in mediastinum with subsequent impairment of central venous return and obstruc...
Ebola virus disease (EVD) (also known as Ebola haemorrhagic fever (EHF) or simply Ebola) is a viral haemorrhagic disease caused by the Ebola Filovirus. Ebola is an extremely virulent virus with case fatality rates of approximately 70% 1.
First recognized in 1967 after polio vaccin...
Ebstein anomaly is an uncommon congenital cardiac anomaly, characterised by a variable developmental anomaly of the tricuspid valve.
The anomaly accounts for only ~0.5% of congenital cardiac defects 6-7, although it is the most common cause of congenital tricuspid regurgitation. ...
The eccentric target sign is considered pathognomonic for cerebral toxoplasmosis. It is seen on postcontrast MRI/CT as a ring enhancing lesion with an eccentrically located enhancing mural nodule. It is believed that this mural nodule is an extension from the abscess wall itself with inflamed ve...
Ecchordosis physaliphora is a congenital benign hamartomatous lesion derived from notochord remnants, usually located in the retroclival prepontine region, but can be found anywhere from the skull base to the sacrum.
There has been some controversy as to whether intradural chordom...
Echo planar imaging is performed using a pulse sequence in which multiple echoes of different phase steps are acquired using rephasing gradients instead of repeated 180o RF pulses following the 90°/180° in a spin-echo sequence. This is accomplished by rapidly reversing the readout or frequency- ...
The echo time refers to time between the application of radiofrequency excitation pulse and the peak of the signal induced in the coil. It is measured in milliseconds. The amount of T2 relaxation is controlled by TE.
Echogenic amniotic fluid can potentially arise from a number of entities which include
vernix caseosa : commonest cause
haemorrhage into amniotic cavity
However according to some studies 2 pathological analysis of echogenic appearing fluid had reveal normal amniotic fl...
Echogenic fetal bowel is an observation in antenatal ultrasound imaging, in which fetal bowel appears to be brighter than it is supposed to be. It is a soft marker for trisomy 21 and has several other associations. When observed, it needs to be interpreted in the context of other associated abno...
Echogenic fetal lung lesions on antenatal ultrasound can be detected in a number of situations. They include:
Airway obstructions: lung are often enlarged and echogenic bilaterally
congenital high airways obstruction syndrome (CHAOS)
congenital tracheal stenosis
Echogenic intracardiac focus (EIF) is a relatively common sonographic observation that may be present on an antenatal ultrasound scan.
They are thought to be present in ~4-5% of karyotypically normal fetuses. They may be more common in the Asian population 5.
Echogenic renal pyramids in children can be due to many different causes.
Iatrogenic (most common cause)
An echogenic yolk sac is an indeterminate finding in first-trimester fetal ultrasound. It differs from a calcified yolk sac, in that the contents of the yolk sac are echogenic, not just the rim.
One study has suggested that this finding is associated with fetal demise, but other reports in the ...
The Eastern Cooperative Oncology Group (ECOG) is one of the largest clinical cancer research organizations in the United States, and conducts clinical trials in all types of adult cancers.
The ECOG performance status is a scale used to assess how a patient's disease is progressing, assess how t...
Ectodermal dysplasia (ED) refers to a heterogeneous group of genetic disorders that cause abnormal ectoderm development. The effect is a non-progressive defect in the development of two or more tissues derived from embryonic ectoderm.
ED is rare with an estimated prevalence of 1:...
Ectopia cordis is an extremely rare congenital malformation where the heart is located partially or totally outside the thoracic cavity. The four main ectopic positions are::
adjacent to the thorax: ~60 %
The estimated ...
Ectopia lentis refers to subluxation or dislocation of the lens secondary to dysfunction or disruption of zonular fibers.
systemic and syndromic disorders
typically upwards and out
most common spontaneous cause 2
homocystinuria - typically do...
Ectopic intracaval liver is a rare congenital abnormality of the liver in which a part of the liver invaginates the inferior vena cava (IVC). Lobar or segmental agenesis, Riedel lobe, and ectopic hepatic lobes have been described as congenital abnormalities 1. The term ectopic intracaval may be ...
Ectopic kidney (or renal ectopia) is a developmental renal anomaly characterised by abnormal anatomical location of one or both of the kidneys.
They can occur in several forms:
cross fused renal ectopia
ectopic thoracic kidney
The estimated inc...
Ectopic pancreatic tissue (or heterotopic pancreatic tissue) refers to the situation where rests of pancreatic tissue lie outside and separate to the pancreatic gland. Most patients are completely asymptomatic.
It is reportedly relatively common, affecting ~5% (range 1-10%) 1 of p...
An ectopic posterior pituitary reflects a disruption of normal embryogenesis and is one of the more common causes of pituitary dwarfism. Although it can be an isolated abnormality, numerous other congenital central nervous system malformations have been identified.
Ectopic pregnancy refers to the implantation of a fertilised ovum outside of the uterine cavity.
The overall incidence has increased over the last few decades and is currently thought to affect 1-2% of pregnancies. There is an increased incidence with in-vitro fertilisation (IVF) ...
Ectopic testes are a rare congenital anomaly, differing from undescended testis (cryptorchidism) in that ectopic testis is congenitally abnormal located testis descended from the abdominal cavity away from the normal path of descent while undescended testis are congenitally abnormal located test...
An ectopic thyroid gland is one which is located in a location other than the normal position anterior to the laryngeal cartilages.
The during embryological development, the thyroid gland migrates down from the foramen caecum at the posterior aspect of the tongue, to its permanent location. Thi...
An ectopic ureter is a congenital renal anomaly that occurs as a result of abnormal caudal migration of the ureteral bud during its insertion to the urinary bladder. Normally the ureter drains via the internal ureteral orifice at the trigone of the urinary bladder.
In females, the most common ...
Ectrodactyly (also known as a split hand-split foot malformation, cleft hand or lobster claw hand) is a skeletal anomaly predominantly affecting the hands (although the feet can also be affected). The condition has a highly variable severity.
The estimated incidence is at ~ 1 in 9...
Ectrodactyly-ectrodermal dysplasia-clefting (EEC) syndrome is a rare genetic syndrome that has high clinical variability but typically comprises of the triad of
ectrodactyly +/- syndactyly 1 +/- polydactyly 5
facial clefts: cleft lip and/or palate
The EDiR day 1 exam is part of the European Diploma in Radiology. It is held on day one of a two day exam and is divided into two parts.
short cases (SC): computer-based (90 minutes)
multiple response questions (MRQ): computer-based (90 minutes)
skills examination: practical-o...
The EDiR day 2 exam is part of the European Diploma in Radiology. It is held on second day of a two day exam and is divided into two parts. Only candidates that pass day 1 are eligible for the day 2 examination.
The examination is oral, and there is one examiner per candidate (30 minutes).
Editors are members of the general editorial team at Radiopaedia.org and have responsibility for content review and development on the site.
Along with the senior editors, editors have responsibility for reviewing all the content that is added to Radiopaedia.org under the dire...
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The editorial team at Radiopaedia.org is made up of a number of contributors who have responsibility for the review of new content and responsibility for the development of the site.
Senior editorial team
The senior editorial team is made up of:
editor-in-chief and founder Dr Frank Gaillard
The role of editor-in-chief at Radiopaedia.org is held by the founder and our benevolent dictator for life (BDFL), Associate Professor Frank Gaillard.
Frank started Radiopaedia.org in 2007 and has run it since that time with a bunch of committed editors with a custom code-base written by Trike ...
Edwards syndrome, also known as trisomy 18, along with Down syndrome (trisomy 21) and Patau syndrome (trisomy13), make up the only three trisomies to be compatible with extra-uterine life in non-mosaic forms, albeit in the case of Edward syndrome only for a week or so.
Efface is a term frequently used by radiologists, most often in the context of CSF containing spaces in the brain (sulci and ventricles). Unfortunately it is often used incorrectly.
The word efface, in general english usage, means to cause something to fade or disappear 1-2.
In the context of...
The effective dose is used to compare the stochastic risk of non-uniform exposure to radiation. Body tissues react differently to radiation and cancer-induction occurs at different rate of dose in different tissues. Hence, the effective dose is the risk of developing fatal cancer in the tissue i...
Antonio Caetano de Abreu Freire Egas Moniz (b. November 29, 1874; d. December 13, 1955) was a Portuguese neurologist that is notable on radiology history by the development of cerebral angiography in 1927. He is also known as the developer of prefrontal leucotomy for which he received a Nobel P...
Egg shell calcifications in the breast are benign peripheral rim like calcifications
They represent calcifications secondary to fat necrosis, calcification of oil cysts.
thin rim like calcification (< 1mm in thickness)
small to several cent...
Egg-on-a-string sign, also referred as egg on its side, refers to the cardiomediastinal silhouette seen in transposition of the great arteries (TGA).
The heart appears globular due to an abnormal convexity of the right atrial border and left atrial enlargement and therefore appears like an egg...
Eggshell calcification refers to fine calcification seen at the periphery of a mass, and usually relates to lymph node calcification.
In 1967 Jacobsen and Felson published criteria to help "avoid over-reading of the incidental circumferential concentrations of calcium and to eliminate conf...
A helpful mnemonic for major causes of eggshell calcification in the thorax and mediastinum is:
A Silly Cool Sergeant Likes His Tubercular Blast
C: coal workers' pneumoconiosis (CWP)
L: lymphoma: (postirradiation Hodgkin disease)
Ehlers Danlos syndrome comprises a heterogenous group of collagen disorders (hereditary connective tissue disease).
There is a recognised male predominance.
Clinically manifests by skin hyperelasticity and fragility, joint hypermobility and blood vessel fra...
Eisenmenger complex is a specific subset of Eisenmenger syndrome, and consists of:
ventricular septal defect (VSD)
severe pulmonary arterial hypertension resulting in
shunt reversal and cyanosis
Eisenmenger syndrome is a complication of an uncorrected high-flow, high-pressure congenital heart anomaly leading to chronic pulmonary arterial hypertension and shunt reversal.
In general the shunts that lead to Eisenmenger syndrome share are high pressure and high flow 3. As suc...
The ejaculatory ducts are paired structures of the male reproductive system and convey seminal fluid.
Each ejaculatory duct is formed by the union of the excretory duct of the seminal vesicle and the ampulla of the vas deferens and is approximately 2cm long. They course through t...
Ejaculatory duct cysts are rare type of prostatic cyst.
They occur due to obstruction of the ejaculatory ducts which in turn can either be congenital or secondary (e.g. inflammation).
They are usually intraprostatic when small but may extend cephalad when large.
A useful mnemonic to remember the ejaculatory pathway of sperm is:
S: seminiferous tubules
V: vas deferens
E: ejaculatory duct
Eklund modified compression technique is a technique which can be used for patients with augmented or reconstructed breasts post mastectomy.
It consists of postero-superior displacement of the implants simultaneously to an anterior traction of the breast, pushing the implants towar...
Elastofibroma dorsi is a benign soft-tissue tumour with a characteristic location and imaging appearance.
It is more frequently seen in older women, with a reported female predilection of 5-13:1. The estimated mean age at diagnosis around 65-70 years.
Elastography is a newer technique that exploits the fact that a pathological process alters the elastic properties of the involved tissue. This change in elasticity is detected and imaged using elastography.
strain elastography (also known as static o...
The elbow is a complex synovial joint formed by the articulations of the humerus, the radius and the ulna.
The elbow joint is made up of three articulations 2, 3:
radiohumeral: capitellum of the humerus with the radial head
ulnohumeral: trochlea of the humerus w...
Elbow arthroplasties are an increasingly common joint replacement, most often used for treatment of late stage rheumatoid arthritis, but which may also be used as a treatment for late stage osteoarthritis or complex fractures of the proximal radius, proximal ulna, or distal humerus.
Elbow dislocation is the second most common large joint dislocation in the adult population.
A dislocation with no fracture is simple whereas an accompanying fracture makes the dislocation complex. The most common fracture is a radial head fracture, although coronoid process fracture is also c...
Recognising an elbow joint effusion on lateral radiographs is an essential radiology skill. While the fluid itself is not discretely seen because it is the same density as the surrounding muscles, an effusion can be inferred by observing displacement of the anterior and / or posterior fat pads s...
Elbow ossification occurs at the six elbow ossification centers in a reproducible order. Being familiar with the order of ossification of the elbow is important in not mistaking an epicodylar fracture for a normal ossification center.
The order of appearances of the elbow os...
Mnemonics for elbow ossification include CRITOE and CRITOL. These are essentially the same, apart from the terminal letter which represents the External or Lateral epicondyle.
R: radial head
I: internal epicondyle
E: external epicon...
Elbow radiographs are common plain films that are obtained frequently in the emergency department.
Check the anterior humeral line:
drawn down the anterior surface of the humerus
should intersect the middle 1/3 of the capitellum
if it doesn't, think distal humer...
The elbow series is a set of radiographs taken to investigate elbow joint pathology, often in the context of trauma. It usually comprises an AP and lateral projection, although other non-standard, modified projections are utilised for specific indications.
Elbow x-rays are indicate...
Elbow synovial fold syndrome refers to a condition where patients experience a cluster of symptoms due to the presence of synovial folds (also known as synovial fringe or plicae).
It tends to be more common in athletic young adults. It is associated with certain sporting activitie...
The elbow AP view is part of the two view elbow series, examining the distal humerus, proximal radius and ulna.
The projection demonstrates the elbow joint in its natural anatomical position allowing for adequate radiographic examination of the articulations of the elbow including the radiohum...
The lateral elbow view is part of the two view elbow series, examining the distal humerus, proximal radius and ulna. It is deceptively one of the more technically demanding projections in radiography 1-3.
The projection is the orthogonal view of the AP elbow allowing for examination of the ulna...
The electron is a subatomic particle that has negligible mass and is negatively charged. The properties of X-rays and their interaction with matter concern the orbiting electrons with the atom.
Electrons orbit the central positively charged nucleus in shells, the outermost one of which is terme...
Electron-positron annihilation is the process in which a positron (from B+ decay) collides with an electron resulting in their annihilation. Being of opposite charges and same mass they act as collision of subatomic particle and anti-particle.
According to the law of conservation of energy , th...
Elevated craniocaudal projection is an additional trouble shooting view.
direct beam superiorly to inferiroly
face patient towards unit, feet forward
lean patient inward, relaxing the shoulders
bring inferior aspect of breast onto the image receptor
pull breast outward and forwar...
Elevated diaphragm refers to the symmetrical elevation of both domes of the diaphragm.
There is some overlap with causes of an elevated hemidiaphragm.
poor inspiratory effort
Elevated hemidiaphragms can result from many causes:
above the diaphragm 1
decreased lung volume
phrenic nerve palsy
contralateral stroke: usually middle cerebral artery distribut...
The atypical 11th rib is one of two floating ribs.
The 11th rib has a single facet on its head for articulation with the T11 vertebra. It has a short neck and no tubercle. The angle is slight. Its costal groove is shallow. The internal surface of this rib faces slightl...
The Elliott et al classification system of cardiomyopathies is one of the cardiomyopathy classification systems. This was published by the European Society of Cardiology Working Group on Myocardial and Pericardial Diseases. This places emphasis on phenotypic classification 1-2.
Eloesser flap is a single stage procedure for the treatment of severe pleural empyema, and involves a U-shaped incision and the resection of a number of subjacent posterolateral ribs. The U-shaped flap is then folded into the pleural space creating a permanent communication.
Unlike the Clagett...
Eloquent cortex is a term that refers to specific brain areas that directly controls function, thus damage to this areas generally produces major focal neurological deficits. Examples of eloquent cortex are:
primary motor cortex (precentral gyrus)
primary somatosensory cortex (postcentral gyr...
An embedded intrauterine contraceptive device is a situation where there is a an abnormally positioned IUCD within the endometrium or myometrium; however without an extension through the serosa. The IUCD should be removed in this situation. An IUCD can become embedded in the wall of the uterus o...
An embryo is a term given to a precursor of a fetus and in humans the term is usually considered to be between the first and the eighth week of development after fertilisation. The term "fetal pole" is sometimes used synonymously with the term embryo. Following this period, the term fe...
The embryonal subtype of rhabdomyosarcoma is the most common variety of rhabdomyosarcoma, accounting for 50-70% of cases 1-2. It is typically seen in children below the age of 15.
Embryonal rhabdomyosarcomas are further divided into three sub types 1:
spindle cell rhabdomyosarcoma
Embryonal tumors with multilayered rosettes (ETMR) are rare small round blue cell tumour of the central nervous system, and are one of the most aggressive brain tumours usually encountered in children.
Previously embryonal tumors with multilayered rosettes (ETMR) where known as em...
Embryonic growth discordance is a term given to a twin growth discordance occurring during the early embryonic period. It is principally manifested by a discrepancy in crown rump length. It can be a relative common finding in early twin pregnancies with the mean discrepancy according to one stud...
The embryonic/fetal rhombencephalon is visible with endovaginal ultrasound at ~8-10 weeks as a hypoechoic region in the embryonic/fetal head. The hypoechoic region represents the developing rhombencephalon/hindbrain (medulla, pons, and cerebellum).
This is a normal structure, and is reportedly ...
A useful mnemonic which is used to read an emergency head CT scan is:
Blood Can Be Very Bad
Using a systematic approach will help to ensure that significant neuropathology will not be missed.
look for epidural hematoma, subdural hematoma, intraparenchymal hemorrhage, intra...
Emphysematous cholecystitis is a rare form of acute cholecystitis. It is a surgically emergent condition, due to a risk of gallbladder gangrene and perforation.
Men are affected twice as commonly as women (reverse is true in most cases of acute cholecystitis).
The majority of pat...
Emphysematous cystitis (EC) refers to gas forming infection of the bladder wall.
The condition is rare and usually confined to certain patient subgroups.
Risk factors include:
considered the commonest predisposing factor 6
may be present in ~50%...
Emphysematous epididymo-orchitis is a rarely reported entity with only a handful of case reports which still lacks a strong evidence for the existence of the disease. It is reported as a rare cause of acute scrotum encountered in poorly controlled diabetics. Pathology of this condition is unknow...
Emphysematous gastritis is a cause of gastric emphysema, and specifically refers to infectious gastritis. It is an uncommon entity with a high mortality rate. In this condition, microorganisms (e.g. Escherichia coli, Clostridium perfringens) produce the gas, which is identified within the stomac...
Emphysematous osteomyelitis is an extremly rare form of osteomyelitis which is complicated by infection with gas forming organims. Only a handful of cases are published in literature.
Commonely reported organisms include 1
Emphysematous pancreatitis is an unusual complication of acute pancreatitis caused by necrotising infection of the pancreas. It is associated with gas-forming bacteria and characterized by the presence of gas within or around the pancreas.
Infection with gas-forming bacteria such as...
Emphysematous pyelitis is defined as isolated gas production inside the excretory system, secondary to acute bacterial infection 1. It is relatively benign entity, and needs accurate differentiation from emphysematous pyelonephritis, which is much morbid condition. It has excellent prognosis wit...
Emphysematous pyelonephritis (EPN) is a morbid infection of kidneys, with characteristic gas formation within or around the kidneys. If not treated early, it may lead to fulminant sepsis and carries a high mortality.
The patient usually presents with flank pain, urinary t...
The empty amnion sign is a sonographic observation where there is visualization of an amniotic sac without concomitant visualization of an embryo. It is an indicator pregnancy failure regardless of the mean sac diameter and is considered to have a sufficiently high positive predictive value 2. ...
The empty delta sign is CT sign of dural venous sinus thrombosis of the superior sagittal sinus, where contrast outlines a triangular filling defect (clot). It is only described with CECT-scan or MRI, not with NECT nor non-contrast MRI.
The exact mechanism for this appearance is unce...
Empty gestational sacs can be due to a number of causes:
anembryonic pregnancy (also known as "blighted ovum")
early pregnancy (intrauterine): by 5.5 weeks gestational age, a yolk sac should be identifiable by transvaginal ultrasound
pseudogestational sac with an ectopic pregnancy