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.

12,346 results found
Article

Anal canal cancer protocol (MRI)

Anal canal cancer is relativity rare, however, there are several protocols that exist for assessment of various pelvic pathology. One method adopted for optimum assessment for anal cancer is (Auckland-New Zealand) Overview: whole pelvis T1 +/- T2FS Fine 3 mm slices through region of concern (...
Article

Anal canal fistula assessment (MRI)

MR of the pelvis can demonstrate hidden areas of pelvic infection and secondary extensions which are important to detect prior to the sugary to minimize high rate of recurrence post intervention. Also pelvic MRI assists to delineate the anatomic relationships of the fistula to sphincters which c...
Article

Anal cancer

Anal cancer is a relatively uncommon, accounting for less than 2% of large bowel malignancies, and most of the cases are made of squamous cell carcinoma.  Epidemiology It accounts for less than 2% of large bowel malignancies and 1-6% of anorectal tumors (~1.5% of all gastrointestinal tract mal...
Article

Anal cancer (staging)

The most recent version of TNM staging of anal cancer is as follows: Primary tumor (T) TX: primary tumor cannot be assessed T0: no evidence of primary tumor Tis: carcinoma in situ (Bowen disease, high-grade squamous intraepithelial lesion [HSIL], anal intraepithelial neoplasia II-III (AIN II...
Article

Anal margin

Anal margin or perianal skin is arbitrarily defined as a skin tissue with a radius of 5 cm from the anal verge, consisting of keratinizing squamous epithelial tissue containing hair follicles. See also anal margin neoplasms
Article

Anal sphincter

The anal sphincter is divided into an internal and external anal sphincter. It surrounds the anal canal.  Gross anatomy Internal anal sphincter continuation of inner rectal muscle thickened, circular muscle fibers, up to 5 mm thick composed of visceral muscle External anal sphincter Compo...
Article

Anal triangle

The anal triangle forms the posterior half of the diamond-shaped perineum. The triangle's three corners are defined by the tip of the coccyx posteriorly and both ischial tuberosities anterolaterally. The anterior border is the transverse perineal muscles and the posterolateral borders are the sa...
Article

Anal verge

The anal verge is part of the anal region and consists of a band of squamous epithelial tissue which lacks hair follicles and extends from the inter-sphincteric groove to the perianal skin. 
Article

Anaplastic astrocytoma

Anaplastic astrocytomas are WHO grade III lesions, with imaging appearances and prognosis between those of diffuse low-grade astrocytomas (WHO grade II) and glioblastomas (WHO IV), and similarly, they are classified on the basis of IDH mutation as IDH-mutant, IDH-wild-type and NOS (when IDH stat...
Article

Anaplastic ependymoma

Anaplastic ependymomas (WHO grade III ependymomas), in comparison to lower grade ependymomas, are characterized by a higher proliferative rate and a greater tendency to infiltrate surrounding brain or disseminate into cerebrospinal fluid causing drop metastases 1. The relevance of grading ependy...
Article

Anaplastic ganglioglioma

Anaplastic gangliogliomas are uncommon aggressive variants of the far more common low-grade ganglioglioma (WHO grade I). The aggressive component is the glial (usually astrocytic) component, which demonstrates nuclear pleomorphism, increased mitotic rate and increased cellularity, as well as mic...
Article

Anaplastic lymphoma kinase (ALK) fusion oncogene positive non small cell lung cancer

Anaplastic lymphoma kinase (ALK) fusion oncogene positive non small cell lung cancer refers to a specific set of non small cell lung cancers that contain an inversion in chromosome 2. They are associated with specific clinical features, including never or light smoking history, younger age, and ...
Article

Anaplastic meningioma

Anaplastic meningiomas (also known as malignant meningiomas) are uncommon, accounting for only ~1% of all meningiomas 1. Along with rhabdoid meningioma and papillary meningioma are considered WHO grade III tumors and demonstrate aggressive local growth and high recurrence rate.  It should be no...
Article

Anaplastic oligodendroglioma

Anaplastic oligodendroglioma is a WHO grade III diffuse infiltrating glioma that has histological features of anaplasia, and molecular markers consistent with an oligodendroglioma (1p19q co-deletion and IDH mutation) as per the current (2016) WHO classification of CNS tumors 1. They make up 20-5...
Article

Anaplastic oligodendroglioma NOS

Anaplastic oligodendroglioma NOS (not-otherwise-specified) is a diagnosis in the current (2016) WHO classification of CNS tumors denoting a diffuse infiltrating glioma that has histological features of anaplastic oligodendroglioma, but without 1p19q co-deletion status or IDH mutation status bein...
Article

Anaplastic pleomorphic xanthoastrocytoma

Anaplastic pleomorphic xanthoastrocytomas are a more aggressive and less common version of pleomorphic xanthoastrocytoma (PXA).  In the current (2016) WHO classification of CNS tumors, they are considered WHO grade III lesions (whereas pleomorphic xanthoastrocytomas are WHO grade II tumors) 1. ...
Article

Anaplastic rhabdomyosarcoma

An anaplastic rhabdomyosarcoma is a subtype of embryonal rhabdomyosarcoma, characterized by extensive anaplastic cells seen throughout the tumor 1.
Article

Anaplastic thyroid carcinoma

Anaplastic thyroid carcinoma (ATC) is a highly aggressive form of thyroid cancer and accounts for ~1-2% of primary thyroid malignancies. Of all the subtypes, this carries the worst prognosis. Epidemiology Typically occurs in the elderly (peak incidence in 6th to 7th decades). A significant pro...
Article

Anatomical snuff box

The anatomical snuff box is a surface anatomy feature. It appears as a triangular depression on the lateral surface of the wrist on full extension of the thumb. Gross anatomy Boundaries medial: tendons of the extensor pollicis longus lateral: tendons of the extensor pollicis brevis and mor...
Article

Anatomical variants

Anatomical variants represent the deviations from the accepted standard human anatomy as printed in the classic textbooks (e.g. Gray's Anatomy 1), and taught in universities, dissecting rooms and clinical practice. Terminology The term "normal anatomic variants" or just "normal variants" is of...
Article

Anatomic position

The anatomic position, also referred to as the standard anatomic position, is the consistent position of the human body in which positional reference is made for anatomical nomenclature. It is not reliant on whether the patient is standing, supine, prone, sitting, etc. The position is defined a...
Article

Anatomy article structure

Articles pertaining to normal anatomy require a different structure, and the following subheadings are recommended: ========================================================================== As with all other articles, the introductory paragraph should introduce the anatomical term and aim to ...
Article

Anatomy article structure (bone)

As with all other articles, the introductory paragraph should introduce the anatomical term and aim to give an interesting summary. The first sentence should contain the title of the article in bold.  Summary location: articulations: blood supply and innervation: relations: Gross anatomy ...
Article

Anatomy article structure (joint)

As with all other articles, the introductory paragraph should introduce the anatomical term and aim to give an interesting summary. The first sentence should contain the title of the article in bold.  Summary location: movement: ligaments and tendons: relations: Gross anatomy Location Mo...
Article

Anatomy article structure: muscle

As with all other articles, the introductory paragraph should introduce the anatomical term and aim to give an interesting summary. The first sentence should contain the title of the article in bold.  Summary origin: insertion: innervation: action: Gross anatomy Origin Insertion Relatio...
Article

Anatomy article structure (nerve)

As with all other articles, the introductory paragraph should introduce the anatomical term and aim to give an interesting summary. The first sentence should contain the title of the article in bold.  Summary location: origin and course: branches and supply: relations: Gross anatomy Locat...
Article

Anatomy article structure (organ)

As with all other articles, the introductory paragraph should introduce the anatomical term and aim to give an interesting summary. The first sentence should contain the title of the article in bold.  Summary location: function: blood supply and drainage: relations: Gross anatomy Location...
Article

Anatomy article structure (space/region)

As with all other articles, the introductory paragraph should introduce the anatomical term and aim to give an interesting summary. The first sentence should contain the title of the article in bold.  Summary location: boundaries: contents: Gross anatomy Location Boundaries Contents Rel...
Article

Anatomy article structure (vessel)

As with all other articles, the introductory paragraph should introduce the anatomical term and aim to give an interesting summary. The first sentence should contain the title of the article in bold.  Summary location: origin and termination: branches and supply: relations: Gross anatomy ...
Article

Anatomy curriculum

The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge for radiologists and imaging specialists. General anatomy Neuroanatomy Head and neck anatomy Thoracic anatomy Abdominal and pelvic anatomy Spinal anat...
Article

Anatomy of an article

The anatomy of an article describes the component parts of any article at Radiopaedia.org. All articles include a title, the main content, references and other attributes. Title The title of the article may seem obvious, but some considerations as to consistency are required. We use sentence c...
Article

Ancient schwannoma

Ancient schwannomas are long-standing, benign (WHO grade I) slow growing schwannomas with advanced degeneration. These can have calcification, hyalinization, and cystic cavitation that can be identified on imaging. The term “ancient” has been traditionally used to describe schwannomas showing de...
Article

Anconeus

The anconeus is a small muscle in the posterior compartment of the arm at the lateral aspect of the elbow. It has little functional significance but should be differentiated from the variably present anconeus epitrochlearis at the medial aspect of the elbow. Summary origin: lateral epicondyle ...
Article

Anconeus epitrochlearis

Anconeus epitrochlearis is an accessory muscle at the medial aspect of the elbow. It is also known as the accessory anconeus muscle and should not be confused with the anconeus muscle which is present at the lateral aspect of the elbow.  Epidemiology The muscle may be unilateral but has been f...
Article

Anderson and D'Alonzo classification of odontoid process fracture

The Anderson and D'Alonzo classification is the most commonly used classification of fractures of the odontoid process of C2. Classification type I rare fracture of the upper part of the odontoid peg above the level of the transverse band of the cruciform ligament usually considered stable...
Article

Andersson lesion

Andersson lesions refer to an inflammatory involvement of the intervertebral discs by spondyloarthritis. Epidemiology Rheumatic spondylodiscitis is a non-infectious condition that has been shown to occur in about 8% of patients with ankylosing spondylitis, as detected at radiography. Patholog...
Article

Androgen insensitivity syndrome

Androgen insensitivity syndrome (AIS), also known as the testicular feminisation syndrome, results from end-organ resistance to androgens, particularly testosterone. AIS may be complete or incomplete with variable imaging findings.  Epidemiology The incidence may vary depending on whether it i...
Article

Anembryonic pregnancy

Anembryonic pregnancy is a form of a failed early pregnancy, where a gestational sac develops, but the embryo does not form. The term blighted ovum is synonymous with this but is falling out of favour and is best avoided.  Clinical presentation The patient may be asymptomatic, presenting for a...
Article

Anembryonic pregnancy in the exam

Getting a film with anembryonic pregnancy in the radiology fellowship examination is one of the many exam set-pieces that the candidate must be prepared for.  Description Transabdominal and transvaginal pelvic ultrasound shows a uterus with an intrauterine gestational sac. MSD is at least 25 m...
Article

Anencephaly

Anencephaly is the most severe form of cranial neural tube defect (NTD) and is characterized by an absence of cortical tissue (although the brainstem and cerebellum may be variably present) as well as an absence of the cranial vault. The morphological spectrum within anencephaly ranges from holo...
Article

Aneuploidy

Aneuploidy refers to an abnormal number of chromosomes, and is a type of chromosomal abnormality.There are large number potential aneuploidic anomalies. The most common three in obstetric practice are: trisomy 21: commonest aneuploidic anomaly trisomy 18 trisomy 13
Article

Aneurysm

Aneurysms are focal abnormal dilatation of a blood vessel. They typically occur in arteries, venous aneurysms are rare. Aneurysms may also occur in the heart. Pathology Pathological types true aneurysm false aneurysm (or pseudoaneurysm) Causes congenital atherosclerosis hypertension v...
Article

Aneurysmal bone cyst

Aneurysmal bone cysts (ABC) are benign expansile tumor-like bone lesions of uncertain etiology, composed of numerous blood-filled channels, and mostly diagnosed in children and adolescents. Epidemiology Aneurysmal bone cysts are primarily seen in children and adolescents, with 80% occurring in...
Article

Aneurysms of the portal venous system

Aneurysms of the portal vein are extremely rare and represent only 3% of all aneurysms of the venous system 1. Clinical presentation Most patients are asymptomatic but may present with nonspecific abdominal pain as a major symptom 2-4. Pathology Both congenital and acquired causes have been ...
Article

Angina

Angina or angina pectoris is cardiac chest pain that occurs as the result of myocardial ischemia. Clinical presentation Angina is classically described as substernal chest discomfort that is of a typical quality and duration (heavy, tight, ‘bandlike’ pain that lasts for minutes at a time). Ang...
Article

Angiocentric glioma

Angiocentric gliomas are rare superficial slow-growing brain tumors typically presenting in young patients with intractable partial epilepsy 1-6. They were first introduced in the 2007 (4th) edition of the WHO brain tumor classification, and are classified as WHO grade I tumors 1.  For a genera...
Article

Angioimmunoblastic T cell lymphoma

Angioimmunoblastic T-cell lymphoma (AITL) is a rare, aggressive (fast-growing) form of peripheral T-cell lymphoma. It only accounts for around 1-2% of all non-Hodgkin lymphoma. It is one of the more common subtypes of mature T-cell lymphomas.  Epidemiology It can be more common in the elderly....
Article

Angioinvasive aspergillosis

Angioinvasive aspergillosis is the most severe and aggressive form of invasive aspergillosis. It is a life-threatening condition that requires prompt treatment. Fortunately, it is not seen in the general population and only occurs in profoundly immunocompromised patients.  Epidemiology Angioin...
Article

Angiolipoma

Angiolipomas (also sometimes known as haemangiolipomas, vascular lipomas, and fibromyolipomas) are rare soft tissue tumors composed of mature adipocytes and vessels. They can occur essentially anywhere and can be subclassified into infiltrating and non-infiltrating variants 1.  Please refer to ...
Article

Angiomatous meningioma

Angiomatous meningiomas are a rare histological variant of WHO grade I meningiomas and account for only 2.1% of all meningiomas 1,3.  The epidemiology and clinical presentation of these tumors do not clearly deviate from that of more common histological variants of meningiomas and is thus not r...
Article

Angiomyofibroblastoma-like tumor of scrotum

Angiomyofibroblastoma-like tumor of the scrotum is a rare, well-defined, slow growing mesenchymal extratesticular nonepididymal tumor rarely seen in the perineum or scrotum of older male patients. A similar tumor can occur in females in the vulval region. Epidemiology  In males, they are seen ...
Article

Angiosarcoma

 Angiosarcomas (like hemangiopericytomas and haemangioendotheliomas) are tumors that arise from vascular structures. They are typically difficult to distinguish from one another on imaging alone. Angiosarcomas, are the most aggressive of the three, frequently having metastases at the time of di...
Article

Angiosarcoma (bone)

Angiosarcoma of bone is a malignant vascular tumor of bone. These are rare and account for less than 1% of malignant bone tumors. The majority of these tumors arising in bone are primary; however, a tiny percentage is either radiation-induced or associated with bone infarction Epidemiology Mos...
Article

Angiosarcoma involving the lung

Angiosarcoma involving the lung includes: metastatic angiosarcoma to lung 1  commoner usual primary sites include the heart and breast 2 primary pulmonary angiosarcoma: very rare See also angiosarcoma
Article

Angiosarcoma of breast

Breast angiosarcomas are a rare vascular breast malignancy. Epidemiology As primary tumors of the breast, they account for ~0.04% 2 of all breast cancers and tend to occur in younger women, in their 3rd to 4th decades. Secondary angiosarcoma, related to prior therapy of breast cancer, has an ...
Article

Angiosarcoma of the spleen

Angiosarcomas of the spleen are rare malignant splenic neoplasms. The term is usually given to describe a primary angiosarcoma of the spleen although angiosarcoma elsewhere can also rarely metastasise to the spleen. Despite its absolute rarity, a splenic angiosarcoma is considered the most commo...
Article

Angle of the longitudinal arch (foot)

The angle of the longitudinal arch is one of the angles drawn on the weightbearing lateral foot radiograph. The angle is formed between the calcaneal inclination axis and a line drawn along the inferior edge of the 5th metatarsal. The normal angle is 150-170°. In pes cavus, as the height of th...
Article

Angular gyrus

The angular gyrus is a portion of the parietal lobe of the brain. It is one of the two parts of the inferior parietal lobule, the other part being the supramarginal gyrus. It plays a part in language and number processing, memory and reasoning 1. Gross anatomy Relations It lies as a horseshoe...
Article

Angular interface sign

The angular interface sign is used to characterize an exophytic renal mass, in which the exophytic renal mass has an angular interface with the renal parenchyma. In other words, the exophytic lesion has a tapered pyramidal contour or definite apex within the renal parenchyma. Due to its high se...
Article

Angular pregnancy

Angular pregnancies are those in which implantation occurs eccentrically along the fundus of the endometrial cavity, along with the lateral upper angle or cornua of the uterus. In contrast to interstitial tubal pregnancy, angular pregnancies have a more medial location and are considered an int...
Article

Angular vein

The angular vein drains the anterior region of the scalp 1. It is formed by the union of the supratrochlear and supraorbital veins and becomes the facial vein 1,2,3. Gross Anatomy The angular vein is formed at the medial canthus as the supratrochlear vein and supraorbital vein unite 1,2. The a...
Article

Anhydramnios

Anhydramnios is a term where there is a complete or near-complete lack of amniotic fluid (sometimes referred to as "liquor volume"). Pathology Anhydramnios can result in a number of situations: fetal renal tract anomalies Potter syndrome (bilateral renal agenesis): most common  large ureter...
Article

Animal and animal produce inspired signs

Animal and animal produce inspired signs may sound a little silly, but the radiology literature is replete with such signs, some more fanciful than others. Fish and seafood endosteal scalloping: medullary cavity masses, e.g. multiple myeloma fish vertebra (also known as codfish vertebra): bic...
Article

Aniridia

Aniridia refers to either the clinical sign of a complete/partial absence of the iris, or more specifically to the disease entity classic aniridia. Rarely other genetic conditions may cause this sign. Epidemiology Classic aniridia is inherited as an autosomal dominant condition and is seen in ...
Article

Anisocoria

Anisocoria is present when an individual's pupils differ in size. If a person's pupils are symmetric there is said to be isocoria. Epidemiology The prevalence of transient physiological anisocoria of >0.4 mm is found in up to 20% population. However persistent anisocoria seems to be rarer, in ...
Article

Anisotropy

Anisotropy is an artefact encountered in ultrasound, notably in muscles and tendons during a musculoskeletal ultrasound. In musculoskeletal applications, the artefact may prompt an incorrect diagnosis of tendinosis or tendon tear. When the ultrasound beam is incident on a fibrillar structure as...
Article

Ankle and foot radiography

Ankle and foot radiography is the plain radiographic investigation of the distal tibia and fibula, the tarsal bones and metatarsals. Radiographic examination of the foot and ankle are often requested together, however, there is a plethora of literature to aid in the correct request of x-ray exam...
Article

Ankle (AP view)

Ankle AP view is part of a three view series of the distal tibia, distal fibula, proximal talus and proximal metatarsals. Patient position the patient may be supine or sitting upright with their leg straighten on the table the foot is in dorsiflexion the toes will be pointing directly toward...
Article

Ankle brachial index

Ankle brachial index (ABI) is a means of detecting and quantifying peripheral arterial disease. It can be performed in conjuction with ultrasound for better results. Indications Many patients with peripheral arterial disease may be asymptomatic (~20-50%), but they may also present with limb p...
Article

Ankle fractures

Ankle fractures account for ~10% of fractures encountered in trauma, preceded only in incidence by proximal femoral fractures in the lower limb. They have a bimodal presentation, involving young males and older females. Ankle injuries play a major part in post multitrauma functional impairment t...
Article

Ankle (horizontal beam lateral view)

The ankle horizontal beam lateral view is a modified lateral view part of a three view ankle series; this projection is used to assess the distal tibia and fibula, talus, navicular, cuboid, the base of the 5th metatarsal and calcaneus. The horizontal beam lateral is a highly adaptable projectio...
Article

Ankle impingement syndromes

There are several ankle impingement syndromes. They are characterized by limited range of motion and pain on attempting specific movements about the joint and often in a load-bearing position. They have variable etiology and pathogenesis. They are best classified according to location. The key ...
Article

Ankle joint

The ankle joint (also known as the tibiotalar joint or talocrural joint) forms the articulation between the foot and the leg. It is a primary hinge synovial joint lined with hyaline cartilage. Gross anatomy The ankle joint is comprised of the tibia, fibula and talus as well as the supporting l...
Article

Ankle (lateral view)

Ankle lateral view is part of a three view ankle series; this projection is used to assess the distal tibia and fibula, talus, navicular, cuboid, the base of the 5th metatarsal and calcaneus. Patient position patient is in a lateral recumbent position on the table the lateral aspect of the kn...
Article

Ankle (mortise view)

Ankle AP mortise view is part of a three view series of the distal tibia, distal fibula, talus and proximal metatarsals. It is the most pertinent projection for assessing the articulation of the tibial plafond and two malleoli with the talar dome, otherwise known as the mortise joint of the ankl...
Article

Ankle radiograph (an approach)

Ankle radiographs are frequently performed in emergency departments, usually, after trauma, the radiographic series is comprised of three views: an anteroposterior, mortise, and a lateral. They may be performed to assess degenerative or inflammatory arthritis as well as to look for the sequela o...
Article

Ankle radiograph (checklist)

The ankle radiograph checklist is just one of the many pathology checklists that can be used when reporting to ensure that you always actively exclude pathology that is commonly missed; this is particularly helpful in the examination setting, e.g. the FRCR 2B rapid-reporting. Radiograph The ma...
Article

Ankle series

The ankle series is comprised of an anteroposterior (AP), mortise and lateral radiograph. The series is often used in emergency departments to evaluate the distal tibia, distal fibula, and the talus; forming the ankle joint. See approach to an ankle series. Indications Ankle radiographs are p...
Article

Ankle x-ray (summary)

This is a basic article for medical students and other non-radiologists An ankle x-ray, also known as ankle series or ankle radiograph, is a set of two x-rays of the ankle joint. It is performed to look for evidence of injury (or pathology) affecting the ankle, often after trauma. Reference ar...
Article

Ankylosing spondylitis

Ankylosing spondylitis (less commonly known as Bechterew disease and Marie Strümpell disease) is a seronegative spondyloarthropathy, which results in fusion (ankylosis) of the spine and sacroiliac (SI) joints, although involvement is also seen in large and small joints. Epidemiology There is a...
Article

Ankylosing spondylitis: thoracic manifestations

Thoracic manifestations of ankylosing spondylitis can be varied. For a general discussion of the condition refer to the parent article on ankylosing spondylitis. It can affect the tracheobronchial tree and the lung parenchyma, and the disease spectrum includes: upper lobe fibrocystic changes -...
Article

Anlage

An anlage in biology refers to the primordial precursor of a tissue or organ, which is still recognisable as a collection of cells that will form that specific tissue. The term is commonly used in medicine to refer to organs, such as the pancreas, when one is describing anatomical variants and ...
Article

Ann Arbor staging system

The Ann Arbor staging system is the landmark lymphoma staging classification system for both Hodgkin lymphoma and non-Hodgkin lymphoma.  It is named after the town of Ann Arbor in the US state of Michigan where the Committee on Hodgkin's Disease Staging Classification met in 1971 to agree on it...
Article

Annular fissure

Annular fissures are a degenerative deficiency of one or more layers that make up the annulus fibrosus of the intervertebral disk.  Terminology Many authors prefer the term annular fissure over annular tear, as the latter seems to imply acute injury 1,2. In the setting of severe trauma with di...
Article

Annular ligament (stapes)

The annular ligament of the stapes, also known as the ligamentum anulare stapedis, attaches the rim of the footplate of the stapes to the rim of the oval window. This forms the stapediovestibular joint; a fully-functional articulation is vital for transmission of sound vibrations in the middle e...
Article

Annular pancreas

Annular pancreas is a morphological anomaly which can cause duodenal obstruction. This condition is important to recognize, as radiologists are frequently the first to make the diagnosis. Epidemiology The incidence is probably 1 in 250, however its incidence is not accurately reported 1. It is...
Article

Annulo-aortic ectasia

Annulo-aortic ectasia refers to a proximal dilatation of the aortic root at the level of the aortic annulus, it is also the same level as the sinus of Valsalva. Pathology Annulo-aortic ectasia occurs with connective tissue diseases such as Marfan disease and Ehlers-Danlos syndrome. It is a cys...
Article

Annulus fibrosus

The annulus fibrosus surrounds the nucleus pulposus and together they form the intervertebral disk. Gross anatomy The annulus comprises 15 to 20 collagenous (type I) laminae which run obliquely from the edge of one vertebra down to the edge of the vertebra below. The direction of the fibers al...
Article

Anode

The anode is the component of the x-ray tube where x-rays are produced. It is a piece of metal, shaped in the form of a bevelled disk with the diameter between 55 and 100 mm, and thickness of 7 mm, connected to the positive side of the electrical circuit. The anode converts the energy of the ele...
Article

Anode angle

The anode angle refers to the angle the target surface of the anode sits at in relation to the vertical.  Most x-ray tubes have an anode angle of 12-15 degrees but greater or lesser angles can also be used depending on the application. The degree of angulation of the anode effects the effective...
Article

Anode heel effect

Anode heel effect refers to the lower field intensity towards the anode in comparison to the cathode due to lower x-ray emissions from the target material at angles perpendicular to the electron beam. Basic concept The conversion of the electron beam into x-rays doesn’t simply occur at the sur...
Article

Anomalous course of coronary arteries

Anomalous course of a coronary artery is a type of congenital coronary artery anomaly. It may represent a benign and incidental finding, but can also be a malignant course predisposing patients to life-threatening myocardial ischemia or arrhythmias, depending on where the artery runs.  Clinical...
Article

Anomalous left coronary artery from the pulmonary artery

Anomalous left coronary artery from the pulmonary artery (ALCAPA), also known as Bland-White-Garland syndrome (BWG), is a rare congenital coronary artery anomaly and is considered one of the most severe of such anomalies. There are two forms, based on onset of disease, each of which has differe...

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.