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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 continuously improved upon by countless contributing members. Our dedicated editors oversee each edit for accuracy and style. Find out more about articles.

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Bone scintigraphy

Bone scintigraphy (a.k.a. bone scans) is a nuclear medicine (scintigraphic) study that makes use of technetium-99m (commonly Tc-99m-methylene diphosphonate (MDP)) as the active agent 2. About 50% of the injected dose will be absorbed by the bones after 2 to 6 hours 2. The study has three phases...

Posterior reversible encephalopathy syndrome

Posterior reversible encephalopathy syndrome (PRES), also known as reversible posterior leukoencephalopathy syndrome (RPLS), is a neurotoxic state that occurs secondary to the inability of the posterior circulation to autoregulate in response to acute changes in blood pressure. Hyperperfusion wi...

Medial posterior choroidal artery

The medial posterior choroidal artery is a small branch (often multiple - 40% of hemispheres) usually arising from the P2 segment of the posterior cerebral artery (PCA). It may also arise from one of the PCA branches, e.g. parieto-occiptal, calcarine, splenial artery. It ascends deep to the res...

Choroid plexus infarct

Choroid plexus infarct is an uncommon location of ischemic stroke that results from ischemia of the choroid plexus, supplied by the medial posterior choroidal artery, which is a branch from the posterior cerebral artery (PCA). Clinical presentation Isolated choroid plexus infarction is rare an...

Bardet-Biedl syndrome

Bardet-Biedl syndrome (BBS), previously known as the Laurence-Moon-Bardet-Biedl syndrome (LMBBS), is a rare autosomal recessive hereditary condition. Clinical presentation The clinical spectrum includes: retinal anomalies: similar to that of retinitis pigmentosa intellectual disability rena...

Iodine-131 iobenguane

Iodine-131 iobenguane, trade name Azedra, sometimes referred to as I-131 MIBG, is a theranostic (i.e. both therapeutic and diagnostic) agent used for the treatment of unresectable pheochromocytomas, paragangliomas, carcinoid, and neuroblastomas. It is created using the high specificity Ultratrac...

Continuous x-ray spectrum

The continuous x-ray spectrum refers the range of photon energies produced in an x-ray tube due to the properties of Bremsstrahlung radiation. The energy of x-ray photons can take a value from zero to the maximum kinetic energy of the incident electrons. Both the continuous x-ray spectrum and ...

Ann Arbor staging system (historical)

The Ann Arbor staging system was 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....

Managing editor

Managing editors at Radiopaedia.org are part of the senior editorial team and have specific roles in developing the site and its content. As of 2024, there are three managing editors: Joachim Feger Andrew Murphy Vikas Shah Responsibilities Between 2007 (launch) and 2014, Radiopaedia.org ha...

Helicobacter pylori

Helicobacter pylori (H. pylori) is a gram-negative spiral flagellate microaerophilic bacterium found in the human gastric mucosa 1. It is classified as a group I carcinogen and is considered necessary but insufficient alone to cause gastric adenocarcinoma. More often than not, it results in chro...

Cerebellar ataxia with neuropathy and vestibular areflexia syndrome (CANVAS)

Cerebellar ataxia with neuropathy and vestibular areflexia syndrome (CANVAS) is a rare neurodegenerative balance disorder and RFC1-related disease characterized by cerebellar ataxia, sensory neuronopathy (ganglionopathy), and bilateral vestibular hypofunction. Epidemiology The epidemiology is ...

Knee series (pediatric)

The knee series for pediatrics consists of an anteroposterior and a lateral projection. Indications trauma with a suspected fracture inability to weight-bear suspected foreign body or bony lesions Projections anteroposterior view lateral view Gonadal shielding The use of gonadal and fet...

Tibia fibula series (pediatric)

The tibia fibula series for pediatrics consists of an anteroposterior and a lateral projection. Indications trauma with a suspected fracture inability to weight-bear suspected foreign body or bony lesions Projections anteroposterior view lateral view Gonadal shielding The use of gonadal...

Femur series (pediatric)

The femur series for pediatrics is comprised of an anteroposterior (AP), and lateral radiograph. The series is utilized to assess for abnormalities pertaining to the shaft of the femur (often requested when fringe abnormality is seen on hip or knee radiographs). It is not an effective series to ...

Anterior temporal lobe perivascular spaces

Anterior temporal lobe perivascular spaces, also known as opercular perivascular spaces, are special variants of tumefactive perivascular spaces, which can mimic cystic tumors with surrounding edema. Epidemiology A predilection for women has been reported 1. Age range is wide, from 24 to 86 ye...

White matter disorders

White matter diseases are a group of conditions that predominantly or significantly affect the white matter of the brain. They comprise a vast heterogeneous group and have a variety of appearances and presentations. They cause disease by altering the process of normal myelination. Useful group...

White matter

The white matter (TA: substantia alba) is the substance of the brain and spinal cord that contains the fiber tracts of neuronal axons in the central nervous system. The term is due to the paler color of the lipid-rich myelin that encases the axons in the tracts compared to the grey matter, which...

Osteonecrosis of the femoral head

Osteonecrosis of the femoral head, previously known as avascular necrosis (AVN) of the hip, is the most common site for osteonecrosis, presumably due to a combination of precarious blood supply and high loading when standing. Idiopathic osteonecrosis of the femoral head epiphysis in children (...

Osteoporosis

Osteoporosis is a metabolic bone disease characterized by decreased bone mass and skeletal fragility. The World Health Organization (WHO) operationally defines osteoporosis as a bone mineral density T-score less than -2.5 SD (more than 2.5 standard deviations under the young-adult mean), which ...

Urinary bladder hernia

Herniation of the urinary bladder is a relatively uncommon but not a rare condition. It occurs when the urinary bladder or ureter herniates into the inguinal canal, scrotal sac or femoral canal. Herniations through ischiorectal, obturator, or abdominal wall openings have also been described. Bla...

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