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.

34 results found
Article

I-131

I-131​ (or 131I) is a radioisotope used in the diagnosis and treatment of thyroid lesions. It is one of the oldest radiotracers used in nuclear medicine, in use for over 50 years. It is predominately used in thyroid ablation therapy, for patients post thyroidectomy, and for metastatic thyroid ca...
Article

Ice-cream cone sign

The ice cream cone sign may refer to: the appearance of the malleus head and the incus body on axial CT scan: failure of this normal configuration suggests incudomalleolar dysarticulation. Ball of the icecream is formed by head of malleus and cone is formed by body of incus. Space between ice c...
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Incisive canal

The maxillary incisive canal runs through the maxilla in the midline. It connects the inferior nasal cavity with the superior oral cavity, opening at the incisive foramen posterior to the central maxillary incisor teeth. It contains the descending palatine artery and the nasopalatine nerve.  Re...
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Incisive canal cyst

Incisive canal cysts, also known as nasopalatine duct cysts (NPDC), are developmental, non-neoplastic cysts arising from degeneration of nasopalatine ducts. These ducts usually regress in fetal life. The persistence of ductal epithelium leads to formation of cyst. It is considered the most comm...
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Incisive foramen

The incisive foramen (also known as nasopalatine foramen or anterior palatine foramen) is the oral opening of the nasopalatine canal. It is located in the maxilla bone in the incisive fossa, midline in the palate posterior to the central incisiors, at the junction of medial palatine and incisive...
Article

Incus

The incus is the middle of the ossicles articulating with the head of the malleus anteromedially and the stapes inferomedially. Its parts include: a body which articulates with the head of the malleus, and to which the superior ligament of the incus is attached (to the roof of the middle ear c...
Article

Inferior alveolar artery

The inferior alveolar artery is a branch of the maxillary artery. It runs with the inferior alveolar nerve as it descends through the infratemporal fossa and enters the mandibular canal and supplies mandibular teeth. In the region of the first premolar it bifurcates into the incisive and mental ...
Article

Inferior median clival canal

The inferior median clival canal also known as the canalis basilaris medianus is a rare anatomical variant of the clivus, which passes in the sagittal plane from the intracranial surface of the clivus to its retropharyngeal surface. It is generally thought to represent a remnant of the notocord....
Article

Inferior nasal concha

The inferior nasal concha is one of the conchae in the nose. It extends horizontally along the lateral wall of the nasal cavity and consists of a lamina of spongy bone, curled upon itself like a scroll. Each inferior nasal concha is considered a facial pair of bones since they arise from the max...
Article

Inferior oblique muscle

The inferior oblique muscle is one of six extraocular muscles that control eye movements. origin: orbital surface of the maxilla insertion: globe (posterior, inferolateral surface) innervation: inferior branch of the oculomotor nerve (CN III) primary function: one of two ocular external rota...
Article

Inferior rectus muscle

The inferior rectus muscles is one of the 6 extraocular muscles that control eye movements. innervation: inferior branch of the oculomotor nerve (CN III) origin: Annulus of Zinn (tendinous ring) insertion: globe (anterior, inferior surface) primary function: one of two ocular depressors sec...
Article

Infrahyoid muscles

The infrahyoid muscles or strap muscles are a group of four paired muscles in the anterior neck below the hyoid bone. They are responsible for elevating the hyoid during swallowing. The four muscles are: sternohyoid: superficial and medial omohyoid: superficial and lateral sternothyroid: dee...
Article

Infraorbital artery

The infraorbital artery, is a branch of the third part of the maxillary artery. It runs through the inferior orbital fissure, orbit, then the infraorbital foramen. Here it gives off the anterior superior alveolar artery which supplies the anterior teeth and the anterior part of the maxillary sin...
Article

Infraorbital foramen

The infraorbital foramen is located in the maxilla bone its facial surface superior to the canine fossa and inferior to the lower margin of orbit. It transmits the superior maxillary nerve (infraorbital nerve) and infraorbital artery.
Article

Infraorbital nerve

The infraorbital nerve is a one of three cutaneous branches of the maxillary division of the trigeminal nerve.  The other branches include the zygomaticofacial nerve and the zygomaticotemporal nerve. Gross anatomy Course emerges through the infraorbital foramen lying between levator labii sup...
Article

Infratemporal fossa

The infratemporal fossa is a complex space that lies posterolateral to the maxillary sinus and many important nerves and vessels traverse it.  Gross anatomy The infratemporal fossa is the space between the skull base, lateral pharyngeal wall and the ramus of mandible.  Boundaries medially - ...
Article

Ingested bones

Ingested bones that become lodged in the throat or gastro-intestinal tract are a common presentation to the emergency department. Recognition is important because these cases can be potentially fatal.  Pathology Patients may present with a 'foreign body' feeling in the throat after eating fish...
Article

Inion

The inion is the tip of external occipital protuberance, the midline bony prominance in the occipital bone where the ligamentum nuchae and trapezius muscle attaches. It is usually easily palpable. It is the the surface marking of the internal attachment of the tentorium cerebelli. It is one of...
Article

Inner ear

The inner ear refers to the bony labyrinth and its contents and the membranous labyrinth. It is divided into three sections: cochlea vestibule semicircular canals
Article

Innervation of the muscles of the middle ear (mnemonic)

A useful mnemonic to remember innervation of the muscles of the middle ear is: S for Stapedius T for Tensor Tympani Mnemonic S: Stapedius is supplied by a branch of the facial nerve- the Seventh cranial nerve. It is also the Smallest muscle in the body, and inserts onto the neck of Stapes T...
Article

Internal acoustic meatus

The internal acoustic canal (IAC), also known as the internal auditory canal or meatus (IAM), is a bony canal within the petrous portion of the temporal bone that transmits nerves and vessels from within the posterior cranial fossa to the auditory and vestibular apparatus. Gross anatomy The op...
Article

Internal auditory canal nerves (mnemonic)

A mnemonic to remember the relative position of nerves inside the internal auditory canal (IAC) is: Seven up coke down Anatomy Four nerves pass through the IAC: facial nerve (CN VII) three components of the vestibulocochlear nerve (CN VIII) cochlear nerve (CN VIIIc) superior vestibular ne...
Article

Internal carotid artery

The internal carotid artery is a terminal branch of the common carotid artery.  Gross anatomy Origin It arises most frequently between C3 and C5 vertebral level, where the common carotid bifurcates to form the internal carotid and the external carotid artery (ECA). Variations in origin Alt...
Article

Internal jugular vein

The internal jugular vein (IJV) is the major venous return from the brain, upper face and neck.  Gross anatomy Origin and course It is formed by the union of inferior petrosal and sigmoid dural venous sinuses in or just distal to the jugular foramen (forming the jugular bulb). It descends in ...
Article

Internal jugular vein tributaries (mnemonic)

A useful mnemonic to remember the branches of the internal jugular vein is: Medical Schools Let Fun People In Mnemonic From inferior to superior: M: middle thyroid vein S: superior thyroid vein L: lingual vein F: facial vein P: pharyngeal vein I: inferior petrosal sinus
Article

Internasal suture

The internasal suture is a single, midline cranial suture between the two nasal bones. It meets the frontonasal suture to form the nasion 1.
Article

Intraconal orbital compartment

The intraconal orbital compartment is a conical space, the base of which is anterior and is formed by the posterior half of the globe. The sides are formed by the extraocular muscles which pass posteriorly and converge on the tendinous ring at the orbital apex. Contents This space contains: ...
Article

Intraconal orbital lesions

Intraconal orbital lesions are broadly divided to two main groups; those with or without involvement of the optic nerves: Lesions with optic nerve involvement: optic nerve glioma optic nerve meningioma optic neuritis pseudotumour lymphoma and leukaemia intracranial hypertension retinobla...
Article

Intracranial dermoid cyst

Intracranial dermoid cysts are uncommon lesions with characteristic imaging appearances. They can be thought of as along the spectrum: from epidermoid cysts at one end (containing only desquamated squamous epithelium) and teratomas at the other (containing essentially any kind of tissue from all...
Article

Intraosseous meningioma

Intraosseous meningioma, also referred as primary intraosseous meningioma, is a rare subtype of meningioma that accounts for less than 1% of all osseous tumours. They fall under the subgroup of primary extradural meningiomas. Terminology It is important to note that this group of meningiomas d...
Article

Intrinsic muscles of the larynx

The intrinsic muscles of the larynx can be considered in two groups: muscles that control the inlet of the larynx muscles that move the vocal ligaments Gross anatomy Muscles of the inlet aryepiglottic muscle: lies within the aryepiglottic fold, runs from the side of the epiglottis and inser...
Article

Inverted papilloma

Inverted papillomas are a type of Schneiderian papilloma. They are uncommon with distinctive pathological and imaging features. Terminology  The term inverted papilloma is also used to describe a urothelial lesion. For a discussion of that entity, please refer to inverted papilloma of the urin...
Article

Iodine-123

Iodine123 (I123) is a radioisotope of the element Iodine (atomic number 53) used in nuclear medicine imaging including to image the thyroid gland.  Uses, dosages, and time of Imaging routine scan: 100-400 microCi po, image at 4-6 or 24 hours thyroid cancer scan: 1.5 mCi po, image at 4-6 or 24...
Article

Isolated cleft palate

An isolated cleft palate is a type of facial cleft. This is a much rarer occurrence than a cleft lip +/- palate and is thought to represent a different pathological entity. Epidemiology The estimated incidence is at ~1 per 2000-2500 pregnancies 4-5. There may be a slight female predilection 4....

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