MRI Protocols: IAC, Trigeminal Nerve, Pituitary, Pineal, and Orbits

This flashcard set covers the anatomy, technical considerations, slice positioning, and clinical indications for MRI protocols of the Internal Auditory Canal, Trigeminal Nerve, Pituitary Gland, Pineal Gland, and Orbits.

Internal Auditory Canal (IAC)

One of the most common protocols scanned in MRI, focusing on high resolution axial and coronal imaging planes.

Cerebellopontine Angle (CPA) Masses

Tumors located in the CPA, where acoustic neuromas account for approximately $60\%$ to $75\%$ of all cases.

Acoustic Neuroma

Also called a vestibular schwannoma because it originates from the Schwann cells; it is the most common CPA mass.

Fat Saturation (Post-Acoustic Neuroma Resection)

A technique applied after contrast to differentiate between bright fat tissue (used to fill empty surgical space) and residual tumor.

Trigeminal Neuralgia (TN)

The most typical indication for scanning the trigeminal nerve, commonly caused by a blood vessel compressing the nerve (vascular compression).

Trigeminal Nerve (V) Branches

The three divisions of the nerve: Ophthalmic Branch, Maxillary Branch, and Mandibular Branch.

Posterior Pituitary Bright Spot (PPBS)

An intrinsic high T1 signal in the posterior pituitary resulting from the storage of vasopressin (ADH), which has a T1-shortening effect.

Pituitary Gland Size (Pregnancy)

The size the gland grows to during pregnancy, approximately $12\,mm$.

Microadenoma

A non-cancerous growth in the pituitary gland that is less than $10\,mm$ in size.

Macroadenoma

A tumor of the pituitary gland that is more than $10\,mm$ in size, often associated with visual field defects.

Empty Sella

An indication for pituitary imaging, also associated with Rathke’s Cleft Cyst.

Germ Cell Tumors (Pineal)

A category of pineal region tumors including Germinomas, Embryonal cell carcinoma, and Teratomas.

Pineal Cell Tumors

A category of pineal region tumors including Pineocytoma and Pineoblastoma.

Retro Orbital Fat

Fat that must be suppressed using Fat Saturation (such as STIR sequences) to detect edema within the optic nerve or pathological processes after contrast.

Eyeliner Artifacts

Susceptibility artifacts in orbit MRIs caused by metallic components in makeup; patients must remove it to reduce motion and signal distortion.

Papilledema

An indication for orbital MRI referring to swelling of the optic disc.

Diplopia

An indication for orbital MRI referring to double vision.

Proptosis

An indication for orbital MRI defined as the forward displacement of the eye.

Optic Neuritis

Inflammation of the optic nerve often associated with Multiple sclerosis (MS).