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Magnetic Resonance Imaging (MRI) of the Posterior Fossa With Intravenous Contrast

Published: August 9, 2026Updated: August 16, 2026

An MRI that examines the lower back of the brain, including the cerebellum and brainstem, using contrast material injected into a vein.

Quick summary

["This imaging study uses IV contrast to help identify and evaluate abnormalities in the posterior fossa of the brain."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
36243-4
Short code
MR Post fossa W contr IV
Synonyms
MR Post fossa W contr IV
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
mr
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

This is a magnetic resonance imaging study of the posterior fossa, the lower rear portion of the brain that includes the cerebellum and brainstem. Intravenous contrast is used to produce clearer images of tissues and abnormalities.

Why might I need this test?

A posterior fossa MRI may be ordered to investigate headaches, dizziness, balance problems, weakness, vision changes, or other neurologic symptoms. It may also be used to evaluate a known lesion or monitor conditions affecting the brain, brainstem, or cerebellum.

How is the test performed?

You will lie on a table inside an MRI scanner while the machine creates detailed images. Contrast material is usually injected into a vein, and the images are reviewed by a radiologist, who sends the report to your ordering clinician.

How do I prepare for the test?

Follow the imaging center's instructions and tell your clinician about pregnancy, kidney disease, prior contrast reactions, allergies, and any implanted medical devices. Metal objects, including jewelry, cards, and some personal items, must usually be removed before entering the scanner.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Abnormal findings may include a mass, swelling, inflammation, infection, demyelinating disease, hydrocephalus, or a blood-flow abnormality in the posterior fossa. The meaning of any finding depends on the symptoms, medical history, and the complete MRI report. Your ordering clinician will explain the results and discuss any further evaluation or treatment.

Short name

Posterior Fossa MRI with IV Contrast

Frequently asked questions

What is the posterior fossa?
The posterior fossa is the lower back portion of the brain and contains the cerebellum and part of the brainstem. These structures help control balance, coordination, and many automatic body functions.
Why is contrast given through a vein?
Intravenous contrast can make certain tissues, blood vessels, and abnormalities easier to see on MRI. It is commonly made from a gadolinium-based agent and is given through an IV line before the images are taken.
Is this test the same as a CT scan?
No. MRI uses magnetic fields and radio waves rather than ionizing radiation, and the contrast agents used for MRI and CT are different. Your clinician will decide which study is most appropriate based on the clinical situation.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy