Facial MRI Scan: A Comprehensive Guide

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Magnetic Resonance Imaging (MRI) of the face is a non-invasive diagnostic technique that utilizes a strong magnetic field and radio waves to create detailed images of the internal structures of the face. Unlike X-rays or computed tomography (CT) scans, MRI does not use ionizing radiation, making it a preferred imaging modality in many situations, especially when repeated imaging is necessary. This article provides a detailed explanation of facial MRI scans, covering their indications, contraindications, the procedure itself, and what to expect during and after the scan.

Indications for a Facial MRI Scan

A facial MRI scan is a valuable tool for diagnosing a wide range of conditions affecting the soft tissues, bones, and other structures of the face. Some common indications for a facial MRI include:

  • Infections: Detection of infections involving the bone, joint, or soft tissues, such as osteomyelitis or facial abscesses.
  • Neoplasms: Diagnosis and staging of both benign and malignant tumors of the bones and soft tissues of the face, including parotid and orbital tumors.
  • Staging of Known Malignancy: Determining the extent of a known cancer in the face.
  • Treatment Planning: Assisting in planning radiation therapy and surgical interventions.
  • Evaluation of Treatment Response: Monitoring how tumors respond to treatment.
  • Pre-operative Evaluation: Assessment before surgical procedures, especially for tumors.
  • Foreign Bodies: Locating and characterizing foreign bodies in the face.
  • Trauma: Assessing facial injuries and trauma.

Contraindications

While MRI is generally safe, certain conditions may make it unsuitable for some individuals. Contraindications for a facial MRI scan include:

  • Electrically, magnetically, or mechanically activated implants: Devices such as cardiac pacemakers, insulin pumps, neurostimulators, cochlear implants, and hearing aids can be affected by the MRI's magnetic field.
  • Intracranial aneurysm clips: Unless made of titanium, these clips can be displaced by the magnetic field.
  • Pregnancy: The risk versus benefit ratio needs to be assessed, as the effects of MRI on a developing fetus are not fully understood.
  • Ferromagnetic surgical clips or staples: These can be displaced or heated by the magnetic field.
  • Metallic foreign body in the eye: This is a significant risk due to the potential for movement and injury.
  • Metal shrapnel or bullet: Similar to foreign bodies in the eye, these can be displaced.

Patient Preparation

Proper preparation is essential for a successful facial MRI scan. The following steps are typically involved:

  1. Consent Form: A written consent form must be obtained from the patient after explaining the procedure, risks, and benefits.
  2. Metal Objects Removal: Patients must remove all metal objects, including keys, coins, wallets, cards with magnetic strips, jewelry, hearing aids, and hairpins.
  3. Claustrophobia: For claustrophobic patients, a chaperone (relative or staff member) can provide support.
  4. Contrast Injection Information: If contrast is to be used, the risks and benefits must be explained, and it should only be administered if the patient's Glomerular Filtration Rate (GFR) is > 30.
  5. Comfort Measures: Earplugs or headphones (possibly with music) should be offered for comfort, as the MRI machine can be noisy.
  6. Procedure Explanation: The procedure should be explained to the patient to alleviate anxiety.
  7. Stillness Instruction: Patients must be instructed to remain still during the scan to ensure clear images.

Positioning for the Scan

The patient's position during the scan is crucial for obtaining the best possible images. The standard positioning involves:

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  • Head First Supine: The patient lies on their back with their head entering the scanner first.
  • Head Coil: The head is positioned within a specialized head coil to improve image quality and immobilized with cushions.
  • Leg Support: Cushions are placed under the legs for added comfort.
  • Laser Beam Localizer: The laser beam is centered over the tip of the nose to ensure accurate positioning.

Recommended Facial MRI Protocols, Parameters, and Planning

Specific protocols and parameters are used to optimize the images obtained during a facial MRI. These include:

Localizer Scan

  • A three-plane localizer is essential for planning the subsequent sequences.
  • These scans are typically T1-weighted, low-resolution, and take less than 25 seconds.

T2 STIR Coronal

  • Planning: Coronal slices are planned on the sagittal plane, angled perpendicular to the hard palate. The angle is checked in axial plane (perpendicular to the nasal septum).
  • Coverage: Slices should cover the entire face, from the tip of the nose to the level of the fourth ventricle.
  • Parameters:
    • TR: 4000-5000
    • TE: 110
    • Flip Angle: 150
    • NEX: 3
    • Slice Thickness: 3 mm
    • Matrix: 256x256
    • FOV: 170-180
    • Phase Resolution: > Large
    • Gap: 10%
    • TI: 150

T1 TSE Coronal

  • Planning: Similar to T2 STIR coronal, slices are planned on the sagittal plane, angled perpendicular to the hard palate. The angle is checked in axial plane (perpendicular to the nasal septum).
  • Coverage: Slices should cover the entire face, from the tip of the nose to the level of the fourth ventricle.
  • Parameters:
    • TR: 400-600
    • TE: 15-25
    • Slice Thickness: 3 mm
    • Flip Angle: 150
    • Phase Resolution: > Large
    • Matrix: 256x256
    • FOV: 170-180
    • Gap: 10%
    • NEX (Average): 2

T1 TSE Axial

  • Planning: Axial slices are planned on the sagittal plane, angled parallel to the hard palate. The angle is checked in coronal plane (perpendicular to nasal septum).
  • Coverage: Slices should cover the face from the glabella (between the eyebrows) down to the larynx.
  • Parameters:
    • TR: 400-600
    • TE: 15-25
    • Slice Thickness: 3 mm
    • Flip Angle: 140
    • Phase Resolution: > Large
    • Matrix: 256x256
    • FOV: 170-180
    • Gap: 10%
    • NEX (Average): 2

T2 STIR Axial

  • Planning: Axial slices are planned on the sagittal plane, angled parallel to the hard palate. The angle is checked in coronal plane (perpendicular to the nasal septum).
  • Coverage: Slices should cover the face from the glabella down to the larynx.
  • Parameters:
    • TR: 4000-5000
    • TE: 110
    • Flip Angle: 130
    • NEX: 3
    • Slice Thickness: 3 mm
    • Matrix: 256x256
    • FOV: 170-180
    • Phase Resolution: > Large
    • Gap: 10%
    • TI: 130

RESOLVE DWI Axial

  • Planning: Axial slices are planned on the sagittal plane, angled parallel to the hard palate. The angle is checked in coronal plane (perpendicular to the nasal septum).
  • Coverage: Slices should cover the face from the glabella down to the larynx.
  • Parameters:
    • TR: 7000-9000
    • TE: 70-115
    • Flip Angle: 130
    • NEX: 1-2
    • Slice Thickness: 3 mm
    • Matrix: 192x192
    • FOV: 200-230
    • Phase Resolution: > Large
    • Gap: 10%
    • B Value: 0, 1000

T2 TSE Sagittal

  • Planning: Sagittal slices are planned on the axial plane, angled parallel to the nasal septum. The angle is checked in coronal plane (parallel to the nasal septum).
  • Coverage: Slices should cover the face from the right pinna (outer ear) to the left pinna.
  • Parameters:
    • TR: 3000-4000
    • TE: 100
    • Flip Angle: 130
    • NEX: 2
    • Slice Thickness: 3 mm
    • Matrix: 256x256
    • FOV: 170-180
    • Phase Resolution: > Large
    • Gap: 10%
    • Oversample: 40%

Post-Contrast Imaging

For post-contrast imaging, VIBE 3D axial sequences are used after the administration of intravenous gadolinium DTPA injection.

  • T1 VIBE DIXON 3D Axial
    • Planning: Axial slices are planned on the sagittal plane, angled parallel to the hard palate. The angle is checked in coronal plane (perpendicular to the nasal septum).
    • Coverage: Slices should cover the face from the glabella down to the larynx. Slice and phase oversampling must be given to avoid wrap-around artifacts.
    • Parameters:
      • TR: 6.9
      • TE: 2.39, 4.77
      • Flip Angle: 12
      • NEX: 2
      • Slice Thickness: 0.7 mm (isotropic)
      • Matrix: 256x256
      • FOV: 170-180
      • Phase Resolution: > Large
      • Slices: 200
      • Oversample: 10% and 100%

Optional Scans

  • T2 SPACE STIR 3D Axial
    • Planning: Axial slices are planned on the sagittal plane, angled parallel to the hard palate. The angle is checked in coronal plane (perpendicular to the nasal septum).
    • Coverage: Slices should cover the face from the glabella down to the larynx.

Some radiologists prefer to perform TSE 2D scans. In that instance, use T1 TSE fat-sat small FOV axial and coronal scans after the administration of IV gadolinium DTPA injection (copy the planning outlined above).

Contrast Material

What is Contrast?

Contrast material, often containing gadolinium, is injected intravenously to enhance the visibility of specific tissues and structures. It alters the magnetic properties of water molecules, improving the quality of the images. Contrast is particularly useful for visualizing tumors, inflammation, infection, blood supply, and blood vessels.

Safety and Side Effects

Gadolinium-based contrast materials are generally safe, but side effects can occur. Severe reactions are rare. It’s crucial to assess kidney function (GFR > 30) before administration, as gadolinium can cause complications in patients with severe kidney problems. Small amounts of gadolinium can remain in the body for extended periods.

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What to Expect During the MRI Scan

The MRI procedure involves several steps:

  1. Positioning: You will lie down on a narrow, flat table that slides into a long, narrow cylinder. Straps or pillows may be used to keep you comfortable and still.
  2. Noise: The machine makes loud, thumping, clicking, and whirring noises as the magnet switches on and off. Earplugs or headphones are provided to minimize discomfort.
  3. Stillness: It is important to remain very still during the image acquisition, which can take a few minutes at a time. You may be asked to hold your breath during certain parts of the test.
  4. Communication: The technologist will be able to see, hear, and speak with you at all times using a two-way intercom.
  5. Duration: MRI scans usually take between 45 and 60 minutes, but can sometimes take up to 2 hours.

Understanding the Radiology Report

After the MRI scan, a radiologist will interpret the images and write a report for your healthcare provider. This report may contain medical terminology and complex information. Key sections of the report include:

  • History: This section describes your symptoms and the reason for the exam.
  • Prior Exams: Lists any previous relevant imaging exams for comparison.
  • Technique: Describes how the exam was performed, including whether contrast was used.
  • Findings: Details what the radiologist saw on the MRI images, including both normal and abnormal findings.
  • Impression: Summarizes the key findings and the radiologist's conclusions, often including recommendations for further evaluation or follow-up.

Specific Findings in Facial MRI Reports

The radiologist may comment on various findings, such as:

  • Infarcts: Evidence of new or old infarcts (strokes) in the brain.
  • White Matter Changes: Changes in the brain's white matter, which can be related to microvascular ischemic disease.
  • Atrophy: Brain volume loss, which is a normal part of aging but can indicate underlying issues if severe.
  • Sinus Abnormalities: Mucosal thickening or mucous retention cysts in the paranasal sinuses, which can cause headaches.
  • Mastoid Air Cell Fluid: Fluid in the mastoid air cells behind the ears, also potentially causing headaches.

After the MRI Scan

  • Recovery: If sedation was not used, you can resume normal activities and diet immediately after the exam. If sedation was used, a recovery period will be necessary.
  • Results: The radiologist will analyze the images and send a report to your doctor, who will discuss the results with you. Follow-up examinations may be necessary for clarification or monitoring.

Alternatives to Facial MRI

While MRI is often the preferred imaging modality, alternatives exist depending on the clinical situation:

  • CT Scan: Uses X-rays to create cross-sectional images. It is faster and less expensive than MRI but involves radiation exposure. CT scans are better for visualizing bony structures and can be used when MRI is contraindicated (e.g., due to certain metal implants).
  • X-ray: Useful for detecting bone fractures and foreign objects, but provides limited detail of soft tissues.

MRI for Children

MRI in children requires special considerations:

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  • Sedation/Anesthesia: Young children often require sedation or anesthesia to remain still during the scan.
  • Child-Friendly Environment: Creating a comfortable and reassuring environment can help reduce anxiety. Child life specialists can assist in preparing children for the procedure.
  • Pediatric Coils: Specialized MRI coils designed for smaller bodies can improve image quality and reduce scan time.

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