Types of MRI Scanners
Understanding the differences between closed, open, and wide-bore MRI machines helps you prepare for your scan and discuss options with your healthcare provider.
Quick Comparison
| Feature | Standard Closed | Open MRI | Wide-Bore |
|---|---|---|---|
| Bore Size | 60 cm diameter | Open on sides | 70 cm diameter |
| Field Strength | 1.5T or 3T | 0.3T - 1.0T (most) | 1.5T or 3T |
| Image Quality | Excellent | Good (lower resolution) | Excellent |
| Scan Time | 30-60 min | 45-90 min (longer) | 30-60 min |
| Claustrophobia | Most challenging | Best for anxiety | Good compromise |
| Weight Limit | ~300-400 lbs | ~500+ lbs | ~450-550 lbs |
Standard Closed MRI (1.5T & 3T)
The most common type of MRI scanner. Patients lie on a table that slides into a cylindrical tube approximately 60 cm (24 inches) in diameter and about 6 feet long.
✓ Advantages
- Highest image quality and resolution
- Faster scan times
- Best for detailed brain, spine, and small joint imaging
- Most widely available
- 3T machines offer even higher resolution for specialized studies
✗ Considerations
- Can trigger claustrophobia (enclosed feeling)
- May not accommodate larger patients
- Louder than open MRI
- Limited positioning options for some patients
Open MRI
Instead of a closed tube, open MRI machines have open sides or are designed like a large donut, allowing patients to see out and feel less confined. The magnet components are above and below the patient.
✓ Advantages
- Best option for severe claustrophobia
- Accommodates larger patients (higher weight limits)
- Children may find it less frightening
- Allows a support person to be closer during scan
- Better for patients who cannot lie flat
✗ Considerations
- Lower magnetic field strength (usually 0.3T-1.0T)
- Lower image resolution/quality
- Longer scan times required
- May not be suitable for all diagnostic needs
- Less widely available
Wide-Bore MRI
A compromise between standard and open MRI. Wide-bore scanners have a larger diameter opening (70 cm vs 60 cm) and are often shorter in length, reducing the enclosed feeling while maintaining high image quality.
✓ Advantages
- Maintains high image quality (1.5T or 3T)
- More comfortable for claustrophobic patients
- Accommodates larger patients
- Shorter tunnel length means head may be outside for some scans
- Same scan times as standard MRI
✗ Considerations
- Still enclosed (not open on sides)
- May not be available at all facilities
- May not fully resolve severe claustrophobia
MRI with Contrast (Gadolinium)
Any type of MRI machine can perform contrast-enhanced imaging. Gadolinium-based contrast agents are injected intravenously to enhance visualization of specific structures.
When Contrast is Used
- Tumor evaluation: Helps distinguish between different tissue types and identify tumor boundaries
- Inflammation: Highlights areas of active inflammation (e.g., multiple sclerosis lesions)
- Blood vessel imaging (MRA): Visualizes arteries and veins without invasive catheterization
- Infection assessment: Helps identify areas of infection and abscess formation
- Post-surgical evaluation: Distinguishes scar tissue from recurrent disease
💡 Gadolinium vs. CT Contrast
Gadolinium-based MRI contrast is different from the iodine-based contrast used in CT scans. If you've had a reaction to CT contrast, you may still be able to have MRI contrast safely (and vice versa). Always tell your doctor about any previous contrast reactions.
⚠️ Kidney Function Warning
Patients with severely reduced kidney function (GFR <30) should generally avoid gadolinium contrast due to the risk of nephrogenic systemic fibrosis (NSF), a rare but serious condition. Blood tests to check kidney function are typically required before contrast administration.
Specialized MRI Types
Functional MRI (fMRI)
Measures brain activity by detecting changes in blood flow. Used for research, pre-surgical brain mapping, and studying neurological conditions. Requires standard closed MRI scanners.
Cardiac MRI
Specialized imaging of the heart with ECG gating to capture images between heartbeats. Evaluates heart structure, function, and blood flow. May take 60-90 minutes.
MR Angiography (MRA)
Focuses on blood vessels. Can be done with or without contrast. Commonly used to evaluate brain vessels, carotid arteries, and peripheral vasculature.
Breast MRI
Used for high-risk breast cancer screening and evaluating known breast cancer. Requires prone positioning (lying face-down) in a specialized coil.
MR Enterography
Specialized abdominal MRI to evaluate the small intestine, commonly used for Crohn's disease monitoring. Requires drinking contrast and fasting beforehand.
Choosing the Right MRI Type
Your radiologist and ordering physician will recommend the appropriate MRI type based on:
- The clinical question being asked (what diagnosis is suspected)
- The body part being imaged
- Required image resolution and quality
- Your physical comfort needs (claustrophobia, body size)
- Available equipment at your imaging center
💡 Ask About Your Options
If you have concerns about claustrophobia or comfort, ask your doctor or the scheduling staff about wide-bore or open MRI options. While not every facility has all types, they can often refer you to one that does if your clinical situation allows.