An open MRI is a magnetic resonance imaging machine designed with open sides or a wide gap between its magnets, rather than the narrow tube shape of a conventional MRI scanner. It produces diagnostic images using the same basic technology (magnetic fields and radio waves, no radiation) but in a configuration that gives patients significantly more space and reduces the feeling of being enclosed.
How an Open MRI Differs From a Standard MRI
A conventional closed MRI is essentially a long, narrow cylinder. You lie on a table that slides into a tube typically about 60 to 70 centimeters (roughly 2 feet) in diameter. The magnets surround you on all sides, which is efficient for generating strong, uniform magnetic fields but leaves very little room.
An open MRI uses a split-magnet design, with magnet poles placed above and below you rather than wrapping around you. This creates a large gap on at least two or three sides of the scanning area, so you’re not fully enclosed. Some open designs look like a sandwich: a flat table between two large magnetic plates. Others use a wider, shorter bore that flares open at the edges. The key difference is that open air surrounds much of your body during the scan, making the experience feel less confined.
Why Open MRIs Exist
Claustrophobia is the primary reason open MRI machines were developed. Roughly 10% of MRI patients experience some degree of claustrophobic reaction during a scan, and studies estimate that 2 to 10% of patients are unable to complete their scans because of it. A large multicenter study found that 2.3% of patients worldwide experienced claustrophobia severe enough to prevent scan completion or require sedation, translating to nearly 2 million affected MRI procedures every year. Even patients who finish their scans may experience panic attacks: one study found 13% of patients reported them during conventional MRI.
Beyond anxiety, open MRIs serve patients who physically cannot fit into a standard bore. Standard MRI tables typically support 450 to 550 pounds, but the bore diameter (about 70 cm before accounting for padding and imaging coils) can be too tight for larger patients. Open and wide-bore systems offer substantially more room.
Open designs also benefit children, who may be frightened by a closed tube, and patients who need a caregiver or parent nearby during the scan. Some newer open systems are specifically built for interventional procedures, where a physician needs to access the patient during imaging.
Field Strength and Image Quality
This is where the tradeoff comes in. Standard closed MRI machines operate at 1.0 to 3.0 Tesla, a unit measuring magnetic field strength. Stronger magnets produce sharper, more detailed images. Traditional open MRI magnets run at just 0.2 to 0.3 Tesla, which means noticeably lower image resolution and longer scan times.
For many routine scans (knees, shoulders, basic spinal imaging), the image quality from a low-field open MRI is perfectly adequate. But for detailed brain imaging, cardiac scans, or detecting small tumors, the difference in clarity matters. Your referring physician and the radiologist will typically determine whether a lower-field open system can answer the clinical question at hand.
The gap is narrowing, though. Siemens Healthineers has introduced systems operating at 0.55 Tesla with bore openings as wide as 100 centimeters. That’s not technically “open” in the traditional sense, but the extra-wide bore creates a similar patient experience while delivering better image quality than older open magnets. These systems are designed for diagnostic use as well as interventional procedures, serving pediatric, bariatric, claustrophobic, and pregnant patients.
Types of Open and Wide-Bore Systems
Not every “open MRI” is the same design. The most common types include:
- Traditional open MRI: Two flat magnet plates above and below, open on all sides. Lowest field strength (0.2 to 0.3 Tesla) but maximum openness.
- Wide-bore MRI: Still a tube shape, but with a diameter of 70 cm or more and a shorter length. Feels more spacious than a standard bore, though you’re still inside a cylinder. These typically operate at 1.5 Tesla or higher, preserving image quality.
- Upright MRI: A specialized open system that lets you sit or stand during the scan. Because there’s no enclosing tube, it works well for claustrophobic patients. Its real advantage, though, is scanning your spine and joints under your body’s actual weight. Lying flat in a standard MRI can mask problems that only appear when you’re upright, bending, or twisting. Upright systems can image you in the exact position that triggers your symptoms.
What to Expect During an Open MRI
The preparation is identical to a standard MRI. You’ll remove metal objects, change into a gown if needed, and answer screening questions about implants or devices. The scan itself still requires you to stay very still, and it’s still loud. You’ll hear the same rhythmic knocking, buzzing, and thumping sounds from the magnets cycling, so you’ll likely be offered earplugs or headphones regardless of the machine type.
Scan times on lower-field open systems tend to run longer than on high-field closed machines. A scan that takes 20 to 30 minutes in a 1.5 Tesla machine might take 45 minutes or more in a 0.2 Tesla open unit, because the weaker magnet needs more time to collect enough signal for a usable image. Wide-bore systems operating at higher field strengths don’t have this penalty.
One practical note: not every imaging center offers open MRI. Availability varies by region, and some insurance plans may require documentation that you need an open system (such as a history of claustrophobia or body size that prevents a standard scan) before covering the cost. It’s worth calling ahead to confirm the specific machine type, since “open MRI” can mean different things at different facilities. Some centers advertise wide-bore systems as open, which is more spacious but still enclosed.
Who Benefits Most From an Open MRI
Open MRI is most valuable for patients with claustrophobia or anxiety severe enough to prevent them from completing a standard scan, patients whose body size exceeds the bore dimensions of a conventional machine, children who need a parent close by, and anyone undergoing a scan where weight-bearing positioning changes the diagnosis (particularly spinal conditions). For patients who can tolerate a closed bore, a high-field machine will generally deliver faster scans and sharper images. But when the choice is between a completed open MRI scan and a conventional scan that never gets finished, the open system wins every time.