A wide bore MRI scanner looks like a slightly wider, often slightly shorter version of a conventional MRI tunnel, with a patient opening (the “bore”) measuring 70 centimeters across instead of the traditional 60 centimeters. That extra 10 centimeters might not sound dramatic on paper, but when you are lying on the scanner table and sliding into the tube, the difference in overhead clearance and shoulder room is immediately noticeable. The exterior housing is a large, rounded unit that resembles a standard MRI machine in overall shape, and to a casual observer the two look similar. The real distinction becomes clear once you are inside.
What the Scanner Looks Like From the Outside
If you walk into an MRI suite and see a wide bore unit for the first time, you will notice it shares the same general silhouette as any closed-bore MRI: a large, cylindrical magnet enclosed in a smooth housing that is usually white or light gray, with a flat patient table extending from its center. The housing sits on the floor or on a low platform, and the overall footprint of the machine is comparable to a conventional scanner. The front face of the unit has a circular opening where you enter, and most manufacturers round or flare the edges of that opening to make it look less tunnel-like.
The main visual giveaway is the proportions of the bore entrance relative to the housing. Because the tunnel is wider, the circular opening looks more generous compared with the exterior casing. On some models, the housing is also shorter from front to back, which makes the machine look less like a deep tunnel and more like a thick ring. Systems from major manufacturers typically measure between about 125 and 150 centimeters in length, depending on the model and field strength.1Saudi Journal of Ophthalmology. Recent advances in MRI technology: Implications for image quality and patient safety By comparison, many older standard-bore scanners stretch to 160 centimeters or longer, which adds to the sense of being enclosed.
Dimensions That Matter to Patients
The defining specification of a wide bore MRI is its 70-centimeter bore diameter. Every wide bore scanner on the market today shares that number, whether it is a 1.5-tesla or 3-tesla system.1Saudi Journal of Ophthalmology. Recent advances in MRI technology: Implications for image quality and patient safety Standard closed-bore machines have a 60-centimeter bore. So when you are lying on the table and looking up, you have roughly 5 additional centimeters of clearance on each side of your body. For someone of average build, this means the walls of the tunnel are noticeably farther from your face and shoulders. For larger patients, it can be the difference between fitting comfortably and not fitting at all.
Bore length also varies. One of the earliest wide bore designs, the Siemens Espree, pushed the concept further with a magnet only 125 centimeters long, which meant that for many exams the patient’s head stayed outside the tunnel entirely. Newer wide bore models from other manufacturers are slightly longer, in the range of 145 to 150 centimeters, but still shorter than many legacy scanners.1Saudi Journal of Ophthalmology. Recent advances in MRI technology: Implications for image quality and patient safety The combination of a wider opening and a shorter tube creates a less confining interior that many patients describe as more tolerable than a standard machine.
What It Feels Like Inside
From the patient’s perspective, the experience begins on the table. You lie down, the technologist positions the appropriate coil (the antenna-like device placed over the body part being scanned), and the table glides you into the bore. With a wide bore scanner, the first thing you notice is that the ceiling of the tunnel is not as close to your face. If you extend your arms slightly, you may still touch the walls, but there is less of the tight, coffin-like sensation that makes standard MRI machines stressful for many people.
Depending on the body part being imaged, your head may remain partially or fully outside the bore. For knee, hip, or lower-spine scans, most wide bore systems position you so that your head and upper body stay outside the tunnel, which dramatically reduces the feeling of enclosure. For brain or upper-spine scans, your head will be inside, but the wider diameter and shorter length still provide a less confined environment. Many patients report that being able to see light at the ends of the tunnel, rather than being surrounded by a long dark cylinder, makes the experience far more manageable.
Claustrophobia and How Wide Bore Scanners Help
Claustrophobia during MRI exams is more common than most people realize. Estimates suggest that somewhere between 1 and 15 percent of all patients scheduled for MRI scans experience enough anxiety to either refuse the exam or need sedation, with one large analysis putting the average at roughly 2.3 percent of all MRI appointments.2PubMed Central. Reduction of claustrophobia during magnetic resonance imaging: methods and design of the “CLAUSTRO” randomized controlled trial Scaled to the tens of millions of MRI exams performed worldwide each year, that translates to an enormous number of scans that are either abandoned or complicated by sedation.
Wide bore scanners were developed in large part to address this problem. Research on wide, short-bore 1.5-tesla scanners has found that they increase the success rate of completed exams in patients with claustrophobia and substantially reduce the need for anesthesia-assisted scans, even in patients whose claustrophobia is severe.3PubMed. Wide, short bore magnetic resonance at 1.5 t: reducing the failure rate in claustrophobic patients The mechanism is straightforward: a wider tunnel with more headroom and a shorter length simply gives your brain fewer spatial cues that you are trapped. You can see more light, you have more room to breathe, and for many exams your head is not inside the machine at all.
This does not mean wide bore machines eliminate anxiety completely. Some patients still find any enclosed scanner distressing. But for the large group of people whose claustrophobia is moderate rather than extreme, a wide bore unit can make the difference between finishing a scan and walking out halfway through.
Ambient Comfort Features
Many modern wide bore installations go beyond the physical dimensions of the bore to address patient comfort. Some facilities equip their scanners with ambient audiovisual systems: projection screens or LED lighting that display calming images (a beach scene, a blue sky, a forest canopy) on the ceiling of the bore, combined with headphones playing music or nature sounds. These features transform the visual experience of being inside the scanner from staring at a blank, close ceiling to looking at something engaging.
The impact of these systems can be striking. One study found that a scanner equipped with ambient audiovisual features had a significantly lower claustrophobia-related discontinuation rate compared with non-equipped scanners, and that among patients who had previously required sedation for MRI, over 93 percent were able to complete their scans without sedation on the ambient-experience scanner.4Radiography. Using ambient audiovisual experiences to reduce the need for sedation in claustrophobic MRI patients These features are not exclusive to wide bore machines, but they are especially common on them because manufacturers and imaging centers understand that the patients seeking out wide bore scanners are often the ones who need every possible comfort measure.
How Loud Is It Inside
One aspect of the MRI experience that no amount of extra bore width can fix on its own is the noise. All MRI scanners produce loud, rhythmic banging and buzzing sounds caused by the rapid switching of magnetic gradient coils during scanning. The sound levels inside a conventional scanner can rival a rock concert, and wide bore machines are no exception. The wider bore does not meaningfully dampen the acoustic output, because the noise originates from the gradient coils that surround the bore regardless of its diameter.
What has changed in recent years is the development of quieter scanning sequences. Traditional approaches to noise reduction have included gradient shielding, vacuum enclosures around the gradient coils, and bandwidth-limited pulse sequences, but none of these bring the noise down to room-level sound. Newer technologies take a different approach by running the gradients continuously at nearly stable levels and adjusting them in very small increments, which produces dramatically less noise during the scan itself.5PubMed Central. Acoustic noise reduction in MRI using Silent Scan: an initial experience These quiet-scan options are available on some wide bore platforms, though not all exams can use them. In practice, you will still be given earplugs or padded headphones before any MRI scan, wide bore or not.
Weight Capacity and Accessibility
Another practical difference you will not see just by looking at a wide bore scanner, but that matters enormously for some patients, is the weight limit of the table. Standard MRI tables typically support patients up to about 300 pounds. Wide bore systems are engineered with substantially higher weight capacities, often in the range of 500 to 550 pounds depending on the model.1Saudi Journal of Ophthalmology. Recent advances in MRI technology: Implications for image quality and patient safety Combined with the larger bore diameter, this makes wide bore scanners the go-to option for patients whose body habitus makes standard machines impractical.
For imaging centers, this expanded capacity also means fewer rescheduled appointments and fewer patients who need to be referred to specialized facilities. Before wide bore scanners became widely available, larger patients sometimes had to be sent to open MRI units, which tend to have lower field strengths and produce lower-quality images. A 70-centimeter bore at 1.5 or 3 tesla gives those patients access to the same image quality as everyone else.
Wide Bore Versus Open MRI
If you have been researching MRI options for comfort, you have probably come across open MRI machines as well. These look very different from any tunnel-based scanner. An open MRI uses two flat magnet plates above and below you, with open sides, so you are not enclosed in a tube at all. Some designs look like a large sandwich with the patient lying on the bottom half. The sense of confinement is minimal, and for patients with severe claustrophobia, open MRI can be the only tolerable option.
The trade-off is image quality. Open MRI systems historically operate at lower field strengths, often around 0.3 to 1.2 tesla, which means the signal-to-noise ratio is lower and the images are less detailed than what a 1.5- or 3-tesla closed-bore scanner produces. Some clinical questions require that higher image quality, and in those cases, a wide bore closed scanner is the better compromise: still a tunnel, but a roomier one with full diagnostic capability.
Open MRI systems do have niche advantages beyond patient comfort. Because the sides are open, they allow procedures like needle biopsies to be performed under real-time MRI guidance, which is difficult or impossible in a closed bore of any width. Research on open 1.2-tesla scanners has explored image-guided needle placement using MRI fluoroscopy, achieving mean insertion accuracy of about 3 millimeters in phantom testing.6Diagnostic and Interventional Imaging. Needle artifact characteristics and insertion accuracy using a 1.2T open MRI scanner: A phantom study For the average patient who simply needs a diagnostic brain or knee scan and finds standard machines uncomfortably tight, though, a wide bore closed scanner usually offers the best balance of comfort and image quality.
Wide Bore in Radiation Therapy Planning
One clinical application where the wider bore is not about patient comfort at all is radiation therapy planning. When oncologists plan radiation treatment, they need imaging that maps the tumor and surrounding anatomy with high spatial accuracy. MRI is increasingly used alongside CT for this purpose because it provides better soft-tissue contrast, but standard 60-centimeter bores can be too narrow to accommodate patients in the treatment position, which sometimes requires arms raised overhead or body immobilization devices that add bulk.
A 70-centimeter bore solves this by providing the room needed to position patients exactly as they will be positioned during radiation delivery. Quality assurance testing of wide bore MRI simulators configured for radiation therapy has shown that geometric distortion, one of the key concerns when using MRI for treatment planning, can be kept within acceptable limits: less than 1 millimeter of error near the center and within 2 millimeters even at 120 millimeters off-center.7Medical Physics. SU‐E‐J‐75: Clinical Commissioning and Quality Assurance Procedures for a Wide Bore MRI Unit Configured for Radiation Therapy Planning This kind of precision is critical because even small distortions in an image can translate into targeting errors during treatment.
Wide bore MRI simulators have become a standard component in many advanced radiation oncology departments. They are not the same machines you will find in a general imaging center marketed for patient comfort, but they use the same fundamental bore geometry. For the patient, the experience of lying in one looks and feels the same as any other wide bore scan.
Radiofrequency Coils and Image Quality
A question that comes up in technical discussions of wide bore scanners is whether making the bore larger compromises the electromagnetic performance of the system. The radiofrequency coils that excite hydrogen atoms in your body during scanning are designed to fit the bore’s geometry, and a wider bore means the coil is farther from the patient’s body. In general, coils that are closer to the tissue they are imaging pick up a stronger signal.
Engineering studies of wide bore body coils have found that the magnetic field uniformity inside a 70-centimeter bore can closely match that of a standard clinical body coil, though the efficiency of the wider coil may be lower. One simulation and bench-testing study of a wide bore 1.5-tesla system found that field uniformity was nearly identical to the standard coil, but the transmit efficiency was about 38 percent lower.8Physics and Imaging in Radiation Oncology. Evaluation of the radiofrequency performance of a wide-bore 1.5 T positron emission tomography/magnetic resonance imaging body coil for radiotherapy planning In practice, manufacturers compensate for this through coil design optimizations and software adjustments, and the resulting image quality on modern wide bore systems is considered clinically equivalent to standard bore machines for the vast majority of diagnostic exams.
For patients, this means you should not expect meaningfully worse images just because you are scanned in a wide bore unit. The engineers have had years to optimize these systems since they were introduced, and the technology has matured to the point where wide bore scanners are not a compromise option. They are simply a different configuration that prioritizes accessibility and comfort alongside diagnostic performance.
How Quickly Wide Bore Became the Norm
Wide bore MRI went from a niche product to an industry standard remarkably fast. When the first 70-centimeter systems appeared in the mid-to-late 2000s, they were positioned as specialty machines for claustrophobic or larger patients. Within just a few years, major manufacturers had incorporated 70-centimeter bores into their mainline product offerings, and many new MRI installations defaulted to wide bore simply because the clinical and patient-experience advantages were so clear.1Saudi Journal of Ophthalmology. Recent advances in MRI technology: Implications for image quality and patient safety
Today, if you are scheduled for an MRI at a facility that installed its equipment within the last decade, there is a good chance you will be scanned in a wide bore machine whether or not you specifically requested one. The 60-centimeter bore is still in service at many older facilities, but the trajectory of new installations is overwhelmingly toward 70 centimeters. For patients, this shift means the cramped, claustrophobia-inducing MRI experience that older generations remember is gradually being replaced by something a little more humane, even if it is still not exactly comfortable.