Magnetic Resonance Imaging (MRI) uses strong magnetic fields and radio waves to generate detailed, cross-sectional pictures of organs and soft tissues. Conventional high-field MRI systems typically enclose the patient entirely within a long, cylindrical tunnel to ensure the magnetic field remains powerful and uniform. This design presents challenges for some patients who find the confined space difficult to tolerate. The development of the Open MRI system introduced a distinct structural alternative, dramatically changing the machine’s external appearance and the patient’s physical experience.
Visual Design and Components
The most immediate difference in an Open MRI system is the absence of the deep, narrow tube that characterizes a traditional scanner. Instead, the machine commonly resembles a large, flattened donut or a “C” shape turned on its side. This structure is defined by two large, horizontal magnetic plates—one positioned above the patient and one below—with a wide-open gap between them.
This configuration leaves the patient’s sides completely open to the room, eliminating the sensation of being fully enclosed. The patient lies on a flat, motorized table that slides into the gap between the upper and lower magnetic components. Unlike the long tunnel of closed systems, the patient’s head or feet often remain outside the machine’s main magnetic field, depending on the area being scanned.
The magnetic field is generated vertically, moving from the top plate to the bottom plate through the area being imaged. Open systems often utilize permanent magnets or resistive electromagnets, which create a lower strength field compared to the superconducting magnets used in high-field closed units. Most open systems operate at field strengths ranging from 0.3 Tesla to 0.7 Tesla, sometimes reaching 1.0 Tesla, compared to the 1.5 Tesla or 3.0 Tesla common in conventional scanners.
The four-post design is another common visual variation, where four vertical support columns hold the upper and lower plates apart. This defines the machine’s box-like, non-cylindrical appearance, maximizing the space around the patient while creating the necessary magnetic environment.
The Patient Experience
The physical openness of the machine translates directly into a different psychological experience for the person undergoing the scan. For many, the ability to see the surrounding room, including the walls and ceiling, significantly alleviates feelings of anxiety and panic associated with enclosed spaces. Patients often maintain direct eye contact with the technologist or can look at a wall mural, which provides a comforting sense of connection to the outside environment.
This increased visibility also allows for easier communication and monitoring throughout the duration of the imaging procedure. In certain situations, the open design permits a parent or family member to sit right next to the patient, holding their hand or offering verbal reassurance, which is especially beneficial for children or anxious adults. The wide access points allow medical staff to interact with the patient without the physical barrier of a narrow tube.
The structural design provides a much larger space for patients of size who may not fit comfortably into the narrow bore of a traditional MRI. The maximum weight capacity of open scanners is frequently higher than closed systems, sometimes exceeding 500 pounds, making imaging accessible to a broader population. The experience also involves a difference in the acoustic environment.
All MRI machines produce loud knocking and buzzing noises as the gradient coils rapidly switch on and off. However, many open systems are perceived as being quieter than their high-field counterparts. Patients still require earplugs or noise-canceling headphones, but the overall intensity of the sound can be less jarring, contributing to a less stressful overall examination.
When Open MRI is Recommended
The selection of an Open MRI is a decision made when patient tolerance or physical constraints outweigh the need for the highest resolution images. The most common indication is severe, unmanageable claustrophobia, where a patient has been unable to complete a conventional MRI scan despite relaxation techniques or sedation. Providing a successful scan for this population is a primary clinical advantage of the open design.
Another frequent use is for patients whose body habitus prevents them from fitting into the standard 60-centimeter or 70-centimeter bore of a closed machine. For individuals exceeding the weight limits of high-field scanners, the increased table capacity and wider access of the open system make the procedure physically possible. This ensures that a broader range of patients can receive necessary diagnostic imaging.
The open structure is also suited for certain orthopedic examinations that require dynamic imaging, where the joint needs to be scanned in a non-standard position. For example, a patient may need their shoulder or elbow positioned in a way not feasible within a narrow tube. This allows the clinician to assess soft tissue damage under specific stress, providing diagnostic information unavailable from a static scan.
The trade-off inherent in many open systems is that lower field strength generally results in a lower signal-to-noise ratio compared to 1.5 Tesla or 3.0 Tesla units. While open systems are excellent for large areas and many joint or spinal assessments, they are often less suitable for intricate studies requiring fine detail, such as high-resolution brain imaging or detailed small vessel angiography. The choice depends on balancing the patient’s needs for comfort and accessibility against the specific diagnostic requirements of the scan.