Magnetic Resonance Imaging (MRI) is a non-invasive medical imaging technique that uses a powerful magnetic field and radio waves to generate detailed images of the body’s internal structures. The typical experience involves lying on a table that slides into a long, cylindrical chamber, often referred to as a “bore.” While this traditional design is effective for generating uniform magnetic fields, it presents physical constraints for many patients. The open bore MRI emerged as an alternative, engineered to provide a less restrictive environment while still delivering necessary diagnostic information.
Defining the Open Bore Design
The open bore MRI machine is defined by its unique physical architecture, which departs from the traditional cylindrical tube. Instead of a solenoid magnet creating a surrounding tunnel, the open bore system typically employs two flat magnet plates positioned above and below the patient. These plates create the necessary magnetic field across an air gap, leaving the sides of the machine completely open.
This structural arrangement often gives the machine a C-shaped or horseshoe appearance, allowing the patient to lie between the magnetic poles rather than inside a confined cylinder. The design provides a much wider field of view for the patient and allows medical staff to stand closer during the procedure.
Wide-Bore vs. Open-Bore
It is important to distinguish this from a “wide-bore” MRI. A wide-bore system is still cylindrical but features a larger diameter (e.g., 70 centimeters) compared to older closed models. An open bore MRI, by contrast, eliminates the tunnel structure entirely on multiple sides.
Patient Comfort and Accessibility
The primary advantage of the open bore design is the significant improvement in the patient experience. By eliminating the enclosed tunnel, the open system directly addresses the anxiety that many individuals feel during traditional scans. Patients can often see out of the machine on three sides, which reduces the feeling of being confined within a tight space.
The physical openness of the system also makes it far more accessible for specific patient populations. Individuals with larger body sizes who may not fit comfortably into a standard bore can be accommodated by the open design. The open sides simplify the process of scanning children or older adults who may require constant physical monitoring or the presence of a parent or guardian during the scan. Maintaining patient contact helps ensure a successful, non-sedated examination.
Image Quality and Diagnostic Trade-offs
The open magnet configuration that provides patient comfort affects the machine’s technical capabilities. Magnetic field strength, measured in Tesla (T), is directly tied to the clarity and detail of the resulting images. Because the magnets in an open system are separated to create the expansive gap, they operate at lower field strengths compared to high-end closed systems.
The magnetic field strength in most open bore MRIs typically ranges from 0.2T to 1.0T, with many older models hovering around 0.3T. This lower field strength can result in images with reduced signal-to-noise ratio, which translates to less resolution and detail, particularly when imaging very small anatomical structures. Consequently, scans for certain complex neurological issues or fine vascular structures may be less precise than those acquired on a high-field 1.5T or 3T closed system.
The decreased magnetic power can necessitate longer scan times to acquire sufficient data, sometimes making the process 1.5 to 2 times slower than a high-field machine. However, for many common examinations, such as general orthopedic assessments, the image quality provided by an open bore system is sufficient for an accurate diagnosis. The decision often involves balancing the patient’s need for a comfortable, successful scan versus the physician’s need for maximum image detail.