Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic tool that uses powerful magnets and radio waves to create detailed pictures of the body’s internal structures, including soft tissues, joints, and bones. The procedure often causes anxiety due to the machine’s tunnel-like appearance and the fear of being fully enclosed. Understanding the positioning requirements for a specific examination, such as an arm MRI, helps alleviate pre-procedure stress. This overview clarifies how much of the body enters the scanner and explains the different types of equipment used.
Answering the Core Question: Positioning for an Arm MRI
For a majority of arm scans, the answer to whether your whole body must go inside the machine is no. The fundamental principle of an MRI is that the specific area being imaged must be centered within the strongest part of the magnetic field, which is called the isocenter of the bore. For scans of the lower arm, wrist, or hand, this often means the patient’s head and upper torso remain outside the opening of the scanner.
You will lie on a movable table that slides into the machine feet-first for an arm scan. The table is advanced only until the portion of your arm being examined is aligned with the center of the magnetic bore. For a wrist or hand MRI, the lower half of your body will be positioned deeper inside the machine. However, your head and upper chest may remain close to or outside the opening.
A specialized component called a surface coil is placed directly around the arm to optimize image quality for the targeted area. This coil must be snug around the limb to gather the necessary data for a clear image. Even for an elbow or upper arm scan, more of your body will enter the bore compared to a hand scan. However, it is often still possible to have your head positioned near the entrance, depending on your height and the exact machine model.
Understanding Different MRI Machines
The standard unit is the closed-bore MRI, a cylindrical tube typically offering the highest magnetic field strength (1.5 to 3.0 Tesla). While these machines provide the most detailed images, their narrow opening, often about 60 centimeters in diameter, causes the most anxiety for patients with claustrophobia.
An alternative is the open MRI, which uses magnets positioned above and below the patient, leaving the sides completely open. This design is a common option for those with body size limitations or severe anxiety. Open MRIs utilize lower magnetic field strengths, which can result in images with slightly less resolution compared to a high-field closed-bore system.
Some facilities use dedicated extremity MRI scanners, which are designed only for limbs. These smaller units are typically chair-like, allowing the patient to sit comfortably with only the limb of interest inserted into a small opening. This option leaves the patient completely outside the main magnetic structure and is a good solution for anxiety, though it is not suitable for all types of scans, such as those requiring a view of the shoulder joint.
Preparing for Your Arm Scan
Because the MRI uses a powerful magnet, all metallic items must be removed before entering the scanning room. This includes jewelry, watches, hearing aids, and clothing with metal zippers or snaps. These items can interfere with the magnetic field and distort the images, so proper preparation is essential for a successful scan.
The procedure typically lasts between 30 and 45 minutes, though the duration varies depending on the complexity of the images and whether a contrast dye is administered. During the scan, the machine produces loud thumping and clicking sounds as the magnetic gradients switch on and off. You will be provided with earplugs or headphones for protection. It is important to remain perfectly still throughout the entire process, as any movement can blur the images and require the sequence to be repeated.
If you experience anxiety about confined spaces, communicate this concern to the technologist before the scan begins. They can offer comfort measures, such as providing a blanket, using mirrors to help you see outside the machine, or suggesting a mild sedative, if approved by your physician. Knowing the physical setup and what to expect during the scan helps reduce apprehension and allows for the clearest possible diagnostic images.