Magnetic Resonance Imaging (MRI) uses a powerful magnetic field and radio waves to create detailed pictures of internal structures. Unlike X-rays or CT scans, MRI does not use ionizing radiation, making it a non-invasive method for examining soft tissues, bones, and joints. Many people feel apprehension about the size of the machine and being completely enclosed. This review clarifies the logistical experience for a focused hip MRI, addressing how much of the body enters the scanner and what to expect.
Positioning for a Targeted Hip MRI
For a hip scan, the procedure is highly localized to the area of interest, meaning the entire body does not need to be deep inside the machine’s tunnel, known as the bore. The patient lies on their back in a supine position, often entering the machine feet first. The goal is to center the hip joint within the scanner’s main magnetic field for the highest image quality.
A laser light is used to precisely align the hip joints, which are centered about four inches below the top of the hip bones, or iliac crest. Because the hip is located toward the lower half of the body, much of the upper torso and head often remain near the opening or outside of the bore entirely. Specialized equipment, such as a body coil, is placed directly over the pelvis and hip region to optimize signal reception for generating clear images.
Essential Preparation Steps
Preparation focuses on patient safety and ensuring the magnetic field is not compromised by foreign materials. Since the MRI machine employs a very strong magnet, all external metal objects must be removed, including jewelry, watches, hearing aids, and clothing with metal snaps or zippers. Patients are asked to change into a hospital gown to ensure no metal items remain. Screening for internal metal devices, such as pacemakers, certain aneurysm clips, and neurostimulators, is required, as these can be hazardous.
While most modern orthopedic implants, including hip replacements, are safe, their presence must be disclosed to the technologist. In some instances, a contrast agent, most commonly Gadolinium, may be used to enhance the visibility of certain tissues or blood vessels. If required, an intravenous (IV) line will be placed in the arm or hand to administer this agent during the scan.
The Patient Experience Inside the Scanner
Once positioned, the experience inside the scanner is characterized by loud, repetitive noises and the requirement for absolute stillness. The duration of a hip MRI ranges from 30 to 60 minutes. Maintaining a motionless position throughout this time is necessary, as any movement can blur the images and require the sequence to be repeated.
The distinctive sounds—tapping, banging, and thumping—are produced by the machine’s gradient coils rapidly switching electrical currents. These sounds can reach high decibel levels, sometimes exceeding 100 decibels, comparable to a power saw. Earplugs or headphones are provided to protect hearing and minimize the noise. The patient remains in constant communication with the technologist via an intercom and is provided with a call button to signal distress.