What is an MRI scan?
An MRI scanner is a special machine that includes a big magnet. It uses strong magnetic fields and radio waves to produce detailed images of the imaged body part. MRI is the imaging of choice when there is concern regarding any internal hip problem.
What happens on the day of the scan?
A hip MRI scan would require you to stay still for approx. 20-30 minutes inside the tunnel of the machine, while the images are being taken. It can be slightly noisy while you are inside the machine; therefore, a headphone (usually with some music) will be used. The technician will see you before the scan to ensure that you do not have any metallic object before going into the scanner. This can be dangerous as the scanner has a very strong magnet, and any small metallic object can become a projectile.
Is it safe to have a hip MRI scan?
An MRI scan is very safe and routinely performed nowadays with very few contraindications. The technician will ask you all the relevant questions to make sure that it is safe for you to undergo an MRI before your appointment. Generally, if you have a metallic object inside your body, then an MRI scan might not be safe for you, as it may result in the movement of the object, which can cause tissue damage if it is in a sensitive area (like in the brain or the eye). Some examples of conditions where you should not go inside an MRI scanner include:
· If you have a metallic foreign body within your eye. This is especially seen in welders. An X-ray might be needed prior to the examination to ensure that there is no significant metallic foreign body near your eyes.
· Surgical clips inside your brain.
· Cochlear implant
· A heart pacemaker or defibrillator
· A recent surgery (within 6 weeks from the scan), especially if it involves inserting a sizeable metallic object into the body (like a joint replacement).
What are the different types of MRI machines, and which one is better?
The newer generations of MRI are called (3T or 3 Tesla) while the older ones are called 1.5T scanners. This refers to the strength of the main magnet of the scanner. Stronger magnets usually result in better images and, therefore, can provide a superior assessment of the imaged body part. 3T scanners are particularly useful for assessing the labrum for any tear. The labrum is a special type of cartilage that forms a ring along the acetabular margin. It functions to increase hip joint stability by deepening the socket. Scanners can also be divided according to the body part they can image into body or extremity scanners. The latter is smaller, with a weaker magnet and can only image the extremities (like knees, elbows, wrists and ankles). Body scanners are larger, with stronger magnets and can image all body parts. The images produced by body scanners are usually superior (because they have stronger magnets and the imaging field is usually more homogenous). These are usually preferred when you are getting a hip MRI.
What type of hip problems will be picked up on an MRI scan?
Generally, MRI is a very good scan to diagnose hip problems. It needs to be interpreted by a specialist musculoskeletal radiologist. The hip conditions that can be assessed on an MRI examination include:
What are the disadvantages of an MRI examination?
A hip MRI examination has a few drawbacks
· Usually, they are costly compared to other types of scans.
· They require you to stay still for 20-30 minutes; otherwise, the images will be unclear.
· People who are not comfortable with small spaces (claustrophobic) may find it challenging to have an MRI scan
· It may be unsafe to perform in a few situations, as explained above.
How much does a hip MRI cost?
This varies depending on the institution. In the UK, the price can range from £300 to £800.
Hip MRI vs hip X-ray and ultrasound scan
A hip X-ray (or hip radiograph) is a black-and-white image produced by sending an X-ray beam through the area and getting the images on a film. It is usually the first type of imaging done when there is a hip problem, particularly if there is suspicion of hip arthritis or fracture around the hip. Unlike MRI, X-rays cannot assess soft tissues. To find out more, please see our article about hip X-rays.
Ultrasound is high-frequency sound waves produced by a special machine and can provide useful images of the tissues within the body. A hip ultrasound is useful for assessing the tendons around the hip (for example, in greater trochanteric pain syndrome/hip Trochanteric bursitis. It cannot assess the deep structures inside the hip joint (the labrum and the articular cartilage). To find out more, please see our article about hip ultrasound scan. Ultrasound is the preferred imaging choice when a hip injection is required. Ultrasound allows for direct visualisation of the needle to ensure the medicines are injected into the targeted site. There is significant evidence that ultrasound-guided injections provide better pain relief and more prolonged effects compared with injections without imaging guidance.
