Duchenne Muscular Dystrophy (DMD) is the most common of the muscular dystrophy’s seen in children. DMD is an X-linked genetic neuromuscular disease affecting mainly boys. DMD results in progressive weakness in muscles as a result of a lack of the protein dystrophin. Over time boys demonstrate a decreased ability to walk and to perform activities of daily living. The purpose of the ImagingDMD study is to learn more about changes that occur in muscles of the arms and legs in boys with DMD. We hope to develop an improved imaging procedure to follow the progression of this disease in people with DMD and to help evaluate upcoming treatments for this disease.
The study will compare the muscles of boys with DMD with muscles of age matched non-affected boys. We will monitor disease progression in boys with DMD over a 5 year period. The amount of muscle damage and fat that we measure will also be related to functional measures such as walking and the loss of muscle strength.
In order to participate in this study you must have the gene abnormality (mutation) associated with DMD*(see Enrollment tab). The boys who choose to enroll in this study will be required to attend a session of MRI/MRS (leg and arm), strength, and functional testing at regular intervals (annually) over a period of 5 years. There will be additional imaging and functional testing (for one time point) once ambulation is lost. We anticipate that measurements will be performed at up to six - eight separate time points depending on functional status.
MRI and MRS
Magnetic Resonance Imaging (MRI) and Spectroscopy (MRS)
MRI is a procedure that allows doctors to look inside the body by using a scanner that sends out a strong magnetic field and radio waves. This procedure is completely painless, non-invasive and uses NO radiation. During the scan participants will lie on a padded table inside the magnet. A series of images (pictures) will be taken from one of the subject's legs and arms. The scanning period takes up to 90 minutes for the arm and 60 minutes for the leg, during which time it is extremely important to lie still to insure the clarity of the images produced. Similar to taking a regular photograph, if you move the picture will be blurry and out of focus.
One of the investigators will be present at all times with each participating boy, making sure he is comfortable and at ease. One parent will also be allowed in the scan room during the imaging. Although the measurement is painless, it is somewhat noisy inside the magnet due to a hammering sound made by the magnet. Disposable earplugs and headphones will be provided to the boys to reduce the noise while the scanner is operating. In addition the child will be able to watch a movie while in the scanner. This helps the time go by quickly.
At the same time, MRS measurements will also be taken. Like the MRI, this procedure is completely painless, non-invasive and uses NO radiation. This technique will give us biochemical information about the subject's muscles and will help us tell the difference between damaged muscle, healthy muscle, water, and fat inside of the muscles.
Muscle and Functional Performance Tests
Arm muscle strength will be tested using a strength testing device. Subjects will be asked to squeeze a handle or pinch a device to determine grip and pinch strength. Boys may be asked to push or pull against a pad however the arm will not move during this test. Subjects may be asked to repeat this procedure as many as three times. We might also test muscle strength manually by demonstrating a movement and then asking the boy to perform the movement with his arms. In addition, subjects may be asked to perform motor tasks such as getting up from the floor, climbing 4 stairs, and walking at different speeds and distances for up to 6 minutes. The boys will be allowed to rest at any time if they become tired.
At each visit we will ask for updated information regarding medical history and medications each subject takes as well as each boy's stage of puberty.
The entire testing session should last between 4-6 hours.
Strength Testing Devices
- Used to measure strength of arms
- Used to test grip strength
- Used to test pinch strength
How Does the Magnet Work?
By using magnetic resonance imaging (MRI), scientists at the University of Florida, Oregon Health Science Center, and the Children's Hospital of Philadelphia are able to take pictures of the inside of a person’s body. Similar to a CAT scan or an X-Ray, MRI machines are able to look through the skin at muscles, bones, or organs. MRI does not use radiation and there are no known side effects from its use.
The magnets we use are different than the magnets that are attached to a refrigerator door that may hold your shopping list or favorite picture. The magnet we use is made by repeatedly coiling wires around a shell, which is around the tube (the bore). If you've seen a “spool of thread”, this is a similar idea. These coils of wire are then put into a bath of liquid helium. This is the same material that is in “helium balloons”, only it is cooled down until it is a liquid instead of a gas. Once the wires are cooled, electricity is run through them until they produce a magnetic field--a magnetic field that is much greater than the earth's own magnetic field. All of this activity is inside the magnet and invisible to the person being scanned. When the images are taken the boys will hear a lot of banging and clanking. This is perfectly normal and although the sound is loud there is no cause for alarm. The noise is made by the wires shaking in their casings which is caused by the electricity running through them: Again, perfectly normal! We will give the boys earplugs and headphones to cover their ears while they are inside the magnet and this will help to decrease the sound while they are being scanned.
When the images are taken, we are actually taking pictures of the water molecules inside the body. Since our body is made up mostly of water (about 70%), this is handy! We'll take a number of different pictures from different angles and use them to get an overall idea of what is going on in each boy's muscles. Similar to a camera, any movement will cause the pictures to be blurry, so it is very important while in the MRI for each person to stay very still.