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A VIEW INSIDE THE BODY

Magnetic Resonance Imaging, or MRI, is a painless and safe diagnostic procedure that uses a powerful magnet and radio waves to produce detailed images of the body's organs and structures, without the use of X-rays or other radiation

The MRI scanner is a modern day medical marvel. It can pick out a very small point inside the patient's body and ask: "What type of a tissue is it?" It scans the body point by point. MRI provides an unparallel view inside the body; the level of detail is extraordinary, and unmatched.

A computer converts signals from the MRI scan into extremely clear, cross-sectional images of the part of the body that has been scanned. Each image is a slice of the body area scanned, and numerous images are created that clearly show all the features of that particular part of the body. So, much so, MRI systems can also image flowing blood in virtually any part of the body making it possible to examine the circulatory system.

"Magnetic Resonance Imaging, or MRI, is a painless and safe diagnostic procedure that uses a powerful magnet and radio waves to produce detailed images of the body's organs and structures, without the use of X-rays or other radiation. Magnetic in MRI stands for magnet in it. The strength of the magnetic field produced by the magnet is rated in units of measure known as Tesla. The magnets in medical MRI units are of 0.5 to 2.0 Tesla," says Dr Subhash Srivastava, radiologist, Zulekha Hospital, Sharjah.

The MRI scanner in Zulekha Hospital is a state of the art 1 Tesla Harmony Maestro class unit.

The images produced by MRI can be compared to a sliced loaf of bread. Just as you can lift each individual slice from the loaf and see both the slice and the inside of the bread, so too the image "slices" produced by the MRI show the exact details of the inside of the body. The computer is able to reconstruct all the images into a single image resembling an X-ray. This reconstruction also can be made into three-dimensional images, allowing complete and remarkable visualisation of the body area scanned from all angles.

MRI is arguably the greatest advance in diagnostic medical techniques over the past century.

"Metallic objects are not taken into the scan room due to the strong magnetic field. MRI systems may also damage bankcards if taken into the unit. Magnetisable implants in a patient's body including pacemakers are contraindications for MRI scan as they could be displaced or could malfunction," says Dr Srivastava, "Our staff is well trained and converse with the patient preparation for the scan, advising the patient to keep any metallic objects, credit cards, mobile phones in a magnet safe room."

"In our bodies, the nuclei of hydrogen atoms (called protons) normally point randomly in different directions. However, when exposed to the magnetic field in an MRI chamber, the nuclei line up in parallel formation, like rows of tiny magnets. Nearly two-thirds of the body's hydrogen atoms are found in water and fat molecules. When the nuclei are subjected to a strong but harmless (and painless) pulse of radio waves from the MRI machine, they are knocked out of their parallel alignment. As they fall back into alignment, they produce a detectable radio signal.

"The signal is recorded by the machine and transferred to a computer. The computer uses these signals to calculate an image that is based on the strength of signal produced by different types of tissue. For example, tissues that contain little or no hydrogen (such as bone) appear black. Those that contain large amounts of hydrogen (such as the brain) produce a bright image," explains Dr Srivastava.

When is an MRI requested?

According to Dr Srivastava, "MRI is used for a variety of diagnostic purposes. It is most often used to obtain information that hasn't been provided by other imaging techniques, including ultrasound, conventional x-ray, or computed tomography."

In general, MRI is used to determine the exact problem inside the body; show exactly where the problem is; rule out certain diseases. "Because MRI produces images in any plane, it is particularly valuable in studying the brain and spinal cord and pinpointing even the smallest abnormality there. Because the water and fat content of tumors is different from surrounding normal tissue, MRI can reveal the precise location and size of tumors," says Dr Srivastava.

"MRI provides images of the internal structure of the eye and ear, detailed images of the heart and major blood vessels, blood flow in the circulatory system, images of joints and soft tissues, particularly of cartilage, ligaments and tendons within joints such as the knee. It is also used to diagnose disorders of chest, lungs, abdominal organs, digestive tract, kidneys, urinary tract, pelvic organs, infections, inflammatory conditions, trauma and other injury," says Dr Srivastava

So MRI is the imaging modality of the future. Excellent tissue contrast makes it the leader in the imaging modality. Diseases can be diagnosed at a very early stage leading to better treatment, prognosis and cure.