MAGNETIC RESONANCE IMAGING By Kha Vi An, Naomi and Shrabanti

The General Purpose of MRI ● In general, MRI (Magnetic resonance imaging) is a type of test used to create detailed images of the tissues and organs within your body ● Its main job is to detect any abnormal structures of the body and provide detailed information about it ● This machine is used when other testing methods have failed to provide accurate information when trying to confirm the diagnosis of a patient

The Purpose of MRI in Medicine In the medical field, doctors use MRI to examine different parts of the body such as the brain, spinal cord, bones, joints, heart, blood vessels, breasts and other internal organs The MRI helps doctors to diagnose many types of diseases or conditions and to detect any injuries of the body This machine is favored by physicians because it can detect the slightest structural change of the body - this provides patients with accurate information they need always

MRI is used for a variety of purposes: To diagnose diseases of the central nervous system - includes the brain and spine To detect musculoskeletal disorders and injuries To identify problems of infectious diseases such as Aids Finding out the stages of types of cancer Helping in the planning of surgery and cancer treatments To assess blood vessels in the brain to detect any strokes or abnormalities Imaging the cardiovascular system

The Use of MRI in Different Parts of the Body Brain and spinal cord MRI is mostly used for imaging test the spinal cord and brain - This machine helps to diagnose: Spinal tumours Brain tumours Aneurysms (a blocked vessel with a torn lining) Nerve injuries Disorders of the eye and inner ear Stroke

Heart and blood vessels An MRI that focuses on the heart and blood vessels diagnoses: Problems of arteries and veins Flow of blood Damage caused by heart attack or heart disease Size and function of the heart's chambers Thickness and movement of the walls of the heart

Bones and joints An MRI can help evaluate: Bone tumours Joint disorders such as arthritis Bone infections Torn ligaments and tendons Joint abnormalities caused by repetitive injuries Disk problems in the spine

Other internal and external organs An MRI can be used to look for tumors and other abnormalities of the organs in and out your body, including the: Breast Liver Gallbladder Pancreas Kidneys Bladder Uterus Ovaries Testicles Prostate

How Can MRI Be Used To Show A Brain Tumor? To show brain tumors, a contrast dye is injected into the veins of the arm to give colour to the different body parts in the body Grey and white is usually used to differentiate the problems in the brain Tumors tend to soak up more dye than normal brain tissue and shows up clearly like the diagram shown The white area indicates a tumour is growing and the grey area indicates the normal brain tissue

MRI radiation is far weaker than X-rays in CT scans, which means it cannot harm you.

How it works: MRIs employ very powerful magnets, creating a strong magnetic field  Your body is full of hydrogen atoms that have a magnetic spin, causing them to spin around an axis A second magnetic field is added, perpendicular to the main magnetic field  Causes precession to occur, turning the proton around the second magnetic field. The second magnetic field is turned off but the proton still continues to spin to realign with the main magnetic field  Detectors to detect how many protons were affected in the magnetic field and the amount of heat released

MRI Imaging To obtain an MRI image, detected information sends out radio signals that are measured by receivers in the MRI scanner In conjunction with a computer, an image is formed from the signals To speed up the process at which protons realign, oftentimes contrast agents are used (ex. gadolinium) The faster the protons realign, the brighter the image

“ Time of Flight” technique Stationary tissue becomes magnetically saturated with multiple radiofrequency pulses. This causes the incoming blood vessels to visualize as a brighter signal than the surrounding tissue. “Phase Contrast” technique This is used to visualize fluid such as blood. Bipolar gradients (two gradients with equal magnitudes but in opposite direction) are used to encode the velocity of the spins of the protons. Functional MRI This measures brain activity by measuring the changes in blood flow to different parts of the brain using blood- oxygen level dependent contrasts Diffusion MRI Uses the random motions of water molecules suspended in a liquid to generate contrast in MRI images for diagnosis Methods of MRI

MRI Machines Old Equipment:  A large cylinder-shaped tube surrounded by a circular magnet  Some short-bore systems are designed in a way that the magnet does not completely surround the body New Equipment:  Have a larger diameter bore which is more comfortable for larger sized patients or claustrophobic patients  Provide very high quality images for many types of exams Future Equipment:  Scientists are developing smaller, more portable devices that are useful for detecting infections and tumours of the soft tissues of the hands and feet  Currently being tested

MRIs are not just used for diagnostic purposes. Because they are safer, scientists have used MRIs in research to record the brain activity of people playing video games, monks, jazz musicians, dyslexics and even women giving birth.

Ethical and Negative Issues Associated With MRI Although MRI’s do provide many medical benefits, there are also some negative issues. MRI scans are helpful to most of society, but not everyone is able to use them. Many people are unable to use the potentially lifesaving piece of technology because certain aspects are fatal to their survival.

People who cannot and should not have an MRI: ● Those who are obese ● Those who are claustrophobic ● Those with tattoos ● Those who are pregnant ● Those who have metal implants Although many people may be in need of an MRI scan, some are unable to be scanned due to factors of size, safety or security.

Claustrophobia and Obesity People who are claustrophobic cannot be in the cramped and confined space. The Bore is too small to accommodate those who are obese. Although there are scanners created to be larger, they have a weaker magnetic field, therefore abnormal tissues are easier to miss.

Pregnant Women There has been limited research on the biological effects of the magnetic fields on a developing fetus. Because of this, most faculties do not want to scan pregnant women during their first three months of their pregnancy because it has a possibility of affecting their fetus.

Tattoo s Some faculties do not allow people with tattoos to enter. Tattoos contain extremely small fragments of metal for pigmentation Some patients with tattoos described a burning sensation around the tattoo ranging from slight discomfort or severe pain. This is caused by the magnetic mull in the MRI. Tattoos also cause distortion of the final image, rendering it useless.

Metal Items Small to large metal Items around the MRI lead to safety hazards. Small objects can be suddenly pulled out and creating great risk by flying towards the MRI at high speeds while big objects can be a large threat. In 2001, a young boy was killed as an oxygen tank was pulled into the bore of the magnetic field of the MRI, he died in the scanner.

Metal Implants People with pacemakers, aneurysm clips, clips in the brain, metal dental implants, etc. cannot take an MRI These metal implants will malfunction or cause bodily harm. Elderly, who are the ones who need MRI most, usually are unable to take an MRI scan because of their metal implants.

Occupational Risk Staff operating in the environment of MRI scanners are exposed to essentially static magnetic fields for hours each day. Workers can also be exposed to gradient fields (this only happen during the examination of patients).

Medical Issues There are very rare cases of medical issues that happens in 1 in 1000 people. The sedation or anaesthesia that may be required for children when cannot stay still. Injections of a dye (a contrast medium), can lead to kidney problems or cause allergic or injection site reactions.

Studies in Health impacts of MRIs There is a concern that the exposure to the magnetic fields may produce adverse long term health effects. Sir William Steward, HPA Chairman, said, “...We need to bear in mind that the more magnetic the field produced by machines are quite substantial and that the fields are increasing in order to achieve improved clarity of an image. “Exposure to patients and medical staff from the field can be at high risk and there is a shortage of information on possible adverse long term health effects.”

Thank you!

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