Physics in Medicine

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Cocker and Walton Prizes 2012

Physics in Medicine

By Fayaz Rahaman

➢ Introduction
Physics is about understanding the laws that govern the world around us. Most people know about the problems solved and the discoveries made by physicists in the past, such as the orbits of planets found by Galileo, the law of gravity first unravelled by Newton and later extended by Einstein. It is not as widely known how diverse the subjects investigated by physicists are now, and how much their discoveries change our everyday life. Modern hospitals are among the best showcases of the remarkable and often unexpected ways in which Physics is used.

For more then a century, Physics has been the key to new treatments and more and more accurate diagnostics. X rays, ultrasounds, optical fibres, ion and neutron beams are all examples of how breakthroughs in Physics become practical tools used in medicine. Physics enables clinicians to cure diseases such as cancer and kidney stones by destroying unhealthy tissues by delivering energy in the most appropriate form and in the most precise way exactly where it is needed.

➢ The Medical Physicist
Medical physics is the use of physics principles in medical diagnosis and treatment. Many medical physicists are heavily involved with responsibilities in these areas, often with specific patients. They are responsible for selecting and specifying the types of equipment that are used in radiation therapy. They also play a vital role on the medical research and development team in key areas such as cancer, heart disease, and mental illness. A Medical Physicist at work

The medical physicist is called upon to contribute clinical and scientific advice and resources to solve the numerous and diverse physical problems that arise continually in many specialized medical areas. In radiation oncology departments, one important example is the planning of radiation treatments for cancer patients, using either external radiation beams or internal radioactive sources.

➢ Physics of the Body
Medicine is full of biological and chemical science, but physics is rapidly taking on a greater role. In the human body, physics is involved in mechanics and movement as well as the pressure, optical and electrical systems of the body. Radiotherapy is used to treat tumours, and scans such as MRI and PET scans are used to look inside the body and check for diseases and disorders related to these areas of medicine which involve physics.

➢ MRI Scans
Magnetic Resonance Imaging (MRI) uses a circular magnet, strong enough to pick up a car, to produce detailed images of internal organs. Doctors can use MRI to see which parts of the brain are active when you perform certain tasks or feel certain emotions and sensations. A large proportion of the human body is made up of fat and water, both of which contain lots of hydrogen atoms. In fact, you are made up of approximately 60% hydrogen atoms. MRI works by measuring the way in which these hydrogen atoms absorb and give off electromagnetic energy.

When you have an MRI scan, you lie inside a machine that contains a powerful magnet. The nucleus of a hydrogen atom is like a tiny magnet, so by lying in line with the strong magnetic field inside the scanner, all of your hydrogen nuclei line up too. Photograph of an MRI scanning machine

The scanner sends out a pulse of radio waves which gives enough energy to the hydrogen nuclei for them to change direction. When the pulse is switched off the nuclei revert back to their original position and each nucleus gives off energy in the form of a radio wave. The frequency of these waves depends on the strength of the magnetic field where each nucleus is and this means that the scanner can work out the location of each nucleus....
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