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Using particle physics in medicine

In this video, Dr. Laura Sinclair explains the role of a medical physicist and the applications of nuclear medicine.
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Hello, my name’s Laura Sinclair and I’m a medical physicist working in hospitals. I specialize in nuclear medicine and diagnostic radiology. Previously, I did my PhD in nuclear physics at the University of York, and I worked in laboratories in Finland and Japan. You may be wondering why a physicist is working in a hospital. So let me explain. Medical physics deals with the interactions of matter and energy in medicine. It is the application of physics to healthcare. We use physics for patient imaging, treatments and measurements. As medical physicist, I’m involved in a lot of different diagnostic and treatment technologies found within the hospital, including ultrasound, radiotherapy, phototherapy, lasers, MRI, radiography, CT, fluoroscopy, PET, and nuclear medicine.
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Nuclear medicine is a unique branch of medicine. We attach radioactive materials to a pharmaceutical, a drug, which can be injected, inhaled or swallowed in capsule form. We can use those radiopharmaceuticals, as we call them, to image a treat patients. The particular radiopharmaceutical we use determines where the radioactive material is deposited within the body. In the case of imaging, the radiopharmaceuticals give off energy in the form of gamma rays, that are detected by a specialized camera called a gamma camera. It works a bit like your optical camera. It takes visible light rays and focuses them with a lens to create an image.
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We can’t see gamma rays, but the gamma camera can focus them with a collimator and then process them through a set of electronics to create an image. The workhorse radionuclide in nuclear medicine is known as technetium-99m, which has a half-life of six hours. This means the radiopharmaceutical stays radioactive long enough to be absorbed by the body for the imaging procedure – but not so long that it causes a large dose of radiation to the patient. Nuclear medicine imaging can be used in a variety of ways.
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We can use it to assess if there’s an infection after knee replacement surgery, to assess how well the kidneys are functioning for potential live donor kidney transplants, to detect cancerous tumors, or to assess how well the blood is flowing to the heart. But we can use nuclear physics for more than imaging – we can use it to treat diseases as well. We can use radio nuclides to target a particular region within the body, such as a tumor with alpha, beta, and gamma radiation. We use this type of therapy to treat blood disorders, hypothyroidism, and specific types of cancer. An example of this is the use of radioactive iodine to treat thyroid cancer.
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The human body cannot distinguish between radioactive iodine and dietary iodine. When radioactive iodine-131 is ingested in the form of a capsule, it enters the bloodstream and is taken up by the thyroid. The iodine-131 atoms decay and emit radiation in the form of beta and gamma rays, which kills thyroid cells. So medical physicists play a vital role within the hospital. Nuclear medicine equipment relies on complex physics principles. Physicists like me make sure that the equipment is set up, tested and running correctly and safely. So we need a clear understanding of the physics fundamentals on which the technology is based.
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Physicists also work on image reconstruction and data analysis to help find the best ways to gather and make sense of the medical data. Physicists work to achieve a balance of image quality and radiation dose when using nuclear medicine equipment. So clearly when working with radioactive materials, we need to understand how to measure and limit the amount of radiation given to the patients, as well as hospital staff and even members of the general public. So medical physicists need to know in detail how radiation interacts with the body to give an accurate estimation of radiation dose.
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We can control exposure time, use shielding, and employ the inverse square law of distance to keep radiation exposure as low as possible to protect members of staff and members of the general public. Understanding the diversity of half-lives, the radiation characteristics of known isotopes, the search for new isotopes, radiation instrumentation, radiation protection, data handling, and data analysis techniques, are all used in the field of medical physics. Being a medical physicist is such a wonderful job. Each day is so varied, no two days are alike, and I get to learn something new every day. And the best part of my job is that I get to use my physics knowledge to make a difference in people’s lives.

Medical physicists work at the cutting edge of experimental and theoretical research. It is an incredibly diverse and growing area of physics, often working across disciplines. An understanding of particle and quantum physics is crucial in order to develop new and innovative technologies that can be used both for medical imaging and therapeutically (for treating disease). In this video, Dr. Laura Sinclair explains the role of a medical physicist and the applications of nuclear medicine.

Medical imaging

Medical imaging requires sensitive particle detectors with high resolution in order to obtain the best possible images. In the next step, PhD student Ruth Hardy will describe her research using quantum entanglement to improve PET scans (Positron Emission Tomography).

Therapeutic applications

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Research into new cancer treatments is a large area of investigation and many techniques involve targeting the tumour with high energy particles. Selecting the most appropriate particles is crucial. In this course, we are going to investigate the differences between radiotherapy using X-ray photons and proton beams.

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