Physics in Medicine

Nelson Valentin Bravo

Physics research is helping people to live longer, healthier lives. Physics is helping doctors to find new cures for many diseases that are affecting people all around the world. In the past decades physics and medicine are moving forward hand to hand. One of the most familiar examples is the use of X-rays to diagnose and treat diseases and fractures. The branch that has to do with the application of physics into the medical field is Medical Physics. This branch has to do with the diagnosis and treatment of human disease. The development of radiotherapy in the 1930’s first led to the presence of physicist in hospitals on a regular basis. In the 1950’s, the contributions that could be made by physics and engineering became more obvious with the creation of radionuclide techniques and the beginning of instrumentation development.

The most important areas of the contribution of physics in medicine include imaging with x-rays, ultrasound, and magnetic resonance. These three are known as “diagnostic radiology”. Another contribution is the treatment of cancer by ionizing radiation; known as “radiation therapy”. Imaging and treatment with radioisotopes; known as “nuclear medicine” is also an area where physics plays an important role. Finally, “health physics” is the latest category in Medical Physics. Diagnostic radiology, with the tool of X-rays, has created a new beginning in medical imaging to see inside the human body. Today X-rays are used for planar projection as well as to see cross-sectional slices of the body using CT scans. Also Magnetic Resonance Imaging (MRI) has made a tremendous contribution to medicine. MRI scan, which does not involve harmful ionizing radiation, has help tremendously in the diagnosis of different types of cancer, reducing suffering for the patient. Ultrasound imaging is a method of imaging inside the human body through the use of high-frequency sound waves. These sound waves are recorded and displayed as a real-time visual image. Ultrasound is mainly used to determine the condition of a pregnant woman and her fetus. It is also useful for imaging many of the body’s internal organs, like the heart, liver, gallbladder, spleen, pancreas, kidneys and bladder. As a real-time scanning instrument, they can show movement of internal tissues and organs which allow physicians to see blood flow and heart functions that can help to diagnose several heart conditions. Million of expectant parents have seen the first “picture” of their unborn child with pelvic ultrasound examinations.

Radiation therapy or radiotherapy is the use of ionizing radiation to treat or control malignant tumor cells (cancers). Total body irradiation (TBI) is a special radiotherapy technique used to prepare the body to receive a bone marrow transplant. Radiotherapy has also a few applications in non-malignant conditions; however it’s not used very often because of the worries about the risk of radiation-induced cancers.

In nuclear medicine radioactive substances are used to diagnose and treat disease too. Nuclear Medicine imaging tests differ from most other imaging techniques in that these tests provide information about both the structure and functionality of the system being investigated. These studies have several applications in neurology, cardiology, oncology, etc. In diagnosis, radioactive substances are administered to patients and the radiation emitted by these substances is measured usually by a gamma camera which creates an image. In therapy, radionuclides are administered to treat diseases or provide pain relief. For example, administration of iodine-131 is used for the treatment of thyroid cancer. Positron-Emission Tomography (PET) is an imaging technique in nuclear medicine that has given the promise of revealing the presence and mechanism of diseases such as cancer, heart disease and brain disorders like Parkinson and Alzheimer.

Finally, Health Physics is the part of physics that deals with the protection of people and their environment from potential radiation hazards, while still enjoying the benefits of the atom. Health physicists work in a variety of disciplines, including research, hospitals, industry, education, environmental protection, and enforcement of government regulations. It is important for physicist and potential physicist to understand that this branch of science can be an extraordinary tool in the advancement of medicine in order to live better and longer lives.