Medical Physics

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Medical physics


Medical physics is the use of physics principles in the practice of medicine. It is most often used to describe physics applications related to the use of radiation in medicine—for example, the physics of diagnostic radiology, radiation oncology, and nuclear medicine. More broadly defined, medical physics may include the physics of other electromagnetic waveforms used in medical procedures such as electrocardiography (the study of electrical impulses in the heart ) and laser surgery .


Medical physics refers to the application of physics in medical diagnosis and treatment. The bulk of medical physics is encompassed by four subfields: diagnostic radiological physics, therapeutic radiological physics, medical nuclear physics, and medical health physics.

Diagnostic radiological physics

Diagnostic radiological physics is the branch of physics associated with diagnostic procedures that use xrays, gamma rays, ultrasound, radio frequency radiation, and magnetic sources (magnetic resonance imaging ). In this subfield, physicists advise on the protocols and technology used for the creation of images that are generated by these diagnostic methods. Responsibilities of the medical physicist include establishing, monitoring, and evaluating procedures related to equipment use; reporting to regulatory agencies on compliance matters; evaluating and monitoring equipment; and acting as consultant on matters related to instrumentation, equipment, and use of these radiological imaging systems.

Therapeutic radiological physics

Therapeutic radiological physics concerns itself with the physics of therapeutic procedures that use x rays, gamma rays, neutrons, charged particles, and radionuclides from sealed sources (radioactive material that is sealed permanently in a container). These therapeutic procedures are often used in the treatment of cancer and include external beam therapy (where ionizing radiation is directed at the cancer site) and brachytherapy (where containers with radioactive material are placed near or in the tumor). Duties of the therapeutic radiological physicist include providing consultation on matters related to appropriate radiation dose and risks to patients; managing procedures and equipment related to dose and delivery of therapeutic radiation; reporting to regulatory agencies on compliance matters; and designing, evaluating, and monitoring radiation safety program related to therapeutic radiological procedures.

Medical nuclear physics

Also known as nuclear medicine physics, medical nuclear physics is the study of physics related to medical procedures requiring the use of radionuclides (except those radionuclides from sealed sources). These procedures may be diagnostic or therapeutic, and include such procedures as single photon emission computed tomography (SPECT), positron emission tomography (PET ), and radioimmunotherapy (radioisotopes attached to molecules that can be targeted to cancer cells). The medical nuclear physicist acts as consultant on matters related to appropriate radionuclide dose and risks; manages procedures and equipment related to dose and delivery of radionuclide imaging equipment; reports to regulatory agencies on compliance matters; and designs, evaluates, and monitors radiation safety program related to the nuclear medicine facility.

Medical health physics

The medical health physicist specializes in issues related to radiation safety in medical procedures. There is some overlap between medical health physics and the three other subfields since the use of radiation for medical purposes always requires some safety safeguards. The medical health physicist takes part in designing and specifying the radiation shielding required to protect patients, health care workers, and the general public; conducts risk assessment of procedures and protective equipment used in radiological and nuclear medicine; acts as consultant on issues related to radiation safety in a medical context; and evaluates and monitors compliance with regulatory radiation guidelines.

Work settings

Medical physicists and medical physics technologists work in clinical settings. Most medical physicists and technologists are employed by hospitals because the equipment used for the radiation-based medical procedures is located in these advanced medical facilities.

At teaching hospitals, medical physicists may, in addition to their role as physicists, be academic faculty at affiliated medical schools and/or clinical residency programs. At larger teaching hospitals, medical physicists may be organized into a medical physics department that provides services to other clinical departments. At nonteaching hospitals, medical physicists are members of individual clinical departments and are part of the hospital staff.

Education and training

The minimum education requirements for a medical physicist are an undergraduate degree—in physics, engineering, mathematics, or a related field—and a master's degree in medical physics. Graduate training should be done in a medical physics program that is accredited by the Commission on Accreditation of Medical Physics Educational Programs, Inc. Graduate work covers the physics principles and technologies associated with the relevant medical procedures and allow for specialization in a medical physics subfield. After the master's degree program, a medical physicist must attend a clinical residency program that lasts one to two years. Medical physicists with master's degrees who have completed residency and have obtained appropriate certification typically provide consultation services in hospitals.

The requirements for a technologist working in medical physics areas are a certificate, associate's degree, or a bachelor's degree in the appropriate subfield (e.g., nuclear medicine, radiography, radiation therapy) from an accredited program.

The requirements for a technologist working in medical physics areas are a certificate, associate's degree, or a bachelor's degree in the appropriate subfield (e.g., nuclear medicine, radiography, radiation therapy) from an accredited program.

Advanced education and training

After formal education, certification in a subfield of medical physics is required for medical physicists but is voluntary for technologists. Certification for United States medical physicists is obtained through one of three organizations: the American Board of Medical Physics, the American Board of Radiology, and the American Board of Science in Nuclear Medicine. Certification to become a qualified medical physicist through the American Board of Medical Physics consists of completing three steps. Part one of the process requires having obtained a graduate degree in physics, medical physics, or other relevant field, and having passed a written exam in general medical physics. The second part requires passing the first part and having finished a clinical residency program, as well as having passed a written exam in a medical physics subfield. The third part requires having passed the first and second parts, having practiced independently as a medical physicist for a specified number of years, and having passed an oral exam in a medical physics subfield.

If a medical physicist wishes to pursue an academic career of teaching and research, a master's degree is generally not sufficient; he or she will need to have completed a PhD program in medical physics to be seriously considered for academic positions. Other requirements for an academic career include a post-doctoral fellowship of one to two years, certification as described above, and licensure if required by the state.

For technologists working in the areas related to medical physics, certification is voluntary and can be obtained through the American Registry of Radiologic Technologists or, if the specialty is nuclear medicine, the Nuclear Medicine Technology Certification Board. Certification may be obtained solely through finishing a specified medical technology program, or through a combination of formal education, clinical experience, and additional Board coursework. Some states also require licensure of their medical technologists.

Future outlook

The demand for medical physicists is expected to grow at a rate of 7% per year, which is about the average rate of job growth. The specialty of radiation therapy is expected to be the source of most new jobs, but developments in nuclear medicine and diagnostic techniques may provide a boost to labor demand in these fields. The average salary of a medical physicist (master's and PhD degree holders combined) in 2000–2001 is estimated to be $57,060.

The demand for nuclear medicine technologists and radiologic technologists is expected to also grow at the same rate as the average rate for all jobs. There is a shift towards the merging of nuclear medicine and radiology departments, so that demand will be greatest for those technologists who have both nuclear medicine and radiologic skills. In 1998, the average salary of a nuclear medicine technologist was $40,000; the average salary of a radiologic technician was $33,000.



Bushberg, Jerrold T., et al. Essential Physics of Medical Imaging. 2nd ed. Philadelphia: Lippincott, Williams, and Wilkins, 2001.

Stanton, Robert, and Donna Stinson. Applied Physics for Radiation Oncology. Madison, WI: Medical Physics Publishing, 1996.


American Association of Physicists in Medicine. One Physics Ellipse, College Park, MD 20740. (301) 209-3350. <>.

American College of Medical Physics. 11250 Roger Bacon Drive, Suite 8, Reston, VA 20190-5202. (703) 481-5001. <>.

American Registry of Radiologic Technologists. 1255 Northland Drive, St. Paul, MN 55120-1155. (651) 687-0048. <>.

Genevieve Pham-Kanter

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Medical Physics

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