History of Medical Physics

Perhaps Leonardo da Vinci, five centuries ago, might be considered the first medical physicist. Certainly it is true that he was profoundly interested in the mechanics of human locomotion. The subsequent gradual development of physical tools contributed to advances in the biological sciences. One outstanding example is the microscope, developed by the Dutch inventor, van Leeuwenhoek, during the 17th century. The development of the science of electro­magnetism in the 19th century enabled physicists to make contributions to medical treatment and diagnosis. D'Arsonval, a French physicist, pioneered the therapeutic use of high-frequency electric currents and pointed the way towards development of electrical measuring instruments. Since then, sensitive recording voltmeters, starting with the Einthoven string galvanometer, have made possible the development of electrocardiography and electroencephalography.

The discoveries of x-rays and radioactivity by the physicists Roentgen in 1895 and Becquerel in 1896 were rapidly followed by the application of ionizing radiations to the diagnosis and treatment of disease. This activity has been primarily responsible for bringing physicists directly into the sphere of the hospital. In 1913, Duane began work on radon sources for cancer treatment in a Boston hospital and was followed in 1915 by Failla in New York. In the 1920's, there was only a handful of physicists in medicine, but today the number exceeds 4,000. The invention of powerful radiation sources to deliver interstitial and intra-cavitary radiation therapy, including Van de Graaff generators, betatrons, cobalt-60 units, linear accelerators, microtrons, and cyclotrons for external beam radiation therapy; the application of man-made radio-nuclides to medical diagnosis and the development of detection devices, such as gamma cameras and positron emission tomography (PET) scanners; the application of ionizing radiation to medical diagnosis and the invention of imaging techniques and devices, such as image intensifiers, computerized tomography (CT), and digital radiology; and, more recently, the utilization of nuclear magnetic resonance (NMR) in medical imaging and spectroscopy have all created a distinct role for medical physicists in the practice of the healing arts. Thus the growth and contribution of medical physics is a natural consequence of the evolution of modern science and technology.

Medical Physics

An applied branch of physics concerned with the application of the concepts and methods of physics to the diagnosis and treatment of human disease. It is allied with medical electronics, bioengineering, and health physics.

What Is a Medical Physicist?

Medical physicists contribute to the effectiveness of radiological imaging procedures by assuring radiation safety and helping to develop improved imaging techniques (e.g., mammography CT, MR, ultrasound). They contribute to development of therapeutic techniques (e.g., prostate implants, stereotactic radiosurgery), collaborate with radiation oncologists to design treatment plans, and monitor equipment and procedures to insure that cancer patients receive the prescribed dose of radiation to the correct location.

What do Medical Physicists Do?

Medical physicists are concerned with three areas of activity: clinical service and consultation, research and development, and teaching. On the average their time is distributed equally among these three areas.

Definition of a Qualified Medical Physicist

A Qualified Medical Physicist is an individual who is competent to practice independently one or more of the subfields of medical physics.

Therapeutic Radiological Physics

Diagnostic Radiological Physics

Medical Nuclear Physics

Medical Health Physics

What do Medical Physicists Do?

Medical physicists are concerned with three areas of activity: clinical service and consultation, research and development, and teaching. On the average their time is distributed equally among these three areas. In many non-teaching hospitals, medical physicists usually hold professional appointments in one of the clinical departments, and are members of the professional staff of the hospital. Medical physicists employed in academic institutions such as universities or university health centers are members of the academic staff of an academic or clinical department, or in an independent medical physics department.

Scope of Practice

The essential responsibility of the Qualified Medical Physicist’s clinical practice is to assure the safe and effective delivery of radiation to achieve a diagnostic or therapeutic result as prescribed in patient care. The medical physicist performs or supervises the pertinent procedures necessary to achieve this objective. The responsibilities of the medical physicist include: protection of the patient and others from potentially harmful or excessive radiation; establishment of adequate protocols to ensure accurate patient dosimetry; the measurement and characterization of radiation; the determination of delivered dose; advancement of procedures necessary to ensure image quality; development and direction of quality assurance programs; and assistance to other health care professionals in optimizing the balance between the beneficial and deleterious effects of radiation. In many non-teaching hospitals, physicists hold professional appointments in one of the clinical departments, and are members of the professional staff of the hospital. Some of the larger teaching hospitals employ a substantial number of medical physicists who are organized into medical physics departments. The medical physics departments are found in the larger centers and provide support to clinical departments for various academic, clinical and service tasks. There is a steadily increasing demand for appropriately trained medical physicists in all large medical centers, smaller hospitals and industry producing radiation-based diagnostic and therapeutic systems.

Clinical Service and Consultation

Many medical physicists are heavily involved with responsibilities in areas of diagnosis and treatment, often with specific patients. These activities take the form of consultations with physician colleagues. 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. An indispensable service is the accurate measurement of the radiation output from radiation sources employed in cancer therapy. In the specialty of nuclear medicine, physicists collaborate with physicians in procedures utilizing radionuclides for delineating internal organs and determining important physiological variables, such as metabolic rates and blood flow. Other important services are rendered through investigation of equipment perfor­mance, organization of quality control in imaging systems, design of radiation installations, and control of radiation hazards. 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.

Research and Development

Medical physicists play a vital and often leading role on the medical research team. Their activities cover wide frontiers, including such key areas as cancer, heart disease, and mental illness. In cancer, they work primarily on issues involving radiation, such as the basic mechanisms of biological change after irradiation, the application of new high-energy machines to patient treatment, and the development of new techniques for precise measurement of radiation. Significant computer developments continue in the area of dose calculation for patient treatment and video display of this treatment information. Particle irradiation is an area of active research with promising biological advantages over traditional photon treatment. In heart disease, physicists work on the measurement of blood flow and oxygenation. In mental illness, they work on the recording, correlation, and interpretation of bioelectric potentials.

Medical physicists are also concerned with research of general medical significance, including the applications of digital computers in medicine and applications of information theory to diagnostic problems; processing, storing, and retrieving medical images; measuring the amount of radioactivity in the human body and foodstuffs; and studying the anatomical and temporal distribution of radioactive substances in the body.

Medical physicists are also involved in the development of new instrumentation and technology for use in diagnostic radiology. These include the use of magnetic and electro-optical storage devices for the manipulation of x-ray images, quantitative analysis of both static and dynamic images using digital computer techniques, radiation methods for the analysis of tissue characteristics and composition, and the exciting new areas of computerized tomography and magnetic resonance imaging for displaying detailed cross-sectional images of the anatomy. Medical physicists are also engaged in research and development on imaging procedures utilizing infrared and ultrasound sources.

Typical examples of the various research areas presently under active investigation may be found in scientific journals dedicated to this field. The journal, Medical Physics, is published by the AAPM. In addition, the AAPM holds two national scientific meetings a year, one in the summer and one in the winter. During the winter meeting, the AAPM conducts scientific sessions in joint sponsorship with the Radiological Society of North America. Special summer courses, workshops, and frequent regional meetings are also held by the AAPM.

Teaching

Often medical physicists have faculty appointments at universities and colleges, where they help train future medical physicists, resident physicians, medical students, and technologists who operate the various types of equipment used to perform diagnosis and treatment. They also conduct courses in medical physics and aspects of biophysics and radiobiology for a variety of gradu­ate and undergraduate students.

Definition of a Qualified Medical Physicist

A Qualified Medical Physicist is an individual who is competent to practice independently one or more of the subfields of medical physics.

      I.            Therapeutic Radiological Physics

This particular field pertains to:

·        The therapeutic applications of x-rays, gamma rays, electron and charged particle beams, neutrons and radiations from sealed radionuclide sources

·        The equipment associated with their production, use, measurement and evaluation

·        The quality of images resulting from their production and use

·        Medical health physics associated with this subfield

 

   II.            Diagnostic Radiological Physics

This particular field pertains to:

·        The diagnostic applications of x rays, gamma rays from sealed sources, ultrasonic radiation, radio frequency radiation and magnetic fields

·        The equipment associated with their production, use, measurement and evaluation

·        The quality of images resulting from their production and use

·        Medical health physics associated with this subfield

Radiology is the medical specialty directing medical imaging technologies to diagnose and sometimes treat diseases. Originally it was the aspect of medical science dealing with the medical use of electromagnetic energy emitted by X-ray machines or other such radiation devices for the purpose of obtaining visual information as part of medical imaging. Radiology that involves use of x-ray is called roentgenology. Today, following extensive training, radiologists direct an array of imaging technologies (such as ultrasound, computed tomography (CT) and magnetic resonance imaging) to diagnose or treat disease. Interventional radiology is the performance of (usually minimally invasive) medical procedures with the guidance of imaging technologies. The acquisition of medical imaging is usually carried out by the radiographer or radiologic technologist. Outside of the medical field, radiology also encompasses the examination of the inner structure of objects using X-rays or other penetrating radiation.

 

III.            Medical Nuclear Physics

This particular field pertains to:

·        The therapeutic and diagnostic applications of radionuclides (except those used in sealed sources for therapeutic purposes)

·        The equipment associated with their production, use, measurement and evaluation

·        The quality of images resulting form their production and use

·        Medical health physics associated with this subfield

 

IV.            Medical Health Physics

This particular field pertains to:

·        The safe use of x rays, gamma rays, electron and other charged particle beams of neutrons or radionuclides and of radiation from sealed radionuclide sources for both diagnostic and therapeutic purposes, except with regard to the application of radiation to patients for diagnostic or therapeutic purposes

·        The instrumentation required to perform appropriate radiation surveys

It is expected that an individual will not hold himself/herself out to be qualified in a subfield for which he/she has not established competency. The American Board of Radiology

 

 

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