The application of physical principles to uncover the internal structures of the human body has been a significant part of medicine for more than a century. These innovations fall within the category of diagnostic radiology, a constantly evolving area that allows for the integration of modern technologies into routine clinical practice.
Since the discovery of X rays, the efforts of physical scientists have fuelled innovation in medical imaging. Medical images are categorized by the techniques used for acquisition; each method is referred to as an imaging modality. Different types and energies of radiation, as well as different acquisition geometries and methods are used to produced images. In principle, diagnostic radiology utilizes electromagnetic radiation for medical imaging. X rays are used in radiography, fluoroscopy, mammography and computed tomography. Radiofrequency waves are used in magnetic resonance imaging and high frequency sound waves for ultrasound imaging. The use of mathematical image reconstruction in computed tomography and magnetic resonance imaging has allowed the visualization of sections of the body free from tissue superposition effects. Furthermore, advancements in computers have allowed the electronic capture, processing, and transfer of medical images.
Quantification of radiation used for X ray imaging is a very important aspect of diagnostic radiology practice, given the continually increasing number, length and complexity of X ray procedures. The measurement of ionizing radiation requires a thorough understanding of the interaction of radiation and matter and an understanding of the mechanisms of the various measurement systems available. Measurements are used in assessing risk to patients and staff in diagnostic radiology. The focus of medical imaging should be on diagnostic outcome for a patient from an imaging procedure, e,g. ensuring adequate imaging quality while minimizing the factors that cause patient detriment.
The medical physicist, together with radiologists and radiographers, plays a vital role in the multi-disciplinary team required for medical diagnosis in this complicated setting. Medical physicists must be able to provide guidance on the theory and use of imaging technology and support the purchasing and quality control processes. They are essential to measuring the radiation dose received by the staff and, most crucially, by the patients undergoing diagnostic examinations. They should be able to advise on the optimal image quality needed for the diagnostic process and to be able to contribute to scientific research. They are also well equipped to assume responsibility for the safe use of radiation at a medical facility.
