Introduction

Radiology is arguably the most technology-dependent specialty in medicine, and which has seen significant changes over the past decade. Computer integration with constant technical innovations have changed the workplace and influenced the role radiology plays in the diagnosis and treatment of disease. Radiologic physics is not an esoteric subject of abstract equations and memorized definitions, but rather the total process of creating and viewing a diagnostic image. A range of physical principles influence the process of image formation. Radiologists and technologists need to understand the technology and the physical principles that constitute the advantages, govern the limitations, and determine the risks of the equipment they use.

Radiologic physics covers the important medical imaging modalities of radiographic and fluoroscopic x-ray imaging, computed tomography, magnetic resonance, nuclear medicine, and ultrasound. Radiologic physics provides an understanding of the factors that improve or degrade image quality. Selection of the most appropriate way of generating a medical image is the responsibility of the radiologic imaging team, consisting of the radiologist, technologist, medical physicist, and equipment manufacturer. Optimizing medical imaging performance requires a solid understanding of how these images are generated, as well as the most important determinants of image quality.

All imaging modalities have a cost associated with their use. For modalities that use ionizing radiations, one of the costs is the radiation dose to the patient and staff working with these systems. Accordingly, radiation protection principles are important. Radiologists and technologists should understand the magnitude of the radiation dose to the patient and personnel exposed, and ensure that radiation levels are kept as low as reasonably achievable (ALARA principle) as well as within any relevant regulatory limits. MR and ultrasound do not have any specific risks, and the cost is generally the time required to perform the study.

II. WHY STUDY RADIOLOGIC PHYSICS?

Radiologists and technologists need to acquire an understanding of the underlying imaging science for each diagnostic modality and be able to pass their respective radiologic physics exams. However, neither will actually practice physics and there is no need to learn how to generate modulation transfer functions in radiographic imaging, write programs to perform filtered back projection algorithms in CT, or design RF pulses in MRI.

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