The text is a guide to the fundamental principles of medical imaging physics, radiation protection and radiation biology, with complex topics presented in the clear and concise manner and style for which these authors are known. Coverage includes the production, characteristics and interactions of ionizing radiation used in medical imaging and the imaging modalities in which they are used, including radiography, mammography, fluoroscopy, computed tomography and nuclear medicine. Special attention is paid to optimizing patient dose in each of these modalities. Sections of the book address topics common to all forms of diagnostic imaging, including image quality and medical informatics as well as the non-ionizing medical imaging modalities of MRI and ultrasound. The basic science important to nuclear imaging, including the nature and production of radioactivity, internal dosimetry and radiation detection and measurement, are presented clearly and concisely.
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Although the topics were, in broad terms, the same as in the course syllabus, the book itself was written de novo. Since the first edition of this book was completed in , there have been many important advances in medical imaging technology.
Consequently, in this second edition, most of the chapters have been completely rewritten, although the organization of the text into four main sections remains unchanged.
In addition, new chapters have been added. An Introduction to Medical Imaging begins this new edition as Chapter 1.
In recognition of the increased sophistication and complexity in some modalities, the chapters on MRI and nuclear imaging have been split into two chapters each, in an attempt to break the material into smaller and more digestible parts. Considerable effort was also spent on integrating the discussion and assuring consistent terminology between the different chapters.
The Image Quality chapter was expanded to provide additional details on this important topic. In addition, a more extensive set of reference data is provided in this edition.
The appendices have been expanded to include the fundamental principles of physics, physical constants and conversion factors, elemental data, mass attenuation coefficients, x-ray spectra, and radiopharmaceutical characteristics and dosimetry. Web sites of professional societies, governmental organizations and other entities that may be of interest to the medical imaging community are also provided.
The field of radiology is in a protracted state of transition regarding the usage of units. Although the SI unit system has been officially adopted by most radiology and scientific journals, it is hard to avoid the use of the roentgen and rem. Our ionization chambers still read out in milliroentgen of exposure not milligray of air kerma , and our monthly film badge reports are still conveyed in millirem not millisieverts. The U. Government has been slow to adopt SI units. Consequently, while we have adopted SI units throughout most of the text, we felt compelled to discuss and use where appropriate the older units in contexts where they are still used.
Furthermore, antiquated quantities such as the effective dose equivalent are still used by the U. Nuclear Regulatory Commission, although the rest of the world uses effective dose. We have received many comments over the years from instructors, residents, and other students who made use of the first edition, and we have tried to respond to these comments by making appropriate changes in the book.
Our intention with this book is to take the novice reader from the introduction of a topic, all the way through a relatively thorough description of it. If we try to do this using too few words we may lose many readers; if we use too many words we may bore others. We did our best to walk this fine line, but if you are in the latter group, we encourage you to readfaster. We are deeply grateful to that part of the radiology community who embraced our first effort.
This second edition was inspired both by the successes and the shortcomings of the first edition. We are also grateful to those who provided suggestions for improvement and we hope that they will be pleased with this new edition.
Jerrold T. JohnM Boone During the production of this work, several individuals generously gave their time and expertise. First, we would like to thank L. Stephen Graham, Ph. We also thank Michael Buonocore, M. Raymond Tanner, Ph. Virgil Cooper, Ph. We are also appreciative of the comments of Stewart Bushong, Ph.
Walter Huda, Ph. The expertise of Mel Tecotzky, Ph. Skip Kennedy, M. In addition, we would like to acknowledge the superb administrative support of Lorraine Smith and Patrice Wilbur, whose patience and attention to detail are greatly appreciated. We are grateful for the contributions that these individuals have made towards the development of this book. We are also indebted to many other scientists whose work in this field predates our own and whose contributions served as the foundation of many of the concepts developed in this book.
Can medical physics be interesting and exciting? Personally, I find most physics textbooks dry, confusing, and a useful cure for my insomnia. This book is different. Bushberg and his colleagues have been teaching residents as well as an international review course in radiation physics, protection, dosimetry, and biology for almost two decades.
They know what works, what does not, and how to present information clearly. A particularly strong point of this book is that it covers all areas of diagnostic imaging. A number of current texts cover only one area of physics and the residents often purchase several texts by different authors in order to have a complete grasp of the subject matter. Of course, medical imagers are more at home with pictures rather than text and formulas.
Most authors of other physics books have not grasped this concept. The nearly exquisite illustrations contained in this substantially revised second edition will make this book a favorite of the medical imaging community. Fred A. Mettler Jr. In the medical imaging techniques used in radiology, the energy used to produce the image must be capable of penetrating tissues.
Visible light, which has limited ability to penetrate tissues at depth, is used mostly outside of the radiology department for medical imaging. Visible light images are used in dermatology skin photography , gastroenterology and obstetrics endoscopy , and pathology light microscopy.
Of course, all disciplines in medicine use direct visual observation, which also utilizes visible light. In diagnostic radiology, the electromagnetic spectrum outside the visible light region is used for x-ray imaging, including mammography and computed tomography, magnetic resonance imaging, and nuclear medicine. Mechanical energy, in the form of high-frequency sound waves, is used in ultrasound imaging.
If energy were to pass through the body and not experience some type of interaction e. In nuclear medicine imaging, radioactive agents are injected or ingested, and it is the metabolic or physiologic interactions of the agent that give rise to the information in the images.
While medical images can have an aesthetic appearance, the diagnostic utility of a medical image relates to both the technical quality of the image and the conditions of its acquisition. Consequently, the assessment of image quality in medical imaging involves very little artistic appraisal and a great deal of technical evaluation.
In most cases, the image quality that is obtained from medical imaging devices involves compromise-better x-ray images can be made when the radiation dose to the patient is high, better magnetic resonance images can be made when the image acquisition time is long, and better ultrasound images result when the ultrasound power levels are large. Of course, patient safety and comfort must be considered when acquiring medical images; thus excessive patient dose in the pursuit of a perfect image is not acceptable.
Rather, the power levels used to make medical images require a balance between patient safety and image quality. Different types of medical images can be made by varying the types of energies used and the acquisition technology.
The different modes of making images are referred to as modalities. Each modality has its own applications in medicine. Radiography Radiography was the first medical imaging technology, made possible when the physicist Wilhelm Roentgen discovered x-rays on November 8, Roentgen also made the first radiographic images of human anatomy Fig.
Radiography also called roentgenography defined the field of radiology, and gave rise to radiologists, physicians who specialize in the interpretation of medical images.
Radiography is performed with an x-ray source on one side of the patient, and a typically flat x-ray detector on the other side. The homogeneous distribution of x-rays that enter the patient is modified by the degree to which the x-rays are removed from the beam i.
The attenuation properties of tissues such as bone, soft tissue, and air inside the patient are very different, resulting in the heterogeneous distribution of x-rays that emerges from the patient. The radiographic image is a picture of this x-ray distribution. The detector used in radiography can be photographic film e. The beginning of diagnostic radiology, represented by this famous radiographic image made on December 22, of the wife of the discoverer of x-rays, Wilhelm Conrad Roentgen.
The bones of her hand as well as two rings on her finger are clearly visible. Within a few months, Roentgen was able to determine the basic physical properties of x-rays. Nearly simultaneously, as word of the discovery spread around the world, medical applications of this "new kind of ray" propelled radiologic imaging into an essential component of medical care. In keeping with mathematical conventions, Roentgen assigned the letter "x" to represent the unknown nature of the ray and thus the term x-ray was born.
Details regarding x-ray production and interactions can be found in Chapters 5 and 3, respectively. Reproduced from Glasser O. Wilhelm Conrad and Rontgen and the early history of the roentgen rays. Springfield, IL: Charles C. Thomas, , with permission. The chest x-ray is the most ubiquitous image in diagnostic radiology.
High x-ray energy is used for the purpose of penetrating the mediastinum, cardiac, and diaphragm areas of the patient without overexposing areas within the lungs. Variation in the gray-scale image represents an attenuation map of the x-rays: dark areas high film optical density have low attenuation, and bright areas low film optical density have high attenuation. The image here shows greater than normal attenuation in the lower lobes of the lungs, consistent with plural effusion, right greater than left.
Projection imaging physics is covered in Chapter 6. Transmission imaging refers to imaging in which the energy source is outside the body on one side, and the energy passes through the body and is detected on the other side of the body. Radiography is a transmission imaging modality. Projection imaging refers to the case when each point on the image corresponds to information along a straight line trajectory through the patient. Radiography is also a projection imaging modality.
Radiographic images are useful for a very wide range of medical indications, including the diagnosis of broken bones, lung cancer, cardiovascular disorders, etc. Fluoroscopy refers to the continuous acquisition of a sequence of x-ray images over time, essentially a real-time x-ray movie of the patient. Fluoroscopy is a transmission projection imaging modality, and is, in essence, just real-time radiography.
Fluoroscopic systems use x-ray detector systems capable of producing images in rapid temporal sequence.
Essential Physics of Medical Imaging
Bushberg - The Essential Physics for Medical Imaging