This book is written for a non-technical audience and provides a collection of rules of thumb based on practical experience but not on rigorous understanding of fundamentals. Many simplifications go too far and some explanations are outright misleading. By reading this book, a radiology tech may glean a few tips to produce a good radiograph on most systems. Yet the book may lead to fallacious intuitions. This book should not be used to gain accurate practical understanding of the physics and system design principles in radiography. The practical rules in the book will probably work fairly well in most cases for conventional systems. New digital imaging systems may render even the practical tips obsolete since they are based on practical experience with conventional systems and not on fundamentals.
Here are some of the most egregious fallacies:
Page 10 states that radiographic images are formed thanks to the polychromatic nature of the x-ray beam: "If all of the x-rays were of the same energy, the image would be extremely poor, essentially a silhouette." In reality, the opposite is true -- a monochromatic beam with all photons carrying the same energy would provide the best image quality (tissue contrast) with best patient dose efficiency (at appropriate keV). Tissue differentiation is produced by differential attenuation of photons in tissues, even if all the photons carry identical energies. X-ray system designers go to great lengths to reduce the polychromaticity of the x-ray beam.
Page 59 states that with the doubling of the number of atoms in some space, the likelihood of x-rays hitting an atom when passing through the space also doubles. Wait a minute! What if the original likelihood of hitting an atom was 70%? Will that probability go to 140% when the number of atoms is doubled in that space? Of course, this description is incorrect. Doubling the number of atoms in a given volume will square the likelihood of the x-ray photon passing through the volume.
On page 129, the author states that "Excessive filtration in the beam defeats the purpose of exposing the radiograph. When density losses become visible, they necessitate an increase in the mAs to compensate. Such an increase in mAs simply reintroduces additional patient skin dose, which the filters were added to eliminate. ...an optimum level of protective filtration has been establishedto achieve maximum level of protection for the patient without affective the radopgrahic density." In reality, no such optimal level can be established. Increasing the filtration will always reduce skin dose from a polychromatic source (x-ray tube) even after the mAs is increased to maintain proper film exposure. Additional spectral filtration equivalent to 2.5 mm of aluminum is simply required by safety regulations. Anything above that is an improvement. The only limitation to adding more spectral filtration is the increased x-ray tube loading and the tube's limited maximum output. This error is particularly disturbing because it cause one to miss opportunities to reduce patient dose while improving image quality when extra mAs can be afforded or to choose to purchase a system that is less dose efficient.
The book's lack of rigor leads to the example on page 154 which states that "bone stops 40 x-rays for every x-ray stopped by soft tissue." In reality, the linear attenuation coefficient of bone is at most 2 or 3 times higher than that of soft tissue at typical x-ray energies.
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Product Description:
This new Seventh Edition is a most expansive and comprehensive text on radiographic exposure and imaging and encompasses the vast and intricate changes that have taken place in the field. As with previous editions, the book is intended to complement radiographic physics texts rather than duplicate them. It bridges the gap between theory and practice, and therefore assumes some basic knowledge of physical principles upon which the concepts of practical technique can be built. This volume also attempts to bridge the gap between quality control and technique. Part I, Producing the Radiographic Image, presents chapters on x-rays and radiographic variables, recording the permanent image, qualities of the image, and interactions of x-rays within the patient. Part II, Visibility Factors, includes chapters on milliampere-seconds, kilovoltage-peak, machine phase and rectification, beam filtration, field size limitation, patient status and contrast agents, pathology and casts, scattered radiation and image fog, grids, intensifying screens, and image receptor systems. Part III, Geometrical Factors, discusses focal spot size, the anode bevel, source-image receptor distance, object-image receptor distance, distance ratios, beam-part-film-alignment, geometric functions of positioning, and motion. Part IV, Comprehensive Technique, presents chapters on analyzing the radiographic image, simplifying and standardizing technique, technique by proportional anatomy, technique charts, exposure controls, patient dose, quality control, and solving multiple technique problems. Part V, Special Imaging Methods, includes mobile radiography, special imaging techniques, fluoroscopic image intensification, digital imaging, and computed radiography. Part VI, Processing the Radiograph, completes the text with chapters on processing steps and chemistry, developmental variables, automatic processors, film handling and duplication procedures, and sensitometry and darkroom control. Each chapter concludes with an examination that will help the student review materials and put them into perspective. Multiple choice, fill-in-the-blank, and identification/explanation questions are all included. An answer section is provided at the back of the text. This book is by far the the best available for schools that are focused on the practical application of radiographic technique. Its greatest strengths are its clear and concise explanations, plentiful examples, and abundant illustrations.
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