《Principles Of Magnetic Resonance Imaging》教学Chapter 1.pdfVIP

Chapter 1 Introduction A journey ofa thousandmiles must begin with a single step. uo a Tomography is an important area in the ever-growing field of imaging science. The term tomos (ro/-LOC;) means cut in Greek, but tomography is concerned with creating images of the internal (anatomical or functional) organization of an object without physically cutting it open. To a beginner, it might seem inconceivable, but as your reading of this book progresses, you will appreciate not only the feasibility but also the inherent beauty and simplicity of tomography. Tomographic imaging principles are rooted in physics, mathematics, com- puter science, and engineering. However, development of these principles is traditionally tied to solving application problems-particularly biomedical prob- lems. Therefore, their theoretical significance has not been well appreciated by researchers outside this field. Like any other scientific discipline, tomography has a unique history. Radon was perhaps the first to address the tomographic imaging issue, albeit from a purely mathematical standpoint. Unfortunately, his seminal work published in 1917 went unnoticed for half a century. The sixties and the seventies were the formative years of tomography when ground-breaking work was done for both X-ray tomography and magnetic resonance imaging (MRI) . Now, a number of tomographic imaging modalities are available for medical and nonmedical uses. A partial list includes X-ray CT (computer tomography), MRI, PET (positron emission tomography), SPECT (single photon emission computed tomography), MEG (magnetoencephalography), SAR (synthetic aperture radar), and various acoustic imaging systems. Although these systems use different phys- ical principles for signal generation and detection, t