Medical Imaging

Preface, x Acknowledgments, xiii Introduction: Dr. Doe's Headaches: An Imaging Case Study, xiv Computed tomography, xiv Picture archiving and communication system, xv T1, T2, and FLAIR MRI, xvi MR spectroscopy and a virtual biopsy, xvii Functional MRI, xviii Diffusion tensor MR imaging, xviii MR guided biopsy, xx Pathology, xxi Positron emission tomography?, xxi Treatment and follow-up, xxii 1 Sketches of the Standard Imaging Modalities: Different Ways of Creating Visible Contrast Among Tissues, 1 "Roentgen has surely gone crazy!", 2 Different imaging probes interact with different tissues in different ways and yield different kinds of medical information, 4 Twentieth-century (analog) radiography and fluoroscopy: contrast from differential attenuation of X-rays by tissues, 7 Twenty-first century (digital) images and digital planar imaging: computer-based images and solid-state image receptors, 16 Computed tomography: three-dimensional mapping of X-ray attenuation by tissues, 17 Nuclear medicine, including SPECT and PET: contrast from the differential uptake of a radiopharmaceutical by tissues, 20 Diagnostic ultrasound: contrast from differences in tissue elasticity or density, 26 Magnetic resonance imaging: mapping the spatial distribution of spin-relaxation times of hydrogen nuclei in tissue water and lipids, 28 Appendix: selection of imaging modalities to assist in medical diagnosis, 30 References, 36 2 Image Quality and Dose: What Constitutes a "Good" Medical Image?, 37 A brief history of magnetism, 37 About those probes and their interactions with matter . . . , 39 The image quality quartet: contrast, resolution, stochastic (random) noise, artifacts - and always dose, 47 Quality assurance, 57 Known medical benefits versus potential radiation risks, 61 3 Creating Subject Contrast in the Primary X-ray Image: Projection Maps of the Body from Differential Attenuation of X-rays by Tissues, 67 Creating a (nearly) uniform beam of penetrating X-rays, 69 Interaction of X-ray and gamma-ray photons with tissues or an image receptor, 75 What a body does to the beam: subject contrast in the pattern of X-rays emerging from the patient, 83 What the beam does to a body: dose and risk, 87 4 Twentieth-century (Analog) Radiography and Fluoroscopy: Capturing the X-ray Shadow with a Film Cassette or an Image Intensifier Tube plus Electronic Optical Camera Combination, 91 Recording the X-ray pattern emerging from the patient with a screen-film image receptor, 92 Prime determinants/measures of image quality: contrast, resolution, random noise, artifacts, . . . and, always, patient dose, 98 Special requirements for mammography, 114 Image intensifier-tube fluoroscopy: viewing in real time, 122 Conclusion: bringing radiography and fluoroscopy into the twenty-first century with solid-state digital X-ray image receptors, 125 Reference, 126 5 Radiation Dose and Radiogenic Risk: Ionization-Induced Damage to DNA can cause Stochastic, Deterministic, and Teratogenic Health Effects - And How To Protect Against Them, 127 Our exposure to ionizing radiation has doubled over the past few decades, 127 Radiation health effects are caused by damage to DNA, 129 Stochastic health effects: cancer may arise from mutations in a single cell, 132 Deterministic health effects at high doses: radiation killing of a large number of tissue cells, 139 The Four Quartets of radiation safety, 146 References, 151 6 Twenty-first Century (Digital) Imaging: Computer-Based Representation, Acquisition, Processing, Storage, Transmission, and Analysis of Images, 152 Digital computers, 153 Digital acquisition and representation of an image, 157 Digital image processing: enhancing tissue contrast, SNR, edge sharpness, etc., 166 Computer networks: PACS, RIS, and the Internet, 168 Image analysis and interpretation: computer-assisted detection, 170 Computer and computer-network security, 172 Liquid crystal displays and other digital displays, 173 The joy of digital, 174 7 Digital Planar Imaging: Replacing Film and Image Intensifiers with Solid State, Electronic Image Receptors, 176 Digital planar imaging modalities, 176 Indirect detection with a fluorescent screen and a CCD, 178 Computed radiography, 178 Digital radiography with an active matrix flat panel imager, 179 Digital mammography, 184 Digital fluoroscopy and digital subtraction angiography, 186 Digital tomosynthesis: planar imaging in three dimensions, 189 References, 190 8 Computed Tomography: Superior Contrast in Three-Dimensional X-Ray Attenuation Maps, 191 Computed tomography maps out X-ray attenuation in two and three dimensions, 192 Image reconstruction, 198 Seven generations of CT scanners, 204 Technology and image quality, 208 Patient- and machine-caused artifacts, 219 Dose and QA, 221 Appendix: mathematical basis of filtered back-projection, 229 References, 233 9 Nuclear Medicine: Contrast from Differential Uptake of a Radiopharmaceutical by Tissues, 234 Unstable atomic nuclei: radioactivity, 235 Radiopharmaceuticals: gamma- or positron-emitting radionuclei attached to organ-specific agents, 245 Imaging radiopharmaceutical concentration with a gamma camera, 248 Static and dynamic studies, 254 Tomographic nuclear imaging: SPECT and PET, 260 Quality assurance and radiation safety, 270 References, 273 10 Diagnostic Ultrasound: Contrast from Differences in Tissue Elasticity or Density Across Boundaries, 274 Medical ultrasound, 274 The US beam: MHz compressional waves in tissues, 277 Production of an ultrasound beam and detection of echoes with a transducer, 280 Piezoelectric transducer elements, 281 Transmission and attenuation of the beam within a homogeneous material, 285 Reflection of the beam at an interface between materials with different acoustic impedances, 288 Imaging in 1 and 1 × 1 dimensions: A- and M-modes, 291 Imaging in two, three, and four dimensions: B-mode, 294 Doppler imaging of blood flow, 300 Elastography, 302 Safety and QA, 303 11 MRI in One Dimension and with No Relaxation: A Gentle Introduction to a Challenging Subject, 307 Prologue to MRI, 308 "Quantum" approach to proton nuclear magnetic resonance, 310 Magnetic resonance imaging in one dimension, 316 "Classical" approach to NMR, 321 Free induction decay imaging (but without the decay), 331 Spin-echo imaging (still without T1 or T2 relaxation), 338 MRI instrumentation, 343 Reference, 351 12 Mapping T1 and T2 Relaxation in Three Dimensions, 352 Longitudinal spin relaxation and T1, 353 Transverse spin relaxation and T2-w images, 364 T2* and the gradient-echo (G-E) pulse sequence, 372 Into two and three dimensions, 374 MR imaging of fluid movement/motion, 382 13 Evolving and Experimental Modalities, 387 Optical and near-infrared imaging, 388 Molecular imaging and nanotechnology, 390 Thermography, 392 Terahertz (T-ray) imaging of epithelial tissues, 393 Microwave and electron spin resonance imaging, 393 Electroencephalography, magnetocardiography, and impedance imaging, 394 Photo-acoustic imaging, 396 Computer technology: the constant revolution, 397 Imaging with a crystal ball, 399 References, 399 Suggested Further Reading, 400 Index, 403