Medical Imaging

H. S. Sanjay, PhD, is a professor in the Department of Medical Electronics, M S Ramaiah Institute of Technology. He earned his PhD in electronics engineering from Jain University and a post graduate degree in biomedical engineering from Manipal University. He has over 10 years of academic experience and has been teaching undergraduate students since 2009. He has contributed to five books and authored over 15 articles in scholarly journals, including being a reviewer for five journals.

M. Niranjanamurthy, PhD, is an assistant professor in the Department of Computer Applications, M S Ramaiah Institute of Technology, Bangalore, Karnataka. He earned his PhD in computer science at JJTU. He has over 10 years of teaching experience and two years of industry experience as a software engineer. He has published four books and 56 papers in technical journals and conferences. He has two patents to his credit and has won numerous awards.

Preface xiii

Acknowledgements xv

1 Introduction to Medical Imaging 1

1.1 Medical Imaging -- An Insight 1

1.2 Types of Diagnostic Imaging Modalities 2

1.3 3D Rendering 23

1.4 Diagnostic Images 23

1.5 Medical Imaging in Pharmaceutical Applications 23

2 Fundamentals of X-Rays 27

2.1 Electromagnetic Radiations 27

2.2 Wave Nature 28

2.3 Photoelectric Effect 34

2.4 Interaction Between X-Ray and Tissues 36

2.5 Factors Affecting Attenuation Coefficients 38

2.6 Attenuation Due to Coherent Scattering (βcom) 39

2.7 Attenuation Due to Compton Scattering (βcom ) and Photoelectric Effect (βpho ) 39

2.8 Generation and Detection of X-Rays 41

2.9 X-Ray Generators 42

2.10 Filters 47

2.11 X-Ray Visualization 51

2.12 Detection of X-Rays 54

2.13 Radiation Detectors 60

2.14 X-Ray Diagnostic Approaches 62

2.15 Fluoroscopy 66

2.16 Angiography 67

2.17 Mammography 68

2.18 Xeroradiography 68

2.19 Image Subtraction 69

2.20 Conventional Tomography 73

2.21 Point Spread Function (PSF) 75

2.22 Image Noise 77

2.23 Image Contrast 78

2.24 Receiver Operating Curve (ROC) 79

2.25 Biological Effects of X-Ray Radiations@79

3 X-Ray Computed Tomography 85

3.1 Introduction to X-Ray Computed Tomography 85

3.2 CT Number 87

3.3 X-Ray Detectors in CT Machines 88

3.4 CT Imaging 89

3.5 Computer Tomography-Based Diagnostics 104

3.6 Image Quality 107

3.7 CT Machine -- The Hardware Aspects 110

3.8 Generations of CT Machines 112

3.9 Biological Effects and Safety-Based Aspects 118

4 Ultrasound Imaging 121

4.0 Ultrasound 121

4.1 Basics of Acoustic Waves 121

4.2 Propagation of Waves in Homogeneous Media 122

4.3 Linear Wave Equation 122

4.4 Loudness and Intensity 123

4.5 Interference 124

4.6 Attenuation 125

4.7 Nonlinearity 126

4.8 Propagation of Waves in Non-Homogeneous Media 127

4.9 Reflection and Refraction 127

4.10 Scattering 129

4.11 Doppler Effect in the Propagation of the Acoustic Wave 130

4.12 Generation and Detection of Ultrasound 133

4.13 Ultrasonic Transducer 134

4.14 Mechanical Matching 135

4.15 Electrical Matching 136

4.16 Ultrasound Imaging 136

4.17 Image Reconstruction 140

4.18 Schlieren System 141

4.19 Doppler Imaging Approaches 141

4.20 Tissue Characterization 144

4.21 Ultrasound Image Characteristics 146

4.22 Biological Effects of Ultrasound 147

5 Radionuclide Imaging 151

5.1 Radionuclide Imaging -- A Brief History 151

5.2 An Insight Into Radioactivity 152

5.3 Generation of Nuclear Emission 159

5.4 Radionuclide Detection 166

5.5 Diagnostic Approaches Using Radiation Detector Probes 174

5.6 Radionuclide Image Characteristics 175

5.7 Biological Effects of Radionuclides 176

6 Magnetic Resonance Imaging 179

6.1 Basics of Nuclear Magnetic Resonance 179

6.2 Larmor Frequency 182

6.3 Relaxation 185

6.4 Image Contrast 188

6.5 Repetition Time (TR) and T1 Weighting 188

6.6 Echo Time (TE) and T2 Weighting 189

6.7 Saturation at Short Repetition Times 191

6.8 Flip Angle/Tip Angle 192

6.9 Presaturation 192

6.10 Magnetization Transfer 192

6.11 Slice Selection 193

6.12 Spatial Encoding 196

6.13 Phase Encoding 196

6.14 Frequency Encoding 197

6.15 K-Space 198

6.16 Image Noise 199

6.17 The MR Scanning Machine 201

6.18 Pulse Sequences 204

6.19 Parallel Imaging 209

6.20 MR Artifacts 210

6.21 Motion Artifacts 211

6.22 Flow Artifacts 211

6.23 Phase Wrapping 211

6.24 Chemical Shift 212

6.25 Magnetic Susceptibility 213

6.26 Truncation Artifact 213

6.27 Magic Angle 213

6.28 Eddy Currents 214 6.29

Partial Volume Artifact 214

6.30 Inhomogeneous Fat Suppression 214

6.31 Zipper Artifacts 214

6.32 Crisscross Artifact 215

6.33 Bioeffects and Safety 215

Glossary-Appendix 215

About the Authors 219

Index 221