1 Physics for security ......................................... 1
1.1 The task ................................................ 1
1.1.1 Stimulation by fear and the search for
security ......................................... 1
1.1.2 Crucial physics for probing ...................... 5
1.1.3 Basic approaches to imaging ...................... 9
1.2 Value of images ........................................ 10
1.2.1 Information from images ......................... 11
1.2.2 Comparing modalities ............................ 12
1.3 Safety, risk and education ............................. 16
1.3.1 Public apprehension of physics .................. 16
1.3.2 Assessing safety ................................ 17
2 Magnetism and magnetic resonance ............................ 21
2.1 An elemental magnetic dipole ........................... 21
2.1.1 Laws of electromagnetism ........................ 21
2.1.2 Current loop as a magnetic dipole ............... 22
2.1.3 The Larmor frequency ............................ 25
2.2 Magnetic materials ..................................... 27
2.2.1 Magnetisation and microscopic dipoles ........... 27
2.2.2 Hyperfine coupling in B-field ................... 31
2.3 Electron spin resonance ................................ 34
2.3.1 Magnetic resonance .............................. 34
2.3.2 Detection and application ....................... 36
2.4 Nuclear magnetic resonance ............................. 37
2.4.1 Characteristics ................................. 38
2.4.2 Local field variations .......................... 39
2.4.3 Relaxation ...................................... 42
2.4.4 Elements of an experiment ....................... 44
2.4.5 Measurement of relaxation times ................. 45
2.5 Magnetic field measurement ............................. 47
2.5.1 Earth's field ................................... 48
2.5.2 Measurement by electromagnetic induction ........ 48
2.5.3 Measurement by magnetic resonance ............... 50
3 Interactions of ionising radiation .......................... 55
3.1 Sources and phenomenology .............................. 55
3.1.1 Sources of radiation ............................ 55
3.1.2 Imaging with radiation .......................... 56
3.1.3 Single and multiple collisions .................. 57
3.2 Kinematics of primary collisions ....................... 58
3.2.1 Kinematics and dynamics ......................... 59
3.2.2 Energy and momentum transfer .................... 59
3.2.3 Recoil kinematics ............................... 60
3.2.4 Applications of recoil kinematics ............... 61
3.3 Electromagnetic radiation in matter .................... 65
3.3.1 Compton scattering .............................. 65
3.3.2 Photoabsorption ................................. 66
3.3.3 Pair production ................................. 68
3.4 Elastic scattering collisions of charged particles ..... 68
3.4.1 Dynamics of scattering by a point charge  ...... 69
3.4.2 Cross section for energy loss by recoil ......... 73
3.5 Multiple collisions of charged particles ............... 73
3.5.1 Cumulative energy loss of a charged particle .... 74
3.5.2 Range of charged particles ...................... 77
3.5.3 Multiple Coulomb scattering ..................... 78
3.6 Radiative energy loss by electrons ..................... 81
3.6.1 Classical, semi-classical and QED
electromagnetism ................................ 81
3.6.2 Weissäcker-Williams virtual photon picture ...... 81
3.6.3 Radiation length ................................ 82
4 Mechanical waves and properties of matter ................... 85
4.1 Stress, strain and waves in homogeneous materials ...... 85
4.1.1 Relative displacements and internal forces ...... 85
4.1.2 Elastic fluids .................................. 87
4.1.3 Longitudinal waves in fluids .................... 88
4.1.4 Stress and strain in solids ................... 92
4.1.5 Polarisation of waves in solids ............... 96
4.2 Reflection and transmission of waves in bounded
media .................................................. 99
4.2.1 Reflection and transmission at normal
incidence ....................................... 99
4.2.2 Relative directions of waves at boundaries ... 100
4.2.3 Relative amplitudes of waves at boundaries ... 103
4.3 Surface waves and normal modes ........................ 111
4.3.1 General surface waves .......................... 113
4.3.2 Rayleigh waves on free solid surfaces .......... 113
4.3.3 Waves at fluid-fluid interfaces ................ 115
4.3.4 Normal mode oscillations ....................... 119
4.4 Structured media ...................................... 120
4.4.1 Interatomic potential wells .................... 121
4.4.2 Linear absorption .............................. 126
5 Information and data analysis .............................. 131
5.1 Conservation of information ........................... 131
5.2 Linear transformations ................................ 135
5.2.1 Fourier transforms ............................. 135
5.2.2 Wavelet transforms ............................. 142
5.3 Analysis of data using models ......................... 143
5.3.1 General features ............................... 144
5.3.2 Least squares and minimum χ2 methods ........... 145
5.3.3 Maximum likelihood method ...................... 149
6 Analysis and damage by irradiation ......................... 157
6.1 Radiation detectors ................................... 157
6.1.1 Photons and ionisation generated by
irradiation .................................... 157
6.1.2 Task of radiation detection .................... 159
6.1.3 Charged particle detectors ..................... 161
6.1.4 Electromagnetic radiation detectors ............ 165
6.2 Analysis methods for elements and isotopes ............ 168
6.2.1 Element concentration analysis ................. 169
6.2.2 Isotope concentration analysis ................. 172
6.2.3 Radiation damage analysis ...................... 177
6.3 Radiation exposure of the population at large ......... 179
6.3.1 Measurement of human radiation exposure ........ 179
6.3.2 Sources of general radiation exposure .......... 182
6.4 Radiation damage to biological tissue ................. 187
6.4.1 Hierarchy of damage in space and time .......... 187
6.4.2 Survival and recovery data ..................... 189
6.5 Nuclear energy and applications ....................... 192
6.5.1 Fission and fusion ............................. 192
6.5.2 Weapons and the environment .................... 193
6.5.3 Nuclear power and accidents .................... 199
7 Imaging with magnetic resonance ............................ 207
7.1 Magnetic resonance imaging ............................ 207
7.1.1 Spatial encoding with gradients ................ 207
7.1.2 Artefacts and imperfections in the image ....... 211
7.1.3 Pulse sequences ................................ 213
7.1.4 Multiple detector coils ........................ 218
7.2 Functional magnetic resonance imaging ................. 221
7.2.1 Functional imaging ............................. 221
7.2.2 Flow and diffusion ............................. 223
7.2.3 Spectroscopic imaging .......................... 225
7.2.4 Risks and limitations .......................... 227
8 Medical imaging and therapy with ionising radiation ........ 233
8.1 Projected X-ray absorption images ..................... 233
8.1.1 X-ray sources and detectors .................... 233
8.1.2 Optimisation of images ......................... 236
8.1.3 Use of passive contrast agents ................. 239
8.2 Computed tomography with X-rays ....................... 241
8.2.1 Image reconstruction in space .................. 241
8.2.2 Patient exposure and image quality ............. 245
8.3 Functional imaging with radioisotopes ................. 246
8.3.1 Single photon emission computed tomography ..... 246
8.3.2 Resolution and radiation exposure
limitations .................................... 252
8.3.3 Positron emission tomography ................... 252
8.4 Radiotherapy .......................................... 256
8.4.1 Irradiation of the tumour volume ............... 256
8.4.2 Sources of radiotherapy ........................ 257
8.4.3 Treatment planning and delivery of RT .......... 259
8.4.4 Exploitation of non-linear effects ............. 262
9 Ultrasound for imaging and therapy ......................... 267
9.1 Imaging with ultrasound ............................... 267
9.1.1 Methods of imaging ............................. 267
9.1.2 Material testing and medical imaging ........... 270
9.2 Generation of ultrasound beams ........................ 272
9.2.1 Ultrasound transducers ......................... 272
9.2.2 Ultrasound beams ............................... 276
9.2.3 Beam quality and related artefacts ............. 278
9.3 Scattering in inhomogeneous materials ................. 280
9.3.1 A single small inhomogeneity ................... 281
9.3.2 Regions of inhomogeneity ....................... 284
9.3.3 Measurement of motion using the Doppler
effect ......................................... 287
9.4 Non-linear behaviour .................................. 290
9.4.1 Materials under non-linear conditions .......... 290
9.4.2 Harmonic imaging ............................... 294
9.4.3 Constituent model of non-linearity ............. 297
9.4.4 Progressive non-linear waves ................... 300
9.4.5 Absorption of high intensity ultrasound ........ 301
10 Forward look and conclusions ............................... 307
10.1 Developments in imaging .......................... 307
10.2 Revolutions in cancer therapy .................... 312
10.3 Safety concerns in ultrasound .................... 313
10.4 Rethinking the safety of ionising radiation ...... 315
10.5 New ideas, old truths and education .............. 318
Appendices
A Conventions, nomenclature and units ..................... 321
В Glossary of terms and abbreviations ..................... 323
С Hints and answers to selected questions ................. 327
Index ......................................................... 331
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