Radiation oncology physics
Автор: E. B. Podgorsak
Год: 2005
Страницы: 696
Язык: Английский
Издательство: IAEA
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Описание:
In the late 1990s the IAF.A initiated for its Member
States a systematic and comprehensive plan to support the development of
teaching programmes in medical radiation physics. Multiple projects were
initiated at various levels that, together with the well known short term
training courses and specialization fellowships funded by the IAEA Technical
Cooperation programme, aimed at supporting countries to develop their own
university based master of science programmes in medical radiation physics.
Chapter 1. Basic radiation physics. 1
Introduction. 1
Fundamental physical constants (rounded off to four significant figures). 1
Important derived physical constants and relationships. 1
Physical quantities and units. 3
Classification of forces in nature. 4
Classification of fundamental particles. 4
Classification of radiation. 5
Classification of ionizing photon radiation. 6
Einstein's relativistic mass, energy and momentum relationships. 6
Radiation quantities and units. 7
Atomic and Nuclear Structure. 7
Basic definitions for atomic structure. 7
Rutherford's model of the atom. 9
Bohr's model of the hydrogen atom. 10
Multielectron atoms. 12
Nuclear structure. 14
Nuclear reactions. 15
Radioactivity. 16
Activation of nuclides. 19
Modes of radioactive decay. 20
Electron Interactions. 22
Electron-orbital electron interactions. 23
Electron-nucleus interactions. 23
Stopping power. 24
Mass scattering power. 25
Photon Interactions. 26
Types of indirectly ionizing photon radiation. 26
Photon beam attenuation. 26
Types of photon interaction. 28
Photoelectric effect. 28
Coherent (Rayleigh) scattering. 29
Compton effect (incoherent scattering). 30
Pair production. 32
Photonuclear reactions. 34
Contributions to attenuation coefficients. 34
Relative predominance of individual effects. 36
Effects following photon interactions. 37
Summary of photon interactions. 38
Example of photon attenuation. 40
Production of vacancies in atomic shells. 41
Bibliography 43
Chapter 2. Dosimetric Principles, Quantities and Units. 45
Introduction. 45
Photon fluence and energy fluence. 45
Kerma. 48
Сема. 48
Absorbed dose. 49
Stopping power. 49
Relationships between various dosimetric quantities. 54
Energy fluence and kerma (photons). 54
Fluence and dose (electrons). 56
Kerma and dose (charged particle equilibrium). 57
Collision kerma and exposure. 60
Cavity Theory. 61
Bragg-Gray cavity theory. 61
Spencer-Attix cavity theory. 62
Considerations in the application of cavity theory to ionization chamber calibration and dosimetry protocols. 64
Large cavities in photon beams. 66
Burlin cavity theory for photon beams. 66
Stopping power ratios. 68
Bibliography. 70
Chapter 3. Radiation Dosimeters. 71
Introduction. 71
Properties of Dosimeters. 72
Accuracy and precision. 72
Type A standard uncertainties. 72
Type В standard uncertainties. 73
Combined and expanded uncertainties. 73
Linearity. 74
Dose rate dependence. 74
Energy dependence. 75
Directional dependence. 76
Spatial resolution and physical size. 76
Readout convenience. 76
Convenience of use. 76
Ionization Chamber Dosimetry Systems. 77
Chambers and electrometers. 77
Cylindrical (thimble type) ionization chambers. 78
Parallel-plate (plane-parallel) ionization chambers. 79
Brachytherapy chambers. 79
Extrapolation chambers. 79
film Dosimetry. 81
Radiographic film. 81
Radiochromic film. 84
Luminescence Dosimetry. 84
Thermoluminescence. 85
Thermoluminescent dosimeter systems. 86
Optically stimulated luminescence systems. 88
Semiconductor Dosimetry. 89
Silicon diode dosimetry systems. 89
Mosfet dosimetry systems. 90
Other Dosimetry systems. 91
Alanine/electron paramagnetic resonance dosimetry system. 91
Plastic scintillator dosimetry system. 92
Diamond dosimeters 92
Gel dosimetry systems. 93
Primary Standards. 94
Primary standard for air kerma in air. 95
Primary standards for absorbed dose to water. 95
Ionometric standard for absorbed dose to water. 96
Chemical dosimetry standard for absorbed dose to water. 96
Calorimetric standard for absorbed dose to water. 97
Summary of some commonly used Dosimetric systems. 97
Bibliography. 99
Chapter 4. Radiation monitoring instruments. 101
Introduction. 101
Operational quantities for Radiation monitoring. 102
Area Survey meters. 103
Ionization chambers. 105
Proportional counters. 105
Neutron area survey meters. 105
Geiger-Muller counters. 106
Scintillator detectors. 107
Semiconductor detectors. 107
Commonly available features of area survey meters. 108
Calibration of survey meters. 108
Properties of survey meters. 110
Sensitivity. 110
Energy dependence. 110
Directional dependence. 111
Dose equivalent range. 111
Response time. 111
Overload characteristics. 111
Long term stability. 112
Discrimination between different types of radiation. 112
Uncertainties in area survey measurements. 112
Individual monitoring. 113
Film badge. 113
Thermoluminescence dosimetry badge. 115
Radiophotoluminescent glass dosimetry systems. 116
Optically stimulated luminescence systems. 116
Direct reading personal monitors. 117
Calibration of personal dosimeters. 118
Properties of personal monitors. 118
Sensitivity. 118
Energy dependence. 119
Uncertainties in personal monitoring measurements. 119
Equivalent dose range. 119
Directional dependence. 120
Discrimination between different types of radiation. 120
Bibliography 120
Chapter 5. Treatment machines for external beam Radiotherapy. 123
Introduction. 123
X Ray beams and X Ray units. 124
Characteristic X rays. 124
Bremsstrahlung (continuous) X rays. 124
X ray targets. 125
Clinical X ray beams. 126
X ray beam quality specifiers. 127
X ray machines for radiotherapy. 127
Gamma Ray beams and Gamma Ray units. 129
Basic properties of gamma rays. 129
Teletherapy machines. 130
Teletherapy sources. 130
Teletherapy source housing. 131
Dose delivery with teletherapy machines. 132
Collimator and penumbra. 132
Particle Accelerators. 132
Betatron. 134
Cyclotron. 134
Microtron. 135
LINACS. 136
Linac generations. 137
Safety of linac installations. 137
Components of modern linacs. 138
Configuration of modern linacs. 138
Injection system. 140
Radiofrequency power generation system. 143
Accelerating waveguide. 143
Microwave power transmission. 144
Auxiliary system. 145
Electron beam transport. 146
Linac treatment head. 146
Production of clinical photon beams in a linac. 147
Beam collimation. 148
Production of clinical electron beams in a linac. 149
Dose monitoring system. 149
Radiotherapy with protons, neutrons and heavy ions. 151
Shielding Considerations. 152
Cobalt-60 Teletherapy units versus Linacs. 153
Simulators and Computed Tomography Simulators. 156
Radiotherapy simulator. 157
Computed tomography simulator. 158
Training Requirements. 159
Bibliography. 160
Chapter 6. External photon beams physical aspects. 161
Introduction. 161
Quantities Used in Describing a Photon Beam. 161
Photon fluence and photon fluence rate. 162
Energy fluence and energy fluence rate. 162
Air kerma in air. 163
Exposure in air. 164
Dose to small mass of medium in air. 164
Photon beam sources. 166
Inverse Square Law. 167
Penetration of Photon beams into a Phantom or patient. 169
Surface dose. 171
Buildup region. 171
Depth of dose maximum zmax. 172
Exit dose. 172
Radiation treatment parameters. 172
Radiation beam field size. 173
Collimator factor. 174
Peak scatter factor. 175
Relative dose factor. 177
Central axis depth doses in water source to surface distance set-up. 179
Percentage depth dose. 179
Scatter function. 181
Central Axis Depth Doses in Water: Source to Axis Distance Set-up. 183
Tissue-air ratio. 184
Relationship between TAR(d, AQ, hv) andPDD (d,A,f,hv). 185
Scatter-air ratio. 189
Relationship between SAR(d, AQ, hv) and S(z, A,f,hv). 190
Tissue-phantom ratio and tissue-maximum ratio. 190
Relationship between TMR(z, AQ, hv) and PDD (z,A,f,hv). 192
Scatter-maximum ratio. 193
Off-Axis ratios and beam profiles. 194
Beam flatness. 196
Beam symmetry. 197
Isodose distributions in water phantoms. 197
Single field isodose distributions in patients. 199
Corrections for irregular contours and oblique beam incidence. 200
Effective source to surface distance method. 201
Tissue-air ratio or tissue-maximum ratio method. 202
Isodose shift method. 202
Missing tissue compensation. 202
Wedge filters. 203
Bolus. 203
Compensators. 203
Corrections for tissue inhomogeneities. 204
Model based algorithms. 205
Clarkson segmental integration. 206
Relative dose measurements withionization chambers. 209
Delivery of dose with a single external beam. 212
Example of dose calculation. 213
Shutter correction time. 215
Bibliography. 216
Chapter 7. Clinical treatment planning in external photon beam radiotherapy. 219
Introduction. 219
Volume Definition. 219
Gross tumour volume. 220
Clinical target volume. 220
Internal target volume. 221
Planning target volume. 221
Organ at risk. 222
Dose Specification. 222
Patient data Acquisition and Simulation. 223
Need for patient data. 223
Nature of patient data. 223
Two dimensional treatment planning. 223
Three dimensional treatment planning. 224
Treatment simulation. 225
Patient treatment position and immobilization devices. 226
Patient data requirements. 228
Conventional treatment simulation. 229
Simulators. 229
Localization of the target volume and organs at risk. 230
Determination of the treatment beam geometry. 230
Acquisition of patient data. 230
Computed tomography based conventional treatment simulation. 230
Computed tomography based patient data acquisition. 230
Determination of the treatment beam geometry. 232
Computed tomography based virtual simulation. 233
Computed tomography simulator. 233
Virtual simulation. 233
Digitally reconstructed radiographs. 234
Beam's eye view. 234
Virtual simulation procedure. 235
Conventional simulator versus computed tomography simulator. 237
Magnetic resonance imaging for treatment planning. 238
Summary of simulation procedures. 240
Clinical Considerations for Photon Beams. 241
Isodose curves. 241
Wedge filters. 241
Bolus. 244
Compensating filters. 245
Corrections for contour irregularities. 246
Isodose shift method. 246
Effective attenuation coefficient method. 248
Tissue-air ratio method. 248
Corrections for tissue inhomogeneities. 248
Tissue-air ratio method. 249
Batho power law method. 250
Equivalent tissue-air ratio method. 250
Isodose shift method. 250
Beam combinations and clinical application. 251
Weighting and normalization. 251
Fixed source to surface distance versus isocentric techniques. 251
Parallel opposed beams. 252
Multiple coplanar beams. 253
Rotational techniques. 254
Multiple non-coplanar beams. 255
Field matching. 255
Treatment plan Evaluation. 256
Isodose curves. 257
Orthogonal planes and isodose surfaces. 257
Dose statistics. 257
Dose-volume histograms. 258
Direct dose-volume histogram. 259
Cumulative dose-volume histogram. 259
Treatment evaluation. 260
Port films. 261
On-line portal imaging. 262
Treatment time and monitor unit calculations. 264
Treatment time and monitor unit calculations for a fixed source to surface distance set-up. 265
Monitor unit and treatment time calculations for isocentric set-ups. 267
Normalization of dose distributions. 270
Inclusion of output parameters in the dose distribution. 270
Treatment time calculation for orthovoltage and cobalt-60 units. 271
Bibliography. 271
Chapter 8. Electron beams physical and clinical aspects. 273
Central Axis Depth dose Distributions in water. 273
General shape of the depth dose curve. 273
Electron interactions with an absorbing medium. 274
Inverse square law (virtual source position). 276
Range concept. 277
Buildup region (depths between the surface and zmax (i.e.0 279
Dose distribution beyond zmax (z>zmax). 279
Dosimetric parameters of Electron beams. 281
Electron beam energy specification. 281
Typical depth dose parameters as a function of energy. 281
Percentage depth dose. 282
Percentage depth doses for small electron field sizes. 282
Percentage depth doses for oblique beam incidence. 283
Output factors. 284
Therapeutic range Rw. 285
Profiles and off-axis ratios. 285
Flatness and symmetry. 285
Clinical considerations in electron beam therapy. 286
Dose specification and reporting. 286
Small field sizes. 287
Isodose curves. 287
Field shaping. 289
Electron applicators. 289
Shielding and cut-outs. 289
Internal shielding. 290
Extended source to surface distance treatments. 290
Irregular surface correction. 291
Bolus. 291
Inhomogeneity corrections. 292
Coefficient of equivalent thickness. 292
Scatter perturbation (edge) effects. 293
Electron beam combinations. 295
Matched (abutted) electron fields. 295
Matched photon and electron fields. 295
Electron arc therapy. 295
Electron therapy treatment planning. 298
Bibliography. 299
Chapter 9. Calibration of photon and electron beams. 301
Introduction. 301
Calorimetry. 302
Fricke dosimetry. 303
Ionization chamber dosimetry. 304
Mean energy expended in air per ion pair formed. 304
Reference dosimetry with ionization chambers. 305
Standard free air ionization chambers. 305
Cavity ionization chambers. 306
Phantom embedded extrapolation chambers. 306
Clinical beam calibration and measurement chain. 307
Dosimetry protocols. 307
Ionization chamber based dosimetry systems. 308
Ionization chambers. 308
Electrometer and power supply. 309
Phantoms. 310
Chamber signal correction for influence quantities. 312
Air temperature, pressure and humidity effects: Ktp. 312
Chamber polarity effects: polarity correction factor Кpol. 313
Chamber voltage effects: recombination correction factor Ksat. 314
Chamber leakage currents. 318
Chamber stem effects. 319
Determination of absorbed dose using calibrated ionization chambers. 319
Air kerma based protocols. 320
Absorbed dose to water based protocols. 323
Stopping Power Ratios. 326
Stopping power ratios for electron beams. 326
Stopping power ratios for photon beams. 327
Mass-energy absorption coefficient ratios. 328
Perturbation correction factors. 329
Displacement perturbation factor Pdis and effective point of measurement. 330
Chamber wall perturbation factor Pwall 331
Central electrode perturbation Pcel. 333
Cavity or fluence perturbation correction Pcav. 334
Beam quality specification. 335
Beam quality specification for kilovoltage photon beams. 336
Beam quality specification for megavoltage photon beams. 337
Beam quality specification for megavoltage electron beams. 339
Calibration of megavoltage photon and electron beams: practical aspects. 342
Calibration of megavoltage photon beams based on the air kerma in air calibration coefficient Nk,Co. 342
Calibration of megavoltage photon beams based on the dose to water calibration coefficient Nd,w,Co. 343
Calibration of megavoltage electron beams based on the air kerma in air calibration coefficient Nk,Co. 345
Calibration of high energy electron beams based on the dose to water calibration coefficient Nd,w,Co. 346
Kilovoltage Dosimetry. 347
Specific features of kilovoltage beams. 347
Air kerma based in-phantom calibration method (medium energies). 348
Air kerma based backscatter method (low and medium photon energies). 349
Air kerma in air based calibration method for very low energies. 351
Absorbed dose to water based calibration method. 351
Error and uncertainty analysis for ionization chamber measurements. 352
Errors and uncertainties. 352
Classification of uncertainties. 352
Uncertainties in the calibration chain. 352
Bibliography. 353
Chapter 10. Acceptance tests and commissioning measurements. 355
Introduction. 355
Measurement Equipment. 355
Radiation survey equipment. 355
Ionometric dosimetry equipment. 356
Film. 356
Diodes. 356
Phantoms. 357
Radiation field analyser and water phantom. 357
Plastic phantoms. 357
Acceptance tests. 358
Safety checks. 359
Interlocks, warning lights and patient monitoring equipment. 359
Radiation survey. 359
Collimator and head leakage. 360
Mechanical checks. 361
Collimator axis of rotation. 361
Photon collimator jaw motion. 361
Congruence of light and radiation field. 362
Gantry axis of rotation. 363
Patient treatment table axis of rotation. 363
Radiation isocentre. 364
Optical distance indicator. 364
Gantry angle indicators. 365
Collimator field size indicators. 365
Patient treatment table motions. 365
Dosimetry measurements. 365
Photon energy. 366
Photon beam uniformity. 366
Photon penumbra. 366
Electron energy. 367
Electron beam bremsstrahlung contamination. 367
Electron beam uniformity. 368
Electron penumbra. 368
Monitor characteristics. 368
Arc therapy. 370
Commissioning. 370
Photon beam measurements. 370
Central axis percentage depth doses. 370
Output factors. 371
Blocking tray factors. 373
Multileaf collimators. 373
Central axis wedge transmission factors. 374
Dynamic wedge. 375
Transverse beam profiles/off-axis energy changes. 376
Entrance dose and interface dosimetry. 376
Virtual source position. 377
Electron beam measurements. 378
Central axis percentage depth dose. 378
Output factors. 380
Transverse beam profiles. 383
Virtual source position. 383
Time required for commissioning. 384
Bibliography. 385
Chapter 11. Computerized treatment planning systems for external photon beam. 386
Radiotherapy. 387
Introduction. 387
System hardware. 388
Treatment planning system hardware. 388
Treatment planning system configurations. 389
System software and calculation algorithms. 390
Calculation algorithms. 390
Beam modifiers. 393
Photon beam modifiers. 393
Electron beam modifiers. 394
Heterogeneity corrections. 395
Image display and dose-volume histograms. 395
Optimization and monitor unit calculations. 396
Record and verify systems. 396
Biological modeling. 397
Data acquisition and entry. 397
Machine data. 397
Beam data acquisition and entry. 398
Patient data. 399
Commissioning and quality assurance. 400
Errors. 400
Verification. 401
Spot checks. 402
Normalization and beam weighting. 402
Dose-volume histograms and optimization. 403
Training and documentation. 403
Scheduled quality assurance. 403
Special considerations. 404
Bibliography. 405
Chapter 12. Quality assurance of external beam radiotherapy. 407
Introduction. 407
Definitions. 407
Quality assurance. 407
Quality assurance in radiotherapy. 407
Quality control. 408
Quality standards. 408
Need for quality assurance in radiotherapy. 408
Requirements on accuracy in radiotherapy. 409
Accidents in radiotherapy. 411
Managing a quality assurance programme. 414
Multidisciplinary radiotherapy team. 414
Quality system/comprehensive quality assurance programme. 416
Quality assurance programme for equipment. 418
Structure of an equipment quality assurance programme. 418
Equipment specification. 419
Acceptance. .419
Commissioning. 420
Quality control. 420
Uncertainties, tolerances and action levels. 421
Quality assurance programme for cobalt-60 teletherapy machines. 423
Quality assurance programme for linacs. 425
Quality assurance programme for treatment simulators. 425
Quality assurance programme for computed tomography scanners and computed tomography simulation. 429
Quality assurance programme for treatment planning systems. 430
Quality assurance programme for test equipment. 431
Treatment delivery. 433
Patient charts. 433
Portal imaging. 434
Portal imaging techniques. 436
Future developments in portal imaging. 439
In vivo dose measurements. 439
In vivo dose measurement techniques. 440
Use of electronic portal imaging systems for in vivo dosimetry. 443
Record and verify systems. 443
Quality audit. 445
Definition. 445
Practical quality audit modalities. 446
Postal audit with mailed dosimeters. 446
Quality audit visits. 446
What should be reviewed in a quality audit visit? 447
Bibliography. 448
Chapter 13. Brachytherapy: physical and clinical aspects. 451
Introduction. 451
Photon source characteristics. 455
13.2.1. Practical considerations 455
Physical characteristics of some photon emitting brachytherapy sources. 456
Mechanical source characteristics. 456
Source specification. 457
Specification of у ray sources. 457
Specification of Xray sources. 459
Clinical use and dosimetry systems. 460
Gynaecology. 460
Types of source. 460
Dose specification. 460
Source arrangement. 460
Applicators. 461
Rectal and bladder dose monitoring. 461
Interstitial brachytherapy. 461
Patterson-Parker system. 461
Quimby system. 462
Paris system. 462
Remote afterloading systems. 463
Permanent prostate implants. 464
Choice of radionuclide for prostate implants. 465
Planning technique: ultrasound or computed tomography. 465
Preplanning, seed placement and dose distributions. 465
Post-implant dose distributions and evaluation. 465
Eye plaques. 466
Intravascular brachytherapy. 466
Dose specification and reporting. 467
Intracavitary treatments. 467
Interstitial treatments. 467
Dose distributions around sources. 468
AAPM TG 43 algorithm. 468
Other calculation methods for point sources. 471
Linear sources. 473
Unfiltered line source in air. 473
Filtered line source in air. 474
Filtered line source in water. 475
Dose calculation procedures. 475
Manual dose calculations. 475
Manual summation of doses. 475
Precalculated dose distributions (atlases). 475
Computerized treatment planning. 476
Source localization. 476
Dose calculation. 476
Dose distribution display. 476
Optimization of dose distribution. 477
Calculation of treatment time. 477
Use of Patterson-Parker tables. 477
Choice of reference points. 478
Decay corrections. 478
Commissioning of brachytherapy computer treatment planning systems. 479
Check of the reconstruction procedure. 479
Check of consistency between quantities and units. 479
Computer versus manual dose calculation for a single source. 479
Check of decay corrections. 479
Source commissioning. 480
Wipe tests. 480
Autoradiography and uniformity checks of activity. 480
Calibration chain. 480
Quality assurance. 481
Constancy check of a calibrated dosimeter. 481
Regular checks of sources and applicators. 481
Mechanical properties. 481
Source strength. 481
Wipe tests. 482
Checks of source positioning with afterloading devices. 482
Radiation monitoring around patients. 482
Quality management programme. 482
Brachytherapy versus External beam radiotherapy. 483
Bibliography. 483
Chapter 14. Basic radiobiology. 485
Introduction. 485
Classification of radiations in radiobiology. 486
Cell cycle and cell death. 487
Irradiation of cells. 488
Direct action in cell damage by radiation. 488
Indirect action in cell damage by radiation. 488
Fate of irradiated cells. 489
Type of radiation damage. 489
Timescale. 489
Classification of radiation damage. 490
Somatic and genetic effects. 490
Stochastic and deterministic (non-stochastic) effects. 491
Acute versus late tissue or organ effects. 491
Total body radiation response. 491
Foetal irradiation. 492
Cell survival curves. 492
Dose response curves. 494
Measurement of radiation damage in tissue. 496
Normal and tumour cells: therapeutic ratio. 497
Oxygen effect. 498
Relative biological effectiveness. 500
Dose rate and fractionation. 501
Radioprotectors and r adiosensitizers. 503
Bibliography. 504
Chapter 15. Special procedures and techniques in radiotherapy. 505
Introduction. 505
Stereotactic irradiation. 506
Physical and clinical requirements for radiosurgery. 506
Diseases treated with stereotactic irradiation. 507
Equipment used for stereotactic radiosurgery. 507
Historical development. 508
Radiosurgical techniques. 509
Gamma Knife. 509
Linac based radiosurgery. 509
Miniature linac on robotic arm. 511
Uncertainty in radiosurgical dose delivery. 512
Dose prescription and dose fractionation. 513
Commissioning of radiosurgical equipment. 514
Quality assurance in radiosurgery. 514
Gamma Knife versus linac based radiosurgery. 515
Frameless stereotaxy. 516
total body irradiation. 516
Clinical total body irradiation categories. 516
Diseases treated with total body irradiation. 517
Technical aspects of total body irradiation. 517
Total body irradiation techniques. 518
Dose prescription point. 519
Commissioning of total body irradiation procedure. 519
Test of total body irradiation dosimetry protocol. 521
Quality assurance in total body irradiation. 521 