Radiotherapy Physics In Practice

by Williams, J. R.; Thwaites, D. I.

• ISBN13: 9780192628787
• ISBN10: 019262878X
• Edition: 2nd
• Format: Paperback
• Copyright: 2000-05-11
• Publisher: Oxford University Press

Summary

Radiotherapy has been one of the principal modalities for the treatment of malignant disease for more than 50 years. From the outset, its advancement has depended on the work of physicists and engineers, in particular for the development of high-energy accelerators for X-ray and electronbeams, and in the production of radioactive sources. In addition, the clinical application of ionizing radiations for therapy is based on the foundation of dosimetric concepts and instrumentation. Medical physics plays a pivotal role in many areas, including treatment equipment, dosimetry,treatment planning, and radiation protection. Radiotherapy physics, second edition is a comprehensive, practical introduction to radiotherapy physics. It provides detailed descriptions of current techniques, written by experienced practitioners who review current methods and give specific guidance in their own areas of expertise. This newedition reflects the significant changes that have occurred in radiotherapy equipment and techniques - the routine use of MLCs, the delivery of IMRT, advances in imaging technology for planning (eg MRI, CT-simulator) and for treatment verification (EPIDs). There have also been significant changes indosimetry, which have resulted in new dosimetry protocols. Trainee and qualified medical physicists, radiographers, radiation oncologists, and other personnel involved in radiotherapy will find this book to be an excellent guide to this important specialty.

Table of Contents

Contributors	xix
Abbreviations	xxi
Introduction	1	(5)
J.R. Williams
D.I. Thwaites
The development of radiotherapy	1	(1)
Radiotherapeutic aims	2	(1)
Radiotherapy methods	2	(1)
External beam therapy	3	(1)
Brachytherapy	3	(1)
Unsealed-source therapy	3	(1)
Requirements for accuracy and precision	3	(1)
Quality assurance	4	(1)
The role of medical physics	5	(1)
References	5	(1)
Planning and acceptance testing of megavoltage therapy installations	6	(25)
P.R. Almond
J.L. Horton
Introduction	6	(1)
Types of equipment	6	(2)
Cobalt-60 machines	6	(1)
Linear accelerators	6	(1)
Special machines and ancillary equipment	7	(1)
Equipment specification	8	(3)
Mechanical	8	(1)
Radiation performance	8	(3)
Machine-selection criteria	11	(2)
Treatment room and design	13	(5)
Location	13	(1)
Size and shape	14	(1)
Shielding calculations	14	(4)
Console area	18	(1)
Other considerations	18	(1)
Acceptance testing	18	(11)
Mechanical	18	(5)
Radiation beam performance	23	(3)
General	26	(1)
Protection surveys	27	(1)
Electrical and mechanical safety	28	(1)
Warning lights, interlocks, and monitors	28	(1)
Summary and conclusions	29	(1)
References	29	(1)
Additional reading	30	(1)
Absolute dose determination for high-energy photon and electron beams	31	(23)
B.J. Mijnheer
D.I. Thwaites
J.R. Williams
Introduction	31	(1)
Specification of beam quality	31	(4)
X-ray beams	32	(1)
Electron beams	33	(2)
Calibration of ionization chambers	35	(2)
Derivation of absorbed dose to water using calibrated ionization chambers	37	(2)
Practical application of protocols	39	(6)
Measurement correction factors	39	(1)
Air calibration correction factors	40	(1)
In-phantom correction factors	41	(1)
Non-water phantoms	42	(1)
Worked examples	43	(2)
Calibration of the dose monitor	45	(2)
Photon beams	45	(1)
Electron beams	46	(1)
Quality control of calibration	47	(1)
Calibration of instruments	47	(1)
Check-source measurements	48	(1)
Reference-point checks	48	(1)
Accessory equipment	48	(1)
Dosimetry intercomparison or audit	48	(1)
Accuracy of the absolute dose determination	48	(2)
Summary and conclusions	50	(1)
References	51	(3)
Appendix	53	(1)
Relative dosimetry	54	(23)
J.L. Horton
Introduction	54	(1)
Dosimetry equipment	54	(6)
Ionometric dosimetry	54	(2)
Diode dosimetry	56	(1)
Film dosimetry	57	(2)
Quality control	59	(1)
Dosimetry notebook	60	(1)
Photon measurements	60	(9)
Central axis per cent depth dose	60	(1)
Output factors	61	(2)
Tissue--maximum ratios	63	(1)
Scatter--maximum ratios	63	(1)
Block and blocking tray transmission ratios	64	(1)
Central axis wedge transmission ratios	65	(1)
Beam profiles	65	(1)
Transition zone dosimetry	66	(1)
Beam quality and field flatness	67	(1)
Distance correction	67	(1)
Asymmetric collimators, dynamic wedges, and multi-leaf collimators	68	(1)
Electron measurements	69	(6)
Central axis per cent depth dose	69	(2)
Output factors	71	(2)
Beam profiles	73	(1)
Air gaps	73	(2)
Summary	75	(1)
References	75	(1)
Additional reading	76	(1)
Quality control of megavoltage therapy units	77	(22)
K.-A. Johansson
G. Sernbo
J. Van Dam
Introduction	77	(1)
General methods and test materials	78	(3)
Methods	78	(1)
Test instrumentation	79	(2)
What should be tested	81	(2)
Optical and mechanical systems	81	(1)
Dose monitor	81	(1)
Beam symmetry	81	(1)
Multi-leaf collimator (MLC)	81	(1)
Computer-controlled systems	81	(1)
Accessories	82	(1)
Interlocks	82	(1)
Electronic portal imaging device (EPID)	83	(1)
Test frequencies	83	(1)
Responsibilities	83	(1)
Reference data set and standard values	83	(1)
Tolerance, action, and incident levels	84	(1)
Instructions and documentation	85	(1)
Patient-specific test	85	(1)
Daily test	85	(2)
Dose-monitor check	86	(1)
`Gross' beam-alignment check	86	(1)
Computer self test	86	(1)
Daily-test procedure	87	(1)
Basic test	87	(5)
Beam-alignment test (optics and mechanics)	88	(2)
Dosimetry test	90	(1)
Safety checks	91	(1)
Computer-controlled systems	91	(1)
Electronic portal imaging device (EPID)	92	(1)
Extended tests	92	(5)
Beam alignment	92	(3)
Extended dosimetry test	95	(1)
Extended safety test	96	(1)
References	97	(1)
Further reading	98	(1)
Kilovoltage X-rays	99	(19)
S.C. Klevenhagen
D.I. Thwaites
R.J. Aukett
Introduction	99	(1)
kV X-ray equipment	100	(1)
Specification of beam quality	100	(3)
Quality parameters	100	(1)
Half-value layer measurement (HVL)	101	(1)
Filtration	102	(1)
Spectral distribution in a phantom	103	(1)
Beam characteristics	103	(6)
Radiation distribution in air	103	(1)
Radiation distribution in phantom	103	(1)
Backscattered radiation	104	(2)
Surface dose	106	(1)
Central axis depth doses	106	(2)
Isodose curves	108	(1)
Absorption in other materials	109	(1)
Absorbed dose determination	109	(4)
Background	109	(1)
ICRU method	110	(1)
IAEA method	110	(1)
IPEMB method	111	(1)
Comparison of methods	112	(1)
Measurement of radiation distribution	113	(2)
Depth dose	113	(1)
Isodoses	114	(1)
Determination of SSD	114	(1)
Stand-off correction/ISL applicability	115	(1)
Acceptance and quality control	115	(2)
References	117	(1)
Simulation and imaging for radiation therapy planning	118	(32)
J. Van Dyk
K. Mah
Introduction	118	(1)
Definitions related to patient planning	118	(3)
Gross tumour volume (GTV)	118	(1)
Clinical target volume (CTV)	119	(1)
Planning target volume (PTV)	120	(1)
Treated volume	120	(1)
Irradiated volume	120	(1)
Organs at risk	120	(1)
Absorbed dose distribution	120	(1)
Methods of deriving patient-specific data	121	(3)
Patient positioning	121	(2)
Measurement of external contours and internal anatomy	123	(1)
Simulators	124	(7)
Role of treatment simulation	124	(1)
Specifications	124	(4)
Selection criteria, purchase, and acceptance	128	(2)
Quality assurance	130	(1)
Additional considerations	131	(1)
CT scanners for therapy planning	131	(6)
Role of CT scanners	131	(1)
Practical considerations	132	(2)
Specifications	134	(2)
Selection criteria, purchase, and acceptance	136	(1)
Quality assurance	137	(1)
CT simulators	137	(8)
Role of CT simulators	137	(3)
Practical considerations	140	(1)
Specifications	140	(4)
Acceptance and implementation of virtual simulation	144	(1)
Quality assurance	144	(1)
Specialized imaging procedures	145	(3)
Magnetic resonance imaging	145	(2)
Simulator with CT mode	147	(1)
Other imaging procedures	147	(1)
Image correlation	147	(1)
Summary and conclusions	148	(1)
References	148	(2)
Treatment planning for external beam therapy: principles and basic techniques	150	(30)
A.T. Redpath
J.R. Williams
Introduction	150	(1)
General principles and planning techniques	151	(12)
Single fields	151	(3)
Opposed coaxial fields	154	(2)
Factors affecting dose distributions	156	(1)
Multiple fields	157	(6)
Dose calculation within the patient	163	(2)
Correction methods for patient shape	163	(1)
Correction methods for patient composition	164	(1)
Optimization	165	(2)
Specification of the planning problem	166	(1)
Visual optimization	166	(1)
Score functions	166	(1)
Mathematical optimization	167	(1)
Computer planning	167	(3)
Hardware requirements	167	(1)
Beam data input and storage	167	(2)
Patient data input and storage	169	(1)
Calculation of dose distributions	169	(1)
Standard-treatment planning	170	(5)
Pelvis	170	(1)
Oesophagus	170	(2)
Bronchus	172	(1)
Breast	173	(1)
Larynx	173	(1)
Floor of mouth	174	(1)
Maxillary antrum	174	(1)
Treatment with non-standard fields	175	(2)
Irregular field calculations	175	(1)
Compensators	175	(1)
Asymmetric collimators	176	(1)
Monitor unit calculations	176	(1)
Quality assurance	177	(1)
QC of the treatment-planning system	177	(1)
QC of the patient's plan	178	(1)
References	178	(2)
Treatment planning for external beam therapy: advanced techniques	180	(25)
A.T. Redpath
S.G. McNee
CT Planning	180	(11)
Scanning techniques	180	(1)
Outlining and target drawing	181	(3)
Tools available for 3-D planning	184	(2)
Dose display and reporting	186	(1)
Dose-calculation algorithms	187	(4)
Conformal therapy	191	(7)
Definition and rationale	191	(1)
Selection of beam directions	192	(1)
Asymmetric collimators	192	(1)
Customized blocking	192	(2)
Multi-leaf collimators (MLC)	194	(3)
Treatment set-up and verification	197	(1)
Dynamic therapy	198	(3)
Arc therapy	198	(1)
Dynamic wedge	199	(1)
Beam-intensity modulation	200	(1)
Automated treatment	201	(1)
Stereotactic radiotherapy	201	(1)
References	202	(3)
Electron beam treatment-planning techniques	205	(15)
D.I. Thwaites
Introduction	205	(1)
Beam characteristics	205	(2)
Depth dose	205	(1)
Isodoses	206	(1)
Field-size variations	206	(1)
Choice of energy and beam size	207	(1)
Field shaping	208	(1)
Output factors	208	(1)
Non-standard treatment distances	209	(1)
Oblique incidence	210	(1)
Inhomogeneities	211	(2)
Absorption (bulk) effects	211	(1)
Scatter (edge) effects	212	(1)
Bolus	212	(1)
Internal shielding	213	(1)
Adjacent fields	214	(1)
Electron arc therapy	214	(1)
Total skin electron irradiation	215	(1)
Other techniques	216	(1)
Electron-beam algorithms	216	(2)
References	218	(2)
Treatment verification and in vivo dosimetry	220	(27)
W.P.M. Mayles
S. Heisig
H.M.O. Mayles
Introduction	220	(1)
Dose verification	220	(17)
Accuracy and precision	220	(1)
Thermoluminescence dosimetry	221	(7)
Semiconductor dosimetry	228	(3)
Other dosimetry systems	231	(1)
Clinical situations	232	(4)
Phantom measurements	236	(1)
Verification of positional accuracy	237	(4)
The nature of set-up errors	237	(1)
Limitations to verification	238	(1)
Therapy verification films	238	(1)
Digital imaging devices	238	(1)
Improving image quality	238	(1)
Quality control	239	(1)
Measurement of field-placement errors	239	(2)
Portal image dosimetry	241	(1)
Treatment machine verification	241	(3)
Verification of machine operation	241	(1)
Verification of treatment parameters	241	(1)
Computer assisted set-up	242	(1)
Recording patient data	242	(1)
Networks	242	(1)
Practical considerations	243	(1)
Summary and conclusions	244	(1)
References	244	(2)
Additional reading	246	(1)
Brachytherapy	247	(42)
E.G. Aird
J.R. Williams
A. Rembowska
Introduction	247	(1)
Sealed radioactive sources	248	(3)
Caesium-137	248	(1)
Iridium-192	249	(1)
Cobalt-60	250	(1)
Gold-198	250	(1)
Iodine-125	250	(1)
Palladium-103	250	(1)
Beta-ray sources	250	(1)
Sealed-source dosimetry	251	(3)
Source strength	251	(1)
Air kerma rate calculations	251	(1)
Absorption and scattering in a medium	252	(1)
Absorbed dose calculation	253	(1)
Radiation protection and quality assurance	254	(5)
Storage of sources	254	(1)
Checking sources on receipt	255	(2)
Protection in theatre and wards	257	(2)
Transport of radioactive sources	259	(1)
Precaution after death of a patient containing sealed sources	259	(1)
Afterloading systems	259	(2)
Manual afterloading	260	(1)
Remote afterloading	260	(1)
Dosimetry systems	261	(19)
Dose prescription and reporting	261	(1)
Interstitial therapy: Manchester system	262	(4)
Interstitial therapy: Paris system	266	(2)
Line sources	268	(1)
Comparison of the Manchester and Paris systems	268	(1)
Seed implants	269	(3)
Gynaecological intracavitary therapy	272	(3)
Dosimetry for high dose-rate afterloading-treatment machines	275	(5)
Practical aspects of absorbed dose calculation	280	(4)
Source-reconstruction methods	280	(2)
Errors	282	(1)
Clinical applications	283	(1)
Radiobiological models	284	(3)
Linear-quadratic model	285	(2)
Clinical applications	287	(1)
References	287	(1)
Additional reading	288	(1)
Unsealed-source therapy	289	(27)
M.A. Flower
S.J. Chittenden
Introduction	289	(1)
Choice of radionuclide	289	(3)
Physical considerations	289	(3)
Radiobiological considerations	292	(1)
Dosimetry techniques	292	(5)
MIRD in theory	293	(1)
MIRD in practice	294	(2)
Limiting organs	296	(1)
General procedures	297	(3)
Consultation with the patient	298	(1)
Dosimetry and prescription of administered activity	298	(1)
Ordering and documentation	299	(1)
Preparation for therapy	300	(1)
Dispensing	300	(1)
Administration	300	(1)
Monitoring and scanning during therapy	300	(1)
Discharge of patient and follow-up	300	(1)
Radiation protection	300	(4)
Laboratory procedures	301	(1)
Movement of sources within the hospital	301	(1)
Monitoring	301	(1)
Procedures and facilities on the ward	301	(2)
Contingency plans	303	(1)
Specific therapy procedures	304	(9)
Thyroid carcinoma and thyrotoxicosis treated with Na131I	304	(2)
Treatment of neuroectodermal tumours with 131I mIBG	306	(1)
Radionuclide therapy in the relief of pain from skeletal metastases	307	(2)
Treatment of polycythaemia vera with 32p sodium phosphate	309	(1)
Instillation of radiocolloids into body cavities and cysts	309	(1)
Treatment with radiolabelled antibodies	310	(2)
Other types of radionuclide therapy	312	(1)
References	313	(2)
Recommended reading	315	(1)
Quality assurance in radiotherapy physics	316	(13)
A.L. McKenzie
T.M. Kehoe
D.I. Thwaites
Introduction	316	(1)
Other approaches to quality assurance	317	(1)
Contents of a quality assurance system for radiotherapy physics	317	(2)
Control of the activities in radiotherapy physics	318	(1)
Management of the radiotherapy physics service	318	(1)
Control of the quality system	318	(1)
Quality audit	319	(1)
Structure of the quality system	320	(1)
The policy statement	320	(1)
Quality system documentation	320	(1)
Level 2 quality assurance management Procedures	321	(1)
Level 3 quality assurance work instructions	321	(1)
Design of system documentation	321	(1)
Practical implementation	321	(2)
Local development	321	(1)
Setting up a quality-management structure	321	(1)
Defining the scope of the quality system	322	(1)
Deciding the tasks and the time scale	322	(1)
Preparing and implementing quality-system documentation	322	(1)
Controlling the quality system	323	(1)
External audit	323	(1)
Accreditation of the quality system	323	(1)
The role of certification	323	(1)
The certification process	323	(1)
Potential benefits of certification	323	(1)
Beyond certification	324	(1)
External practical audit	324	(2)
Dosimetry intercomparisons	324	(1)
Routine dosimetry audit	324	(1)
Mailed dosimeter audit systems	325	(1)
Audit systems based on on-site visits	325	(1)
Participation in external practical-audit systems	325	(1)
References	326	(3)
Index	329