Physics for Diagnostic Radiology, Second Edition

by Dendy; Philip Palin

• ISBN13: 9780750305914
• ISBN10: 0750305916
• Edition: 2nd
• Format: Nonspecific Binding
• Copyright: 1999-05-01
• Publisher: CRC Press

Summary

This textbook is a complete course for radiologists studying for the FRCR part one exam, physicists and radiographers on specialised graduate courses in diagnostic radiology, or other appropriate undergraduate degrees. It follows the guidelines issued by the European Association of Radiology for training.It is a comprehensive, compact primer, appropriate to a teaching course some 50 hours in length. Its analytical approach deals in logical order with the wide range of imaging techniques available, and explains how to use imaging equipment.It includes the background physics necessary to understand the production of digitised images, nuclear medicine, and magnetic resonance imaging, It is assumed that students will be familiar with high school physics.It features extensive cross-referencing, practical analogies, further reading at the end of each chapter, exercises, exercises and a comprehensive selection of multiple choice questions (with answers) to test and reinforce student's understanding of the material presented.Major new features include: detailed discussion of patient dose; the use of digital radiography; image qual

Table of Contents

List of Contributors	vii
Acknowledgments	viii
Introduction	1	(2)
Fundamentals of Radiation Physics and Radioactivity	3	(17)
Structure of the atom	3	(1)
Nuclear stability and instability	3	(3)
Radioactive concentration and specific activity	6	(1)
Radioactive decay processes	6	(1)
Exponential decay	7	(1)
Half-life	8	(1)
Secular and transient equilibrium	9	(2)
Biological and effective half-life	11	(1)
Gamma radiation	11	(1)
X-rays and gamma rays as forms of electromagnetic radiation	12	(1)
Quantum properties of radiation	13	(1)
Inverse square law	13	(1)
Interaction of radiation with matter	14	(2)
Linear energy transfer	16	(1)
Summary of energy changes in radiological physics	16	(4)
Production of X-Rays	20	(39)
Introduction	20	(1)
The X-ray spectrum	20	(6)
The continuous spectrum	20	(2)
The low and high energy cut-off	22	(1)
Shape of the continuous spectrum	23	(1)
Line or characteristic spectra	23	(1)
Factors affecting the X-ray spectrum	24	(2)
Components of the X-ray tube	26	(10)
The cathode	26	(1)
The anode material	27	(1)
Anode design	28	(1)
Electrical circuits	29	(4)
The tube envelope and housing	33	(1)
Switching and timing mechanisms	34	(1)
Electrical safety features	35	(1)
Spatial distribution of X-rays	36	(3)
Rating of an X-ray tube	39	(10)
Introduction	39	(1)
Electrical rating	40	(2)
Thermal rating---considerations at short exposures	42	(3)
Overcoming short-exposure rating limits	45	(1)
Multiple or prolonged exposures	46	(2)
Falling load generators	48	(1)
Safety interlocks	49	(1)
X-ray tube lifetime	49	(1)
Mobile X-ray generators	49	(3)
Single phase full wave rectified generators	50	(1)
Constant potential generators	50	(1)
Capacitor discharge units	51	(1)
Quality assurance of performance for standard X-ray sets	52	(3)
Summary	55	(4)
Interaction of X-rays and Gamma Rays with Matter	59	(24)
Introduction	59	(1)
Experimental approach to beam attenuation	59	(3)
Introduction to the interaction processes	62	(1)
Bound and free electrons	62	(1)
Attenuation, scatter and absorption	63	(1)
The interaction processes	63	(7)
Elastic scattering	63	(1)
Photoelectric effect	63	(2)
Compton effect	65	(4)
Pair production	69	(1)
Combining interaction effects and their relative importance	70	(2)
Absorption edges	72	(1)
Broad beam and narrow beam attenuation	73	(2)
Filtration and beam hardening	75	(4)
Conclusions	79	(4)
The Image Receptor	83	(31)
Introduction---band structure in solids	83	(1)
Fluorescence, phosphorescence and thermoluminescence	84	(2)
Phosphors and fluorescent screens	86	(2)
Properties of phosphors	86	(2)
Production of fluorescent screens	88	(1)
Film--phosphor combinations in radiography	88	(1)
X-ray film	88	(5)
Film construction	88	(1)
Characteristic curve and optical density	89	(3)
Film gamma and film speed	92	(1)
Latitude	93	(1)
Film used with a fluorescent screen	94	(1)
Cassettes	95	(1)
Reciprocity	96	(1)
Film--screen unsharpness	96	(1)
Digital radiography	97	(1)
Read out process	97	(1)
Properties	97	(1)
Eye--phosphor combination in fluoroscopy	98	(1)
Phosphors used with image intensifiers	99	(4)
Construction and mode of operation	99	(3)
Quantum mottle	102	(1)
Factors affecting the image	103	(1)
The vidicon camera	103	(2)
Cinefluorography	105	(2)
Spot films	107	(1)
Quality control of recording media and image intensification systems	107	(3)
Summary	110	(4)
The Radiological Image	114	(21)
Introduction---the meaning of image quality	114	(1)
The primary image	114	(1)
Contrast	115	(3)
Contrast on a fluorescent screen	116	(1)
Contrast on a radiograph	116	(1)
Origins of contrast for real and artificial media	117	(1)
Effects of overlying and underlying tissue	118	(1)
Reduction of contrast by scatter	119	(1)
Variation in scatter with photon energy	119	(1)
Reduction of scatter	120	(2)
Careful choice of beam parameters	120	(1)
Orientation of the patient	121	(1)
Compression of the patient	121	(1)
Use of grids	121	(1)
Air gap technique	121	(1)
Design of intensifying screen and film holder	121	(1)
Grids	122	(4)
Construction	122	(1)
Use of grids	123	(2)
Movement of grids	125	(1)
Resolution and unsharpness	126	(3)
Geometric unsharpness	126	(1)
Patient unsharpness	127	(1)
Combining unsharpnesses	128	(1)
Geometric relationship of film, patient and X-ray source	129	(2)
Magnification without distortion	129	(1)
Distortion of shape and/or position	130	(1)
Review of factors affecting the radiological image	131	(4)
Choice of tube kilovoltage	131	(1)
Exposure time	131	(1)
Focal spot size	131	(1)
Quality of anode surface	131	(1)
Tube current	131	(1)
Beam size	132	(1)
Grids	132	(1)
Focus--film and object--film distance	132	(1)
Contrast enhancement	132	(1)
Films and screens	132	(1)
Film processing	132	(3)
Radiation Measurement and Doses to Patients	135	(28)
Introduction	135	(1)
Ionization in air as the primary radiation standard	136	(1)
The ionization chamber	137	(2)
The Geiger--Muller counter	139	(3)
The Geiger--Muller tube	140	(1)
Comparison of ionization chambers and Geiger--Muller counters	141	(1)
Relationship between exposure and absorbed dose	142	(1)
Conversion of exposure in air to dose in air	142	(1)
Conversion of dose in air to dose in tissue	143	(1)
Practical radiation monitors	143	(3)
Secondary ionization chambers	143	(2)
Dose--area product meters	145	(1)
Pocket exposure meters for personnel monitoring	146	(1)
Thermoluminescent dosimeters (TLDs)	146	(1)
Scintillation detectors and photomultiplier tubes	147	(1)
Spectral distribution of radiation	148	(1)
Semiconductor detectors	149	(2)
Photographic film	151	(1)
Variation of detector sensitivity with photon energy	152	(1)
Patient doses in diagnostic radiology	153	(6)
Principles	153	(3)
Entrance doses in plain film radiography	156	(1)
Entrance doses in fluoroscopy examinations	157	(2)
Doses to organs	159	(1)
Patient dose reduction in diagnostic radiology	159	(1)
Technical factors	160	(1)
Non-technical factors	160	(1)
Conclusions	160	(3)
Diagnostic Imaging with Radioactive Materials	163	(29)
Introduction	163	(1)
Principles of imaging	164	(9)
The gamma camera	166	(5)
Variations on the standard camera	171	(2)
Factors affecting the quality of radionuclide images	173	(9)
Information in the image and signal-to-noise ratio	173	(1)
Choice of radionuclide	174	(3)
Choice of radiopharmaceutical	177	(1)
Performance of the imaging device	177	(4)
Data display	181	(1)
Dynamic investigations	182	(5)
Data analysis	182	(4)
Camera performance at high count rates	186	(1)
Quality standards, quality assurance and quality control	187	(2)
Radionuclide calibrators and accuracy of injected doses	187	(1)
Gamma camera and computer	188	(1)
Summary	189	(3)
Assessment and Enhancement of Image Quality	192	(27)
Introduction	192	(1)
Factors affecting image quality	192	(1)
Analogue and digital images	193	(1)
Operation of the visual system	194	(3)
Response to different light intensities	194	(1)
Rod and cone vision	194	(1)
Relationship of object size, contrast and perception	195	(1)
Eye response to different spatial frequencies	196	(1)
Limitations of a subjective definition of contrast	196	(1)
Physical definition of contrast---signal-to-noise ratio	197	(1)
Quantum noise	198	(2)
Digital radiography (principles)	200	(3)
Assessment of image quality	203	(7)
Modulation transfer function	203	(4)
Physical/physiological assessment	207	(3)
Receiver operator characteristic (ROC) curves	210	(5)
Principles	210	(2)
ROC curves in practice	212	(3)
Design of clinical trials	215	(1)
Conclusions	216	(3)
Special Radiographic Techniques	219	(30)
Introduction	219	(1)
High voltage radiography	219	(3)
Macroradiography	222	(2)
Digital radiography (practical detail)	224	(6)
Introduction	224	(1)
Methods of image formation	225	(4)
Resolution requirements	229	(1)
Patient doses	230	(1)
Subtraction techniques	230	(3)
Digital subtraction angiography	231	(1)
Dual energy subtraction	232	(1)
Time interval differencing	232	(1)
Mammography	233	(5)
Optimum kilovoltage and tube design	234	(1)
Molybdenum anode tubes	234	(1)
Tungsten anode tubes	235	(1)
Film--screen combinations	235	(2)
Patient doses	237	(1)
Contrast improvement	237	(1)
Quality control	237	(1)
Xeroradiography	238	(3)
Mode of use	239	(1)
Formation of powder image	239	(2)
Advantages and disadvantages of xeroradiography	241	(1)
Paediatric radiology	241	(2)
Dental radiology	243	(6)
Intra-oral radiography	245	(1)
Panoramic radiography	245	(1)
Receptors	245	(1)
Protection	246	(1)
Quality assurance	246	(3)
Tomographic Imaging	249	(30)
Introduction	249	(1)
Longitudinal tomography	250	(4)
The linear tomograph	250	(1)
Thickness of plane of cut	251	(2)
Miscellaneous aspects of longitudinal tomography	253	(1)
Computed axial transmission tomography	254	(18)
Principles	254	(1)
Data collection	255	(3)
Data reconstruction	258	(6)
Data presentation and storage	264	(1)
System performance and quantum mottle	265	(1)
Patient doses	266	(3)
Spiral CT	269	(1)
Artefacts	270	(1)
Quality control	271	(1)
Single photon emission computed tomography (SPECT)	272	(2)
Positron emission tomography	274	(2)
Conclusions	276	(3)
Radiobiology and Radiation Risks	279	(27)
Introduction	279	(1)
Radiation sensitivity of biological materials	280	(3)
Evidence for high radiosensitivity	280	(1)
Cells particularly at risk; `law' of Bergonie and Tribondeau	280	(1)
Time course of radiation-induced death	281	(1)
Other mechanisms of radiation-induced death	281	(2)
Evidence on radiobiological damage from cell survival curve work	283	(4)
Cellular recovery and dose rate effects	283	(3)
Radiobiological effectiveness (RBE)	286	(1)
Radiation weighting factors, equivalent dose and the sievert	287	(1)
Radiation effects on humans	288	(5)
Deterministic and stochastic effects	288	(1)
Carcinogenesis	289	(1)
Mutagenesis	290	(3)
Risk factors and collective doses	293	(2)
Risks from radiological examinations	295	(2)
Tissue weighting factors and effective dose	295	(1)
Effective doses and risks in radiology	296	(1)
Radiation risks in context	296	(1)
Special high-risk situations---irradiation of children or in utero	297	(3)
Lethal effects	297	(1)
Malformations and other developmental effects	298	(1)
Radiation effects on the developing brain	298	(1)
Cancer induction	299	(1)
Pre-conception risk (leukaemia clusters)	299	(1)
Hereditary effects	299	(1)
Summary---current thinking on risks of foetal irradiation (NRPB 1993b)	300	(1)
Worked example on risk associated with an abdominal examination during undeclared pregnancy	300	(2)
Basic data on good radiographic set-up	300	(1)
Calculation	300	(1)
Risk assessment	301	(1)
Notes	301	(1)
Risk from ingested or injected activity	302	(1)
Summary	302	(4)
Practical Radiation Protection and Legislation	306	(24)
Introduction	306	(1)
Role of radiation protection in diagnostic radiology	306	(4)
Principles of protection	306	(1)
Patient protection	307	(2)
Staff protection	309	(1)
Public protection	309	(1)
European and UK legislation	310	(8)
Introduction	310	(1)
European legislation	310	(1)
Basic Safety Standards Directive 96/29/Euratom (1996)	310	(1)
Medical Exposures Directive 97/43/Euratom (1997)	311	(1)
Outside Workers Directive 90/641/Euratom (1990)	312	(1)
UK legislation	313	(1)
Radioactive Substances Act 1993	313	(1)
The Medicines (Administration of Radioactive Substances) Regulations 1978	313	(1)
The Ionising Radiations (Protection of Persons Undergoing Medical Examination or Treatment) Regulations 1988	314	(1)
Radioactive Material (Road Transport) Great Britain Regulations 1996	315	(1)
Ionising Radiations Regulations 1985	315	(3)
The Ionising Radiations Regulations (Outside Workers) 1993	318	(1)
New UK legislation	318	(1)
Doses to staff and patients	318	(2)
Staff doses	318	(1)
Patient doses	319	(1)
X-ray rooms	320	(1)
Introduction	320	(1)
Points of note on room design	320	(1)
Nuclear medicine	321	(2)
Introduction	321	(1)
Annual limit on intake	321	(1)
Derived limits for airborne and surface contamination	322	(1)
Special precautions in nuclear medicine	322	(1)
Personal dosimetry	323	(7)
Range of response	323	(1)
Linearity of response	323	(1)
Calibration against radiation standards	323	(1)
Variation of sensitivity with radiation energy	323	(1)
Sensitivity to temperature and humidity	323	(1)
Uniformity of response within batches	324	(1)
Maximum time of use	324	(1)
Compactness	324	(1)
Permanent visual record	324	(1)
Indication of type of radiation	324	(1)
Indication of pattern of radiation	325	(1)
Cost	326	(1)
Electronic personal dosimeters	326	(4)
Diagnostic Ultrasound	330	(48)
Introduction	330	(1)
Ultrasound waves and their properties	331	(5)
Longitudinal and transverse waves	331	(1)
Excess pressure and frequency	332	(1)
Speed of sound	332	(1)
Wavelength	332	(1)
Characteristic acoustic impedance	333	(1)
Energy, power and intensity	333	(1)
Decibels	334	(1)
Pulse waves, energy spectra and bandwidth	335	(1)
The propagation of ultrasound waves in tissue	336	(3)
Speed of sound	336	(1)
Attenuation	336	(1)
Attenuation coefficient	337	(1)
Reflection	337	(2)
Refraction	339	(1)
Scattering	339	(1)
The ultrasound transducer	339	(2)
Ultrasound beams	341	(2)
Ultrasonic imaging modes	343	(2)
Pulse--echo range finding	343	(1)
A-mode scans	344	(1)
M-mode scans	344	(1)
B-mode scans	345	(1)
Doppler imaging	345	(1)
B-mode scanners	345	(19)
Factors that are important for the quality of a B-mode image	345	(3)
Beam forming	348	(1)
Single element mechanical sector scanners	348	(1)
Annular array mechanical sector scanners	348	(3)
Linear and curvilinear array scanners	351	(2)
Phased array scanners	353	(1)
Intra-corporeal probes (endoprobes)	354	(1)
Write zoom	355	(1)
Amplifying, processing and displaying the echo signals	355	(5)
Artefacts of B-mode images	360	(4)
The Doppler effect	364	(2)
Spectral Doppler techniques	366	(5)
The Doppler signal and Doppler spectrum from blood flow	366	(1)
Continuous wave Doppler systems	366	(1)
Pulsed Doppler and duplex systems	367	(2)
Interpretation of Doppler signals	369	(2)
Doppler artefacts	371	(1)
Doppler imaging	371	(1)
The safety of ultrasound	372	(2)
Damage mechanisms and biological effects	373	(1)
Minimizing hazard	374	(1)
Summary	374	(4)
Magnetic Resonance Imaging	378	(30)
Introduction	378	(1)
Basic principles of electromagnetism	378	(1)
Magnetic properties of nuclei	379	(1)
Effect of an external magnetic field	380	(2)
Resonance	382	(1)
The rotating frame	382	(2)
Excitation	384	(1)
MR signal reception	385	(1)
Relaxation processes	385	(3)
Spin-lattice relaxation	385	(2)
Spin-spin relaxation	387	(1)
Inhomogeneity effects	387	(1)
Production of spin echoes	388	(2)
Magnetic field gradients	390	(5)
Fourier or reciprocal space	391	(1)
Selective excitation	391	(1)
Phase encoding gradient	392	(1)
Frequency encoding gradient	392	(1)
Review of image formation	393	(2)
Dephasing effects of gradients	395	(1)
Production of gradient echoes	395	(3)
Imaging sequences	398	(3)
Spin echo	398	(1)
Gradient echo	399	(1)
Inversion recovery	399	(2)
Gated sequences	401	(1)
Cardiac gating	401	(1)
Respiratory gating	401	(1)
MR angiography	401	(1)
Contrast agents	402	(1)
Technical considerations	402	(2)
Hazards of MRI	404	(2)
Main magnetic field	404	(1)
Projectile effect of B0	404	(1)
Gradient fields	405	(1)
RF fields	405	(1)
MRI in pregnancy	406	(1)
Conclusions and future developments	406	(2)
Appendix	408	(17)
Answers	425	(3)
Index	428