放射物理学英文版完整版课件

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1、BME College Sherman sheenWhy we study this subject?Diagnostic radiology放射诊断学Radiotherapy放射疗法Radiobiology放射生物学Nuclear medicine 核医疗学 Diagnostic radiology放射诊断学 CT scanner; CT扫描X-ray machine;爱克斯光机DR;C-arms;PET;Performance Evaluation Test 性能鉴定试验radiological imaging放射影像学CT SCANNERPETRadiotherapy放射疗法tradit

2、ional methods to kill tumors治疗肿瘤的传统方法clinical physicist;临床物理学家，医学物理师TPS;Technical Problem Summary 技术问题摘要 Radiobiology放射生物学the interaction between the radioactive particles and the cells在放射性的粒子和细胞之间的交互作用research work to make the radiology more advantageous for human研究工作让 X 光线学变得更有利于人类Nuclear medicine

3、核医疗学 ECT, 电休克治疗 SPECT;单光子发射计算机化断层显像very popular abroad;bright future;Basic ConceptsQuantities and units量和单位(physical quantity)=(numerical value)*(some unit)International system of units (SI)单位的国际系统Fundamental Units基本的单位Q: review the fundamental units?masslengthtimecurrent1.massmKilogram (kg )2.lengt

4、hl meter (m)3.time4.currenttI second (s) ampere (A) Basic ConceptsBasic ConceptsDerived units导出单位 velocity 速度ratio 比率of the increment增长 of distance to timeacceleration 加速度 ratio of the change of velocity to timeforce (newton)力（牛顿）related to acceleration defined 界定by Newtons law of motion 运动定律运动定律Bas

5、ic ConceptsDerived units导出单位 work or energy (joule焦耳 )W=F*lpower (watt),功率rate of doing workfrequency 频率(hertz赫兹) number of oscillation per unit time单位时间振动次数Example 1-1. A young scientist of mass 75 kg at the Ontario Cancer Institute, in a foolish trial of endurance, ran from the basement to the sev

6、enth floor (height 25.8 m) in 23.6 s（在（在 23.6 秒中从地下室秒中从地下室跑到七楼（高度跑到七楼（高度 25.8 m） .Calculate the work done and the power developed . In Toronto the acceleration due to gravity is 9.8 ms-2 .课本P4Basic ConceptsElectrical units电单位电单位 charge (coulomb)电荷电荷(库仑库仑)1 coulomb = 1 C = 1 ampere second = 1 A s pot

7、ential difference (volt)位差位差,电电势差势差(伏特伏特) Potential difference = Electrical circuits电路电路 Work done = Q V = I t V Basic ConceptsElectrical units capacity（电容）（电容）: ability to store charge resistance（电阻）（电阻）Example 1-2 . A potential of 12 volts placed across a heating coil暖管暖管 produces a current of 1.5

8、 amperes. Find the resistance （电阻）（电阻）of the coil, the charge which passes through the coil in 1.0 min, the energy dissipated（消耗的能量）（消耗的能量）, and power 功率developed. Example 1-3. A current of 2.5 10-6A flows into a 20.0 10-6 F condenser电容器电容器 for 20 seconds. Find the potential （电电势差势差）to which the con

9、denser is charged.Basic ConceptsRadiation units辐射单位辐射单位 absorbed dose吸收剂量吸收剂量 energy deposited吸收吸收 by ionizing （电电离离）radiation per unit mass of material 1 Gy = 100rads = 1J/kgexposure 曝光曝光 the charge（电荷电荷 ）liberated（释放）（释放） by ionizing radiation ( output of an X ray generator发生器发生器) per unit mass of

10、 air 1 roentgen （伦琴）（伦琴）= 2.58*10-4 C kg -1 Basic ConceptsRadiation units activity 活性活性 the number of disintegration（裂变）（裂变） per unit time of a radioactive isotope （放射性同位素）（放射性同位素） unit: becquerel 贝可勒尔贝可勒尔(放射性强度放射性强度单位单位, 每秒有一个原子衰变每秒有一个原子衰变) 1Bq = 1s-1 1Ci = 3.70*1010 Bq SummaryThe physics of radiol

11、ogy（X 光线学光线学的物理学的物理学Fundamental units基本的单位Derived units导出单位Units used in radioactive field（放（放射领域）射领域）TWOTWOBME College Sherman sheenAtoms原子原子Matter is composed by atoms物质物质由由原原子组成子组成Structure of Atomsnucleus(原子原子)核核-radius半径半径 10-14melectrons clouds-radii 半径半径10-10mAtomic number原子序数原子序数: Z number o

12、f electrons chemical properties化学特性化学特性Constitution结构，构造结构，构造 protons (质子质子) neutrons(中子中子)Q: How to know the structure of the nucleus?Q: Properties of protons and neutrons: charge and massmass number(原子原子)质量数质量数: A protons + neutrons neutrons = A-ZNucleus原子核原子核nucleon核子核子Isotope同位素同位素 definition(定义

13、定义): Atoms composed of nuclei 原子核原子核(nucleus的复数形的复数形)with the same number of protons (质子质子)but different number of neutrons(中子中子) are called isotopes. stable 稳定的稳定的or unstable ; disintegration（裂变）（裂变） and radioactive;（ 放射性的放射性的）Nucleus原子核原子核Atomic Mass原子质量原子质量Carbon 碳碳 mass number 原子序数原子序数12 represe

14、nted by A【mass number(原子原子)质量质量数数】Notation for atomic species原子种类的标记法原子种类的标记法 subscripts（下标下标）-Z and superscripts（上标）（上标）-AIsotope of Hydrogen氢氢, Helium氦氦, Cobalt钴钴(符号符号为为Co), Hydrogen（氢）氢氢氢氢Z = 1111012123StableStableRadioactiveProton(质质子子)Deuteron（氘核HydrogenDeuterium（氘Tritium（三重氢Helium氦氦Z = 232He42

15、He52He62He82He222221234634568StableStableRadioactiveRadioactiveRadioactiveAlpha（）Elemental particles基本粒子 pproton 1.007277, +1 The proton is the nucleus of the hydrogen atom. The hydrogen atom consists of 1 proton in the nucleus and 1 external（外部的外部的） electron. The mass of the neutral atom （中性中性原子原子）

16、is 1.007277 +0.000548 = 1.007825 mass units. The proton is one of the fundamental building blocks of all nuclei. Beams（束（束, 柱）柱） of protons are being used in radiotherapy.（放射疗法）（放射疗法） Elemental particles基本粒子nneutron 1.008665, 0 The neutron(中子中子) is the other fundamental building block of all nuclei.

17、 Neutrons have nearly the same mass as protons. Since the neutrons is an uncharged particle （不带电粒子）（不带电粒子）it is hard to stop and difficult to detect（查明查明，发现，发觉，发现，发觉. ）Beams of neutrons are being used in radiotherapy. Elemental particles基本粒子 e- - 0.000548, -1The electron has a very small mass compar

18、ed with the proton. Electrons abound in nature. Every atom contains electrons outside the nucleus. The electron is easily detected. It is sometimes called a negatron（阴电子阴电子 ）or beta particle（粒子）粒子） and represented by e, e- or -.Beams of high energy electrons are extensively（广泛（广泛地）地） used in radioth

19、erapy. Elemental particles基本粒子 e+ + 0.000548, +1The positron（正电子）（正电子） has the same mass as an electron but carries a positive charge. Positrons exist in nature only while they are in motion（在运（在运转中转中;处于兴奋状态）处于兴奋状态）. A slowly moving or stationary(静止的静止的) positron quickly combines with an electron to

20、 form a burst (爆炸爆炸, 爆裂爆裂)of radiation in the form of （用（用的形式）的形式）two gamma rays（射射线）线） (see below). Positrons are represented by e+, or + and referred to as beta plus particles They are used in nuclear medicine（核医疗学）（核医疗学）. Elemental particles基本粒子 Hv , 0, 0Strictly speaking, the photon （光子）（光子）is n

21、ot a particle, but a bundle一捆一捆 of energy which travels at the speed of light (3108ms-1). In many interactions（相互作用）（相互作用） it acts much like a particle. Photons are referred to almost interchangeably（可替换地）（可替换地） as quanta 量子量子(quantum的复数形式的复数形式)or gamma rays and are represented symbolically（象征性地）（象征

22、性地） by h or . Beams of photons account for the major part of external beam （外粒子束（外粒子束;外束）外束）radiotherapy（放射疗法）（放射疗法）. Elemental particles基本粒子neutrino 中微子e , 0The neutrino （中微子中微子）is a very small particle with practically （几乎）（几乎）no mass and no charge. For this reason, it has been very difficult to d

23、etect experimentally（根据实验地）（根据实验地）. Its interaction （相互作用）（相互作用） with protons to form neutrons and positrons according to the reaction（反应）（反应）e+ p n + +has been observed. The neutrino was introduced originally from theoretical （假设的假设的，理论的）理论的）considerations to help explain beta decay（衰变）（衰变）. Elemen

24、tal particles基本粒子 Mu mesons（介子）（介子） , + , - , 207m0 ,+1 or -1 Mu mesons may be either positively or negatively charged （带负电荷的）（带负电荷的）and have a mass 207 times the mass of the electron. They are produced indirectly（间接地）（间接地） by the interaction of very high energy particles with matter（物质（物质,物体）物体）. T

25、he particles are unstable and decay spontaneously （自发地（自发地衰变）衰变）into electrons and neutrinos（中微子 according to the reactions+ e+ + 2- e- + 2The mean life（平均寿命）（平均寿命） of the particles is 2.1510-6 sec.Elemental particles基本粒子Pi mesons （介子）（介子） ,+ 273 m0 +1 - 273 m0 -1 0 265 m0 0Pi mesons may have a posi

26、tive a negative charge or may be neutral（中性的）（中性的）. They are produced by the bombardment （炮击；轰炸）（炮击；轰炸）of matter with high energy protons or photons. The charged mesons decay into mu mesons and neutrinos（中微子）（中微子） according to + + + - - + with a mean life of 2.510-8 s. The neutral 0 meson decays（衰变）

27、（衰变） into 2 photons0 h1 + h2with a mean life of 10-15 seconds. Beams of negative mesons are being used in radiotherapy（放射疗法）（放射疗法）. Elemental particles（放射疗法）（放射疗法）（放射疗法）（放射疗法） pproton 1.007277, +1 nneutron 1.008665, 0 e- - 0.000548, -1 e+ + 0.000548, +1 H 0, 0 e , 0 Mu mesons 207m0 ,+1 or -1 Pi meso

28、ns 273m0 ,+1 or -1 265m0 0 Extranuclear structure核外的结构Arrangement of planetary electrons 行星式电子outside the nucleusThe outermost orbit最外层轨道Chemical properties and valence(化合)价 repeat inert gas惰性气体 : He, Ne, alkaline elements碱性元素: lithium锂, sodium钠,Extranuclear structure行星式电子chemical properties化学特性Atom

29、ic Energy levels原子能级Optical radiation 光辐射and X radiationNuclear Energy levels核能级Gamma ray（伽马射线,射线）伽马射线,射线Quantum nature（量子种类，性质） of radiationQuantum (量子)or Photon（光子） bundle of energy 能量束 Energy of a PhotonFor a diagnostic （诊断的）X-ray Generator（发生器）, wavelength （波长）10pm, 1 photon:Quantum nature of ra

30、diationImportant equation方程式, 等式 Wavelength （波长） and energy Quantum nature and continuous radiation连续辐射 Electromagnetic Spectrum电磁波频谱Frequency(Hz)频率Wavelength波长PhotonEnergyProperties特性特性1.01053.01010103 km0.01 m413 peV124 eV Radio waves（无线电波） ranging（排列） from long waves through the broadcast band（广播

31、波段;广播频带, to short waves and to ultra（极端的） short waves in radar（雷达）. These waves are produced by electrical oscillations（振荡） and detected（发现; 发觉, 查明） by electronic equipment. They will pass through nonconducting layers （不传导层）of materials but are reflected（反射） by electrical conductors.（导电体;电导线）Electro

32、magnetic Spectrum电磁波频谱Frequency(Hz)WavelengthPhotonEnergyProperties特性特性3.01001012123.03.010101414100 m1 m12.4 meV1.24 eVInfrared radiations（红外辐射）（红外辐射）. These are produced by molecular vibration（分子振动）（分子振动） and the excitation 激激发(过程程)of the outer electrons of the atom. They are generated（产生）（产生） by

33、heat in stores（堆积物）（堆积物）, radiators（散热器）（散热器）, et cetera（及其他（及其他,等等）等等）, and can be detected by heat devices（装置（装置, 设备）设备） and films（薄层，胶卷）（薄层，胶卷）. Most solid materials are opaque （不透明的）（不透明的）to infrared radiations.Electromagnetic Spectrum电磁波频谱Frequency(Hz)WavelengthPhotonEnergyProperties4.310310141

34、47.57.510101414700 nm400 nm1.77 eV3.1 eV Visible light （可见光）（可见光）ranging from red through yellow, green and blue to violet紫紫. Produced by the excitation of the outer electrons of an atom. Generated（产生）（产生） in lamps and in gas tubes（导气管）（导气管） by electrical discharge（释放，排放出的物体）（释放，排放出的物体）. Detected by

35、 films, by photoelectric cells（光电管）（光电管）, and by the eye. Transmitted（传播传播）by materials such as glass. Electromagnetic Spectrum电磁波频谱Frequency(Hz)WavelengthPhotonEnergyProperties7.51051014143.0103.0101616400 nm10 nm3.1 eV124 eV Ultraviolet light（紫外辐射（紫外辐射;紫外光）紫外光）. Produced by the excitation of outer

36、 electrons in the atom. Detected by films, Geiger counters盖格盖格计数器数器（用于（用于测量放射性）量放射性）, and ionization chambers（电离室）（电离室）. Produces erythematic（红斑）（红斑） of the skin; kills bacteria （细（细菌）菌）and is an agent（原动力（原动力, 动因动因; 作用剂）作用剂） in the production of vitamin D.Electromagnetic SpectrumFrequency(Hz)Wavele

37、ngthPhotonEnergyProperties3.01001016163.0103.010181810 nm100 pm124 eV12.4 keVSoft x rays. Produced by the excitation of the inner electrons （内层电子）（内层电子）of an atom. Detected by films, Geiger counters, and ionization chambers. Have the ability to penetrate（穿过）（穿过） very thin layers of material. Of litt

38、le value in radiology （放射学（放射学,辐射学）辐射学）because of their limited power of penetration.穿透能力穿透能力3.01001018183.0103.0101919100 pm10 pm12.4 keV124 keVDiagnostic x rays and superficial （表表面面(上上)的的）therapy（治疗，（治疗，疗法法）.Electromagnetic SpectrumFrequency(Hz)WavelengthPhotonEnergyProperties3.01001019193.0103.0

39、10202010 pm1 pm124 keV1.24 MeVDeep therapy（深部疗法）（深部疗法） x rays and gamma rays from radium decay products（镭衰变产（镭衰变产物）物）.3.0100102121100 fm12.4 MeVRadiation from a small betatron（电子感应加（电子感应加速器）速器） or linear accelerator（直线加速器）（直线加速器）.3.010010222210 fm124 MeVRadiation from a large linear accelerator.3.01

40、001023231 fm1.24 GeVProduced in the operation of large proton synchrotrons （同步加速器）（同步加速器）or linear accelerators（直线加速器）（直线加速器）.Electromagnetic SpectrumFrequency(Hz)WavelengthPhotonEnergyProperties1.01053.010103 km0.01 m413 peV124 eVRadio waves ranging from long waves through the broadcast band, to sh

41、ort waves and to ultra short waves in radar. These waves are produced by electrical oscillations and detected by electronic equipment. They will pass through nonconducting layers of materials but are reflected by electrical conductors.3.010123.01014100 m1 m12.4 meV1.24 eVInfrared radiations. These a

42、re produced by molecular vibration and the excitation of the outer electrons of the atom. They are generated by heat in stores, radiators, et cetera, and can be detected by heat devices and films. Most solid materials are opaque to infrared radiations.4.310147.51014700 nm400 nm1.77 eV3.1 eVVisible l

43、ight ranging from red through yellow, green and blue to violet. Produced by the excitation of the outer electrons of an atom. Generated in lamps and in gas tubes by electrical discharge. Detected by films, by photoelectric cells, and by the eye. Transmitted bymaterials such as glass. 7.510143.010164

44、00 nm10 nm3.1 eV124 eVUltraviolet light. Produced by the excitation of outer electrons in the atom. Detected by films, Geiger counters, and ionization chambers. Produces erythematic of the skin; kills bacteria and is an agent in the production of vitamin D.3.010163.0101810 nm100 pm124 eV12.4 keVSoft

45、 x rays. Produced by the excitation of the inner electrons of an atom. Detected by films, Geiger counters, and ionization chambers. Have the ability to penetrate very thin layers of material. Of little value in radiology because of their limited power of penetration.3.010183.01019100 pm10 pm12.4 keV

46、124 keVDiagnostic x rays and superficial therapy.3.010193.0102010 pm1 pm124 keV1.24 MeVDeep therapy x rays and gamma rays from radium decay products.3.01021100 fm12.4 MeVRadiation from a small betatron or linear accelerator.3.0102210 fm124 MeVRadiation from a large linear accelerator.3.010231 fm1.24

47、 GeVProduced in the operation of large proton synchrotrons or linear accelerators.Electromagnetic SpectrumBinding energy结合能结合能 K radiation, BE: 70000ev L radiation, BE: 11000ev M radiation, BE: 2500evRadiation of energy （能量辐射）（能量辐射）from an atomRadiation of energy from an atomsummaryAtoms原子原子The Nucl

48、eus原子核原子核Elemental Particles基本粒子基本粒子Extranuclear Structures核外结构核外结构Atomic Energy Levels原子能级原子能级Nuclear Energy Levels核能级核能级Electromagnetic Radiation电磁辐射电磁辐射Quantum Nature of RadiationThe Electromagnetic Spectrum电磁波频谱Radiation of Energy from an Atom 原子的原子的能量辐射能量辐射ThreeThreeBME College BME College Sher

49、man sheenSherman sheenMass and energy质量和能量，质能Einsteins theory E = m c2 C代表光速Energy corresponding to one electron能量相当于1 kg m2S-2 = 1 joule Because:Mass and energy质能mass of one carbon atom = Example 1-7. Calculate the energy equivalent(能当量能当量) of 1 atomic mass unit (amu). Avogadros number(阿伏伽德罗数阿伏伽德罗数

50、 )= 6.022045 1023 carbon has a mass number【(原子原子)质量数质量数】 of 12, it contains 12 amuHence, the conversion （ 转化）转化）of 1 amu to energy two important mass-to-energy conversion factors 转换因数:Mass and velocitym0 , the rest mass静止质量静止质量 1/10 the velocity of light , increase in mass of 0.5% 98% of light (v/c0

51、.98), 5 times of the rest massMass and velocityKineticEnergy（动能）ElectronsProtonsTotalEnergy(MeV兆电子伏)VelocityRelative toVel. of LightMassRelative toRest Mass（静止质量）VelocityRelative toVel. of LightMassRelative toRest Mass10 keV100 keV200 keV500 keV1 MeV2 MeV5 MeV10 MeV20 MeV50 MeV100 MeV 0.521 0.1950 1

52、.020 0.611 0.5483 1.196 0.711 0.6954 1.392 1.011 0.8629 1.979 1.511 0.9411 2.957 2.511 0.9791 4.916 5.511 0.9957 10.79 10.511 0.998817 20.58 20.511 0.999689 40.16 50.511 0.999949 99.01 100.511 0.999987 192.31 0.0046 1.0000 0.0147 1.0001 0.0208 1.0002 0.0326 1.0005 0.0465 1.0011 0.0657 1.002 0.1026 1

53、.0053 0.1451 1.0107 0.2033 1.0213 0.3141 1.0533 0.4283 1.1066Exponential behavior指数式变化 the rate of change of a function（函数）（函数） is proportional （比例的（比例的, 成比例的）成比例的）to the function. If a quantity changes by a certain factor （一个特（一个特定的因素）定的因素）in a given interval of time（时间时间间隔）间隔）, then there will be

54、exponential behavior if in any other equal interval of time （相等时间间隔）（相等时间间隔）it changes by the same factor 相同的因素相同的因素 Exponential behavior指数式变化the growth of money in a bank account银行存款银行存款, the growth of populations, the growth of cells, the decay（衰变）（衰变） of radioactive isotopes（放射性同位素）（放射性同位素） the k

55、illing of cells by radiation, the attenuation （变细；变薄变细；变薄;减弱）减弱）of x ray beams Occurred（发生）（发生） while:EXPONENTIAL DECAY（指数式衰减）（指数式衰减） OF A RADIOACTIVEISOTOPEHALF-LIFE（半衰期）（半衰期）on the average, after the half-life, half the radioactive atoms（放射性原子）（放射性原子） will disintegrate（破裂分裂）（破裂分裂）. In the next hal

56、f-life, one-half of the remaining （剩下的）（剩下的）atoms will decay. For example, a source of radioactive gold (198Au) with a half-life of 2.69 days, , started with 100106 atoms, after 2.69 days there would be 50 106 remaining, after 5.38 days 25 106, after 8.07 days 12.5 106. EXPONENTIAL DECAY OF A RADIOA

57、CTIVEISOTOPEHALF-LIFEEXPONENTIAL DECAY OF A RADIOACTIVEISOTOPEHALF-LIFEMathematical relation数学关系:substituting t = th , 2th, 3th. （取代取代）The number, N, after these times is N0 /2, N0 /4, N0 /8 EXPONENTIAL DECAY OF A RADIOACTIVEISOTOPEHALF-LIFEExample 1-8. Calculate the number of atoms of 198Au (th = 2

58、.69 days) after 7 days if initially （开始（开始,最初）最初）there were 108 atoms present. We now determine（测定） with a calculator（计算器） that 22.606.06 atoms e0.693 = 2.00 N = N0(2)-t/th = N0(e0.693) -t/th = N0e -0.693t/th Decay time (in units of half-lives) = Transformation constant变换变换衰变衰变,转变转变常数常数 N = -N t , p

59、rovided（只有（只有才）才） t 1 dN = - N dt N = N0e-t Exponential growth of cells细胞的指数生长 N = + N t its solution leads to N = N0et and = Exponential killing of cells N = - N D N = N0e-D = N0e-D/D0Graphs showing exponential growth of cells and exponential killing（指数式消灭） of cells. Exponential attenuation指数减弱 N =

60、 -N x N = N0e-x , the linear attenuation coefficient线性衰减系数线性衰减系数 the solution is :is called the half-value thickness（半吸收厚度;半值层;强度减半厚度）, or half-value layer Summary of Exponential BehaviorProcess(过程程, 进程程)Variable(变数变数)Constant ofProportionality(常数常数比例比例)Useful RelationsUsualEquation(方程式方程式, 等式等式)Rad

61、ioactivedecay ofatoms, Ntime, ttransformationconstant,（变形（变形常数）常数）mean life,th = 1/half-lifeth = 0.693/Growth of investment（投投资），Vtime, tinterest rate,r（利率）（利率）doubling time（倍增时（倍增时间）间）,td = 0.693/rGrowth of pop. ofcells, Ntime, tgrowth constant（常数）（常数）, doubling time,td = 0.693/Killing ofcells, N,

62、byradiationdose, D（剂（剂量）量）killing constant, mean lethaldose,D0 = 1/dose to kill50%, Dh = 0.693D0Attenuation（变细；变薄变细；变薄;减弱）减弱）of a beam ofphotons, Nthickness, x（厚（厚度）度）attenuationcoefficient, （变薄（变薄系数）系数）mean freepath, 1/half-value layerxh = 0.693/summaryMass and energyMass and velocityExponential be

63、haviorThe Production and Properties of X RaysThe Production and Properties of X RaysPart OnePart OneBME College Sherman sheenX-Ray Tubes（X射线管）射线管） and Simplified Circuit单一化的线路单一化的线路Q: How to produce X radiation?Substance(物质，物物质，物) bombarded (轰击轰击)by high speed electronsX-ray tubeQ: Structure of an X

64、 ray tube? cathode（阴极）（阴极）, anode（阳极）（阳极）, filament(灯丝灯丝), focusing cup(聚焦杯聚焦杯)X-Ray Tubes and Simplified CircuitA big problem ? -efficiency（效率（效率, 效能）效能） -Nobel prizeUnderstand X-ray tube in a circuit space charge （空间电荷）（空间电荷） effect saturation 饱和饱和（状态状态）tube voltage （管电压（管电压 ）increasedfilament emi

65、ssion（灯丝发射灯丝发射）X-Ray Tubes and Simplified CircuitX-Ray Tubes and Simplified CircuitThree important parameters（参量）（参量）Tube current 管电流管电流Filament current 灯丝电流灯丝电流KV anode-cathode 伏特伏特 阳极阴极阳极阴极 A kind of special tubes grid-controlled tubes 控制栅电子管控制栅电子管 rapid switching and short exposure time 迅速的转变和短暴露

66、时间迅速的转变和短暴露时间Self-rectified （自整流）（自整流）X ray circuitSelf-rectified X ray circuit自我自我整流整流的的X光线路光线路Some basic conceptstransformer变压器变压器iron core铁芯铁芯primary winding初级线圈初级线圈secondary winding复卷绕组复卷绕组 line compensate 线线补补偿偿milliammeter毫安表毫安表filament control灯丝调节灯丝调节Alternating Currents & Voltages交交流流电电电电压压R

67、ectification（整流）整流）the target of an x ray tubehot enough to emit（发出，射出）（发出，射出） electronselectrons will flow from anode（阳极）（阳极） to cathode（阴极）（阴极）the inverse cycle逆循环逆循环the delicate filament（细灯丝）（细灯丝） will be destroyedSilicon rectifier硅整流器Half wave & full wave（全波）Three phase units三相单位Anode and Cathod

68、e StructureDiagnostic x ray tubesproduce a sharp shadow picture point source and very short exposure the line focus tube 行聚焦管 rotating anode tube旋转阳极旋转阳极管管 Diagrams illustrating anode construction and focal spots（焦斑（焦斑(点点)）. (a) Line focus fixed anode（行聚焦固定的阳极）（行聚焦固定的阳极）. (b) Line focus rotating ano

69、de（旋转阳极旋转阳极）, viewed from the end. (c) Line focus rotating anode viewed from the side. (d) Alternative arrangement（间隔布置）（间隔布置） of rotating anode using two separate tracks at different angles as in the Siemens Biangulix series. （替换以不同的角度使用两个分开（替换以不同的角度使用两个分开 轨道轨道 的阳极为在姆的阳极为在姆欧的新项目中欧的新项目中 Biangulix 系列

70、的间隔布置）。系列的间隔布置）。 Rotating anode tube（旋转阳极旋转阳极管管 ）, adapted from diagram图解、示意图图解、示意图 by Philips. Anode and Cathode StructureRadiotherapy x ray tubesLarge average energy & focal spot 焦斑焦斑(点点)Problem: secondary emission次级发射次级发射Hooded anode被罩上的阳极被罩上的阳极 Hooded anode therapy tube被罩上的阳极治疗管被罩上的阳极治疗管 adapted

71、 from diagram by Philips 从飞利浦公司的图表适应 summaryX-ray tube and simplified circuit X射线射线管管和和单一化线路单一化线路Rectification 整流整流Three phase unit 三相单位Anode and cathode structure 阳极和阴极结构阳极和阴极结构The Production and Properties of X RaysThe Production and Properties of X RaysPart TwoPart TwoBME College Sherman sheenRat

72、ings of Diagnostic Tubes诊断管的等级诊断管的等级，类别，类别First, the focal spot 焦斑焦斑(点点)must not be loaded beyond a certain power input. （负（负载超过特定输入载超过特定输入功率）功率）Second, the anode must not be loaded by successive exposures beyond a certain limit.（负载超过一个特定界限的连续曝光）（负载超过一个特定界限的连续曝光）Finally the housing（外壳外壳, 外罩外罩） must

73、not be expected to dissipate its energy at rates beyond a certain value. （预期在特定的价值之外的比率驱散它的预期在特定的价值之外的比率驱散它的能量能量)Example 2-1. Calculate the rise in temperature(升温升温) of a rotating anode after an exposure of 100 mA for 2 s at constant potential of 100 kV. Assume (假设假设)the target to have a mass of 500

74、 g and the surface area of the bombarded region(被轰击的区域被轰击的区域) to be 30 cm2 ; take the density of tungsten（钨的密度）（钨的密度） to be 19.3 g/cm3 and specific heat（比热）（比热） 0.03 cal g-1 oC-1. Perform the calculations for two limiting conditions（限制条件）（限制条件）: (a) assume the heat instantly distributes itself over

75、the whole of the anode and none is lost by heat transfer（假设热量立（假设热量立即扩散到整个阳极且没有传热的损失）即扩散到整个阳极且没有传热的损失）; (b) assume no heat escapes from the immediate area of the bombarded region but is concentrated to a depth of 1 mm under the bombarded area.（ 假设没有热量量从当前被轰击的区域逃出但是集中到在被轰击的区域下面的 1 毫米的深度）Energy input

76、（能量输入）（能量输入） = 100103 V0.1A2s =2104J Heat input to anode = 2104J = 2 104/4.18 cal 5103 calFor whole anode, thermal capacity（热容量）（热容量） = 500g0.03 cal g-1 OC-1 =15 cal OC-1(a) Rise in temperature = (b) Mass of bombarded volume = 300.1cm319.3 g cm-3 = 58g Rise in temperature = 4.18J=1 calorie卡路里卡路里, 卡卡

77、(热量单位热量单位)the average tube current in mA, the peak voltage (峰值电压峰值电压)in kV, the exposure time（曝光时间）（曝光时间） in seconds HU: a heat unit(热量单位热量单位)HU = voltage (kV)current (mA)time (s) Energy deposited（能源能源储储存存 ） 0.75 HU joules In practical engineering（在实际的工程学中在实际的工程学中）:X ray Spectra（X光谱光谱）Interactions(相

78、互作用相互作用) of Electrons with the Target to Give X Rays (X光光)ionizational collisions(离子化碰撞离子化碰撞)_ ionization（电离）（电离） produced, delta rays（ 三角线）三角线）, heat energy（热能）（热能）, radiative collisions（辐射碰撞）（辐射碰撞） high speed electron hitting(碰撞碰撞) mass Chances depend on the energy of the electronTypical electron

79、interactions with a target典型的一个目标的电子典型的一个目标的电子相互作用相互作用Characteristic Radiation 标识辐射标识辐射Critical X ray Absorption Energies (keV)X光吸收能光吸收能量量Shell外壳外壳OxygenZ = 8Calcium钙Z = 20Copper铜Z = 29 Molybdenum钼 Z = 42Tin锡Z = 50Tungsten钨Z = 74Lead铅Z = 82K0.5334.0378.98120.00029.20069.52588.004LILIILIII0.0240.0090

80、.0091.4380.3500.3461.0960.9530.9332.8672.6252.5214.4654.1563.92912.09811.54110.20415.86115.20013.035MIMIIMIIIMIVMVnotfilled0.0440.0250.0250.1220.0740.0740.0070.0070.5050.4100.3920.2300.2280.8840.7560.7140.4930.4852.8202.5752.2811.8711.8093.8513.5543.0662.5862.484Principal Emission Lines in keV for T

81、ungsten and Molybdenum钨和钼在千电子伏特的主要发射谱线钨和钼在千电子伏特的主要发射谱线K Lines TungstenL Lines TungstenTransition（转（转换）换）Symbol符号符号Energy(keV)RelativeNumberTransitionSymbolEnergy(keV)RelativeNumberK-NIINIIIK-MIIIK-MII K-LIIIK-LIIK-MIIMIIIK-LIIIK-LIIK2 69.081 7K1 67.244 21K3 66.950 11K1 59.321 100K2 57.984 58K lines

82、Molybdenum K31 19.602 24K1 17.479 100K2 17.375 52LI-NIIILII-NIVLIII-NVLI-MIIILII-MIVLI-MIILIII-MVLIII-MIVL5L1L2L3L1L4L1L211.67411.2859.6929.8179.6709.5328.3958.333102418371272910011White Radiation（白光）（白光）, or Bremsstrahlung（轫致辐射）（轫致辐射） (a) paths （轨迹）（轨迹）of the electron into the target(b) change in d

83、irection at each interaction （每交互作用的方向改变）（每交互作用的方向改变）(c) chance of an ionizational loss and the chance of a radiation loss in each increment（增长）（增长） of path(d) direction of emission（排放（排放,散发散发,发出）发出） of the bremsstrahlung(e) attenuation （变薄（变薄 ）and scattering（散射）（散射） in emerging（显露）（显露） from the tar

84、get. THE ANGULAR DISTRIBUTION （角分布（角分布;角向分布）角向分布）OF X RAYS Thin Target 薄靶薄靶 bombarding （轰击）（轰击）a foil of aluminum（铝箔）（铝箔） 200 nm thick with 34 keV electrons: maximum intensity（强烈）（强烈）-550 intensity in forward direction-small intensity in backward direction-zeroIncrease energy of the bombarding elect

85、rons : energy forward direction THE ANGULAR DISTRIBUTION OF X RAYS Thick Target （厚靶）（厚靶） maximum yield（产出）（产出） is usually 5 to 10o to the cathode side （阴极,负极） heel effect（倾斜效果）（倾斜效果） :reduced intensity on the anode side summaryRatings of Diagnostic tubesX-ray spectraInteractions of Electrons with th

86、e target to give X raysCharacteristic radiationWhite radiation or bremsstralungAngular distribution of X raysThe FundamentalsThe Fundamentals（原理）（原理）（原理）（原理） of Nuclear Physics of Nuclear PhysicsPart oneBME College Sherman sheenThe Physics of RadiologyNatural Radioactivity天然放射性天然放射性General state of

87、particles粒子的一般状态粒子的一般状态Continual motion持续不断的运动持续不断的运动Uncertainty for a single particleStatistical rules（统计规划）（统计规划） in radioactive nucleus some certain percentageStable atom when Z 1/3of the maximum value Energy absorption from Radioactive IsotopesElectron Capture电子俘获电子俘获Most of the available energy

88、（有效能（有效能;有用能）有用能） in the reaction is carried away by neutrinos（中微子）（中微子）. When the K or L shell holes resulting from the capture（俘获）（俘获） are filled, fluorescent radiation（荧光性辐射）（荧光性辐射） is emitted and Auger electrons（奥格电子奥格电子） are produced. Most of the energy from these two processes will be locally

89、absorbed. Energy absorption from Radioactive IsotopesGamma Rays（射线射线）When gamma rays are emitted they will be absorbed if their energy is small and thebiological material large in extent（就面积（就面积而言）而言）. If they are of high energy only a fraction of （一小部分）（一小部分）their energy will be absorbed.Energy abs

90、orption from Radioactive IsotopesInternal conversion内部变换内部变换A high energy electron with energy EEK or EEL is emitted and absorbed where E is the excess energy（高速成形的（高速成形的)过剩能量）过剩能量） in the nucleus. In addition fluorescent radiation（荧光性辐（荧光性辐射）射） from the daughter nucleus （子核）（子核）will be emitted and

91、usually absorbed in the biological material（ 生物学的材料）生物学的材料）. Some of the fluorescent radiation may be absent and in its place will appear Auger electrons, which are absorbed. Energy absorption from Radioactive IsotopesAuger electrons奥格电子奥格电子The excess energy （高速成形的（高速成形的)过剩能量）过剩能量）arising from holes

92、 in the electronic shells（电子层）（电子层） can give rise to（引起（引起, 导致）导致） Auger electrons, which are locally （局部地）（局部地）absorbed. Growth of Radioactive Daughter放射性子体放射性子体N1 = (N1)0e-1 t Solution:Nuclear Fission （核子分裂，核裂变）（核子分裂，核裂变）& Fusion（核聚变）（核聚变）n fission fragment 分裂碎片分裂碎片 + 200 MeVn fission fragmentSumm

93、ary Isomer and Isomeric transition异构体和同质异能跃迁异构体和同质异能跃迁Energy absorption from Radioactive Isotopes放射性同位素的能量吸收放射性同位素的能量吸收Growth of Radioactive Daughter放射性子体放射性子体的增长的增长Nuclear Fission & Fusion核裂变和核聚变核裂变和核聚变Measurement（测量）（测量） of Radiation: Dosimetry（放射量测定）（放射量测定）Part OneBME College Sherman SheenThe Phy

94、sics of RadiologyDifferent way to describe a radiationdescribe a radiation beam itself describe the amount of energy it may deposit in some medium (介质介质)describe a radiation in terms of（ 从从方面说来）方面说来） its ability to ionize air （电离空气）Quantities（工程量）（工程量） to Describe a Radiation BeamFluence流量流量Energy F

95、luence 能量流量能量流量注量注量Quantities to Describe a Radiation BeamFluence rateEnergy Fluence rate能量流量率能量流量率 Energy transfer（能量转移）（能量转移）A two stage processKerma （比释动能）（比释动能）and absorbed Dose（吸收剂量）（吸收剂量）Two stage process of energy transfer:(a)involves the interaction of the photon with an atom, causing an ele

96、ctron or electrons to be set in motion（在运转中（在运转中;处于兴奋状态）处于兴奋状态）. (b) involves the transfer of energy from the high energy electron to the medium through excitation and ionization. Energy transferA two stage processKerma and absorbed DoseKERMA: （比释动能）（比释动能） Kinetic Energy Released in the Medium (/) g

97、ives the number of photon interactions that take place per unit mass of material KERMA: Kinetic Energy Released in the Medium In any actual irradiated medium（发光媒介）（发光媒介）, there will of courbe a spectrum of photon energies（光谱，光能波谱）（光谱，光能波谱）. If this spectrum is described by d(h)/d h, the kerma will b

98、e given by: Example : Suppose a beam of 10.0 MeV（兆电子伏）（兆电子伏） photons with fluence of 1014/m2 is incident on a small block of carbon. Calculate the kerma. Kerma = KAbsorbed Dose The absorbed dose equals （等于）（等于）the kerma less（少于）（少于） the energy carried away by bremsstrahlung 1 rad = 100 erg/g （ erg尔格

99、尔格(功的单位功的单位)）1 Gy (gray) = 1 J/kg = 107 erg/103g = 100 rad Unit of Absorbed Dose:Electronic EquilibriumElectronic Equilibrium电子平衡电子平衡电子平衡电子平衡the part of the average kinetic energy （平均动能）（平均动能）transferred to electrons that contributes to ionization (it excludes（不包括）（不包括） energy lost by bremsstrahlung

100、) g is the fraction（小部分）（小部分） of the energy that is lost to bremsstrahlungK is the kerma collision kerma（碰撞动能）（碰撞动能） The Bragg-Gray Cavity（腔（腔, 洞）洞）average energy causing one ionization in the gas is constant（常数）（常数）dose absorbed in the gas:Example. A cavity with 1 cm3 volume（体积（体积; 容积）容积）, filled w

101、ith air at STP（屏蔽双绞线）（屏蔽双绞线）, is exposed to a radiation field that liberates（释放）（释放） 3.336 10-10 C in a given time. Determine （测定）（测定）the dose to the air.Bragg-Gray formula（公式（公式, 方程式）方程式） the ionizationin a cavitythe absorbed dosein the wall surrounding the cavityrelationshipExample. A 1 cm3 air ca

102、vity in a block of carbon is exposed to Co-60 gamma rays and acharge of 3 10-8 C is produced and collectedfrom the cavity. Find the absorbed dose to thecarbon, assuming（假设）（假设） the air is at STP. Summary Quantities to describe a radiation beamKerma and absorbed doseElectronic equilibrium电子平衡电子平衡Brag

103、g-Gray FormulaMeasurement of Radiation: DosimetryPart TwoBME College Sherman Sheen(辛辛学学刚)The Physics of RadiologyDeterminationDetermination（测定）（测定）（测定）（测定） of Absorbed Dose Using an of Absorbed Dose Using an Absolute Ion ChamberAbsolute Ion Chamber（完全电离室）（完全电离室）（完全电离室）（完全电离室） 1、the air cavity（气孔）（气孔

104、） (radius半径半径 a) is small enough to produce negligible perturbation （轻微颤动，变化）（轻微颤动，变化）of the radiation field（辐射场辐射场）、the shell of wall material has essentially（基本上）（基本上） the same atomic number （原子序数）（原子序数）and density（密度）（密度） as the mediumExample. Suppose a carbon ion chamber with a 1 cm3 air cavity

105、is placed in a water phantom and exposed to Co-60 gamma rays, which produce a charge of 3 10-8 C. Find the dose to the water. Assume the carbon walls are slightly thicker thanthe range（变化幅度（变化幅度, 范围）范围） of electrons. Dose to water = 0.792 Gy 1.111 = 0.890 Gy CORRECTION FACTORS（校正系数）（校正系数） FOR THE FI

106、NITE（有限的）（有限的） SIZE OF THE ION CHAMBER Effects of Temperature and Pressure on Ionization Measurements（电离测量）（电离测量） Exposure-The Roentgen（伦琴）（伦琴） 1 R 2.5810-4 C/kg of air Or 1 C/kg = 3876 R Since air at STP has a density（密度）（密度） of 0.001293 g/cm3, 1 kg of air has a volume（体积）（体积） of 103/.0012937.734 1

107、05 cm3 and 1 roentgen is equivalent to（等于，相当于）（等于，相当于）:to produce 1 coulomb of charge by the ionization of air requires an energy absorption of 33.85 joules Standard（标准标准 ）Air Chamber Example. In a standard air chamber the limiting diaphragm（光圈（光圈,光孔）光孔） has an area of 0.500 cm2 and the length of th

108、e sensitive electrode（灵敏电极）（灵敏电极） is 8.00 cm. In an irradiation（放射（放射,照射）照射） a charge of 1.12 10-7 coulombs is collected. Air is at STP (density 1.293 kg m-3 ). Determine the exposure X at point P. Exposure in R .02166 3876 R83.9 R Practical （实际的）（实际的）Ion ChambersThe Thimble Chamber（套管型电离箱套管型电离箱 ） D

109、etermination of Absorbed Dose in “Free Space”（自由空间）（自由空间） X: the exposure at point P the ratio（比率）（比率） of averaged mass energy absorption coefficients（程度（程度;系数）系数） for the material of m to air the attenuation factor 衰减因数衰减因数因子因子,常数常数,系数系数the absorbed dose at point P 衰减因数因子,常数,系数the absorbed dose in

110、free space at a point in air: Summary Determination of Absorbed Dose Using an Absolute Ion Chamber （完全电离室完全电离室）Effects of Temperature and Pressure on Ionization MeasurementsExposure-The RoentgenStandard Air ChamberPractical Ion ChambersThe Thimble Chamber（套管型电离箱套管型电离箱）Determination of Absorbed Dose

111、in “Free Space”Measurement测量测量 of Radiation放射物、辐放射物、辐射能射能: Dosimetry剂量学剂量学 Part ThreeBME College Sherman Sheen(辛辛学学刚)The Physics of RadiologyDeterminationDetermination确定、决定确定、决定确定、决定确定、决定 of Absorbed Dose of Absorbed Dose吸收吸收吸收吸收剂量剂量剂量剂量 in a Phantom in a Phantom 影像、幻象影像、幻象影像、幻象影像、幻象using an Exposur

112、eusing an Exposure暴露暴露暴露暴露 Calibrated Calibrated量口径、校准量口径、校准量口径、校准量口径、校准 IonIon离子离子离子离子 Chamber Chamber腔、室腔、室腔、室腔、室Kerma比释动能，柯玛比释动能，柯玛 in the cavity洞、穴洞、穴 : imagine a small mass, m, of phantom material 体膜材料体膜材料placed at point P”，at the center of the air cavity. The (collision碰撞碰撞) kerma to m would b

113、e: fill in the cavity, of radius半径半径 c, with phantom material. This would alter改变改变 the kerma to the small mass, m, by the attenuation减弱减少减弱减少 factor因素要素因素要素, k(cmed), and the kerma to mass m would now be: the absorbed dose at point P in the homogeneous同种类同性质的同种类同性质的 phantom may be obtained from: to

114、 have a dosimeter剂量计、仪剂量计、仪calibrated 量口径、校量口径、校准准in terms of absorbed dose吸收剂量吸收剂量 instead of exposure暴露暴露 A Farmer type ionization chamber 电离箱电离箱is used to make a determination测定测定 确定确定 of absorbed dose in a water phantom irradiated用射线照射用射线照射 by Co-60 gamma rays. It is protected against the water

115、by thin rubber tubing一截薄橡胶管一截薄橡胶管 and is held with its center at a point such as P of Figure 4-12. After a given irradiation辐射辐射 the electrometer静电计静电计 connected to it gives a scale reading刻度读数刻度读数 of 74.0. The exposure calibration factor校准因素校准因素 Nx for the chamber with this electrometer is 1.06 for

116、 Co-60 radiation. Determine the absorbed dose in the phantom. The outer radius外半径外半径 of the chamber with its cap顶、盖子顶、盖子 is 0.8 cm. Determine also the dose calibration factor校准因素校准因素. Determination of Absorbed Dose 吸收剂量吸收剂量at Energies Above超过超过 3 MeV 1、Use of Exposure Meter with Calibration Factor校准

117、因素校准因素at Cobalt 60钴的放射性同位素钴的放射性同位素,钴钴60 to Determine 确定确定Absorbed Dose at Energies above 3 MeV an exposure calibration factor：Nx Determination of Absorbed Dose at Energies Above 3 MeV 、the cavity-gas calibration factor determined from an absorbed dose calibration. the much simpler equation简化式简化式 ： A

118、greed-on 商定、同意商定、同意Dose Calculation Factors for High Energy PhotonsDosimetry剂量计剂量计 for Electron Beams电子束电子束Relation between Energy Fluence 能量流量能量流量and Exposure 照射量照射量Summary of Methods to Determine Absorbed Dose 对测量吸收剂量方法的总结This is the Bragg-Gray relation布拉格布拉格-格雷关系格雷关系To relates the absorbed dose a

119、t a point in a medium媒介媒介 to Q, the charge liberated 电荷荷释放放 in an air cavity centered at the point. mair is the mass of the gas气体质量气体质量 and is the ratio比例比例 of averaged mass平均质量平均质量 stopping powers. This relation forms形成形成 the basis基础基础 of all dosimetry using ion chambers.12Q is the charge liberated

120、电荷释放电荷释放 in a cavity containing包含包含 a known mass已知质量已知质量, m, of air; is the ratio of averaged stopping powers制动功率制动功率kc is the attenuation衰减衰减 or replacement factor.更换系数更换系数 is the ratio of averaged mass energy absorption coefficients 吸收系数吸收系数This equation is used for absolute dosimetry and is valid

121、 有效的有效的for all photon3M ,is the dosimeter reading 度数读数度数读数Nx, is its exposure calibration factor 照射量校准照射量校准因素因素is the ratio of averaged mass energy absorption coefficients 吸收系数吸收系数the attenuation衰减衰减 correction纠正纠正 for the material of radius r 半径半径456789Measurement测量测量 of Radiation放射物、辐射能放射物、辐射能: In

122、strumentation测量仪器测量仪器&Techniques技术技术Part OneBME College Sherman Sheen(辛辛学学刚)The Physics of Radiologysaturation饱和饱和 in ion chambers电离室电离室 Mobility 移动能力、移动能力、in inert gases惰性气体惰性气体 M negative ions阴离子阴离子 M positive ions阳离子阳离子 in airRecombination Coefficient复合系数复合系数 number of recombinations重新结合重新结合 per

123、unit volume in time, t = C+ C- t charge电荷电荷 lost to recombination per unit volume in time, t = recombination coefficientC+ , C-Ions concentration 离子浓度离子浓度 Q is the charge concentration电荷浓度电荷浓度 at time t, and Q0 is the initial concentration.初浓度初浓度 Example. In an air ion chamber电离室离室 there are present

124、 initially最初最初 10 pC of positive ions阳离子阳离子 and an equal number of negative ions阴离子阴离子 in each cm3. Determine测量测量 the charge lost to recombination in the first ms.Calculation of Efficiency效率效率 of Ion CollectionPulsed Radiation 脉冲辐射脉冲辐射Calculation of Efficiency of Ion CollectionPulsed Radiation 脉冲辐射脉

125、冲辐射 Pulsed RadiationExample. Find the fraction of the ions collected in a parallel plate 平行板平行板 ion chamber电离室电离室 exposed to radiation that liberates释放释放 10 pC per cm3 per pulse脉冲脉冲 when the plate separation分开分开 is 1.5 cm and 300 volts is applied to 施加施加the chamber. What voltage电压电压 would be require

126、d to collect 99.5% of the ions离子离子? yielding 产生产生a p of about 100 To collect 99.5% of the ions requires p 100 reduce d by a factor of about 2and increase the potential 电势电势V by a factor of about 6Calculation of Efficiency of Ion CollectionContinuous Radiation 连续辐射连续辐射Charge lost to recomb.per second

127、 in width dx Example. A parallel plate平行板平行板 ion chamber with 1.20 cm gap is placed in a continuous radiation field, which produces 10.0 nC of charge/cm3s. The potential across the chamber is 150 volts. Estimate估计、判断估计、判断 the fraction分数、百分比分数、百分比 of ions collected. What conditions条件条件 would allow fo

128、r collection of 99.9% of the ions? To collect .999 of the ions, Figure数字数字 shows that c should be about 30Cylindrical 圆柱体圆柱体 and Spherical 球型球型Chambers1 roentgen = 3.33510-10 C/cm3 for air at NTP Example. A cylindrical圆柱圆柱 air wall chamber of radius半径半径 0.5 cm with a central electrode中央电极中央电极 of rad

129、ius 0.05 cm is used to measure continuous radiation from a cobalt 化学元素）钴化学元素）钴(符号：符号：Co) unit with an exposure rate照射量率照射量率;照射率照射率 of 240 R/min with a collection voltage of 150 volts. Find the efficiency 效率效率of ion collection.Summary Saturation in ion chambersCalculation of efficiency of ion collect

130、ion-pulsed radiationCalculation of efficiency of ion collection-continuous radiationMeasurement of Radiation: Instrumentation&TechniquesPart TwoBME College Sherman Sheen(辛辛学学刚)The Physics of RadiologyOperational amplifiers 放大器放大器 Example. Suppose the amplifier of Figure has an open loop环、圈环、圈 gain o

131、f 105 and an input voltage of 1.0 volts is applied to the circuit. Let R = 1.0 M, and Rf = 10.0 M. Calculate the output voltage and the error voltage. Output voltage Error voltage Practical Devices for Measuring Radiation测量辐射的实用装置测量辐射的实用装置 1.Position the center of the ion chamber（室、房间）（室、房间） with it

132、s buildup cap at the point where one wishes to determine the exposure rate.2. Set the electrometer to measure current.3. Ground the sensitive lead of the electrometer with switch S and use the zero adjustment to null the reading. Open S and observe the leakage（泄漏）（泄漏） current, IL.4. Open S and turn

133、on the unit. A steady current reading should appear on the electrometer. Observe it for a few seconds and record its average value I. If I is large compared with IL the calibration（刻度、校正）（刻度、校正） is complete. If it is not, an attempt should be made to reduce the leakage current by carefully cleaning

134、insulation （隔离）（隔离）at the end of the cable.5. The exposure rate is Nx(IIL). 6. This should now be corrected for temperature and pressure A calibration （校准）（校准）can equally well be performed using the electrometer（静电计）（静电计） as a charge measuring device and the same answer should be obtained. One would

135、 proceed as follows: 1. Set the electrometer to measure charge.2. Ground S and null the device, open S.3. Turn on the unit for 10 s and measure the charge Q1.4. Ground the electrometer and readjust the zero, open S.5. Turn on the Unit for 70 s and measure a charge Q2.6. The Charge produced in the io

136、n in 1 min is Q2-Q1.7. Measure the leakage QL in 1 min with the machine off. It should be negligible（可以忽略的）（可以忽略的） compared to Q2-Q1. If it is not, clean the insulator（绝缘体）（绝缘体）. Guarded Construction1、the central electrode（中心电极）（中心电极）, as before, is imbedded in a good insulator、insulator is covered

137、with a thin layer of graphite（石墨）（石墨） and surrounded by a metal braid（编织、辫子）（编织、辫子）、covered by a sheath（护套）（护套） of insulation and another metal braid、finally covered by a rubber（橡胶）（橡胶） sheathCondenser冷凝器冷凝器 Chambersconducting layer of carbon on the inside of the hollow空的空的 insulator, the outer meta

138、l shield that is connected to the conducting layer of carbon on the inside wall of the ion chamberthe Victoreen R-meter 维克多林维克多林伦琴伦琴计计Townsend BalanceQCV Farmer dosimeter Types of Ion Chambers and application ABSOLUTE DOSIMETRY precisely known calibration factor a stable ion chamber Farmer type dosi

139、meter BUILDUP组合组合 MEASUREMENTS测量值、尺寸测量值、尺寸 the dose计量计量 to the surface of the skin thin walled chamber BEAM PROFILE MEASUREMENTS explore the edges of a beam cylindrical圆柱形圆柱形 ion chamber of small diameter 直径直径DOSE TO PERSONNEL全体全体 the condenser type STRAY RADIATION MEASUREMENTS condenser types with

140、high sensitivity and big volume体积体积LEAKAGE relevant errors in measurementsSTEM IONIZATION ISOTROPIC RESPONSE MONITORS CORRECTION FOR INVERSE 倒转倒转SQUARE LAW 二乘法二乘法Summary Operational amplifiersPractical devices for measuring radiationTypes of ion chambersstructureprocedureprinciplesClassification and

141、 errorMeasurement of Radiation: Instrumentation&TechniquesPart ThreeBME College Sherman Sheen(辛辛学学刚)The Physics of Radiologysolid state detectorsthe diode二极管二极管Short response timeEnormous dynamic rangeHigh sensitivityFlexible formsThermoluminescent Dosimetry (TLD) PRECISION OF TLD热至发光剂量计热至发光剂量计 AND

142、DOSE RANGE MATERIALS FOR TLD USES OF TLD-CLINICAL DOSIMETRY PERSONNEL MONITORING DOSE CALIBRATION SERVICES Chemical Dosimetry A is the change in absorbance at following a dose D to the ferrous亚铁亚铁 sulphate 硫酸盐硫酸盐 is the molar磨碎的磨碎的 extinction消灭消灭 coefficient系数系数 of the ferrous ion is the density of

143、the solution in kg/m3 G is the yield in number per 100 eV Example. It is required to determine the average dose to a sample of water in a complexly shaped radiation container near a cobalt source. This is most easily done using the Fricke dosimeter. The container is filled with Fricke solution and e

144、xposed. A sample of the well-mixed irradiated 照耀照耀solution is then placed in a quartz石英石英 cuvette试管试管 of 2 cm path length and its absorbance measured against the stock solution at 304 nm. Suppose the measured absorbance is 0.360. Calculate the dose.Film as a Dosimeter radiant 辐射的辐射的energycrystals 晶体

145、晶体of silver bromide溴化物溴化物latent潜在的潜在的 imageFile developedfilm fixednegative film resultsareas that have been exposed to x rays appear darkDirect Measurement of Absorbed Dose The Calorimeter 热量计热量计Summary of Calibration Procedures Exposure Rate Determinationsa.Select a suitable treatment applicator涂药

146、器涂药器 or reference field size (for example 10 by 10 cm) and direct the beam in such a way as to avoid scattering 散射散射from nearby objects.b. Select filter过滤器过滤器, tube current (mA), and voltage (kV) and determine the half-value layer for these settings of the machine.c. Select a suitable practical dosi

147、meter that has an exposure calibration factor traceable to a standardization laboratory (see section 4.09) for the half-value layer of the radiation beam to be measured. The ionization chamber should be one that has been designed specifically特别地特别地 for the energy of radiation being measured. It may

148、be necessary to interpolate 篡改、插入篡改、插入between two calibration factors to obtain the required one.d. Fasten the dosimeter in a clamp夹紧夹紧 so that its position is accurately known and can be reproduced for repeated readings. The center of the sensitive volume of the ion chamber should be at the center

149、of the field and even with the end of the treatment cone if there is one, or else at the reference distance chosen for the calibration. Sometimes this is not possible, in which case an inverse square correction will have to be madee. Set the timer to an appropriate value, turn on the machine, and br

150、ing it to the operating point selected in b. Open the shutter快门快门, or in the case of a cobalt钴钴 unit simply turn the beam on. If the ion chamber is operated as an exposure rate measuring instrument, its reading can now be taken directly. If it is to be operated as an exposure meter, timer, settings

151、should be chosen so that a set of readings are obtained at both relatively high scale readings (say about 3/4 scale) and relatively low scale readings. The exposure rate may then be obtained by taking differences of sets of readings to determine the slope of the reading versus time curve.曲线曲线 Severa

152、l sets of readings should be averaged to give M/ t, the reading per unit time. Alternatively, since many computers and calculators are equipped with “least squares routines常规常规,” it is convenient to take a series of readings Mi at times t extending across the range of the dosimeter and determine the

153、 slope, M/ t, of the M versus与。相对与。相对 t line. This latter procedure gives information about the precision of determining this slope; it can also give information about the shutter timing error.f. During the exposure, for an x ray machine it may be necessary to adjust either the kV or mA. If this is

154、not possible the average tube current and voltage over the time of the exposure should be recorded.g. Measure temperature and pressure. The exposure calibration factor as issued by the standardization标准化标准化 laboratory is valid only for the temperature and pressure stated by them. It is usually 22oC

155、and 101.3 kPa but this should be confirmed.h. The corrected exposure rate is:where M/t is the average uncorrected exposure rate as obtained in paragraph e, f is the SSD稳态分布稳态分布, x is the distance from the SSD to the center of the chamber, P and T are the pressure and temperature of the gas in the io

156、n chamber when the measurement is made, and Tx is the temperature for which the calibration factor, Nx, applies.i. A number of other small corrections may be required. Efficiency of ion collection and the problems of leakage, stem ionization are discussed. A dosimeter should also be checked for cons

157、tancy of sensitivity, and if it has changed since the calibration was performed, allowance must be made. Some instruments are equipped with a device containing a long-lived radioactive isotope for this purpose. Alternatively, careful measurements of a cobalt unit can be used. j. These procedures, ca

158、refully carried out, should allow an output calibration for the conditions measured, to an accuracy of better than 2.5%（I7).Determination of Absorbed Dose in a Phantom幽灵、幻影幽灵、幻影 The phantom should be clamped夹紧夹紧 to the treatment unit or located in such a way that its position can be reproduced for r

159、epeated measurements and the distances from the source to the ion chamber should be known with a precision of at least 2 mm An appropriate phantom must be chosen. These procedures, carefully carried out, should yield an absorbed dose determination in the phantom to an accuracy of approximately 2.5 S

160、ummary Solid state detectorsthe diodeThermoluminescent网络访问失败，暂无汉英互译结果网络访问失败，暂无汉英互译结果 dosimetryChemical dosimetryDirect measurement of absorbed dosecalorimeterFilm as a dosimetryRadiobiologyPart OneBME College Sherman Sheen(辛辛学学刚)The Physics of Radiologyfour Rs the repair of sublethal damagerepopulat

161、ion by surviving cells in the irradiated tissuesredistribution of cells throughout the division cyclereoxygenation of hypoxic cellsInitial EventThe Passage of the Charged Particles EFFICIENCY of RADIATION DAMAGE TRACKS of CHARGED PARTICLES DISTRIBUTIONS IN SPACE of ENERGY RELEASES LINEAR ENERGY TRAN

162、SFER (LET) the electron tracks 0.25 keV/m an alpha particle 250 keV/m SPECTRUM OF LET VALUES velocity charge IMMEDIATE RADIOCHEMICAL EFFECT Production of Solvated Electrons and RadicalsDependence of Radiation Damage on LET the radiobiological equivalent (RBE) the relative efficiency of killingASSAYS

163、 FOR PROLIFERATIVE CAPACITYSURVIVAL CURVES COLONY ASSAY METHODIN VITRO IN VIVO ASSAYS spleen-colony method Limiting dilution assayIn situMATHEMATICAL ASPECTS OF SURVIVAL CURVES SINGLE HIT SURVIVAL CURVE The mean lethal dose (D0) is the dose required to reduce the population of entities from any valu

164、e N to 0.37 N MULTI-TARGET SINGLE HIT SURVIVAL CURVE THERAPEUTIC RATIO where D2 is the dose that leads to serious complications in 50% of the patients D2/D1and D1 is the dose that gives tumor control inthe same % of patients. RADIOBIOLOGICAL EQUIVALENT (RBE) RBE =Dose from standard radiation to prod

165、uce a given biological effectDose from the test radiation to produce the same biological effectCELL CYCLE AND RADIOSENSITIVITY Summary four Rs EFFICIENCY of RADIATION DAMAGE TRACKS of CHARGED PARTICLES IMMEDIATE RADIOCHEMICAL EFFECT ASSAYS FOR PROLIFERATIVE CAPACITYSURVIVAL CURVES MATHEMATICAL ASPEC

166、TS OF SURVIVAL CURVES THERAPEUTIC RATIO RADIOBIOLOGICAL EQUIVALENT (RBE) CELL CYCLE AND RADIOSENSITIVITY RadiobiologyPart TwoBME College Sherman Sheen(辛辛学学刚)The Physics of RadiologyFRACTIONATION the total dose, the number of fractions, the dose per fraction, and the overall treatment time ISORESPONS

167、E CURVES THE OXYGEN EFFECT oxygen - a sensitizing agent The oxygen enhancement ratio (OER) ISOEFFECT CURVES AND NOMINAL STANDARD DOSE (NSD) the number of fractions Nthe overall time TTime Dose and Fractionation Factors(TDF) a series of time, dose, fractionationTDF factors:The Oxygen EffectEXAMPLES O

168、F THE APPLICATION OF RADIOBIOLOGY TO RADIOTHERAPY optimum treatment for a given tumor or type of tumor in patients High LET Radiation and the Oxygen EffectCHOICE OF FRACTIONATION SURVIVAL OF PATIENTS SUMMARY OF THE APPLICATION OF RADIOBIOLOGY TO RADIOTHERAPY SUMMARY OF THE APPLICATION OF PHYSICS TO RADIOLOGY