【醫(yī)學課件】核醫(yī)學物理基礎(BasicPhysicsofNuclear)

1、Basic Physics of Nuclear Zhang Yongxue核醫(yī)學物理基礎9/28/20221Basic Physics of Nuclear ZhanKLMAtomneutrons protonsnucleon +electrons -Configuration of AtomAtomNucleusProtonQuark10-8 cm 10-12 cm 10-13 cm 20, ratio of n:p neccesary more than will be stable.9/28/20224Stable & radionuclideStable nStable & radi

2、onuclideP83的核素，核力不能與質子間的斥力保持平衡，故全是不穩(wěn)定的放射性核素。 P83的核素，核Proton rich nucleiNeutron rich nucleiZ=N05010015050100PROTON NUMBERNEUTRON NUMBERNeutron-proton ratio with line nuclear stability9/28/20226Proton rich nucleiNeutron richNuclear decayAlpha()decay Alpha particles is a helium nuclei consisting of 2 p

3、rotons and 2 neutrons.4He9/28/20227Nuclear decayAlpha()decay Characteristic of alpha particle粒子實質上是He原子核，衰變發(fā)生在原子序數(shù)大于82的重元素核素。粒子的速度約為光速的1/10，即萬km/s，2s繞地球周。在空氣中的射程約為3-8cm，在水中或機體內為0.06-0.16mm。因其射程短，一張紙即可阻擋但粒子的電離能力很強。9/28/20228Characteristic of alpha particBeta decayEmit particles and capture orbital el

4、ectrons.To be a companion to increase or decrease of atomic number,but the mass number of the new nuclei is the same. Including , and electron capture. Velocity of particle is 200 thousand km/s in vacuum.Penetrability is more than alpha particle.9/28/20229Beta decayEmit particles and- decayEmit part

5、iclesNeutron rich nucleiNeutron protonThe mass number of new nuclei is the same as the parent nuclei,atomic number increase 1n p+ +Q9/28/202210- decayEmit particlesn decayEmission of particleNeutron poor nucleiA proton to neutron transformationArtificial radionuclidep n+e+189F188O + + + 0.66MeV9/28/

6、202211 decayEmission of particlElectron capture,ECAn orbital electron is captured to form a neutron.Neutron poor nucleiA proton to neutron P+e- nCharacteristic X-rayAuger electron9/28/202212Electron capture,ECAn orbital Gamma decay and internal conversionGamma decay may be a part of another decay pr

7、ocess,such as ,EC or -Metastable to stable state transition and emission of electromagnetic(transition)New nuclei mass and proton is the same,but energy changed Internal conversion and Internal conversion electronInternal conversionelectronray9/28/202213Gamma decay and internal conve Characteristic

8、of rayGamma ray is photonNo electric chargePenetrability is more than charged particleLow ionization ability9/28/202214 Characteristic of rayGamma rComparison of three decayalpha decaybeta decaygamma decayMass changedyesnonoProton changedyesyesnoEnergy changedyesyesyes9/28/202215Comparison of three

9、decayalphaThe law of nuclear decay 放射性核素是不穩(wěn)定的，它要自發(fā)地發(fā)生衰變而變成新元素的核。放射性原子核并不是同時衰變的，對于某一個原子核而言，何時衰變是各自獨立沒有規(guī)律的，但對于某一種原子核的群體而言，它的衰變是有規(guī)律的，即原子核數(shù)目隨時間增長按指數(shù)規(guī)律減少。9/28/202216The law of nuclear decay 放射性核素Decay constant()衰變常數(shù)：某種放射性核素的核在單位時間內自發(fā)衰變的幾率；它反映該核素衰變的速度和特性；值大衰變快，小則衰變慢，不受任何影響。9/28/202217Decay constant()衰變常數(shù)：某種放射性核素的The formula of decayDecay formula：Nt=Noe-tCharacteristic：不同的放射性核素有不同的Commonness：任何放射性核素的衰變，原子核數(shù)目隨時間增長按指數(shù)規(guī)律減少 tNlogNt9/28/202218The formula of decayDecay formHalf life 半衰期Physical half life，(T1/2) 在單一的放射性核素衰變過程中，放射性活度降至原來一半所需的時間；長者可達1010a，短者僅有10-10s。半衰期1.02 MeVPositron,