Mgr. Hedvika Goliášová Nuclear medicine 040903NuclExplIvymike.jpg 1.Basic Principles 2.Detection of radiation 3.SPECT, PET Nuclear Medicine lIn Vitro methods lIn Vivo methods lTherapy The Structure of Atoms l lNucleus: (nucleons)- protons (p), neutrons (n) lShell: electrons (e) l lAtom description: lAtomic number – Z (p) lNeutron number- N (n) lMass number (nucleons) – A (p+n) lIzotop (Z), izobar (A), izomer (same Z+A; different energy) Radioactivity and radionuclides lRadioactivity is effect, when atom´s nuclei of definite element spontaneously change to nuclei of other element, during which time is emitted high energy radiation. l l lNuclei with this property are radionuclides lSubstances with radionuclides are radioactive emitter lRadioactivity as quantity is number of nuclei´s disintegrations in given quantum of substance per time lInternational units is Becquerel – Bq (Curie: 1Ci=3,7.1010 Bq) lMass activity: Bq/mg lSpecific activity: Bq/ml lPhysical half-life is defined as the time required for the number of radioactive atoms in a sample to decrease by exactly one half l - physical, biological, effective lA(t) = Ao . e -λ. t = Ao . 2,7183 - (0,693/T½) . t lE is Euler´s Number Radionuclides and Radiations 1 lAlfa emission •emission of Alfa particles ( He nuclei) is common in elements with the higher atomic number – 82. •High radiation, but short radius (cca 0,03 mm) •Only for therapy - 226Ra Radionuclides and Radiations 2 lBeta emission: lBeta- - electron + antineutrino lBeta+ - positron + neutrino lElectron Capture – neutrino + photon X l lBeta emission – continuous spectrum – particles with different energy, low ionizing effect – higher radius lBeta- - 131I – radius 2,4mm. 32P, 99Mo lBeta+ - reaction positron with electron – positron annihilation 511 keV – PET - 11C lElectron Capture – 67Ga Radionuclides and Radiations 3 lGamma emission •following the alfa or beta emission •radiations that originate in the excited unstable atomic nucleus- line spectrum •essential gamma emitters don‘t exist in nature– preparation 99mTc from 99Mo, • Radioaktivita.gif X-RAYS (RTG) EMISSION lbraking radiation lSpring from braking free-flying electrons in heavy metals lcontinuous spectrum l lcharacteristic X-Rays lSpring from cascading electrons between atom´s shells lline spectrum l 201Tl, 125I X-ray x gamma emission lSource lX-ray: atomic shell lGamma emission: atomic nucleus l lSpectrum lX-ray: continuous lGamma emission: line l Interactions with matter lDirectly ionizing emission – kinetic energy of particles inductive ionization or/and excitation in matter l lAlfa particles – strong ionization lBeta particles lbeta- - braking radiation, dependence on atomic number lbeta+ - positron annihilation l lIndirectly ionizing emission– uncharged particles induce emission other particles, which inductive ionization or/and excitation in matter lElectromagnetic radiation lGamma, X-rays emission lUncharged particles lneutrons lPhotoelectric effect, Compton scattering, pair production, nucleus fotoeffect l l Radionuclides lNatural – cca 100, without usage in NM lSynthetic - necessary artificially changed neutron or protons number – shelling nuclei fit elements will evoke nuclear reaction, form daughter nucleus in excited state - radioactive Radioisotopy-vyroba.gif Radionuclides II lCharacteristic: lPhysical half-life – 99mTc - 6,03 h lCharacter of decay – 99mTc – isomeric transition lCharacter of emission – 99mTc – gamma emission lEnergy of emission – 99mTc - 140 keV l Detection of radiation lDetector •Radiation shield, collimator •Detector •Evaluation device • lType of detectors: •Gas-filled – ionization chambers, Geiger Müller counters, proporcional counters •Scintillation – organic (in vitro), anorganic •Solid-state – research • • Ionization chambers lGas-filled chamber with positive and negative electrodes. Radiation evokes in gass ionization and excitation, ions are high voltage oriented on electrode. Linear dependence between radiance and current. lHas low detection sensitivity Geiger – Müller Counters lGas detector with high voltage, that the speeds electrons, avalanche ionisation rise – strong discharge. lInterrupt discharge – voltage drop and quenching gas lFor monitoring workplace l Scintillation Detectors lRadiation evokes in material scintillation – flashing lights lThalium Activated Sodium Iodide and LSO l Scintillation spectrum Without scattering environment With scattering environment Solid-state detectors lFor Nuclear Medicine - In Research lVery good energy resolution, but long „dead time“ and low sensitivity lGermanium as solid-state detector l Interference qualities detection •Detection sensitivity •Time resolution – „dead“ time •Spatial resolution •Energy resolution •Volume dependence – in vitro •Geometry metering – in vitro •Metering errors (systematic, random) •Radioactivity in background •Better from picture- •„ hot" lesion than „ cold„ •surface placing lesion than at a depth Principle dosimeters lFilming dosemeter l Photographic detection ionizing radiation – blackening film density is proportional to density ionizing – quantity of absorbed energy lThermoluminescence dosemeter l Radiation in material will excite electrons to the higher energy level; after warm up will electrons return back and gained energy release in flashlight Dosimeters II lFilming Dosimeter Shielding material: •Plastic •Metals: Copper, Lead •Free space Instrumentation lInstrumentation for in vivo detection l lScintillation probe lGammagraf lGamma Scintillation Camera, PET Camera lHybrid systems – SPECT-CT, PET-CT Scintillation probe lwithout visual information lTime histograms activities above examinate region lTo examination kidney – renography; metering activities above thyroid gland – 131I Gammagraph lHistorical system l Source- detection- supporting strut- register Scintillation camera lAnger´s camera – for the first time used 1958, same principle to this day lMakes it possible to display distribution of radiopharnaceutical in body lDetector, scoring and imaging and recorder system lSome or more detectors lAnalog or digital l Scintillation camera II. Source- detection- comparator+kicksorter-image Scintillation camera III. Siemens E.CAM PB051063 Scintillation camera IV. lDetector: lCollimator, scintillation crystal, photomultiplier l l lCollimator: lDefine the geometric field of the crystal and specifically define desired direction of photons to reach crystal l • Effect on sensitivity and spacial resolution Scintillation camera V. lScoring, imaging and recorder system •photopeak window •Photon position analysis, attenuation correction •use filters improving image quality /simple filters, filtered backprojection, iterative reconstruction/ •List mode x frame mode •Gated mode •Region of interest - ROI • Positron emission tomography – PET camera •Pair of annihilation photons is detected •20 000 detectors in ring, 30 rings •Detector materials: BGO (bismuth germanate) or LSO (luteciumortosilicate) •Electronic collimation – opposite coincidence window •Radionuclids for PET • short half-life – necessity of cyclotron. • 18F – half-life cca 2 hours, 18F-FDG •Interference: Compton scattering, false coincidence •better sensitivity and spacial resolution than SPECT • PET camera II lPositron annihilation PET camera III. Hybrid systems •Camera system consist of two independent systems – scintigraphy camera and CT camera • •Most often SPECT-CT and PET-CT • •Fusion images from both systems – information on function organ gained scintigraphy methods are inosculation with anatomical images from CT Princip of CT (Computed tomography) lX-Rays Helical CT - x-ray tube rotation and patient table shift Fusion of pictures C:\Dokumenty\PET\Prezentace\nmpet_clinical\fam2.jpg l ADT22 l ADT20A l ADT21A PB091071 SPECT/CT Symbia Exploring techniques lStatic scintigraphy lDynamic scintigraphy l lPlanar imaging lTomography imaging l lQualitative classification lQuantitative classification l l Static scintigraphy lScan one picture lInformation on distribution radiopharmaceutical in body lPartial information about function examinate organ lSkeletal system, thyroid imaging G:\Obrazy\Plice\obr2a.PCX Static scintigraphy -lungs Dynamic scintigraphy lScan pictures in predetermined time period lFollowing radiopharmaceutical kinetics lIt is possible obtain waveform activities radiopharmaceutical in given areas in time – next evaluation and calculation functional parameters lPossibility synchronizing studies lDynamic scintigraphy kidney, liver F:\renal\renal1.bmp Planar scintigraphy lTwo - dimensional display lDetectors are in one position lgeneral picture is real – it is possible trace him e.g . on oscilloscope lSumming integrator principle – all tissue layers sum to one picture – overlapping layer lSumming background too – decrease contrast AJV01 Tomography scintigraphy •SPECT and PET •Scan by one or more detectors from many positions (full circle-360°) •Resulting picture is reconstructed – calculated from impulses of all positions •Makes it possible to display only one layer tissues, without disturbing influence surrounding layers – increasing contrast 3-5x •Three-dimensional vision – extract information on depth • Tomography scintigraphy II lReconstruction techniques lBackprojection lIterative reconstrustion l Benefits and disadvantages SPECT lBenefits: •Increasing contrast 3-5x •Information on third proportion – depth of lesion •Don´t sum one layer with others layers • lDisavantages •Field uniformity – generate noise-rings •Attenuation – reduction radiation from deeper layers •Increased noise – is freshening at reconstruction, as far as 10x •Worse spatial resolution – detector mostly cannot be as near to bodies, as with planar scan, resolution SPECT cca 15 mm, planar scan cca 10 mm •Necessary longer time scan PET lAs well three-dimensional vision as with SPECT l30x higher sensitivity than SPECT lBetter spacial resolution than SPECT 5-6 mm lPossibility exact quantification of radiofarmaceutical lQuantitative assesment flow and capacity blood in tissue, metabolism oxygen, glucose l PET camera EXACT.jpg 00068B2A Macintosh HD ABA78158: l Pratt_demo.tif 00068D78 Macintosh HD ABA78158: Thank you for your attention J Good luck at exam!