Introduction to SPECT & PET TBMI02 - Medical Image Analysis 2017

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1 Introduction to SPECT & PET TBMI02 - Medical Image Analysis 2017 Marcus Ressner, PhD, Medical Radiation Physicist, Linköping University Hospital Content What is Nuclear medicine? Basic principles of Functional Imaging with radioisotopes Basic principals of SPECT and PET Camera technology Image acquisition Image reconstruction Clinical applications 1

2 What is Nuclear Medicine? CT SPECT (or PET) Nuclear Medicine Functional imaging Visualization of physiological processes i.e study how the body works, not how it looks (anatomical imaging) Study a tracers way through the body Gives quantitative functional information 2

Glucos analog: 18 F FDG oraly injected inhaled Diagnostic imaging

3 Basic principle SPECT 99m Tc Radioactiv isotope Isotope PET 18 F 123 I 11 C 131 I 13 N 111 In 15 O Target molecule Tracer Salt analog: 99 Tc m HDP Glucos analog: 18 F FDG oraly injected inhaled Diagnostic imaging Illustration modified from Mehran M. Sadeghi et al. J Nucl Med 2010;51:51S-65S 3

Radioactive nuclides Instable nuclides that decays and emit its surplus energy by radiation Types of ionisation radiation: alfa( beta( gamma ( Radionuclides in nuclear medicin

4 Radioactive nuclides Instable nuclides that decays and emit its surplus energy by radiation Types of ionisation radiation: alfa( beta( gamma ( Radionuclides in nuclear medicin Photons within the energy range of kev Half life in the range hours Minimal emission of other ionising particles Stabilty in the chemical bond Easy chemical label procedures 4

Radionuclides in nuclear medicin 99m Tc 140 kev 6 h

Tumordiagnostics 11 C 511 kev 20 m Neuro imaging 13 N

5 Radionuclides in nuclear medicin 99m Tc 140 kev 6 h Various (almost all) 123 I 159 kev 13 h Adrenal glands, Thyroid 111 In 171, 245 kev 67,9 h Neuroendocrine tumors 18 F 511 kev 110 m Tumordiagnostics 11 C 511 kev 20 m Neuro imaging 13 N 511 kev 10 m Cardiac imaging 15 O 511 kev 2 m Hypoxia, Cardiac Hotlab 99m Tc generator 5

6 99m Tc eluate activity Production of PET radioisotopes Cyclotron 6

7 Cyclotron vid US 2015 PET/CT CYCLOTRON The Accelerator 14 7

8 Production of F O 18 F, p(p,n)n 16 8

9 Which Imaging Modality? ANTERIOR POSTERIOR Bone Scintigraphy Tracer: Sodium oxidronate Accumulates in active osteogenisis (bone metabolism) ANTERIOR POSTERIOR 9

10 Neuroendocrine tumors In 111 Octreotid SPECT Treatment response monitoring Somatostatin receptor imaging In 111 Octreotid SPECT Ga 68 DOTA-TOC PET 2 receptor types 5 receptor types 10

11 Gamma camera GE NM Discovery Gamma camera principles 11

12 The collimator Gamma detection Position X Position Y Energi Z 12

13 Energy resolution Peak energy Count rate Compton scatter Energy window ± 10% 140 kev Voltage pulse hight / Energy Energy window 13

14 X,Y and Z Y The Z-dimension is given by the pulse height -Y -X X Acquisition types Planar or Static Scanning Dynamic Time interval ECG tigger Tomographic 14

Radioisotope: Tc-99m The distribution of the radiotracer

15 Static acquisition Perfusionsscintigraphy of the lungs ANT POST WB scanning Tracer: Natrium oxidronate Radioisotope: Tc-99m The distribution of the radiotracer show the osteoblast activity, and blood perfusion of the bone tissue 15

60 1 sec images over the kidneys showing the

16 Dynamic acquisition A group of images taken at set time intervals e.g sec images over the kidneys showing the distribution of the radiotracer as a function of time. Dynamic acquisition 16

17 Distance - resolution FWHM Tomographic acquisition detector (projection) Planar images from different angles around the patient (projections) The same activity distribution renders different projections. object 17

18 Sinogram Projection data Original data Sinogram Sinogram Projection data Original data Sinogram 18

(FBP) Statistical Maximum Likelihood Expectation

19 Sinogram Projection data Data acq Sinogram Image reconconstruction Analytical Filtered Back Projection (FBP) Statistical Maximum Likelihood Expectation Maximization (MLEM) Ordered Subset Expectation Maximization (OSEM) 19

20 FBP - Forward projection view 1 view 2 view 3 Back projection view 1 view 2 view 3 Using 3 views Using many views 20

21 Back projection blurred by 1/r Back projection original 8 proj 16 proj 32 proj 64 proj 128 proj 256 proj 21

22 Filtered Back projection filtered view 1 filtered view 2 filtered view 3 Using 3 views Using many views Filtered back projection 8 proj 32 proj 128 proj 256 proj 22

23 Iterative reconstruction (MLEM) original projections BP original NO CHANGE estimate patient update (x ratio) FP Estimated projections Estimate Contrast recovery Contrast [%] iterations Noise [%] 23

24 Post filter FBP vs OSEM Advanced image processing. S. Ted Treves et al. J Nucl Med 2011;52:

25 Projection overview 3D Representation CBF examination with 120 projections 25

26 SPECT/CT Image Fusion Attenuation effects Reduction of the number of detected photons. Absorption Spread Depend on Photonenergy Density of tissues 26

27 Attenuation effects Water filled cylinder, well mixed. Transaxial image with intensity profile Count statistics Injected activity Image aquisition time More pulses less noise and better contrast 27

28 Antal pulser i bilden 5 s 1 x Aktivitetsmängd 30 s 6 x Aktivitetsmängd 300 s 60 x Aktivitetsmängd New technologies Natriumjodid (NaI) PM-tube Cadmium Zink Tellurid(CZT) Semiconductor Kan arbeta i rum 56 28

Semiconductor collimation Holes match CZT pixels Collimator to match semiconductor energies: 20 200 kev

29 Semiconductor collimation Holes match CZT pixels Collimator to match semiconductor energies: kev Semiconductor detectors: Higher signal-to-noise Better spatial resolution Better energy resolution 57 29

30 Dedicated heart cameras D-SPECT from Spectrum Dynamics Installed in Linköping summer 2013 Discovery NM 530c GE 59 Alcyone Technology with Lightspeed VCT Discovery NM/CT 570c Courtesy of University Hospital, Zurich, Switzerland 60 30

31 PET (/CT) Principle Radioactive isotope Address Tracer SPECT 99m Tc PET 18 F 123 I 11 C 131 I 13 N 111 In 15 O Tracers Fluorodeoxyglucose 31

32 Metabolic Imaging PET Pre-treatment Post-treatment Positron decay and annihilations (511 kev) + e - (511 kev) Radio nuclide 32

33 PET radioisotopes Radioisotope Half-life Energy (mean) C min 0.39 MeV N min 0.50 MeV O min 0.72 MeV F min 0.25 MeV Cu min 1.3 MeV Ga min 0.83 MeV Rb min 1.5 MeV The PET camera 33

34 Data acquisition 511 kev e+ e- 180 degrees 511 kev 34

35 Coincidence Positron annihilation Detection within coincidence window Energy within energy window Bild från Siemens Coincidence Philips 35

36 Coincidence Bild från Siemens Reconstruction FBP, OSEM r Data Acquisition Sinogram (raw data) Reconstructed Image 36

37 ToF Time of Flight ToF Improved SNR 37

38 SUV Standard Uptake Value C(t) (kbq/ml) SUV = Dose (kbq)/ Weight (kq) PET 3D MIP Image 38

39 PET/CT 39

Nuclear Medicine Intro & Physics from Medical Imaging Signals and Systems, Chapter 7, by Prince and Links

Nuclear Medicine Intro & Physics from Medical Imaging Signals and Systems, Chapter 7, by Prince and Links NM - introduction Relies on EMISSION of photons from body (versus transmission of photons through