RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM 1 LIP, Laboratório de Instrumentação e Física Experimental de Partículas, Coimbra, Portugal 2 ISEC, Instituto Superior de Engenharia de Coimbra, Coimbra, Portugal 3 IBILI-FMUC, Instituto Biomédico de Investigação da Luz e Imagem, Faculdade de Medicina da Universidade de Coimbra, Coimbra, Portugal 4 ICNAS, Instituto de Ciências Nucleares Aplicadas à Saúde, Universidade de Coimbra, Coimbra, Portugal 5 Departamento de Física da Universidade de Coimbra, Coimbra, Portugal M. Couceiro 1,2, P. Crespo 1,2, L. Mendes 3,4, N. Ferreira 3,4, R. Ferreira Marques 1,5, P. Fonte 1,2

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro Summary 1.Introduction to RPC-PET a.Brief PET overview b.RPC-PET vs. crystal PET 2.Spatial Resolution of Human Single-Bed RPC-PET a.Simulation Setup and Methods b.Characterization of Image Spatial Resolution in RPC-PET c.Results 3.Conclusions, and Acknowledgments

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro State of the art PET Scanners  Acquire several bed positions, to obtain a full body image  Costs time (money)  Increased injected activity (patient dose)  Discontinuous uptake signal (image quality degradation and loss of biological significance)  “Easy” image reconstruction 1.Introduction to RPC-PET Brief PET Overview

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro Full body PET Scanner  Full body image obtained in a single bed position, hence, a single acquisition  Saves time (money)  Reduced injected activity (patient dose)  Continuous uptake signal (image quality improved without loss of biological significance)  Inexistence of adequate image reconstruction algorithms, yet 1.Introduction to RPC-PET Brief PET Overview

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro RPC-PET is a Falloff of HEP into Nuclear Medicine (Blanco et al. NIMA 2003) Advantages  Inexpensive  Suitable for large area detectors, covering a large solid angle  Increased system sensitivity (Couceiro et al. NIMA 2007, Crespo et al. MIC 2009)  Increased position accuracy, allowing full 3D detection, minimizing gross parallax errors;  Excellent timing resolution of 300 ps FWHM for 511 keV photon pair, allowing TOF-PET Disadvantages  Much smaller detection efficiency: 20% to 50%.  No energy resolution, although energy sensitivity. Full-Body Human TOF-PET 1.Introduction to RPC-PET RPC-PET vs. Crystal PET

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 1.Introduction to RPC-PET System Sensitivity (according to NEMA NU ) P.Crespo et al, IEEE2009 MED.IMAG.CONF. M09–353

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 2. Spatial Resolution of Human Single-Bed RPC-PET Physical and instrumental effects considered Source Positron range Photon pair non-collinearity Instrumental Photon scatter in detector Compton electron propagation in glass Compton electron propagation in gap Readout granularity

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 2. Spatial Resolution of Human Single-Bed RPC-PET Simulation Setup and Methods Simulations performed with GEANT 4, release 9.2 Tomograph has a parallelepipedic shape, with 4 detection walls, each of them containing 20 RPC detectors (~2400x1000x10 mm), with 10 gaps (350  m thick) and glass resistive electrodes (200  m thick) Phantom is a sphere with 10  m diameter water core, surrounded by a 1990  m diameter PMMA shell, located at the center of Field Of View (FOV)

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 2. Spatial Resolution of Human Single-Bed RPC-PET Simulation Setup and Methods Source consists of a positron created at rest, uniformly distributed in the phantom core Perfect back-to-back photon emission provided by GEANT4, and photon non-collinearity provided by GATE Detection hit is considered when an electron reaches a gas gap Glass Plate Forward Gas Gap Backward Gas Gap Incident Photon Hit Hits

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 2. Spatial Resolution of Human Single-Bed RPC-PET Simulation Setup and Methods Recorded information (only for events giving rise to an electron hit):  Photon entry point in the scanner heads  Photon interaction point prior to electron extraction  Electron extraction point  Electron detection point (worst possible case) Incident Photon

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 2. Spatial Resolution of Human Single-Bed RPC-PET Characterization of Image Spatial Resolution in RPC-PET Data acquired in full 3D mode 3D data reduced to 2D transaxial slices by means of Single Slice Rebinning (SSRB) Z axis Z2Z2 Unscattered LOR Scattered LOR Central slice in image space Z1Z1

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 2. Spatial Resolution of Human Single-Bed RPC-PET Characterization of Image Spatial Resolution in RPC-PET 2D sinograms are constructed for each transaxial projection Image reconstructed from the 2D transaxial sinograms, by 2D Filtered Backprojection (FBP2D)

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 2. Spatial Resolution of Human Single-Bed RPC-PET Characterization of Image Spatial Resolution in RPC-PET

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 2. Spatial Resolution of Human Single-Bed RPC-PET Characterization of Image Spatial Resolution in RPC-PET

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 2. Spatial Resolution of Human Single-Bed RPC-PET Characterization of Image Spatial Resolution in RPC-PET

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 2. Spatial Resolution of Human Single-Bed RPC-PET Characterization of Image Spatial Resolution in RPC-PET Image reconstructed from 2D transaxial sinograms by Filtered Backprojection (FBP) Point Spread Functions (PSFs) taken at three perpendicular directions  Three highest points in PSF fitted with a parabola, to determine the maximum value  Left and right half maximum values determined by linear interpolation  Spatial Resolution computed by multiplying FWHM number of pixels by pixel size

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 3. Spatial Resolution of Human Single-Bed RPC-PET Results Photon Entry PointPhoton Detection Point 0.8X Y 0.9Z ~0.8MEAN~0.8 Image Spatial Resolution (  m)

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 3. Spatial Resolution of Human Single-Bed RPC-PET Results Electron Extraction PointElectron Detection Point (Worst Possible Case) 3.3X Y Z312 ~3.3MEAN~208 Image Spatial Resolution (  m)

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 3. Spatial Resolution of Human Single-Bed RPC-PET Results Electron Detection Point + Photon acolinearity XYZMEAN ~481 Image Spatial Resolution (  m)

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 3. Spatial Resolution of Human Single-Bed RPC-PET Results – Electron Readout Point Only DOIDOI mm BinningDOI mm Binning Mean = 2.1 mmMean = 1.4 mmMean = 0.8 mm

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 3. Spatial Resolution of Human Single-Bed RPC-PET Positron range C.S.Levin and E.J.Hoffman, Phys.Med.Biol. 44 (1999)781 Well studied FWHM  0.1mm to be convoluted with the PSF…

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro Conclusion 1.Detailed simulations suggest that RPC-PET will show a sensitivity advantage of more than 1 order of magnitude over current technology. May trigger a paradigm-shift in PET clinical use. 2.We studied the factors influencing the image spatial resolution of human single-bed RPC-PET a.Physics limitation (source + detector): ~ 0.44 mm FWHM b.Readout granularity (X,Y mm DOI): i.3.4 mm DOI: ~ 0.8 mm FWHM ii. 1mm XY mm DOI: ~ 1.4 mm FWHM iii. 2mm XY mm DOI: ~ 2.1 mm FWHM

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro Acknowledgments Portuguese Foundation for Science and Technology Advanced Computation Laboratory of the University of Coimbra

RPC February 2010 SPATIAL RESOLUTION OF HUMAN 3D RPC-PET SYSTEM M. Couceiro 2. Characterization of Image Spatial Resolution in PET (NEMA: SSRB, 2D-FBP) ● 2D-FBP (filtered backprojection) after sinogram construction |f sampling | / f Nyquist Gain (f)