Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Introduction to PET Dmitri Soloviev, PhD, MRSC radiochemist, Wolfson Brain Imaging Centre UNIVERSITY OF CAMBRIDGE Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Positron Emission Tomography • PET - Diagnostic method in Nuclear Medicine – imaging of cancer – organ perfusion and metabolism – receptor studies • Tomograph (PET camera) – creates image of radioactivity distributed throughout the human body – detects g-radiation from positron annihilation • Radiopharmaceutical (PET radiotracer ) – delivers radioactive isotope to the tissue • Positron Emitter (PET isotope) – decays by emitting positrons • Cyclotron – produces positron-emitting isotopes 50 year-old male with colon CA 720 MBq FDG, 162 min p.i. Data courtesy of NC PET Imaging Center, Sacramento, USA Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich History of PET • • • • • • 1953 – first positron emission clinical images (15O; 68Ga). G.Brownell, S. Aronow, W.Sweet, Massachusets General Hospital 1971 – first computed tomographic images ( PET). D.Chesler, PC I , MGH 1973 – first 32-detector ring PET camera, Robertson, Brookhaven National Laboratory 1974 – first Human PET camera, M.Phelps, E.Hoffmann, Washington University. 1977- first [18F]FDG synthesis and images. A.Wolf, J.Fowler, BNL; D.Kuhl, A.Alavi, M.Reivich, L.Sokoloff, University of Pennsylvania. 1985- first block detector. M.Casey, R.Nutt, CTI [18F]NaF Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Principle of PET • Patient is injected with a radiotracer • Blood distributes the radiotracer in the body • Cells and tissues accumulate radiotracer • Isotope decays by positron emission, two opposite g-quants fly out of the body • Camera detects gamma-irradiation of 511 keV in coincidence mode at 180° • Computer reconstructs the image of radioactivity distribution slice by slice • PET - tomographic image of radiotracer distribution in the patient`s body FDG Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Positron mode of decay Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Classical PET isotopes Isotope T 1/2 min Type of Decay Daughter Isotope % b+ b+ Energy MeV 15O 2.04 b+ 15N 99.89 2.75 13N 9.96 b+ 13C 100 2.22 11C 20.39 b+ 11B 99.76 1.98 68Ga 67.63 b+ 68Zn 89.1 2.92 18F 109.69 b+ 18O 96.9 1.66 Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Why use positron emission ? • Positron produces always two opposite g at 180°of 511 KeV energy • Detection in coincidence mode allows to: – localise precisely place of radiotracer decay – decrease the influence of background radiation (randoms) – quantify radioactivity in the region of interest • High image resolution – is limited to the distance of positron flight in the tissue (0.6-6 mm, depending on b+ energy) g2 g1 Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Isotope 18F Main clinical PET applications T1/2 Radiotracer Action Application [18F]FDG Glucose metabolism Oncology, cardiology, neurology Bone activity Oncology Oxidative metabolism Fatty acid synthesis Aminoacid utilisation Cardiology Brain tumours 110 [18F]fluoride [11C]acetate 11C 20 [11C]methionine Oncology 13N 10 [13N]ammonia Heart perfusion Cardiology 15O 2 [15O]water Brain perfusion Psychology, psychiatry, neurology Dmitri Soloviev Global Imaging Summit Workshop X [18F]FDG October 2007, Zurich Use of PET-Tracers in Europe per year Use of PET tracers [15O]H 2O [13N]NH 3 [11C]Meth. 18 [ F]F-DOPA 18 [ F] F15 [ O]Butanol [15O]H2O [11C]Flumac. [11C]Acetate [11C]Raclopr. [15O]CO very important most important FDG H2O, NH3 11 [ C]HED 13 [ N]N 2 11 [ C]Diprenorph. [11C]Choline [11C]MDL100.907 [11C]Hyd-Trypt. [11C]SCH23390 [11C]PK1195 important Methionine DOPA, F- 18 [ F]Thymidine 18 [ F]Uracil 11 [ C]M-Spip. [11C]N AIB [11C]Thyr. [11C]WAY100.635 [18F]UdR [18F]MPPF less used 11 [ C]CO2 11 [ C]DOPA [18F]MISO [18F]ESP G.J.Meyer, Wart 17.Sept.1999 1 10 100 1000 10000 100000 Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Example: regional blood flow studies with 15O •Studied: action of odours and pheromones on women’s brain •PET used to measure regional cerebral blood flow changes •average image of 5 subjects •Radiotracer diffuses in the brain following the changes in blood flow •2 min half-life allow repeated injection in the same subject •[15O]butanol as a radiotracer •Other modalities (fMRI) are available to measure rCBF •Requires repeated injections for reasonable statistics •2 min half-life is too short: only fast chemistry, and on-line delivery •cyclotron needs to be close to the patient •number of studies with oxygen-15 goes down Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Example: [18F]fluoride and FDG 18F- fluoride 18F FDG Http://www.crump.ucla.edu/lpp Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Example: [11C]acetate Carbon-11-Acetate PET imaging in recurrent prostate cancer: Initial experiences at the University of Vienna S. Wachter et al. 11C EANM 2002 Congress, August 31 September 4, 2002 University of Vienna, Austria Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Transmission and Emission Scans Rotating external g- source (68Ge) • Transmission scan: – uses external source of radioactivity – helps to improve image quality – quantifies absorption of g-rays in the patient's body – calibrates detectors – is a supplementary tool • Emission scan: – – – – uses g from positron emitting radiotracer works in coincidence mode serves to build a PET image is a true PET scan g2 g1 511 KeV g- rays from injected radiotracer Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Modern PET developments: fusion of images • PET + CT • PET+ MRI PET image shows activity of the cells – functional or metabolic imaging. Very poor anatomical structure. CT or MRI show very fine anatomical structures – morphological imaging. Combining function with morphology provides additional information. University of Vienna Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Modern PET developments: PET/CT scanners PET/CT : •combination of two cameras •morphology & function •CT used for transmission scan •better quality of PET •more sensitive •more accurate localisation •synergy of two modalities Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Modern PET developments: PET/SPECT, microPET scanners Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Modern PET developments Mobile PET Fast PET Emission scan time: 27 min ECAT ACCEL High resolution PET ECAT HR+ Advance NXi Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich g2 g1 Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Modern PET developments: microPET/MRI scanners UNIVERSITY OF CAMBRIDGE Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Modern PET developments: microPET/MRI scanners Brookhaven National Laboratory Rat Conscious Animal PET (RatCAP) Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich Clinical PET statistics (as of 2004) Country Justified need: 1 PET camera per 1 million of habitants 1 Cyclotron can deliver FDG to 5-8 PET cameras nearby or 2-4 cameras up to 1000 km distance Number of PET installed Need in PET % of needed USA 600 294 204% Belgium 19 10 198% Sweden 4 7 196% Switzerland 7 4 175% Germany 80 56 143% Spain 28 24 116% Denmark 4 4 100% Finland 2 2 100% Italy 25 47 53% Portugal 2 4 50% Great Britain 13 42 31 % France 11 35 31% Russia 6 145 4% Dmitri Soloviev Global Imaging Summit Workshop X October 2007, Zurich References • A HISTORY OF POSITRON IMAGING. Gordon L. Brownell, 1999 Physics Research Laboratory, Massachusetts General Hospital ftp://deas-ftp.harvard.edu/pub/tuan/pethis/pethis.pdf • THE HISTORY OF POSITRON EMISSION TOMOGRAPHY. Ronald Nutt, PhD, CTI PET Systems, Knoxville, TN. Molecular Imaging and Biology, Vol. 4, No. 1, 11–26. 2002 • Let’s play PET: http://www.crump.ucla.edu/lpp • Nuclides 2000: An electronic chart of the nuclides. Version 1.00. European Communities 1999.
