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PET MR Biomedical Engineers Perspective

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  • 1. Nicholas Plaxton, MD, MS Emory University October 11, 2013PET/MRI BIOMEDICAL ENGINEERS PERSPECTIVE

2. First PET/MR 1990s small-animal imaging Multiple scans - decrease radiation exposureSan Raffaele Scientific Institute, Milano, Italy 3. Clinical PET/MR Development Success of PET/CT in 2000s Better anatomic correlation Improved attenuation correction techniques PET/CT limited in soft tissue contrast Brain lesions Genitourinary cancers Breast and colon cancers PET/MR could provide superior soft tissuecontrast 4. Major Challenge in PET/MR MR high field magnets interfere with PETphotomultiplier tube electrons 5. Types of PET/MR Scanners Developed PET/CT and MR in attached rooms withpatient shuttled in between PET and MR gantries arranged along axis with patient handling system between Integrated PET and MR 6. PET/CT and MR Suite GE prototype 2010 installed in Zurich, Switzerland PET/CT with patient shuttled into next room MR Utilizes CT for attenuation correction Cheaper Can upgrade and use components independently 7. Hybrid PET/MR Phillips Gemini 2012 coplanar PET TF withplatform rotation into MR Minor shielding on PET Installed in NYU, NY and Geneva, Switzerland PETMRIMAGMA Nov 21, 2012 8. Integrated PET/MR PET and MR imaged simultaneously withoutmoving patient Excellent registration of PET and MR images No time required to shuttle patient Less physical space needed Need to overcome electronic interference 9. Electronic Conflict Solution Replace photomultiplier tubes avalanche photodiode detectors (APD) sold-state semiconductor detectors i.e cadmium zinc tellurideDigiRad Corp. 10. Integrated Prototype PET/MR Developed by Siemens in 2006 Utilized standard MR scanner PET insert placed in MR bore Multiple institution research project University of Tubingen, Germany Forschungszenrum Julich, Germany Massachusetts General Hospital, Boston, MA Emory University, Atlanta, GA 11. BrainPET by Siemens PET insert ring into MR 35.5cm diameter ring with 2.5mm LSO crystals Coupled with Avalanche Photo Diodes (APD)MAGMA Nov 21, 2012 12. PET Insert SchematicMAGMA Nov 21, 2012 13. First PET/MR Image in 2006 66 y/o female with Siemens BrainPETJ Nucl Med 2012; 53:19161925 14. Siemens Biograph mMR 2010 Siemens developed whole body PET with3-T MR with a 60 cm gantry (Biograph mMR) FDA approved for purchase in 2011MAGMA Nov 21, 2012 15. Cross section of Biograph mMRMAGMA Nov 21, 2012 16. Institutions using Biograph mMR Mass. General Hospital - Boston, MA NIH - Bethesda, MD Washington University, St. Louis, MO UNC, Chapel Hill, NC UPMC, Pittsburgh, PA NYU, New York City Mt. Sinai Univ, NYC Univ Hospital Stonybrook, NYC 17. Benefits of PET/MR Soft-tissue characterization Lower ionization than PET/CT Questionable benefit for oncology patients MR breast imaging has high sensitivity butlow specificity, FDG PET has high specificity but low sensitivity, therefore benefit combining PET/MR 18. Disadvantages of PET/MR Attenuation correction with MR Image truncation, RF coils Longer acquisition and multiple sequences TOF can shorten PET acquisition time MR sequences would need to be limited 2 to 5 sequences per study takes ~ 30 min Total time of 1 hour still shorter than separate studies Incapable with metal artifacts (pacers or implants) Claustrophobia CT superior for lung imaging 19. Types of Attenuation Correction Template based Atlas based Direct Segmentation Sequence Segmentation 20. Template Attenuation Suitable for brain imagingMAGMA Nov 21, 2012 21. Atlas Attenuation Representative CT data set created CT data set is deformed to fit patient MR info Pseudo CT created for attenuation 22. Direct Segmentation Attenuation Standard T1-weighted MR images Bone and air have similar intensity on T1MAGMA Nov 21, 2012 23. Direct Segmentation Attenuation Neural network used to distinguish tissues Large computation powerMAGMA Nov 21, 2012 24. Sequence Segmentation Attenuation Ultrashort echo time(UTE) sequences Developed for very short spinspin relaxation times Distinguish bone from air Seconds to acquire each bed positionMAGMA Nov 21, 2012 25. Oncologic Applications PET/MR Liver and bone metastases Brain tumors Prostate cancer Gynecological cancers Breast cancer Head and Neck cancers 26. Liver Metastases Rectal NETAm J Nucl Med Mol Imaging 2012;2(4):458-474 27. Brain Tumors Fluorodeoxyglucose (FDG)metabolism Fluoromisonidazole (FMISO)tissue hypoxia Fluorothymidine (FLT)cellular proliferation Fluoroethyltyrosine (FET)amino acid transportJ Nucl Med 2012; 53:19161925 28. Cervical Cancer with Lymph NodeAm J Nucl Med Mol Imaging 2012;2(4):458-474 29. Recurrent Peritoneal CarcinomatosisAm J Nucl Med Mol Imaging 2012;2(4):458-474 30. Breast CancerNYU Lagune 31. Non-Oncologic Applications Neurology Dementia Stroke Epilepsy Cardiology Atherosclerotic inflammation 64 Cu-DOTA-vascular endothelial growth factor Ventricular remodeling 32. AlzheimhersJ Nucl Med 2012; 53:19161925 33. Stroke PenumbraJ Nucl Med 2012; 53:19161925 34. EpilepsyJ Nucl Med 2012; 53:19161925 35. Take Home Message PET/ MR emerging cutting edge technology Applications being developed alongside novelradiotracers PET/MR will not replace PET/CT 36. Summer Fun in Atlanta 2013