Innovation is in our genes. 1 Siemens Medical Solutions Molecular Imaging What are SPECT basics?

Innovation is in our genes. 2 Siemens Medical Solutions Molecular Imaging Anger camera  Hal O. Anger invented the scintillation camera in 1958  Established basic design:  NaI(Tl) crystal  PMT array  Position weighted signals Hal O. Anger

Innovation is in our genes. 3 Siemens Medical Solutions Molecular Imaging Overview PULSE HEIGHT ANALYZER POSITION SIGNALS ENERGY SIGNAL XYZ Image Display COLLIMATOR NaI(Tl) Crystal PMT ARRAY

Innovation is in our genes. 4 Siemens Medical Solutions Molecular Imaging Scintillation camera components Detector  NaI(Tl) crystal  Photomultiplier tube (PMT) array  Analog-to-digital converters (ADCs) Collimator  Low energy  Medium energy  High energy  Axial shields (coincidence imaging)  Pinhole

Innovation is in our genes. 5 Siemens Medical Solutions Molecular Imaging Scintillation camera components Computer(s)  Acquisition  Processing  Acquisition & processing  Physicians viewing Patient Table  Pallet  Accessories

Innovation is in our genes. 6 Siemens Medical Solutions Molecular Imaging Nal(TI) Scintillator  Sensitive material for gamma ray detection  Large rectangular (40 x 50 cm), thin (9.5 mm) crystal*  Converts gamma ray energy into visible light (Total absorption of a 140 keV gamma ray yields 5000 photons)  Fragile: Sensitive to trauma and temperature changes

Innovation is in our genes. 7 Siemens Medical Solutions Molecular Imaging Nal(TI) Crystal Advantages  85% 140 keV  Moderate energy resolution 140 keV)  Moderate cost Disadvantages  Hygroscopic (requires hermetic seal)  Limiting component in count rate performance (200 nSec scintillation decay time)

Innovation is in our genes. 8 Siemens Medical Solutions Molecular Imaging PMT array FOV 3" PMTs 2" PMTs 30 x 40 cm x 55 cm PMT Cross Sections PMTs are arranged in a close-packed array to cover the crystal surface Side View Circular Hexangonal Square

Innovation is in our genes. 9 Siemens Medical Solutions Molecular Imaging Analog position electronics Weighted Sum Total Sum Position Signal (x or y) Energy Signal (Z) Normalization Normalized Position Signal (x or y) X/Z Y/Z Position-based Signal Weights Pulse Height Analyzer

Innovation is in our genes. 10 Siemens Medical Solutions Molecular Imaging POSITION SIGNALS ENERGY SIGNAL PULSE HEIGHT ANALYZER X Y Z Image Display COLLIMATOR NaI(Tl) Crystal PMT ARRAY 1 Y X

Innovation is in our genes. 11 Siemens Medical Solutions Molecular Imaging Collimation  Purpose: To project gamma ray distribution onto the detector  Basic design  Distance performance  Spatial resolution vs. count sensitivity

Innovation is in our genes. 12 Siemens Medical Solutions Molecular Imaging Collimator design 25 mm 1.2 mm Collimators are fabricated from lead. Gamma rays that hit the septa are absorbed. Image forming aperture of the scintillation camera. Limiting component in spatial resolution & count sensitivity.

Innovation is in our genes. 13 Siemens Medical Solutions Molecular Imaging Collimator performance Count sensitivity  ~ 1/5,000 gamma rays are transmitted  Requires short holes with large diameters  Inverse relationship with resolution Spatial resolution  mm 10 cm  Requires long holes with small diameters  Distance dependent

Innovation is in our genes. 14 Siemens Medical Solutions Molecular Imaging Spatial resolution Dependence on source to collimator distance 5 cm 10 cm 15 cm 20 cm 25 cm 30 cm

Innovation is in our genes. 15 Siemens Medical Solutions Molecular Imaging Energy correction  Corrects for the difference in energy responses within and between PMTs  Digitize local spectra 64 x 64 locations)  Set local photopeak windows  Event must fall within local window Before energy correction After energy correction

Innovation is in our genes. 16 Siemens Medical Solutions Molecular Imaging Linearity correction Event location is estimated as x’,y’ New location x = x’ + Dx’ y = y’ + Dy’  Image a known rectangular hole pattern  Calculate x & y correction offsets  Interpolate values over entire field Before linearity correctionAfter linearity correction

Innovation is in our genes. 17 Siemens Medical Solutions Molecular Imaging Linearity correction Correcting the mispositioning of events (spatial linearity) has a profound effect on field uniformity. Before correctionAfter correction

Innovation is in our genes. 18 Siemens Medical Solutions Molecular Imaging Uniformity correction After energy and linearity corrections are performed, residual non- uniformities are corrected using a reference flood image. The high count reference flood image is used to regionally weight events. Energy & linearity correction Energy, linearity & uniformity correction

Innovation is in our genes. 19 Siemens Medical Solutions Molecular Imaging Scintillation camera performance specifications  Field uniformity (2% - 4%)  Intrinsic spatial resolution ( mm)  System spatial resolution at 10 cm (8-12 mm)  Energy resolution (9-10%)  Multi-energy window spatial registration (< 2 mm)

Innovation is in our genes. 20 Siemens Medical Solutions Molecular Imaging Spatial resolution Ideal point Image of point with real system pixels Count profile FWHM  Specifies amount of image blur  Quantified by the full-width-at-half maximum (FWHM) of the point or line spread function

Innovation is in our genes. 21 Siemens Medical Solutions Molecular Imaging Clinical Applications Planar & SPECT  Cardiac  Whole-body bone  Renal  Gastric  Hepatobiliary  Thyroid  Pulmonary  Brain

Innovation is in our genes. 22 Siemens Medical Solutions Molecular Imaging Acquisition types  Static  Dynamic  Whole-body  SPECT  Gated SPECT  Dynamic SPECT  Whole-body SPECT  Coincidence imaging

Innovation is in our genes. 23 Siemens Medical Solutions Molecular Imaging SPECT Reconstruction Algorithms  FBP (Filtered Back Projection)  Iterative reconstruction (MLEM, OSEM)  2D  3D

Innovation is in our genes. 24 Siemens Medical Solutions Molecular Imaging Iterative reconstruction process If the correct physical model for the collimation is used in estimating the projections, then the feedback of the iterative process drives the convergence with implicit recovery of resolution. Enhancement filtering of projection data is not required. Estimated Reconstruction VolumeAcquired (measured) ProjectionsEstimated Projections Estimate Projections Compare Projections Update Image Estimate

Innovation is in our genes. 25 Siemens Medical Solutions Molecular Imaging Bone SPECT comparison FBP Flash 3D 2D - OSEM e.cam 3/8” Hx: 36-year-old female. Indication staging for osteosarcoma

Innovation is in our genes. 26 Siemens Medical Solutions Molecular Imaging Myocardial perfusion SPECT FBP Flash 3D 2D Iterative

Innovation is in our genes. 27 Siemens Medical Solutions Molecular Imaging GATED SPECT Aufsummierte Datensatz Gates Gate 7 Gate 8 Gate 1 R-Wave Gate 1 Gate 2 Gate 3Gate 4 Gate 5 Gate 6 R-R interval

Innovation is in our genes. 28 Siemens Medical Solutions Molecular Imaging Clinical software  Organ specific software (cardiac, renal, gastric, pulmonary, brain, etc.)  Cardiac quantification software  Cedars Sinai QGS, QPS, QBS  4D-MSPECT (Univ. of MI)  Emory Cardiac Toolbox  3D display software  Image fusion software  CT-based attenuation correction

Innovation is in our genes. 29 Siemens Medical Solutions Molecular Imaging Physician Review Schedule Acquisition Processing Administrative Data Data Aquisition Quality Control Automatic Reconstruction Automatic Processing Data Display HARDCOPY Activity Printing Innovative Workflow Concept SYNGO e.soft

Innovation is in our genes. 30 Siemens Medical Solutions Molecular Imaging Fully Automated Data Distribution Archiving Printing e.station OEM Workstation Workflow Complete PACS e.soft Administrative Data Data Aquisition Quality Control Automatic Reconstruction Automatic Processing Data Display HARDCOPY Activity SYNGO