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Geometry Calibration for High Resolution Small Animal Imaging Vi-Hoa (Tim) Tran Thomas Jefferson National Accelerator Facilities. Rotating SPECT Gantry. slider. heavy duty rotation disk. pinhole detector. AOR. parallel detector. Gamma Cameras. optical tracking CCD cameras.
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Geometry Calibration for High Resolution Small Animal ImagingVi-Hoa (Tim) TranThomas Jefferson National Accelerator Facilities
Rotating SPECT Gantry slider heavy duty rotation disk pinhole detector AOR parallel detector Gamma Cameras optical tracking CCD cameras
Geometry Calibration To determine the spatial relationship between the coordinate systems of the rotating detectors and the objects
Calibration Phantom with 3 Point Sources pinhole detector 360 degree acquisition AOR Co-57 parallel hole detector
Pinhole Projections Over 360 Degrees Transaxial direction (u) measured predicted axial motion (v) Axial direction (V) Transaxial motion (u)
Bequé’s Calibration Model (2003) The detector and object coordinate systems are not aligned y y v z z x x u v u
slider ideal case: rigid body heavy duty rotation disk Normal ray B pinhole detector AOR AOR A possible cause A real case: flexing/rotation parallel hole detector radial movement C z0 axial movement
A Model of Detector Motion v Normal Ray z f pinhole d z
Extension To Bequé’s Model g=z.sin(+ξ) sinusoidal axial motion
measured before and after correction predicted w/o correction predicted w/ correction axial motion
Improved tracking for both pinhole & parallel hole collimators
Summary • Prediction errors due to flexing gantry • Modeling of detector movement • Extension to Bequé’s calibration model • Prediction errors minimized