Geometry Calibration for High Resolution Small Animal Imaging Vi-Hoa (Tim) Tran Thomas Jefferson National Accelerator Facilities

heavy duty rotation disk slider pinhole detector AOR parallel detector Gamma Cameras optical tracking CCD cameras Rotating SPECT Gantry

Geometry Calibration To determine the spatial relationship between the coordinate systems of the rotating detectors and the objects

AOR 360 degree acquisition pinhole detector parallel hole detector Calibration Phantom with 3 Point Sources Co-57

Pinhole Projections Over 360 Degrees axial motion (v) Transaxial motion (u) measured predicted Transaxial direction (u) Axial direction (V)

Bequé’s Calibration Model (2003) v u z y x z y x v u   The detector and object coordinate systems are not aligned

heavy duty rotation disk slider pinhole detector AOR ideal case: rigid body real case: flexing/rotation radial movement axial movement AOR z0z0 parallel hole detector A B C Normal ray A possible cause

A Model of Detector Motion Normal Ray z d f v z pinhole

Extension To Bequé’s Model g =  z.sin(  +ξ) sinusoidal axial motion

measured predicted w/ correction predicted w/o correction axial motion before and after correction

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