Exxim Computing Corporation. Position Dependent Geometry


	Cone-Beam CT Scanner with non-uniform motion characteristics. Cone-beam scanner with non-uniform reproducible geometry and flat x-ray source orbit. Description by set of .bin files Cobra can reconstruct CT scans when a geometrical hardware setup gets different characteristics in every trajectory point. When x-ray orbit is flat then a comprehensive description can be made by a set of files representing distances, angular coordinate, detector tilt (pivot) and u-/v-offsets in every position of trajectory. A typical example of application is non- equiangular tube trajectory Reproducible geometry and non-flat x-ray source orbit Non-equiangular tube trajectory Cone-beam scanner with non-uniform reproducible geometry and non-flat x-ray source orbit Description by .gxm files Cobra can reconstruct CT scans when a geometrical hardware setup gets different characteristics in every trajectory point. When x-ray orbit is not flat then a comprehensive description can be made by a projective transform matrices associated with every position of trajectory.

Describing a reconstruction task

Within the COBRA reconstruction package, all input, output and intermediate data are kept on the hard disk. The user defines and controls the reconstruction task through a parameter file, a text file with extension .xxm. This file contains tags and assigned values, and describes the scanner hardware setup, input and output data characteristics and representation, and the chosen reconstruction method. Some of the reconstruction options are only accessible through SDK API’s. These are related to synchronization and control of in-line reconstruction (recon concurrent with acquisition), and the setup of COBRA’s working folders.

Describing non-uniform geometry

angle.bin

Values of angular source positions in degrees angle.bin is a binary file, no header, one 4-byte floating point per position Defaults to the value assigned in xxm parameter file if angle.bin is omitted.

uoffset.bin

Values of horizontal detector offsets (u-offsets) in pixels uoffset.bin is a binary file, no header, one 4-byte floating point per position Defaults to the value assigned in xxm parameter file if uoffset.bin is omitted.

voffset.bin

Values of vertical detector offsets (v-offsets) in pixels voffset.bin is a binary file, no header, one 4-byte floating point per position Defaults to the value assigned in xxm parameter file if voffset.bin is omitted.

SrcOrigDist.bin

Distance in mm between the X-ray source and the origin (rotation center) SrcOrigDist.bin is a binary file, no header, one 4-byte floating point per position Defaults to the value assigned in xxm parameter file if SrcOrigDist.bin is omitted.

OrigDetDist.bin

Distance in mm between the detector and the origin (rotation center) OrigDetDist.bin is a binary file, no header, one 4-byte floating point per position Defaults to the value assigned in xxm parameter file if OrigDetDist.bin is omitted.

HorTilting.bin

Angle in degrees of the detector tilt relative to its horizontal axis (u-axis). HorTilting.bin is a binary file, no header, one 4-byte floating point per position Defaults to 0 if this file is omitted.

VrtTilting.bin

Angle in degrees of the detector tilt relative to its vertical axis (u-axis). VrtTilting.bin is a binary file, no header, one 4-byte floating point per position Defaults to 0 if this file is omitted.

Pivoting.bin

Angle in degrees of the detector tilt relative central ray. HorTilting.bin is a binary file, no header, one 4-byte floating point per position Defaults to the value assigned in xxm parameter file if HorTilting.bin is omitted.

COBRA_Generic.gxm

Contains projective transform matrices. Each projective matrix defines the correspondence between each volume voxel and its projection (voxel’s “shadow”) on the detector. COBRA_Generic.gxm is a text file containing 12-element matrix in each row, one row per position Defaults to the value assigned in xxm parameter file if COBRA_Generic.gxm is omitted.

Cone-Beam CT Scanner with non-uniform motion characteristics.

Reproducible geometry and non-flat x-ray source orbit

Non-equiangular tube trajectory