Exxim Computing Corporation. Reconstructed Volume


	Reconstructed volume and field of view. Reconstructed data formats. Volume auto-detection In Cobra a reconstructed volume is represented by a set of files; each file contains a quadrangle cross-section through the scanned object (axial cross-section). In Cobra user has a full control of the reconstructed volume size, resolution (volume pixels, a.k.a. voxel size) and position in the space (controlled by coordinates with origin in the point where the axis of rotation is crossing the x-ray tube trajectory plane). Defined cube might be smaller, bigger or accurately correspond the field of view (FOV). The cube also can be non-coaxial with FOV cylinder. Parameters of reconstructed cube (including position offsets) can be automatically calculated; one just need to omit the corresponding tags in xxm parameter file or set them to –1. The reconstructed slices (files) can be saved in raw (no header 2-dimensional array of signed 16-bit integers ) or in DICOM format Reconstructed volume element size (voxel size) Reconstructed volume size Reconstructed volume center offset (translation of cube center from coordinate origin)

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.

Tags describing cube size and format

PARTAG_CUBESIZEX

Defines: Reconstruction volume size along X in pixels
Value type: integer
Default value: 512

PARTAG_CUBESIZEY

Defines: Reconstruction volume size along Y in pixels
Value type: integer
Default value: 512

PARTAG_CUBESIZEZ

Defines: Reconstruction volume size along Z in pixels
Value type: integer
Default value: 512

PARTAG_CUBEPITCHX

Defines: Volume element size (voxel pitch) along X, mm
Value type: float
Default value: 1

PARTAG_CUBEPITCHY

Defines: Volume element size (voxel pitch) along Y, mm
Value type: float
Default value: 1

PARTAG_CUBEPITCHZ

Defines: Volume element size (voxel pitch) along Z, mm
Value type: float
Default value: 1

PARTAG_CUBEORIGINX

Defines: Reconstruction volume center offset, relatively origin, along X, pixels (One can reconstruct an eccentric cube)
Value type: integer
Default value: 0

PARTAG_CUBEORIGINY

Defines: Reconstruction volume center offset, relatively origin, along Y, pixels (One can reconstruct an eccentric cube)
Value type: integer
Default value: 0

PARTAG_CUBEORIGINZ

Defines: Reconstruction volume center offset, relatively origin, along Z, pixels (One can reconstruct an eccentric cube)
Value type: integer
Default value: 0

PARTAG_DICOM

Defines: Volume file output format (0 – raw; 1 – uncompressed DICOM; 2 – compressed loss-less DICOM; 3 - compressed lossy DICOM)
Value type: integer
Default value: 0

Reconstructed volume and field of view. Reconstructed data formats. Volume auto-detection

Reconstructed volume element size (voxel size)

Reconstructed volume size

Reconstructed volume center offset (translation of cube center from coordinate origin)