Exxim Computing Corporation. Source data


	Source two-dimensional projections (views). Formats and representation on the disk Input projection representation Input projections are represented by files (one file per projection) using arrays of 16-bit integers or 32-bit floats. Input values are assumed to contain data pixel by pixel (u-coordinate), row by row (v-coordinate). U-axis is the axis, which is perpendicular to the axis of rotation. Typical logged attenuation projection Detector size and pitch Every input X-Ray image (input projection) are characterized by its size and pixel resolution. This information is typically available in detector documentation Typical intensity projection Intensity and logged attenuation Input projections may contain intensity or logged attenuation values. Intensity projection is 16-bit integer data array (file) containing a digitized signal, which corresponds X-Ray sensor exposure in every detector pixel. In many cases X-Ray sensor output is calibrated against gain (bright field) and zero-level (dark field) uniformity. Logged attenuation projection is 32-bit float point data array (file) containing values that correspond X-Ray attenuation along every particular ray hitting every particular sensor (detector) pixel. Supported formats Signed/unsigned values and MAC standard (big endian) are supported. A projection file may have a header or may be header-less. COBRA does not support extracting any parameters from the headers. Input data have to be comprehensively described in a parameter file.

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 input projections

PARTAG_DETSIZEU

Defines: Projection size in pixels in horizontal direction (perpendicular to the axis of rotation)
Value type: integer
Default value: 512

PARTAG_DETSIZEV

Defines: Projection size in pixels in horizontal direction (parallel to the axis of rotation)
Value type: integer
Default value: 512

PARTAG_DETPITCHU

Defines: Projection element size (pixel size) in mm in horizontal direction (perpendicular to the axis of rotation)
Value type: float
Default value: 1.0

PARTAG_DETPITCHV

Defines: Projection element size (pixel size) in mm in vertical direction (parallel to the axis of rotation)
Value type: float
Default value: 1.0

PARTAG_TRANSPOSED_PRJ

Defines: If set to 1 then projection files contain transposed projections
Value type: integer (can be 0 or 1)
Default value: 0

PARTAG_INPUTHEADERLEN

Defines: Projection file has a header. The length of the header (in bytes) is defined by this tag
Value type: integer
Default value: 0

PARTAG_INPUTISUNSIGNED

Defines: If set to 1 then projection files contain unsigned 16-bit integers
Value type: integer (can be 0 or 1)
Default value: 0

PARTAG_INPUTREQSWAP

Defines: If set to 1 then projection files contains big-endian 16-bit integers
Value type: integer (can be 0 or 1)
Default value: 0

PARTAG_INPUTLOGGEDFLOAT

Defines: If set to 1 then projection files contain logged attenuation data
Value type: integer (can be 0 or 1)
Default value: 0

PARTAG_PRJSTARTFROM

The projection counter starts from this number
Value type: integer (0-255)
Default value: 0

PARTAG_SRCDATAPATH

Defines: Source data folder (folder where files with input views are located)
Value type: character
Default value: The folder where the current xxm file exists

OPTTAG_PRJNAMEFORMAT

Defines: Format string for source file in C-syntax (projection name convention)
Value type: character
Default value: raw.%04i

Source two-dimensional projections (views). Formats and representation on the disk

Typical logged attenuation projection

Typical intensity projection