Gantry geometry - xcist/documentation GitHub Wiki

The overall gantry geometry is by

cfg.sid = Source-To-IsocenterDistance_Millimeters;
cfg.sdd = Source-To-DetectorDistance_Millimeters;

The detector can be positioned slightly off-center relative to isocenter. This is specified by

cfg.col_offset = ColumnOffset_Columns;
cfg.row_offset = RowOffset_Rows;

which give the relative offset in the u and v direction respectively, in units of columns and rows.

This can be used to achieve quarter detector offset.

The lateral center of the detector, in units of columns, is

cfg.col_center = (1 + cfg.col_count)/2.0 - cfg.col_offset;

The longitudinal center of the detector, in units of rows, is

cfg.row_center = (1 + cfg.row_count)/2.0 - cfg.row_offset;

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