has_metric_category has relation has_units has value type intensity unit total ion current matrix ID free metric single run based metric imaging metric total ion current image The most general measure of signal level. Because the values retain their spatial arrangement, the metric additionally exposes spatially structured acquisition faults, such as intensity gradients across a long acquisition, dropped scan lines, or striping arising from the raster pattern. A value of 0 is distinct from null, which indicates a position that was not acquired. The total ion current (MS:1000285) of each spectrum, arranged as a matrix in which the row and column indices correspond to the y and x pixel coordinates of the acquisition grid. Positions that were not acquired are reported as null. MS:4000228 MS