Computer-implemented method and corresponding apparatus for identifying subcellular structures in the non-chemical staining mode from phase contrast tomography reconstructions in flow cytometry

A computer-implemented method for identifying a subcellular structure of interest of a cell analysed by flow cyto-tomography, which method comprises the following steps:

• i) retrieving a 3D Refractive Index (RI) tomogram of said cell;
• ii) identifying a single voxel supposed belonging to said subcellular structure of interest;
• iii) defining a reference cloud of voxels (CR) having as the center said single voxel in ii), wherein said reference cloud of voxels (CR) means a group of adjacent voxels belonging to a cube having a side of ε pixels;
• iv) calculating a statistical similarity between the reference cloud of voxels and all non-overlapped investigated clouds of voxels (CI) of the same size by using a statistical similarity test, wherein said statistical similarity test can be a hypothesis test on mean value;
• v) grouping the non-overlapped investigated clouds of voxels having simultaneously higher statistical similarity and spatial proximity among them and respect to the references cloud of voxels;
• vi) removing statistical outlier clouds of voxels erroneously grouped in v), wherein said statistical outlier clouds of voxels are clouds of voxels that differ significantly from other non-overlapped investigated clouds of voxels grouped in v);
• vii) repeating steps iii) to vi) by setting as the reference cloud of voxels a sub-group of voxels randomly selected from the grouped non-overlapped investigated clouds of voxels of vi) with a halved value of ε;
• viii) repeating K times steps iii) to vii) to create K estimations of the said subcellular structure of interest;
• ix) adding up all the K estimations in viii) to create a tomogram of occurrences, wherein said tomogram of occurrences is the tomogram of occurrences wherein each voxel can take integer values within [0, K], according to how many times that voxel has been included within an estimation of said subcellular structure of interest;
• x) defining a threshold value for each voxel belonging to the tomogram of occurrence for which values greater than said threshold value are assigned to said subcellular structure of interest.