# Neural Network Ensemble to Detect Dicentric Chromosomes in Metaphase Images
## 3 Experimental Results
### Preprocessing
#### 3.2.2 Morphological Filters  
The erosion filter consists of converting all the pixels of the image that are surrounded, in any of their eight neighboring pixels, by a pixel with a white value to white. On the other hand, the dilation filter consists of turning all the pixels of the image that are surrounded, in any of its eight neighboring pixels, by a pixel with a black value to black.  
Figure 5: Preprocessing techniques applied on example image. First row: original image. Second row: comparison between filter sizes for image 2 Gy-023. In this example, the thresholding technique (Spline) and the type of morphological filter (closing) have been kept constant. Third row: comparison between opening and closing morphological filters for image 2 Gy-023. In this example, the thresholding technique (Spline) and the filter size (3 × 3) were kept constant. Fourth and fifth rows: comparison between filter sizes for image 2 Gy-023. In this example, the thresholding technique (Spline) and the type of morphological filter (closing) have been kept constant.  
In addition, the opening filter consisted of the sequential application of an erosion filter and a dilation filter (in this order), while the closing filter consisted of the sequential application of a dilation filter and an erosion filter (in this order). While the opening filter was used to remove protruding elements, the closing filter was used to join elements separated by a narrow gap.  
On the other hand, the size chosen for these filters will eventually determine the proportion to which the image will be affected. In this experiment, opening and closing filters with filter sizes of \(2\times 2\), \(3\times 3\), \(4\times 4\) and \(5\times 5\) were applied and each combination was studied separately.  
After applying binarization, it was observed that in some chromosomes, gaps in the pixels had higher gray values when viewed in grayscale. In particular, this occurrence around the centromeres as well as the ends of the chromosomes (telomeres) could be problematic, since it might miss one of the centromeres of a dicentric chromosome, resulting in the erroneous interpretation of a dicentric chromosome as a false negative. In such scenarios, the opening filter proved to be useful by recovering the bonds between sister chromatids. However, in other cases, the opening filter caused the appearance of closing points between chromatids that are not real centromeres and could therefore be interpreted as a false positive by the model.  
On the other hand, the closing filter worked optimally in the opening of non-centromeric regions between sister chromatids that appeared as a product of binarization. However, in other cases, it removed centromeres from the chromosomes and could lead to the interpretation of false negatives by the model (see second row of Figure 5).  
With respect to filter size, the use of \(2\times 2\) size filters introduced very few noticeable changes in the images, while \(5\times 5\) size filters greatly distorted the chromosomes. The \(3\times 3\) and \(4\times 4\) filters introduced changes that varied between the two extremes (see fourth and fifth rows of Figure 5).  
As can be seen, each of the configurations introduced a number of advantages and disadvantages depending on the image quality and variations in chromosome morphology.