1. A method for segmenting a sheet object represented in an image generated using radiation imaging modality, comprising: identifying a plurality of elements in the image, respective elements associated with a value; for a first element of the plurality of elements: selecting a first plurality of neighboring elements in spatial proximity to the first element to define a first neighborhood and a second plurality of neighboring elements in spatial proximity to the first element to define a second neighborhood; computing a constant false alarm rate (CFAR) score for the first element, the CFAR score determined by comparing the value associated with the first element to a statistical measure for the first neighborhood; computing a topological score for the first element, the topological score determined by comparing the value associated with the first element to respective values associated with elements comprised within the second neighborhood; and labeling the first element as being associated with the sheet object when the CFAR score is within a first specified range and when the topological score is within a second specified range.