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Methods
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A is the ROIs image and Aij is a certain pixel in that image. M is the number of entries in
horizontal direction and N is the number of entries in vertical direction. The image has MN
pixels. Once it has been deformed, an overlay for the measured phase image can be created.
The overlay can mark visual areas or boundaries between adjacent visual areas.
5.4 Quality Measure
To evaluate the quality of the identified visual areas obtained by using mrFindBorders, it is
useful to visually inspect the results. The user interface has been designed so that visual in-
spection is possible for different stages of the process and for different kinds of results. In ad-
dition, a quantitative quality measure is helpful. This section describes how it was defined and
what its properties are.
When the wedge energy component is calculated, a difference measure between the de-
formed wedge atlas image and the corresponding measured phase image is calculated. This
leads to a useful measure for the matching procedure because at this stage, it is the aim to de-
form the atlas so that it matches the measured image. However, one task of mrFindBorders is
to find the visual areas, respectively the boundaries that segregate them. For this, the phases in
the atlas are not important. Only the derived regions of interests and their boundaries are of
interest. It is therefore useful to define a quality measure that is only based on the ROIs that
represent the visual areas.
As mentioned in section 4.7, reference visual-area ROIs (gold standard) need to be de-
fined in order to calculate the quality of the visual-area ROIs that were found by mrFindBor-
ders. The gold standard is a set of visual-area ROIs that are expected to be correct. They can
be created by manually modifying (correcting) results that were found by mrFindBorders.
Then, latter can be compared with the gold standard, i.e., a numerical quality that tells how
similar the two sets of visual-area ROIs are, can be calculated.
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