how to calculate area of tumor in mm^2 from the segmented image??

i have read paper for finding area and applying threshold which is as shown below: i did Area= sum(p(:)) instruction for summing all white pixel from the final image.kindly provide suggestions how to proceed to get the final equation from attachment'

Answer 1

[meghna meghna]

[r,c]=size(image);%image =detected tumor

count=0;

for i=1:r

for j=1:c

if image(i,j)==1

count=count+1;

end

end

end

defect_area=count*0.0055;

[Karan Gandhi]

Can you please tell me why would you multiply 0.0055 with count????