how can ignore the other circle in the below image and extract the markers only

i want extract the circle on the markers only , this is the code i use

%extract all frames of the video 
a=VideoReader('walk.avi');
for img = 1:a.NumberOfFrames;
    filename=strcat('frame',num2str(img),'.jpg');
    b = read(a, img);
    imwrite(b,filename);
end

I = imread('frame11.jpg')
Ibw = im2bw(I);
Ibw = imfill(Ibw,'holes');
Ilabel = bwlabel(Ibw);
stat = regionprops(Ilabel,'centroid');
imshow(I); hold on;
for x = 1: numel(stat)
  plot(stat(x).Centroid(1),stat(x).Centroid(2),'ro');
end 
grid on;
axis on;
hAx=gca;% make the y cordinate not flip
ytk=hAx.YTick;
hAx.YTickLabel=max(ytk)-ytk;

[KSSV]

Get the pixel value at each circle and check which one equals to white pixel.

[Mustafa Alhandhali]

how, can you do it for me please