How to remove small portion in an image?

I am segmenting liver from CT data. Its 2d segmentation on multiple imaging. I trained my system using deep learning method. Now the results of segmentation are as follows...

I want to remove the circle parts from my image. I already tried bwareaopen() function from matlab. Using bwareaopen() function I got the whole image white. please help me.

Thanks

[KSSV]

If you have the locations of those highlighted images, cant you replace those pixel values with black?

[Ahmad]

I want to do automatically. sunkara manoj code working perfectly but now I need to smoothen the boundaries.

Answer 1

[sunkara manoj]

the result is a binary image but the part is extracted.

if true
I=imread('liver.png');
im = imclearborder(im2bw(I));
im_fill = imfill(im, 'holes');
s = regionprops(im_fill, 'Area', 'PixelList');
[~,ind] = max([s.Area]);
pix = sub2ind(size(im), s(ind).PixelList(:,2), s(ind).PixelList(:,1));
out = zeros(size(im));
out(pix) = im(pix);
imshow(out);  end

[Ahmad]

Thanks Sankara Manoj its work very well. But now i want to smoothen the borders. so if you have an idea so please share.

[KSSV]

How about using convexhull?

[Ahmad]

I never tried. I dont know the purpose of convex hull.