Selecting elements in an image based on area

[Samuel Setchell]

I am currently struggling to remove unwanted elements from a busy image. 
The elements are essentially incomplete halos, some of which are only half 
included in the image. Originally I wanted to use imfill.m 'holes' to fill in 
these elements and remove them, however this was not possible. Is there a way 
for separating these elements based on area form a binary? i.e. mask out all 
areas of ones that are connected that are greater than 400 pixels? Any help 
would be greatly appreciated.

Regards

Sam Setchell