Remove annotation

Hello,I'm developing an application aphometric signing in and I need to know how to remove a specific
type annotation(file_attach) to the document at runtime.
The annotations were first saved the  document and later wish I could erase just a specific annotation.
In the document there are other types of annotations, so I need to cancel own a particular annotation.
At the time of creation I used the code like myAnnot.setTitle  = "myTitle", hoping later to be able to seek and
clear, but I can not set the reference.
You can help me?
Thanks in advance for the help.