The PTO traditionally has employed an ex parte reexamination procedure. At any time during the term of the patent, any person may request reexamination by the PTO of any claim of a patent on the basis of prior patents or printed publications cited under 37 C.F.R. 1.501. The request must be in writing and must be accompanied by payment of a reexamination request filing fee as set forth in 37 C.F.R. 1.20(c). If the request raises a substantial new question of patentability affecting any claim of the patent, reexamination is commenced. The same ex parte procedures that apply to initial examinations govern traditional reexamination. Patentees often invoke reexamination themselves, seeking to insulate their patents from late-surfacing prior art by cutting back the claims. Potential infringement