Home -> Law Blog Directory -> Patent Law Blogs -> Patently Obvious

Patent Law

: Patently Obvious

Preambles as Limitations

By Jason Rantanen

By Jason Rantanen

American Medical Systems, Inc. v. Biolitec, Inc. (Fed. Cir. 2010)
Panel: Bryson (author), Dyk (dissenting), and Prost

It may come as no surprise that the law on whether claim preambles can serve as limitations is unclear.  The Federal Circuit is aware of this issue, and at least one judge suggests that it may be time for the court to address this issue en banc.

The patent in this case, No. 6,986,764, relates to technology for vaporizing tissue using laser radiation.  The invention can be used to treat Benign Prostatic Hyperplasia, a condition in which growth of the prostate gland restricts the passage of urine out of the bladder and through the urethra.  By vaporizing or ablating some tissue, the size of the prostate is reduced, thus reducing bladder outlet obstructions.  Although laser radiation was known in the art, various problems were associated with its use.

The inventors of the '764 patent determined that by using high "volumetric power density" (a high amount of energy delivered to a given volume of tissue) they could produce increased vaporization efficiency while minimizing one of the problems associated with the procedure, residual coagulation.  The patent is directed to various methods and devices for achieving this high volumetric power density by manipulating variables such as wavelength, output power, beam quality, irrigant composition, and distance between the optical fiber and the tissue.

The dispute on appeal hinged on whether the preamble constituted a limitation.  Claim 31 is representative of the method claims. (The apparatus claims are similar, but recite "[a]n apparatus for photoselective vaporization of tissue.")  It recites:

A method for photoselective vaporization of tissue, comprising:

delivering laser radiation to a treatment area on the tissue, the laser radiation having a wavelength and having irradiance in the treatment area sufficient to cause vaporization of a substantially greater volume of tissue than a volume of residual coagulated tissue caused by the laser radiation, wherein the delivered laser radiation has an average irradiance in the treatment area greater than 10 kiloWatts/cm2 in a spot size at least 0.05 mm2.

During claim construction, the district court determined that the preamble phrase "photoselective vaporization" was a "fundamental characteristic" of the invention, and construed the term to mean "using a wavelength that is highly absorptive in the tissue, while being absorbed only to a negligible degree by water or other irrigant."  Based on this construction, the court granted summary judgment in favor of the accused infringer.

On appeal, the majority disagreed, concluding that the preamble phrase "photoselective vaporization of tissue" does not limit the claims of the '764 patent.  The court first noted the limited circumstances in which the preamble may limit claim scope:

?Generally,? we have said, ?the preamble does not limit the claims.?  Nonetheless, the preamble may be construed as limiting ?if it recites essential structure or steps, or if it is ?necessary to give life, meaning, and vitality? to the claim.? A preamble is not regarded as limiting, however, ?when the claim body describes a structurally complete invention such that deletion of the preamble phrase does not affect the structure or steps of the claimed invention.?  If the preamble ?is reasonably susceptible to being construed to be merely duplicative of the limitations in the body of the claim (and was not clearly added to overcome a [prior art] rejection), we do not construe it to be a separate limitation.?  We have held that the preamble has no separate limiting effect if, for example, ?the preamble merely gives a descriptive name to the set of limitations in the body of the claim that completely set forth the invention.?

Slip Op. at 8-9 (internal citations omitted).  After rejecting a prosecution history-based argument and the argument that the preamble phrase provided a necessary antecedent basis, the court determined that the phrase "does not embody an essential component of the invention":

Instead, the term ?photoselective vaporization? is simply a descriptive name for the invention that is fully set forth in the bodies of the claims....The bodies of the asserted apparatus claims (claims 63-64) describe a structurally complete device, including a laser adapted to deliver ?radiation at a wavelength and irradiance . . . sufficient to cause [tissue] vaporization[.]? The bodies of those claims identify the covered wavelengths by function (?sufficient to cause vaporization?), and nothing in the claim language suggests that the term ?photoselective? further limits those wavelengths.

Slip Op. at 10 (internal citations omitted).

Judge Dyk disagreed.  After first noting the confusing and unclear nature of the court's jurisprudence on this issue, he suggested that the court should dispense with the current articulation and instead apply the rule that preambles always limit claims:

It seems to me that a rule recognizing that all preambles are limiting would make better sense and would better serve the interests of all concerned. There is, after all, little to be said in favor of allowing an applicant, in the claim drafting process, to include material in the claims that is not binding. If patentees are allowed to include material in the claim definitions that is not bind-ing, patentees can suggest or imply one position before the U.S. Patent & Trademark Office (?PTO?) to secure allowance of the patent on the theory that the preamble is limiting and another, inconsistent position in infringe-ment litigation on the theory that it is not limiting. Principles of fairness thus dictate that the patentee should be required to clearly define the claimed inven-tion?s scope. By creating a uniform rule that all pream-bles are limiting, we would ensure the patentee has the burden of drafting a patent that avoids confusion as to the scope of the claims....Neither the Supreme Court nor our court sitting en banc has ever addressed the preamble limitation issue. I think the time may have come for us to eliminate this vague and confusing rule.

Dissent at 3-4.  He then turned to the issue of whether the preamble phrase in this case limited the scope of the patent, and concluded that it did based on the prosecution history and what he viewed as a definition of the term in the Summary of the Invention.  He also disagreed with the majority that the district court's construction would be inconsistent with the specification. 

Full post as published by Patently Obvious on September 13, 2010 (boomark / email).