  United States Court of Appeals
      for the Federal Circuit
                ______________________

                  BRAIN LIFE, LLC,
                  Plaintiff-Appellant,

                           v.

                    ELEKTA INC.,
                  Defendant-Appellee.
                ______________________

                      2013-1239
                ______________________

   Appeal from the United States District Court for the
Southern District of California in No. 12-CV-0303, Judge
Cathy Ann Bencivengo.
                ______________________

                Decided: March 24, 2014
                ______________________

    PAUL ADAMS, The Adams Law Firm, of Albuquerque,
New Mexico, argued for plaintiff-appellant. Of counsel on
the brief were MICHAEL T. COOKE, JONATHAN T. SUDER,
and BRETT M. PINKUS, Friedman, Suder & Cooke, of Fort
Worth, Texas.

    THERESA M. GILLIS, Mayer Brown LLP, of New York,
New York, argued for defendant-appellee. With her on
the brief were THOMAS W. JENKINS and ERICK J. PALMER,
Mayer Brown LLP, of Chicago, Illinois.
                 ______________________
2                               BRAIN LIFE, LLC   v. ELEKTA INC.



Before O’MALLEY, BRYSON, and WALLACH, Circuit Judges.
O’MALLEY, Circuit Judge.
    Brain Life, LLC (“Brain Life”) filed suit against El-
ekta, Inc. (“Elekta”) alleging infringement of the method
claims of U.S. Patent No. 5,398,684 (“the ’684 patent”).
The district court granted summary judgment in favor of
Elekta, holding that Brain Life’s claim was barred on res
judicata grounds. See Brain Life LLC v. Elekta, Inc., No.
3:12–cv–303 (S.D. Cal. Jan. 31, 2013), ECF No. 43 (“Brain
Life II”). Brain Life appeals from that determination.
While we agree with Brain Life that neither claim nor
issue preclusion bars its claims, we find that the Kessler
Doctrine as announced in Kessler v. Eldred, 206 U.S. 285
(1907), precludes the majority of Brain Life’s claims.
Accordingly, we affirm-in-part and vacate-in-part the
district court’s judgment and remand for further proceed-
ings.
                      I. BACKGROUND
    In December 1997, Medical Instrumentation Diagnos-
tics Corporation (“MIDCO”) sued Elekta alleging that
Elekta’s GammaKnife, GammaPlan, and SurgiPlan
products infringed the ’684 patent (“MIDCO Litigation”).
See Brain Life II, ECF No. 43 at 2. The ’684 patent is
entitled “Method and Apparatus For Video Presentation
From Scanner Imaging Sources.” The ’684 patent is
directed to both a method and apparatus for generating a
video image from a variety of separate scanner imaging
sources such as a computerized axial tomography image,
a nuclear magnetic resonance image, and an X-ray.
See ’684 patent at col. 6, l. 25 – col. 7, l. 25. According to
the ’684 patent, in the past, images acquired by various
scanner imaging sources were not standardized in a
common format, and there was no existing method for
comparing and using the images obtained from various
scanners. ’684 patent at col. 4, ll. 31–34. The inventors of
the ’684 patent purported to solve this problem by teach-
BRAIN LIFE, LLC   v. ELEKTA INC.                          3



ing how to use these various images and display them on
a single device. Id. at col. 4, ll. 34–36. We provided a
more detailed description of the claimed invention in
Medical Instrumentation and Diagnostics Corp. v. Elekta
AB, 344 F.3d 1205, 1207–08 (Fed. Cir. 2003) (“MIDCO”)
and only recite the summary above to provide context.
    The ’684 patent has 109 claims, only two of which are
independent: claims 1 and 53. See ’684 patent at col. 19, l.
14 – col. 26, l. 30. Claim 1 discloses an apparatus, while
claim 53 discloses a method. See id.
   Claim 1 of the ’684 patent discloses an apparatus
comprising a collection of means intended to acquire,
convert, store, recall, manipulate, compare, and use the
separate scanner images collected:
    1. An apparatus for generating a presentation of
    images from a variety of imaging sources, the ap-
    paratus comprising:
    means for acquiring a plurality of images from a
    plurality of separate imaging sources;
    means for converting said plurality of images into
    a selected format;
    means for storing said plurality of images;
    means for selectively recalling and displaying at
    least two images of said plurality of images upon a
    single display device;
    means for manipulating at least one of said at
    least two images independently of the other im-
    age;
    means for comparing said at least two images;
    means for determining stereotactic coordinates
    and performing volumetric determinations from
    said at least two images; and
4                                BRAIN LIFE, LLC   v. ELEKTA INC.



    means for determining distances and areas from
    said at least two images.
’684 patent at col. 19, ll. 14–32. Claim 53 discloses a
method claiming a series of similar steps:
    53. A method for generating a presentation of im-
    ages from a variety of imaging sources, the meth-
    od comprising the steps of:
    acquiring a plurality of images from a plurality of
    separate imaging sources;
    converting the plurality of images into a selected
    format;
    storing the plurality of images;
    selectively recalling and displaying at least two
    images of the plurality of images upon a single
    display device;
    manipulating at least one of the at least two im-
    ages independently of the other image;
    comparing the at least two images;
    determining stereotactic coordinates and perform-
    ing volumetric determinations from the at least
    two images; and determining distances and areas
    from the at least two images.
’684 patent at col. 22, ll. 19–38.
    As the MIDCO Litigation proceeded through discov-
ery, MIDCO focused its efforts on claim 1 of the ’684
patent and neglected the method claims. See Brain Life
II, ECF No. 43 at 2. At the parties’ request, the trial
court only construed terms from apparatus claims 1, 3,
14, and 15 of the ’684 patent. The district court construed
the function of the “means for converting said plurality of
images into a selected format” in claim 1 of the ’684
patent to be “converting multiple acquired images into a
BRAIN LIFE, LLC   v. ELEKTA INC.                          5



particular selected digital format.” MIDCO, 344 F.3d at
1209. The trial court also found “that the structures
corresponding to this function were the VME bus based
framegrabber video display board, the computer video
processor (‘CVP’), and ‘[s]oftware routines for converting
digital-to-digital known to those of skill in the art.’” Id.
In other words, the district court’s construction both
included analog-to-digital and software based digital-to-
digital conversion. Id.
    Elekta requested that the district court dismiss the
method claims prior to trial. See id. MIDCO did not
oppose Elekta’s motion, and the district court dismissed
the method claims without prejudice. See id. The case
proceeded to trial, and the jury found that Elekta’s prod-
ucts infringed claim 1 of the ’684 patent. See id. The jury
also awarded $16 million in damages. See id.
    On appeal, “[t]he key dispute between the parties
[was] whether the district court was correct in including
software for digital-to-digital conversion as a correspond-
ing structure for the converting means.” Id. We found
that the inclusion of such software as a corresponding
structure was incorrect. See id. at 1211. In particular, we
found that the disclosure of the patent did not encompass
software for digital-to-digital conversion because it was
not clearly linked to the claimed function of converting
images into a selected format. See id. at 1212. As such,
we held that claim 1 of the ’684 patent did not provide for
digital-to-digital conversion, reversed the infringement
finding, vacated the damages award, and remanded to the
district court to enter judgment of noninfringement as a
matter of law in favor of Elekta. Id. at 1211–22.
    On remand, MIDCO attempted to revive the ’684 pa-
tent method claims that had been dismissed prior to trial,
presumably believing those claims were broader than the
system claims, as limited by our construction on appeal.
See Brain Life II, ECF No. 43 at 2. The district court
6                             BRAIN LIFE, LLC   v. ELEKTA INC.



refused to reopen the case and entered final judgment in
favor of Elekta. Id. MIDCO appealed that final judgment
and we summarily affirmed the trial court’s refusal to
reopen the case in a per curiam decision. See MIDCO v.
Elekta, 128 F. App’x 774 (Fed. Cir. 2005). As such, the
judgment that Elekta did not infringe the apparatus
claims of the ’684 patent was final.
     In September 2009, MIDCO licensed the ’684 patent
to a company, which, in turn, licensed the patent to Brain
Life. 1 See Brain Life II, ECF No. 43 at 3. Brain Life then
filed suit against several defendants, including Elekta, in
July 2010. Brain Life alleged that Elekta’s GammaKnife,
GammaPlan, SurgiPlan, and ERGO++ treatment systems
infringed the method claims of the ’684 patent. See Brain
Life LLC v. Elekta, Inc., No. 3:10–cv–1539, (S.D. Cal. July
23, 2010), ECF No. 1 at 8–10 (“Brain Life I”). Elekta
moved to dismiss Brain Life’s complaint for failure to
state a claim on res judicata grounds. See id. at ECF No.
32. The trial court and parties narrowed the issue to
whether the same “claim” was involved in the MIDCO
and Brain Life Litigations. See Brain Life II, ECF No. 43
at 3–5. The district court held that the primary dispute
was whether the newly accused Elekta products were
essentially the same as the products in the first suit and,
consequently, barred from further litigation. See id.
    The trial court denied Elekta’s motion to dismiss be-
cause it found that the complaint sufficiently pleaded that
the accused products were materially different. See id.
The court, however, ordered the parties to conduct discov-
ery on the question of whether the products in both suits


    1   There was no challenge to Brain Life’s right to
bring this action. See Morrow v. Microsoft Corp., 499 F.3d
1332, 1340 n. 7 (Fed. Cir. 2007) (noting that an exclusive
licensee who holds all substantial rights may sue in its
own name).
BRAIN LIFE, LLC   v. ELEKTA INC.                         7



were essentially the same. See id. The court also severed
Elekta from the remaining defendants to allow the claims
against the other defendants to proceed on the merits
while the court resolved the res judicata issue. See id.
After some discovery, Brain Life moved to dismiss El-
ekta’s res judicata and collateral estoppel defenses, and
Elekta moved for summary judgment on its res judicata
defense. See id.
    The district court granted summary judgment in favor
of Elekta, finding that Brain Life’s claims were barred.
See id. at 5–8. The court first found it undisputed that
there was no material difference between the currently
accused products and the previously adjudicated non-
infringing products regarding the limitations of the appa-
ratus claims. Id. On this point, Brain Life conceded that
the differences between the products were not material to
infringement of the apparatus claims of the ’684 patent.
Because it found that Elekta’s GammaKnife, Gam-
maPlan, SurgiPlan, and ERGO++ products employed
software for digital-to-digital conversions, the district
court concluded that those products could not infringe the
claims of the ’684 patent, any more than the products in
the MIDCO suit did. See id. Brain Life argued, however,
that the similarity of the products in the Brain Life Liti-
gation to the products in the MIDCO Litigation did not
bar its allegations of infringement of the ’684 patent’s
method claims. See id. It also argued that, because the
ERGO++ product was entirely new to Elekta—having
been purchased from a third party after the MIDCO
judgment and appeal—the question of whether it in-
fringed any of the claims of the ’684 patent had never
been addressed.
    The trial court concluded that allowing Brain Life to
assert the ’684 patent’s method claims against Elekta
would amount to impermissible claim splitting. See id.
The court noted that MIDCO accused Elekta’s products of
infringing the method claims in the original action, but
8                              BRAIN LIFE, LLC   v. ELEKTA INC.



chose to forgo those allegations. See id. In other words,
the trial court found that MIDCO had the opportunity to
adjudicate the method claims in the first suit. See id.
MIDCO voluntarily proceeded to trial on only claim 1 of
the ’684 patent, even though it could have proceeded to
trial on claim 53 and the claims dependent therefrom as
well. See id. The trial court found that, once final judg-
ment was entered in favor of Elekta, Elekta proceeded to
develop and sell its products with an understanding that
its products did not infringe the ’684 patent. See id. The
trial court held that, because MIDCO could have pursued
the method claims in the first litigation, but chose not to,
Brain Life’s attempt to revive those claims in the second
litigation was barred. See id. The trial court did not
differentiate the ERGO++ product from the other Elekta
products at issue. Brain Life then appealed that determi-
nation.
    Meanwhile, the action against the other defendants in
Brain Life I proceeded. In February 2013, the trial court
issued its claim construction order construing the terms
contained in the method claims of the ’684 patent. See
Brain Life I, ECF No. 126. The court rejected defendants’
proposed construction that would have limited the scope
of the method claims to only analog-to-digital conversions
akin to our construction of the apparatus claims in the
MIDCO Litigation. See id. at 5–6. Instead, the trial court
concluded that the method claims were broader than the
apparatus claims construed in the MIDCO Litigation, and
construed “converting the plurality of images into a
selected format” to mean “changing the image format of
two or more images, whether analog or digital, into a
common chosen digital format.” Id. In other words, the
court construed the method claims to include digital-to-
digital conversion—unlike the apparatus claims in the
MIDCO Litigation.
BRAIN LIFE, LLC   v. ELEKTA INC.                         9



                    II. STANDARD OF REVIEW
    Whether a cause of action is barred by claim preclu-
sion is a question of law which we review without defer-
ence. See Hallco Mfg. Co. v. Foster, 256 F.3d 1290, 1294
(Fed. Cir. 2001). Generally, in determining whether claim
preclusion bars a later lawsuit, we apply the law of the
regional circuit in which the trial court resides. See
Acumed LLC v. Stryker Corp., 525 F.3d 1319, 1323 (Fed.
Cir. 2008). The Ninth Circuit has held that claim preclu-
sion applies where the prior suit: (1) involved the same
claim or cause of action as the later suit; (2) reached a
final judgment on the merits; and (3) involved the same
parties or privies. See Mpoyo v. Litton Electro-Optical
Sys., 430 F.3d 985, 987 (9th Cir. 2005) (quoting Sidhu v.
Flecto Co., 279 F.3d 896, 900 (9th Cir. 2002)). Whether
two claims of infringement constitute the same claim or
cause of action is an issue particular to patent law and we
apply our own law without reference to the regional
circuit law on that issue. See Hallco, 256 F.3d at 1294.
     We review a grant or denial of summary judgment
under the law of the regional circuit. See SkinMedica,
Inc. v. Histogen Inc., 727 F.3d 1187, 1194–95 (Fed. Cir.
2013). The Ninth Circuit reviews the grant or denial of
summary judgment de novo. See Leever v. Carson City,
360 F.3d 1014, 1017 (9th Cir. 2009). We must view the
evidence in the light most favorable to the nonmovant and
determine whether there are any genuine issues of mate-
rial fact. See id.
                         III. DISCUSSION
    Brain Life makes three primary arguments in urging
reversal of the district court’s holding that its claims
against Elekta are barred. First, Brain Life contends
that, because the asserted claim limitations in this suit
differ from the asserted claims in the MIDCO suit, claim
preclusion is inapplicable. Next, Brain Life contends that,
because the trial court in the MIDCO Litigation dismissed
10                              BRAIN LIFE, LLC   v. ELEKTA INC.



the method claims without prejudice, Supreme Court
precedent counsels that those claims are not subject to res
judicata. Brain Life contends that, when a claim is dis-
missed without prejudice, a party can sue again on the
same claim, against the same defendant, in the same
court. Finally, Brain Life argues that Elekta’s ERGO++
product did not exist until after the first suit reached final
judgment. Because that product did not exist, Brain Life
contends that it could not have been accused in the
MIDCO Litigation and that neither claim nor issue pre-
clusion could apply to that product.
                   A. CLAIM PRECLUSION
     “In the simplest construct, [claim preclusion bars] the
relitigation of a claim, or cause of action, or any possible
defense to the cause of action which is ended by a judg-
ment of the court.” Nystrom v. Trex Co., 580 F.3d 1281,
1284–85 (Fed. Cir. 2009) (quoting Foster v. Hallco Mfg.
Co., 947 F.2d 469, 476 (Fed. Cir. 1991)). Claim preclusion
applies “whether the judgment of the court is rendered
after trial and imposed by the court or the judgment is
entered upon the consent of the parties.” Id. at 1285.
And, claim preclusion bars both claims that were brought
as well as those that could have been brought. See, e.g.,
Mars Inc. v. Nippon Conlux Kabushiki–Kaisha, 58 F.3d
616, 619–20 (Fed. Cir. 1995) (“It is well established that a
party may not split a cause of action into separate
grounds in successive lawsuits; instead a party must raise
in a single lawsuit all the grounds of recovery arising from
a single transaction or series of transactions that can be
brought together.”) (citing RESTATEMENT (SECOND) OF
JUDGMENTS § 24(2) (1982)).
    For claim preclusion to apply in a patent case, the al-
leged infringer must demonstrate that the accused prod-
uct or process is “essentially the same” as the accused
product or process in the first litigation. Nystrom, 580
F.3d at 1285 (quoting Foster, 947 F.2d at 480). As we
BRAIN LIFE, LLC   v. ELEKTA INC.                           11



have previously stated, “[a]n essential fact of a patent
infringement claim is the structure of the device or devic-
es in issue.” Foster, 947 F.2d at 479. An “‘infringement
claim,’ for purposes of claim preclusion [does not] em-
brace[ ] more than the specific devices before the court in
the first suit. Adjudication of liability for infringement is
a determination that a thing is made, used or sold with-
out authority under the claim(s) of a valid enforceable
patent.” Young Eng’rs Inc. v. U.S. Int’l Trade Comm’n,
721 F.2d 1305, 1316 (Fed. Cir. 1983).
     Without a doubt, these principles bar the assertion of
infringement of either the method or system claims to the
extent the alleged acts of infringement predate the final
judgment in the MIDCO Litigation. Brain Life does not
seem to dispute this fact as to the system claims, since it
asserts no cause of action relating to them. It does argue,
however, that the final judgment in the MIDCO action
would not act to bar the assertion of any claims of in-
fringement of the method claims in the ’684 patent. It
premises this argument on its belief that the dismissal
without prejudice of those claims gave it carte blanche to
reassert those claims. We disagree. While the dismissal
without prejudice allowed for the possibility that acts of
infringement of the method claims could be subject to a
future cause of action, that possibility was cut-off for all
such acts predating the final MIDCO judgment once that
judgment was entered. The trial court’s refusal to reopen
its judgment, moreover, does not affect the application of
claim preclusion. See Guild Wineries & Distilleries v.
Whitehall Co., 853 F.2d 755, 761 (9th Cir. 1988) (“The
date of judgment . . . controls the application of res judica-
ta principles.”).
    Having concluded that claim preclusion did bar all al-
legations of infringement relating to activity that predat-
ed the final MIDCO judgment, we turn to whether claim
preclusion would also bar claims relating to acts of in-
12                             BRAIN LIFE, LLC   v. ELEKTA INC.



fringement that postdate that judgment. We find that it
does not.
    Brain Life argues that claim preclusion cannot apply
to those claims. Brain Life argues that the trial court
erred by focusing on whether there was a difference
between the products in the two suits. According to Brain
Life, the same transactional facts analysis involved in
connection with application of claim preclusion requires
an inquiry into whether the same patent claim, same
limitation, and same claim construction of that limitation
are applicable in both suits. In particular, Brain Life
argues that, because the method claims may be (and have
been) construed to include digital-to-digital conversions—
directly contrary to the construction of the apparatus
claims—the transactional facts in the two suits are not
the same, and claim preclusion cannot bar the second
suit.
     We agree with Brain Life that claim preclusion does
not wholly bar its second suit against Elekta, but not for
the reasons Brain Life contends. Instead, we find that
Brain Life’s second suit is not barred by claim preclu-
sion—regardless of whether the same transactional facts
are present in both suits—to the extent Brain Life’s
current infringement allegations are temporally limited to
acts occurring after final judgment was entered in the
first suit.
    Claim preclusion does not bar Brain Life from assert-
ing either the apparatus or method claims against Elekta
because “the claim that gives rise to preclu-
sion . . . encompass[es] only the particular infringing
acts . . . that are accused in the first action or could have
been made subject to that action.” Aspex Eyewear Inc. v.
Marchon Eyewear, Inc., 672 F.3d 1335, 1343 (Fed. Cir.
2012). As explained in Aspex, it is well-settled that
     a party who sues a tortfeasor is ordinarily not
     barred by a prior judgment from seeking relief for
BRAIN LIFE, LLC   v. ELEKTA INC.                           13



    discrete tortious action by the same tortfeasor
    that occurs subsequent to the original action.
    That rule is based on the principle that res judica-
    ta requires a party to assert all claims that the
    party could have asserted in the earlier lawsuit; it
    follows that if the party could not have asserted
    particular claims—because the tortious conduct in
    question had not occurred at that time—those
    claims could not have been asserted and therefore
    are not barred by res judicata.
Id. at 1333–34 (citing Lawlor v. Nat’l Screen Serv. Corp.,
349 U.S. 322, 328 (1955); Manning v. City of Auburn, 953
F.2d 1355, 1359 (11th Cir. 1992); Blair v. City of Green-
ville, 649 F.2d 365, 368 (5th Cir. 1981); Kilgoar v. Colbert
Cnty. Bd. of Educ., 578 F.2d 1033 (5th Cir. 1978)). And,
those well-settled principles have been applied to patent
cases involving sequential acts of infringement. See id. at
1343 (citing Young Eng’rs, 721 F.2d at 1306; Cordis Corp.
v. Boston Scientific Corp., 635 F. Supp. 2d 361, 369–70 (D.
Del. 2009); Williams v. Gillette Co., 887 F. Supp. 181,
183–85 (N.D. Ill. 1995); MGA, Inc. v. Centri-Spray Corp.,
699 F. Supp. 610, 614 (E.D. Mich. 1987)). Much like the
Aspex case, to the extent Brain Life’s allegations of in-
fringement are directed to products created and, most
importantly, acts of alleged infringement occurring after
entry of the final judgment in the MIDCO Litigation,
those claims are not barred by the doctrine of claim
preclusion. Quite simply, Brain Life could not have
asserted infringement claims against the products in
question for acts of alleged infringement that postdate the
final judgment in the MIDCO Litigation in the current
litigation.
    This conclusion does not end our inquiry, however,
because other preclusion doctrines must still be ad-
dressed.
14                             BRAIN LIFE, LLC   v. ELEKTA INC.



                   B. ISSUE PRECLUSION
     Issue preclusion bars subsequent litigation on an is-
sue of law or fact that was actually litigated. See Foster,
947 F.3d at 480 (citing RESTATEMENT (SECOND) OF
JUDGMENTS § 27). If an issue of fact or law is actually
litigated and determined by a final judgment, and the
determination is essential to the judgment, that determi-
nation is conclusive in any later action between the par-
ties on the same or a different claim. See id. Importantly,
where the parties consent to a judgment on an issue prior
to trial, it cannot be said that the issue was actually
litigated to finality. See id. (citing RESTATEMENT § 27
cmt. (e)).
    MIDCO, Brain Life’s predecessor, unsuccessfully as-
serted the apparatus claims against Elekta in the MIDCO
Litigation. Brain Life has not asserted the apparatus
claims against Elekta in the current suit. To the extent it
had, the trial court’s findings that Elekta’s own prod-
ucts—the GammaKnife, GammaPlan, and SurgiPlan
products—were not materially different from the products
at issue in the MIDCO Litigation would bar it from as-
serting those claims. Foster, 947 F.2d at 480 (“A rationale
for the rule of issue preclusion is that once a legal or
factual issue has been settled by the court after a trial in
which it was fully and fairly litigated that issue should
enjoy repose.”). The method claims, however, are a sepa-
rate matter, particularly to the extent they relate to the
ERGO++ product.
    While MIDCO asserted the method claims against El-
ekta in the MIDCO Litigation, it is evident that those
claims were not fully, fairly, and actually litigated to
finality. Neither party requested that any terms of the
method claims from the ’684 patent be construed, nor did
either party move for a determination of summary judg-
ment regarding infringement, validity, or enforceability of
the method claims. Indeed, the trial court only construed
BRAIN LIFE, LLC   v. ELEKTA INC.                         15



terms from apparatus claims 1, 3, 14, and 15 of the ’684
patent. See Brain Life II, ECF No. 43 at 2. The ’684
patent method claims languished during the MIDCO
Litigation until Elekta requested, via a motion in limine,
that they be dismissed prior to trial for want of prosecu-
tion. See id. MIDCO did not oppose Elekta’s motion, and
the district court dismissed the method claims without
prejudice. See id.
     After a panel of this court reversed and remanded the
judgment in favor of MIDCO, MIDCO attempted to revive
the method claims. See id. The district court refused to
reopen the case and entered final judgment in favor of
Elekta. See id. MIDCO appealed that final judgment to
us, and we summarily affirmed the trial court’s refusal to
reopen the case in a per curiam decision. See MIDCO,
128 F. App’x 774. Accordingly, because the ’684 patent
method claims were not fully, fairly, and actually litigated
to finality between these parties, issue preclusion does not
stand as a bar to a second suit on those claims.
    Similarly, the ERGO++ product was never at issue in
the MIDCO Litigation. While similarities between it and
the products actually litigated may mean that certain
questions regarding infringement of the system claims
effectively may be foregone conclusions, they are not
barred by our case law applying issue preclusion to previ-
ously challenged products which have not been materially
altered. And, issue preclusion is no bar to assertion of the
method claims based on use or sales of the ERGO++
product.
    Again, the inquiry continues, however.
                     C. KESSLER DOCTRINE
    There exists a separate and distinct doctrine, known
as the Kessler Doctrine, that precludes some claims that
are not otherwise barred by claim or issue preclusion.
Elekta identifies the doctrine, but does so under the
16                              BRAIN LIFE, LLC   v. ELEKTA INC.



general rubric of claim preclusion. As explained above,
however, traditional notions of claim preclusion do not
apply when a patentee accuses new acts of infringement,
i.e., post-final judgment, in a second suit—even where the
products are the same in both suits. Such claims are
barred under general preclusion principles only to the
extent they can be barred by issue preclusion, with its
attendant limitations. The Kessler Doctrine fills the gap
between these preclusion doctrines, however, allowing an
adjudged non-infringer to avoid repeated harassment for
continuing its business as usual post-final judgment in a
patent action where circumstances justify that result.
While our past reliance on the Kessler Doctrine has been
sparse, we have applied it before.
     In Kessler v. Eldred, 206 U.S. 285 (1907), Eldred filed
suit against his competitor Kessler alleging infringement
of U.S. Patent No. 492,913 (“the ’913 patent”) directed to
an electric lighter. Eldred first filed suit against Kessler
in the District of Indiana, but the court found that Kess-
ler’s product did not infringe, a ruling that the Seventh
Circuit affirmed. See id. at 285–86. Eldred subsequently
filed suit in the Western District of New York against
Breitwieser for infringement of the ’913 patent. Breitwie-
ser was a customer of Kessler and was selling the same
electric lighters at issue in the Indiana action. See id.
Kessler stepped in to indemnify its customer, but also
filed a separate suit in Illinois to enjoin Eldred from filing
suit in any court alleging infringement of the ’913 patent
in connection with those of Kessler’s lighters that had
already been found to be non-infringing in the Indiana
action. See id. at 286–87. Both the district court and
Seventh Circuit agreed with Kessler’s position and grant-
ed the injunction in the Illinois action. See id. at 287.
    The Supreme Court agreed with Kessler and stated
that the final judgment in the first action between Eldred
and Kessler “settled finally and everywhere . . . that
Kessler has the right to manufacture, use, and sell the
BRAIN LIFE, LLC   v. ELEKTA INC.                         17



electric cigar lighter” in question. Id. at 288. Flowing
from that final decision in the first suit, the Court held
that Kessler is entitled to sell its electric lighters unmo-
lested by Eldred because those rights were established by
the final judgment in the Indiana action. See id. at 289.
In sum, the Court granted Kessler a limited trade right to
continue producing, using, and selling the electric lighters
that were the subject of the first suit and to do so without
fear of allegations of infringement by Eldred—even when
the acts of infringement occurred post-final judgment and
even when it was third-parties who allegedly engaged in
those acts of infringement. The Supreme Court concluded
that Kessler was entitled to continue the same activity in
which it engaged prior to the infringement allegations
once it had defeated those contentions in the first suit.
The Court did not rely on traditional notions of claim or
issue preclusion in crafting this protection for Kessler.
    We recognized the Kessler Doctrine in MGA, Inc. v.
General Motors Corp., 827 F.2d 729 (Fed. Cir. 1987). In
that case, MGA, Inc. (“MGA”) owned U.S. Patent No.
3,570,656 (“the ’656 patent”). See id. at 761. In 1979,
MGA and LaSalle Tool (“LaSalle”) executed a license
agreement under the ’656 patent for LaSalle’s accumula-
tor conveyer machines which LaSalle sold to General
Motors Corporation (“GM”). See id. LaSalle then devel-
oped and manufactured a newly designed machine that it
claimed was outside the scope of the claims of the ’656
patent. See id.
    MGA sued LaSalle in Michigan state court for non-
payment of royalties under the license agreement stem-
ming from the sales of the new machines. See id.
Following a bench trial, the state court found that the
new machines were not covered by the license agreement.
In affirming that decision, the Michigan Court of Appeals
noted that the trial judge implicitly found that the new
machines were not covered by the relevant claims of
the ’656 patent. See id. Meanwhile, MGA filed suit in the
18                             BRAIN LIFE, LLC   v. ELEKTA INC.



United States District Court for the Eastern District of
Michigan against GM for infringement of the ’656 patent
based on GM’s use of LaSalle’s new machines. See id.
LaSalle intervened on GM’s behalf and asserted that the
suit against GM was barred by claim and issue preclu-
sion, as well as the Kessler doctrine, by virtue of the
Michigan state court ruling. See id. The district court
granted summary judgment in favor of LaSalle (and GM),
holding that relitigation of infringement was barred by
the state court final judgment. See id.
     On appeal, we held that the Kessler Doctrine applied
to bar MGA’s suit against GM. We noted that Kessler
granted “a limited trade right which is ‘the right to have
that which [a court has determined] it lawfully produces
freely bought and sold without restraint or interference.
It is a right which attaches to its product—to a particular
thing—as an article of lawful commerce.” Id. at 734
(alteration in original) (quoting Rubber Tire Wheel Co. v.
Goodyear Tire & Rubber Co., 232 U.S. 413, 418–19
(1914)). And, because the new machines were “admittedly
the same in both suits it [was] LaSalle[’s] right that the
accused machines be freely traded without interference by
MGA.” Id. at 734–35. The Kessler Doctrine, therefore,
gave LaSalle (an accused infringer) rights with respect to
specific products that had been held to be noninfringing,
even when the specific acts of infringement would not be
barred by claim preclusion because they occurred post-
final judgment.
     The principle that, when an alleged infringer prevails
in demonstrating noninfringement, the specific accused
device(s) acquires the “status” of a noninfringing device
vis-à-vis the asserted patent claims is “[a]n essential fact
of a patent infringement claim.” See Foster, 947 F.2d at
479. “[T]he status of an infringer is derived from the
status imposed on the thing that is embraced by the
asserted patent claims.” Id. And, when the devices in the
first and second suits are “essentially the same,” the
BRAIN LIFE, LLC   v. ELEKTA INC.                         19



“new” product(s) also acquires the status of a noninfring-
ing device vis-à-vis the same accusing party or its privies.
See id. at 479–80.
    As we recognized in MGA, Kessler “was handed down
by the United States Supreme Court in the heyday of the
federal mutuality of estoppel rule.” See MGA, 827 F.2d at
733 (citing Blonder-Tongue Labs., Inc. v. Univ. of Illinois
Found., 402 U.S. 313, 320–27 (1971)). At the time Kessler
was decided, “the judge-made doctrine of mutuality of
estoppel, ordain[ed] that, unless both parties (or their
privies) in a second action [were] bound by a judgment in
a previous case, neither party (nor his privy) in the second
action may use the prior judgment as determinative of an
issue in the second action.” Blonder-Tongue, 402 U.S. at
320–21. The Supreme Court, therefore, may have created
the Kessler Doctrine as an exception to the strict mutuali-
ty requirement that existed at that time, rather than to
espouse a specific doctrine of substantive patent law.
    Since that time, state and federal courts have created
exceptions to the mutuality requirement, primarily when
estoppel is pleaded defensively. See id. at 324–26. And,
the continuing force of the Kessler Doctrine in the face of
the development of defensively applied issue preclusion
may be questionable on the precise set of facts presented
in the case at bar. But, the Kessler Doctrine exists, and
we are bound by it, even if its viability under current
estoppel law may be of less value now than it was at the
time it was handed down. Whether the Kessler Doctrine
is an exception to the mutuality of estoppel rule or a
matter of substantive patent law is a question we cannot
answer. We may only apply the law as it continues to
exist.
    The Kessler Doctrine, therefore, is directly applicable
to the case at bar. Brain Life’s predecessor-in-interest
asserted all of the ’684 patent claims against Elekta in the
MIDCO Litigation. See Brain Life II, ECF No. 43 at 2.
20                              BRAIN LIFE, LLC   v. ELEKTA INC.



While MIDCO ultimately abandoned the method claims
prior to trial, it could have continued to assert those
claims. Thus, once the accused devices in the MIDCO
Litigation were adjudged to be noninfringing with respect
to the asserted claims and judgment was entered as to all
claims, Elekta was free to continue engaging in the ac-
cused commercial activity as a non-infringer.         See
MIDCO, 344 F.3d at 1209; MIDCO, 128 F. App’x. at 774.
Elekta, thereafter, continued manufacturing and selling
products accused in the MIDCO Litigation post-final
judgment. Consequently, some of the accused devices in
this suit have acquired a noninfringing status vis-à-vis
the ’684 patent by virtue of the first case, and Elekta is
entitled to continue manufacturing, using, and selling
those products without molestation from MIDCO or Brain
Life. Simply, by virtue of gaining a final judgment of
noninfringement in the first suit—where all of the claims
were or could have been asserted against Elekta—the
accused devices acquired a status as noninfringing devic-
es, and Brain Life is barred from asserting that they
infringe the same patent claims a second time. 2
    The district court found that Brain Life’s current alle-
gations of infringement are directed to “subsequent ver-
sions” of the previously litigated Elekta GammaKnife,
GammaPlan, and SurgiPlan products. Brain Life II, ECF
No. 43 at 5. The court also stated that it was undisputed
that there are “no material differences between the cur-
rently accused products and the previously adjudicated



     2   Notably, though it asserts only method claims in
the current litigation, it is the making, using, or selling of
the Elekta products that Brain Life asserts infringe or
induces infringement of those method claims. In other
words, if the products are materially the same, it would
be the same allegedly infringing commercial activity that
is at issue in both proceedings.
BRAIN LIFE, LLC   v. ELEKTA INC.                          21



non-infringing products as to the limitations of claim 1.”
Id. During the summary judgment proceedings, moreo-
ver, Brain Life conceded that the products in the two suits
were materially the same. See J.A. at 1271. And, Brain
Life does not contend otherwise on appeal. As such,
because Elekta’s GammaPlan, GammaKnife, and Surgi-
Plan are essentially the same accused products, Brain
Life’s claims are barred under the Kessler Doctrine.
     As noted, Brain Life does not dispute that the new it-
erations of Elekta’s GammaPlan, GammaKnife, and
SurgiPlan are essentially the same as the previously
litigated versions. Brain Life instead focuses its efforts on
demonstrating that the patent claims in the two suits are
not essentially the same. That is beside the point under
the Kessler Doctrine because Elekta’s GammaKnife,
GammaPlan, and SurgiPlan products have acquired the
status of noninfringing products as to the ’684 patent, i.e.,
all claims that were brought or could have been brought
in the first suit. Brain Life’s allegations of infringement
as to Elekta’s GammaKnife, GammaPlan, and SurgiPlan,
therefore, are barred.
     Elekta’s ERGO++ treatment planning system, howev-
er, is a different matter. Brain Life, and its predecessor
MIDCO, have never accused Elekta’s ERGO++ product of
infringing any of the ’684 patent claims. Indeed, Elekta
only acquired the ERGO++ product after the MIDCO
Litigation was finalized. Accordingly, the ERGO++ has
never acquired the status of a noninfringing device in
connection with the ’684 patent. Unlike Elekta’s other
products, neither claim preclusion, issue preclusion, nor
the Kessler Doctrine stand as a bar to Brain Life’s current
allegations of infringement regarding the ERGO++. The
district court’s judgment regarding Elekta’s ERGO++
product, therefore, must be reversed and remanded for
further proceedings.
22                             BRAIN LIFE, LLC   v. ELEKTA INC.



                      IV. CONCLUSION
    Based on the foregoing, Brain Life’s assertions of post-
judgment infringement of the ’684 method claims are not
barred by claim or issue preclusion. The Kessler Doctrine
precludes Brain Life from asserting any claims of the ’684
patent against Elekta’s GammaKnife, GammaPlan, and
SurgiPlan products, however, because they are essentially
the same as the iterations litigated in the first suit. Brain
Life’s allegations of infringement against Elekta’s
ERGO++ product, however, are not barred and may
continue on remand. The district court’s judgment is
vacated to the extent it relates to the ERGO++, and this
case is remanded to the district court for further proceed-
ings consistent with this opinion. Otherwise, the district
court’s judgment is affirmed.
     AFFIRMED IN PART, VACATED IN PART, AND
                   REMANDED
