United States Court of Appeals 

for the Federal Circuit ______________________ 

ELEKTA LIMITED,

Appellant

v.

ZAP SURGICAL SYSTEMS, INC.,

Appellee

______________________ 

2021-1985

______________________ 

Appeal from the United States Patent and Trademark 

Office, Patent Trial and Appeal Board in No. IPR2019-

01659.

______________________ 

Decided: September 21, 2023

______________________ 

JENNIFER LIBRACH NALL, DLA Piper US LLP, Austin, 

TX, argued for appellant. Also represented by STANLEY JOSEPH PANIKOWSKI, III, San Diego, CA; AARON PATRICK 

BOWLING, Arnold & Porter Kaye Scholer LLP, Chicago, IL. 

 APRIL ELIZABETH ISAACSON, Kilpatrick Townsend & 

Stockton LLP, San Francisco, CA, argued for appellee. 

Also represented by ANDREW JAMES ISBESTER; MATTHEW 

MEYER, Menlo Park, CA. 

 ______________________ 

Before REYNA, STOLL, and STARK, Circuit Judges.

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2 ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 

REYNA, Circuit Judge.

Appellant Elekta Limited appeals from a Final Written 

Decision of the United States Patent Trial and Appeal 

Board that found certain claims of U.S. Patent No. 

7,295,648 unpatentable as obvious. Elekta challenges the 

Board’s findings related to motivation to combine and reasonable expectation of success. We affirm. 

BACKGROUND

U.S. Patent No. 7,295,648 

Elekta Limited (“Elekta”) is the owner of U.S. Patent 

No. 7,295,648 (the “’648 patent”), titled “Method and apparatus for treatment by ionizing radiation.” J.A. 2–3. The 

’648 patent discloses a device for treating a patient with 

ionizing radiation for certain types of radiosurgery and radiation therapy. ’648 patent, 1:6–8. The invention uses a 

radiation source, e.g., a linear accelerator (referred to as a 

“linac”), mounted on a pair of concentric rings to deliver a 

beam of ionizing radiation to the targeted area on the patient. See id. at 4:4–13; see also id. at 4:33–34; see also id

at 7:24–25. Figures 5 and 7 illustrate the claimed device 

features. 

Id. at Figs. 5 & 7. 

Figure 5 shows the claimed apparatus’ interior structure from the foot end with the patient table [18] and all 

exterior covers removed. Id. at 5:8–9; id. at 7:5–6. Figure 

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ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 3

7 shows the claimed apparatus’ interior structure from the 

head end. See id. at 5:10–12. A rotatable ring [24] is supported by a mounting ring [20]. Id. at 7:12–13. The rotatable ring [24] rotates around the patient [18]. Id. at 7:13–

14. Extending out of the rotatable ring [24] are two mounting brackets [26, 28], which provide a pivotal mounting 

point [30]. Id. at 7:14–23. A linac [32] is mounted to the 

pivotal mounting point [30], and a motor [36] is used 

around the linac housing [34] to assist in rotating the linac 

[32] around the pivotal mounting point [30]. Id. at 7:24–

27. The apparatus allows the linac to be manipulated such 

that it can move closer to and further from the patient and 

approach the patient at various angles. Id. at 7:31–34. 

This movement allows for the delivery of ionizing radiation 

to different target areas from different angles on the patient, as well as in differing intensities. See id. at 7:41–49. 

The ’648 patent contains apparatus and method 

claims. There is one independent, apparatus claim (Claim 

1) and one independent, method claim (Claim 18). We do 

not find it necessary to reach Claim 18. The parties agree 

that Claim 1 is illustrative. Claim 1 recites: 

1. A device for treating a patient with ionising radiation comprising:

a ring-shaped support, on which is provided a 

mount,

a radiation source attached to the mount;

the support being rotateable about an axis coincident with the centre of the ring;

the source being attached to the mount via a 

rotateable union having a [sic] an axis of rotation axis which is non-parallel to the support 

axis;

wherein the rotation axis of the mount passes 

through the support axis of the support and the 

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4 ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 

radiation source is collimated so as to produce 

a beam which passes through the co-incidence 

of the rotation and support axes.

Id. at 9:54–67. 

On September 27, 2019, ZAP Surgical Systems, Inc. 

(“ZAP”) filed before the United States Patent Trial and Appeal Board (“Board”) a petition for inter partes review 

(“IPR”) challenging claims 1–4, 7–13, 16–18, 20, and 22–23

of the ’648 patent. On April 1, 2020, the Board instituted 

an IPR on all grounds asserted in the petition. The petition 

relied on several prior art references, but pertinent to this

appeal are three references: U.S. Patent No. 4,649,560 

(“Grady”); a publication, K.J. Ruchala et al., Megavoltage 

CT image reconstruction during tomotherapy treatments, 

PHYS. MED. BIOL. 45, 3545–3362 (2000) (“Ruchala”); and 

U.S. Patent No. 4,998,268 (“Winter”). 

Grady discloses an X-ray tube mounted on a sliding 

arm connected to a rotating support. Grady, Abstract. Figure 1 illustrates the X-ray stand, where inner rings [3, 4] 

rotate around the patient lying on the table [T]. Id. at

1:46–52. Figures 1 and 2 illustrate a rectangular sleeve [8] 

that extends from the rings, in which an arm [9] slides via 

motor drive. Id. at 1:53–56. The outer end of the arm [9] 

is connected to a carriage [10], which carries an X-ray tube

that is rotated around a patient to take X-ray images. See 

id. at 1:56–66. 

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ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 5

Grady Figures 1 and 2 are illustrated as follows:

Id. at Fig. 1. 

Id. at Fig. 2. 

Ruchala discloses a linac-based tomotherapy treatment system, whereby, like a computerized tomography 

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6 ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 

(“CT”) scanner, “the patient remains still, but the linac and 

detector rotate about the patient” to deliver a treatment 

dose to the target tumor. J.A. 2147; see also J.A. 2144–61. 

Ruchala notes that the linac is fitted with a “multileaf collimator” to “allow for a highly conformal treatment that 

will deliver [a] dose to the tumour while sparing sensitive 

structures.” J.A. 2144. The CT imaging capability, according to Ruchala, ensures “properly positioning the patient’s 

body and interior organs” and “know[ledge] that the treatment was delivered as intended.” Id. 

Winter—relied on as background art in the petition—

discloses the “combination [of] a diagnostic CT scanner using radiant energy for imaging,” which is used “for therapeutically irradiating a target.” Winter, Abstract; see J.A. 

7. It touted the combination as “provid[ing] more accurate 

localization of the area to be irradiated than prior art use 

of the gamma knife as a standalone radiation therapy 

unit.” Winter, 2:23–26. According to Winter, this is because the combination allows for “more accurate positioning of the patient due to the fact that a single device having 

diagnostic imaging capability is used for both imaging and 

therapy purposes.” Id. at 2:41–45. 

BOARD’S FINAL WRITTEN DECISION 

On March 30, 2021, the Board issued its Final Written 

Decision, concluding that all the challenged claims were 

unpatentable as obvious. Specifically, the Board found 

that claims 1–4, 7–8, 11, 12, 17, 18, 20, and 23 were obvious

over the combination of Grady and Ruchala (and independently obvious over the combination of U.S. Patent No. 

5,207,223 (“Adler”), and Grady); and that claims 9, 10, 13, 

16, and 22 were obvious over of the combination of Grady, 

Ruchala, and U.S. Patent No. 5,945,684 (“Lam”) (and 

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ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 7

independently obvious over the combination of Adler, 

Grady, and Lam). J.A. 70.1 

The Board addressed Elekta’s arguments that a skilled 

artisan would not have been motivated to combine, and

would not have had a reasonable expectation of success in 

combining, the Grady device with the linac described in 

Ruchala. See J.A. 27–36. The Board also considered 

whether a skilled artisan would have been dissuaded from 

combining the devices because one device was an imaging 

device, rather than a radiation device, and because the 

linac’s weight would render the Grady device inoperable, 

imprecise, and unsuitable for treatment. J.A. 34–35. The 

Board concluded that a skilled artisan would have been 

motivated to combine Grady and Ruchala. J.A. 36. 

Elekta appealed. We have jurisdiction under 28 U.S.C. 

§ 1295(a)(4)(A).

STANDARD OF REVIEW 

We review the Board’s legal conclusions de novo and its 

factual findings for substantial evidence. ACCO Brands 

Corp. v. Fellowes, Inc., 813 F.3d 1361, 1365 (Fed. Cir. 

2016). Substantial evidence means “such relevant evidence as a reasonable mind might accept as adequate to 

support a conclusion.” In re Gartside, 203 F.3d 1305, 1312 

(Fed. Cir. 2000) (citation omitted). 

Obviousness is a question of law with underlying factual issues relating to the “scope and content of the prior 

art, differences between the prior art and the claims at issue, the level of ordinary skill in the pertinent art, and any 

objective indicia of non-obviousness.” Randall Mfg. v. Rea, 

1 Elekta also moved during the proceeding to amend 

its claims. J.A. 2; J.A. 67–68; J.A. 71. The Board denied 

that motion. J.A. 71. Elekta does not challenge that denial 

on appeal. 

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8 ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 

733 F.3d 1355, 1362 (Fed. Cir. 2013) (first citing KSR Int’l 

Co. v. Teleflex Inc., 550 U.S. 398, 406 (2007); then citing 

Graham v. John Deere Co. of Kansas City, 383 U.S. 1, 17–

18 (1966)). Whether a skilled artisan would have been motivated to combine references or would have had a reasonable expectation of success in combining references are 

questions of fact reviewed for substantial evidence. Regents of Univ. of California v. Broad Inst., Inc., 903 F.3d 

1286, 1291 (Fed. Cir. 2018).

DISCUSSION 

On appeal, Elekta makes three principal arguments:

that the Board’s findings on a motivation to combine are 

unsupported by substantial evidence, Appellant’s Br. 26; 

that the Board failed to make any findings, explicit or implicit, on a reasonable expectation of success, id. at 4, 18; 

and that even had the Board made such findings, those 

findings are not supported by substantial evidence, id. at 

2. 

I 

We first address Elekta’s argument that a skilled artisan would not have been motivated to combine prior art

references disclosing radiation imagery with the references 

disclosing radiation therapy. Appellant’s Br. 26. 

Obviousness requires, inter alia, a finding that a 

skilled artisan would have been motivated to combine the 

teachings of prior art in such a way that the combination 

discloses the claimed limitations. See OSI Pharms., LLC 

v. Apotex Inc., 939 F.3d 1375, 1382 (Fed. Cir. 2019). The 

inquiry into the existence of a motivation to combine assumes that a skilled artisan is a person of ordinary creativity with common sense, common wisdom, and common 

knowledge. See Fleming v. Cirrus Design Corp., 28 F.4th 

1214, 1223 (Fed. Cir. 2022). Thus, an obviousness determination does not always require prior art to expressly 

state a motivation for every obvious combination. See, e.g., 

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ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 9

id. Nor does an obviousness showing “require that a particular combination must be the preferred, or the most desirable, combination described in the prior art in order to 

provide motivation for the current invention.” Novartis 

Pharms. Corp. v. West-Ward Pharms. Int’l Ltd., 923 F.3d 

1051, 1059 (Fed. Cir. 2019) (citation omitted). 

Elekta contends that “[n]o substantial evidence supports the Board’s finding that there was a motivation to 

combine these references by replacing the X-ray imaging 

source in Grady with a linac therapeutic source as proposed 

in the Petition,” because the linac “ionising radiation 

source [would] not offer any imaging improvement and also 

requires extreme precision due to its potentially lethal side 

effects.” Appellant’s Br. 29, 31. According to Elekta, the 

Grady device is for imaging and does not contemplate a 

heavy linac or account for the lack of precision that would 

result from the linac’s additional weight. Id. at 30–31. 

The Board acknowledged Elekta’s argument that a 

skilled artisan would not have been motivated to combine 

Grady and Ruchala because the weight of the linac would 

render the device essentially inoperable and thereby fail to 

provide a viable solution for focusing therapeutic radiation

on the target. See J.A. 31–33. But the Board found that 

heavy linacs were known in the art during the pertinent 

period and that their weight could be adequately handled 

by robotic arms. J.A. 35. The Board supported this conclusion by reviewing “the prosecution of the ’648 patent, 

[which demonstrated that] patents directed to imaging devices were cited, and were not distinguished based on an 

argument that imaging devices were not relevant art.” J.A. 

32. In addition, the Board framed the pertinent field as one 

that “includes the engineering design of sturdy mechanical 

apparatus[es] capable of rotationally manipulating heavy

devices in three dimensions oriented in a variety of approach angles with high geometrical accuracy, in the context of the radiation imaging and radiation therapy 

environment.” J.A. 34 (emphasis added). The Board 

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10 ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 

credited ZAP’s expert as having experience with such devices. Id. It also recognized the differences between radiation imaging devices and radiation therapy devices, and it 

found that a skilled artisan would not have been dissuaded 

from combining the references based on these differences. 

See J.A. 35. 

The Board determined that “persons of ordinary skill 

in the applicable art would have readily understood the advantages of the three-dimensional manipulation capabilities of the Grady approach” and not been dissuaded by the 

“difficulty in accommodating heavy linacs” or the need for 

“precision” in making that combination. Id. On that basis,

the Board determined that a skilled artisan would have 

been motivated to combine the references disclosing radiation imaging with references disclosing radiation therapy. 

J.A. 36.

We hold that the Board’s finding that a skilled artisan 

would have been motivated to combine the Grady device 

with Ruchala’s linac is supported by substantial evidence, 

including the prosecution history of the ’648 patent, the 

teachings of the asserted prior art references, and the expert testimony of record. Specifically, as explained above, 

during prosecution, the patentee notably did not argue that 

prior art references directed to imaging devices were not 

relevant art. See J.A. 32 (citing J.A. 949–81). In addition, 

Ruchala teaches that combining imaging with the delivery 

of radiation is advantageous because it can improve the accuracy of radiation delivery and verify that the dose of radiation was received. See, e.g., J.A. 2144, Abstract. 

Another prior art reference in the record before the Board, 

Winter, discloses that combining an imaging system with 

a radiation source is preferable because it allows for “more 

accurate positioning of the patient due to the fact that a 

single device having diagnostic imaging capability is used 

for both imaging and therapy purposes.” Winter, 2:41–45. 

And ZAP’s expert, Dr. McCarthy, opined that a person of 

ordinary skill in the art would have been motivated to 

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ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 11

make the proposed combination because it would “eliminat[e] the need to move a patient from an imaging apparatus to a separate treatment apparatus” and would 

“reduce the patient’s exposure to radiation.” J.A. 1378–84 

¶ 74. Taken together, this evidence provides substantial 

support for the Board’s finding that a person of ordinary 

skill in the art would have been motivated to make the proposed combination. 

II 

Elekta argues that the Board erred as a matter of law 

because it failed to articulate any findings on reasonable 

expectation of success. Appellant’s Br. 18. We disagree. 

To be clear, an obviousness determination requires 

finding that a person of ordinary skill in the art would have 

had a reasonable expectation of success. Regents of Univ. 

of Cal., 903 F.3d at 1291. Reasonable expectation of success refers to the likelihood of success in combining references to meet the limitations of the claimed invention. 

Intelligent Bio–Systems, Inc. v. Illumina Cambridge Ltd., 

821 F.3d 1359, 1367 (Fed. Cir. 2016). 

Unlike a motivation to combine determination, which 

requires an explicit analysis, KSR, 550 U.S. at 418, a finding of reasonable expectation of success can be implicit, see

Merck & Cie v. Gnosis S.P.A., 808 F.3d 829, 836 (Fed. Cir. 

2015). We understand that requiring less than an explicit 

statement may appear to be in tension with our review of 

Board determinations under the Administrative Procedure 

Act (“APA”), which requires the Board to “explain[] its decisions with sufficient precision, including the underlying 

factfindings and [its] rationale.” Packard Press, Inc. v. 

Hewlett-Packard Co., 227 F.3d 1352, 1357 (Fed. Cir. 2000). 

But there is no such tension where the Board makes an 

implicit finding on reasonable expectation of success by

considering and addressing other, intertwined arguments, 

including, as we hold today, a motivation to combine. See 

Merck, 808 F.3d at 836. In those circumstances, we can 

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12 ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 

“reasonably discern” an implicit finding by the Board on 

reasonable expectation of success. In re NuVasive, Inc., 

842 F.3d 1376, 1382 (Fed. Cir. 2016). 

We have previously held that an implicit finding on 

reasonable expectation of success under such circumstances is acceptable. Merck, 808 F.3d at 836–37. In 

Merck, the patent owner argued that the prior art teaches 

away from the proposed combinations. Id. at 834. The 

Board disagreed. Id. On appeal, the patent owner faulted

the Board’s final written decision for failing to make an express finding that a skilled artisan would have had a reasonable expectation of success in combining the references. 

Id. at 836. We held that “[b]y rejecting [the patent owner’s] 

argument that the prior art taught away from combining 

[the references], the Board impliedly found a reasonable 

expectation of success.” Id. Under these circumstances, we 

declined to overturn the Board’s decision simply because it 

did not “state expressly” that a skilled artisan would have 

had a reasonable expectation of success. Id. at 836–37. 

Here, as in Merck, we can reasonably discern that the 

Board considered and implicitly addressed reasonable expectation of success based on the arguments and evidence 

presented to the Board on motivation to combine. See id. 

For example, Elekta raised reasonable expectation of success arguments before the Board in asserting that ZAP’s 

proposed combination would result in an inoperable device, 

result in an inferior quality product, and would teach away 

because the combination would not produce the result 

sought by the ’648 patent owner due to the heavy weight of 

the linac. See J.A. 3385–87; see also J.A. 3170. 

Elekta also argued that because the prior art combination would not “provide a viable solution for focusing a therapeutic radiation source on the target,” it would not work 

for its intended purposes, and thus would “negat[e] any 

reasonable expectation of success.” J.A. 914–15; J.A. 3885–

87. And when asked during oral argument what 

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ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 13

reasonable expectation of success arguments it made before the Board, Elekta reiterated its argument that “a 

POSITA would not have expected the structure to be a viable solution for focusing the therapeutic radiation source 

on the target, which was the stated goal of the invention.” 

Oral Arg. 4:22–5:25. Elekta’s briefing and expert declarations also focused on how the weight of the device, and the 

resulting lack of precision and control, evidenced a lack of 

expectation of success and motivation to combine. J.A. 

3887; J.A. 3375. 

These and other of Elekta’s similar arguments also 

were made in connection with whether a skilled artisan 

would have been motivated to combine the prior art. In 

these circumstances, the Board made no error in addressing the issues of motivation to combine and reasonable expectation of success in the same blended manner that

Elekta chose to present those very issues. 

In finding that “persons of ordinary skill in the applicable art would have readily understood the advantages” of 

Grady and would not have been dissuaded by the “difficulty 

in accommodating heavy linacs” or concerns related to “precision” in targeting for radiation therapy in making that 

combination, the Board implicitly addressed Elekta’s argument on reasonable expectation of success. See J.A. 35. On 

this basis, we hold that the Board made a sufficient, implicit finding that a skilled artisan would have had a reasonable expectation of success in combining the prior art 

references. See Merck, 808 F.3d at 836–37. 

III 

We next address Elekta’s argument that, even if the 

Board made an implicit finding, “there is [no] substantial 

evidence that could support a finding that a skilled artisan 

would have reasonably expected to succeed” in combining 

the asserted references. Appellant’s Br. 2, 4. 

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14 ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 

Evidence of a reasonable expectation of success, just 

like evidence of a motivation to combine, “may flow from 

the prior art references themselves, the knowledge of one 

of ordinary skill in the art, or, in some cases, from the nature of the problem to be solved.” Brown & Williamson Tobacco Corp. v. Philip Morris Inc., 229 F.3d 1120, 1125 (Fed. 

Cir. 2000). The evidence need not lead to a single conclusion to support a finding of substantial evidence. Velander

v. Garner, 348 F.3d 1359, 1378–79 (Fed. Cir. 2003). 

In this case, and as explained above, the arguments 

and evidence of reasonable expectation of success are the 

same for motivation to combine. To be clear, a finding of a 

motivation to combine does not necessarily establish a finding of reasonable expectation of success. Eli Lilly & Co. v. 

Teva Pharms. Int’l GmbH, 8 F.4th 1331, 1344 (Fed. Cir. 

2021). But in some cases, such as here, the evidence establishing a motivation to combine may establish a finding of 

reasonable expectation of success. 

In view of the foregoing, we conclude that the Board’s 

finding that a skilled artisan would have had a reasonable 

expectation of success in combining Grady and Ruchala is 

supported by substantial evidence. 

IV 

Elekta argues that “no substantial evidence in the record would support a finding that ZAP met its burden to 

show reasonable expectation of success by clear and convincing evidence.” Appellant’s Br. 21–22. 

Elekta misstates the applicable burden of proof. See 

id. In an IPR, the petitioner bears the burden in the petition to demonstrate by a preponderance of the evidence 

that the challenged patent (or portions thereof) is unpatentable. See 35 U.S.C. § 316(e) (“In an inter partes review instituted under this chapter, the petitioner shall 

have the burden of proving a proposition of unpatentability 

by a preponderance of the evidence.”). Apart from its 

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ELEKTA LIMITED v. ZAP SURGICAL SYSTEMS, INC. 15

erroneous statement of the law, Elekta further failed to develop an argument concerning ZAP’s correct burden of 

proof. See Reply 11–13. We therefore deem this argument 

frivolous and waived. See Monsanto Co. v. Scruggs, 459 

F.3d 1328, 1341 (Fed. Cir. 2006). 

CONCLUSION

We have considered Elekta’s other arguments and find 

them unpersuasive. We hold that the Board’s findings on 

a motivation to combine and its implicit finding on a reasonable expectation of success are supported by substantial 

evidence. We affirm. 

AFFIRMED 

COSTS

No costs.

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