What constitutes "substantial evidence" in medical malpractice cases?

The term "substantial evidence" "describes a quality of evidence ... intended to indicate that the evidence that is inconsistent with the opinion need not prove by a preponderance that the opinion is wrong." SSR 96-2p³, 1996 SSR LEXIS 9 at *8. "It need only be such relevant evidence as a reasonable mind would accept as adequate to support a conclusion that is contrary to the conclusion expressed in the medical opinion." Id.; see also Orn v. Astrue, 495 F.3d 625, 630 (9th Cir. 2007) (defining "substantial evidence" as "such relevant evidence as a reasonable mind might accept as adequate to support a conclusion").