What constitutes deliberate indifference in a medical malpractice case?

Defendant's acts or omissions must involve more than an ordinary lack of due care, as "[a] difference of opinion" between a doctor and an inmate, or even between medical professionals, regarding what medical care is appropriate "does not amount to a deliberate indifference." Sanchez v. Vild, 891 F.2d 240, 242 (9th Cir. 1989) (citing Gamble, 429 U.S. at 107).