WASHINGTON (Bloomberg) - The US Supreme Court refused to shield three units of Covidien Ltd., the medical-supplies maker spun off from Tyco International Ltd., from a patent suit pressed by a Bayer AG unit over magnetic resonance imaging technology.

The justices, without comment, turned away an appeal by the Covidien units and Japan's Nemoto Kyorindo Co. They argued that US patent examiners should not have re-issued a defective patent to Medrad Inc., now part of Bayer.

The rejection left intact a federal appeals court decision that let a 2001 lawsuit against the companies go forward. Medrad is seeking damages for alleged infringement of a patent on a device used to inject a contrast agent into patents undergoing magnetic resonance.

The suit names Covidien's Tyco Healthcare, Mallinkrodt and Liebel-Flarsheim units. Covidien, like Tyco, is based in Pembroke, Bermuda.