"The Swedish radiologist Nils Johan Hugo Westermark (1892-1980) 7 first described this sign in 1938 5. Westermark was also an accomplished sailor and won a silver medal, as a member of the Swedish team, at the 1912 Olympics in Stockholm 7."
"In one study (PIOPED), this sign was present on ~10% of chest x-rays of patients with confirmed pulmonary embolus 2."