When it was acquired by German health care giant Bayer AG in 2006, Medrad Inc., a Pittsburgh company that makes medical imaging devices, came up with a growth strategy that included scouting for businesses it might purchase.

When Bayer gave it the go-ahead to look into acquisition candidates last August, Possis Medical Inc., a Minneapolis company that makes devices to treat blocked arteries and veins, "was at the top of our list," said John Friel, Medrad president and chief executive.

Yesterday the companies announced that Medrad would buy Possis in a cash deal valued at $361 million. Shareholders in Possis, which is traded on the Nasdaq exchange, will receive $19.50 per share, or about 39 percent more than Possis' average price before last Friday. Possis' shares soared nearly 35 percent on the news yesterday to close at $19.36, up $5.01.

"There's a lot that makes sense about this deal; it's a great mix," Mr. Friel said yesterday in a phone interview.

Medrad, founded in 1964 by a Pittsburgh physician and entrepreneur, M. Stephen Heilman, makes injection devices used to diagnose cardiovascular diseases. It has about 1,750 employees worldwide including about 1,200 in the region at its Marshall headquarters and at facilities in O'Hara, Indiana Township, and Saxonburg. Sales in 2006, the most recent available, were $478 million.

"We've known [Possis] for a long time," Mr. Friel said. "We've pursued and looked into partnerships that for one reason or another didn't come to fruition."

Founded in 1952, Possis employs 280 and had revenues of $67 million for the fiscal year ended July 31.

The merger, which the companies expect will close in the first quarter, will bridge Medrad's diagnostic systems with Possis' treatment devices for heart diseases, Mr. Friel said. Possis' primary product, AngioJet, is a catheter system that sucks out blood clots.

Most of Possis' workforce is expected to stay in place, Mr. Friel said.

"The idea of shutting down operations or a big move is not contemplated."

Robert Dutcher, Possis president and chief executive, said in a conference call yesterday that its board unanimously approved the deal which will commence with a tender offer within 10 business days.

"We believe it's a very fair price. Medrad is paying about four times our estimated 2008 sales."

Bayer, which has its U.S. headquarters in Robinson, became Medrad's parent when it bought Medrad's former owner, Schering AG, for $22.5 billion.