Merge buying Etrials for about $18.3 million.

Medical imaging and information software company Merge Healthcare Inc. said Monday it is buying Etrials Worldwide Inc. for about $18.3 million in a cash-and-stock deal.

Morrisville, N.C.-based Etrials, which makes clinical trial software, accepted the offer as superior to a $14.5 million cash-and-stock bid by Bio-Imaging Technologies Inc.

Milwaukee-based Merge said it will pay 80 cents and 0.3448 shares of Merge common stock for each of Etrials common shares, amounting to about $1.70 per share. That marks a 32 percent premium to Etrial's closing stock price of $1.29 Friday.

Newtown, Pa.-based Bio-Imaging's last offer included 0.124 shares of newly issued Bio-Imaging common stock, 0.076 shares of newly issued Bio-Imaging preferred stock, and 62 cents per share. That amounted to $1.35 per share.

Bio-Imaging said Etrials is now obligated to pay a termination fee of $500,000 and reimburse Bio-Imaging for reasonable out of pocket expenses up to $250,000 on or before June 2. The fees are based on the companies' previous definitive agreement on a deal.

Merge said it will structure the buyout as a tender offer and expects the deal to close in the third quarter. It expects the deal to boost its imaging and data portfiolio for clinical trials.

"Clinical trials are vital to the approval of new pharmaceutical treatments and medical devices, and Etrials has developed applications designed to accelerate the process, improve data quality and reduce overall trial costs," Merge said, in a statement.

Merge shares fell 33 cents, or 10.5 percent, to $2.81 in morning trading. The stock has traded between 26 cents and $3.24 over the last 52 weeks. Meanwhile, shares of Etrials rose 39 cents, or 30.7 percent, to reach $1.66, while Bio-Imaging shares fell 12 cents, or 3 percent, to $3.88.