SonoSite Inc. (SONO) has agreed to a $50 million stock buyback, the latest since January, when  its board approved a plan to buy up to $150 million of stock.

So far in 2010, SonoSite has bought back about 3 million shares, totaling about $88 million. It had planned to repurchase about $100 million worth of shares.

SonoSite is one of many companies that have begun buybacks as the economy has shown signs of improving.

Shares of the company were up about 1.6% in Friday trading.