Shares in RadNet Inc. closed up more than 3 percent Monday but quickly retreated in after-hours trading when the company's profit fell short of expectations.

The L.A.-based medical imaging services provider reported a loss of $5.5 million (-15 cents per share), compared with a loss of $5.6 million (-16 cents) in the same period a year earlier falling far below Wall Street's expectations of a loss of one cent per share, according to Thomson Financial.

Revenues for the Los Angeles-based medical imaging services provider rose 8.4 percent to $115 million, beating estimates of $114 million.

Chief Executive Howard Berger said the company made investments in the first quarter related to acquisitions and new initiatives which should boost earnings in the second quarter.

RadNet attributed the revenue increase to a 4.2 percent rise in customer volume during the quarter, as well as acquisitions and operating initiatives.

Shares in Radnet closed up 3.1 percent but quickly lost ground, trading down 7.1 percent to $6.14 in after-hours trading.

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