Sanarus Medical, maker of a device used to diagnose and treat breast cancer, brought in $3 million in convertible note funding from existing investors, reports VentureWire. It’s currently working on a product that uses ultrasound technology to detect the early stages of the disease.

The Pleasanton, Calif. company already has several devices on the market, many of which are based on cryotechnology — basically, the freezing of small, targeted sections of breast tissue — which gives doctors a clear, non-invasive window into what is going on in the tissue at any given time. The new money will probably go toward clinical trials for Sanarus’ early-stage cryoablation product, which may be able to replace often damaging lumpectomies.

Before this investment, the company had raised $59 million to date (most recently a $15 million fifth-round of funding at the start of 2007). Its backers include Easton Capital Partners, Alta Partners, Channel Medical Partners, Federated Kaufman Fund, Forward Ventures, Pequot Ventures and US Venture Partners. Sanarus executives wouldn’t say which of these investors did not return for the latest round.