North American Scientific Inc. said Wednesday that it has agreed to sell its Nomos Radiation Oncology business to privately held Best Medical International Inc. for about $3.6 million.

The Chatsworth-based cancer treatment facility operator said the sale is expected to close by Sept. 17. The purchase price also includes $3.1 million of warranty and maintenance agreements as well as the Nomos facility lease in Cranberry Township, Pa.

Nomos makes radiation systems used mainly to treat tumors of the prostate, head, neck and spinal cord. North American said the sale will allow it to cut costs and focus resources on its brachytherapy products for the treatment of cancer. Brachytherapy treats some forms of cancer by implanting radioactive seeds in cancerous tissue.

Shares in North American were down 3.2 percent, or 3 cents, to 92 cents per share in Wednesday trading on the Nasdaq.