4. PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property and equipment, gross	$ 57,561	$ 54,191
Accumulated depreciation and amortization	(43,809)	(40,346)
Property and equipment, net	13,752	13,845	$ 17,794
Medical equipment [Member]
Property and equipment, gross	39,841	36,618
Office equipment, furniture and fixtures [Member]
Property and equipment, gross	3,280	3,238
Leasehold improvements [Member]
Property and equipment, gross	$ 14,440	$ 14,335