9. Intangibles

Intangible assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. No impairment charges were recorded for the three months ended March 31, 2018 and 2017.

Amortization of capitalized patent costs associated with the application and award of patents in the U.S. and various other countries are capitalized and amortized on a straight-line basis over the term of the patents as determined at the award date, which varies depending on the pendency period of the application, generally approximating seventeen years.

Amortization of intangible assets acquired is calculated using the straight-line method over the estimated useful lives of the assets.

	Estimated Life	March 31,			December 31,
	(years)	2018			2017
Capitalized patent costs	17-20	$	8,200		$	7,978
Intangible assets acquired:
Purchased patents and intellectual property	3-10		250			250
Existing technology	5		1,560			1,560
Customer relationships	7		290			290
Backlog	2		760			760
Tradenames	3		290			290
Non-solicitation agreements	1		120			120
Gross intangible assets			11,470			11,248
Accumulated amortization			(4,992	)		(4,867	)
Intangibles, net		$	6,478		$	6,381