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, 2022 and 2021.

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)	2022			2021
Capitalized patent costs	17-20	$	10,319		$	10,219

Intangible assets acquired:
Purchased intellectual property	10		250			250
Developed technology	5		24,929			1,560
Customer relationships	10		13,684			290
Gross intangible assets			49,182			12,319
Accumulated amortization			(7,349	)		(5,708	)
Intangibles, net		$	41,833		$	6,611

The amortization of capitalized patent costs, purchased intellectual property, and developed technology is recorded in “cost of revenue” and the amortization of customer relationships is recorded in “sales and marketing” in the Consolidated Statements of Operations.

	Three		Three
	Months		Months
	Ended		Ended
	March 31,		March 31,
	2022		2021
Amortization expense	$	1,677	$	142

For intangible assets recorded at March 31, 2022, the estimated future aggregate amortization expense for the years ending December 31, 2022 through December 31, 2026 is as follows:

	Amortization
As of March 31, 2022:	Expense
Remaining in 2022	$	4,933
2023		6,571
2024		6,558
2025		6,538
2026		6,506