Intangible Assets

9 Months Ended

Sep. 30, 2021

Intangible Assets, Net (Excluding Goodwill) [Abstract]

Intangible Assets

10. INTANGIBLE ASSETS: 

Intangible assets consist of the following: 

	September 30, 2021							December 31, 2020
(In thousands)	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
Patents	$	2,041	$	(1,678	)	$	363	$	1,832	$	(1,542	)	$	290
Software	206		(206		)	—		206		(200		)	6
Marketing assets and customer relationships	86		(68		)	18		101		(72		)	29
Total intangible assets	$	2,333	$	(1,952	)	$	381	$	2,139	$	(1,814	)	$	325

Amortization expense in the three and nine months ended September 30, 2021 and September 30, 2020 was as follows:   

	Three Months Ended September 30,				Nine Months Ended September 30,
(In thousands)	2021		2020		2021		2020
Patents	$	50	$	38	$	137	$	111
Software		—		7		6		22
Marketing assets and customer relationships		2		2		6		7
Total amortization expense	$	52	$	47	$	149	$	140

Estimated aggregate amortization expense based on current intangible assets for the next four years is expected to be as follows: $51,000 for the remainder of 2021; $174,000 in 2022; $126,000 in 2023; and $30,000 in 2024.