Intangible Assets

6 Months Ended

Jun. 30, 2021

Intangible Assets, Net (Excluding Goodwill) [Abstract]

Intangible Assets

10. INTANGIBLE ASSETS: 

Intangible assets consist of the following: 

	June 30, 2021							December 31, 2020
(In thousands)	Gross Carrying Amount		Accumulated Amortization			Net		Gross Carrying Amount		Accumulated Amortization			Net
Patents	$	1,991	$	(1,628	)	$	363	$	1,832	$	(1,542	)	$	290
Software	206		(206		)	—		206		(200		)	6
Marketing assets and customer relationships	86		(66		)	20		101		(72		)	29
Total intangible assets	$	2,283	$	(1,900	)	$	383	$	2,139	$	(1,814	)	$	325

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

	Three Months Ended June 30,				Six Months Ended June 30,
(In thousands)	2021		2020		2021		2020
Patents	$	44	$	35	$	87	$	73
Software		—		7		6		15
Marketing assets and customer relationships		2		3		4		5
Total amortization expense	$	46	$	45	$	97	$	93

Estimated aggregate amortization expense based on current intangible assets for the next four years is expected to be as follows: $96,000 for the remainder of 2021; $158,000 in 2022; $109,000 in 2023; and $20,000 in 2024.