8. INTANGIBLE ASSETS

12 Months Ended

Dec. 31, 2022

Goodwill And Intangible Assets Disclosure Abstract

8. INTANGIBLE ASSETS

8. INTANGIBLE ASSETS

Our intangible assets consist exclusively of technology-based purchased patents. The gross book value of our intangible assets was $951,000 in the years ended December 31, 2022 and 2021, respectively. Amortization expense was $40,000 in 2022, $49,000 in 2021 and $57,000 in 2020. The following table outlines our estimated future amortization expense related to intangible assets held at December 31, 2022 (in thousands):

Years Ended December 31,	Amount
2023		32
2024		22
2025		14
2026		7
		75