Note 6 - Equity - Stock based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Stock-based compensation expense	$ 2,373	$ 1,680
General and Administrative Expense [Member]
Stock-based compensation expense	1,461	1,347
Research and Development Expense [Member]
Stock-based compensation expense	$ 912	$ 333

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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