Note 8 - Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accrued expenses	$ 87	$ 10
Accrued salaries and employee benefits	961	652
Accrued director compensation		648
Accrued clinical trial costs	452	519
Grant liability	615	630
Customer deposits	90	102
Total	$ 2,205	$ 2,561