Note 8 - Stockholders' Equity (Details Textual) - USD ($)		3 Months Ended
	Mar. 28, 2018	Mar. 31, 2019	Mar. 31, 2018
Stock Issued During Period, Shares, New Issues	609,636
Shares Issued, Price Per Share	$ 2.27
Payments of Stock Issuance Costs	$ 171,000
Proceeds from Issuance of Common Stock, Net	$ 1,213,000		$ 1,213,000
Share-based Payment Arrangement, Expense		$ 81,000	$ 137,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period		0
Warrants Issused in Private Placement [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	304,818
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 2.68
Warrants and Rights Outstanding, Term	5 years 182 days