Note 2 - Significant Accounting Policies (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Retained Earnings (Accumulated Deficit)	$ (72,450,000)	$ (60,142,000)
Cash and Cash Equivalents, at Carrying Value	12,689,000	21,352,000	$ 3,557,000	$ 3,184,000
Allowance for Doubtful Accounts Receivable, Current	6,000	2,000
Write-off of Deferred Offering Costs			1,634,000
Impairment of Long-Lived Assets Held-for-use	0	0	0
Sales Returns Reserve	$ 1,000	1,000
Standard Product Warranty, Term	2 years
Standard Product Warranty Accrual	$ 0	0
Income Tax Examination, Penalties and Interest Accrued	0	0	0
Cost of Goods Sold [Member]
Shipping, Handling and Transportation Costs	$ 5,000	$ 7,000	$ 11,000