Note 2 - Summary of Significant Accounting Policies (Details Textual)		6 Months Ended	12 Months Ended
	Sep. 18, 2019 USD ($)	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Nov. 30, 2019 shares	Jan. 01, 2019 USD ($)
Payments for Fractional Shares of Reverse Stock Split	$ 6,000
Common Stock, Par or Stated Value Per Share | $ / shares		$ 0.0001	$ 0.0001	$ 0.0001
Common Stock, Shares Authorized | shares		75,000,000	75,000,000	75,000,000
Operating Lease, Right-of-Use Asset			$ 395,000			$ 629,000
Number of Financial Institutions			1
Accounts Receivable, Allowance for Credit Loss, Ending Balance		$ 284,000	$ 407,000	$ 284,000
Accounts Receivable, Allowance for Credit Loss, Writeoff			1,028,000	0
Inventory, Finished Goods, Net of Reserves		3,232,000	4,051,000	3,232,000
Inventory, Raw Materials, Net of Reserves		887,000	810,000	887,000
Deferred Income			662,000
Contract with Customer, Asset, after Allowance for Credit Loss, Total		0	0	0
Contract with Customer, Liability, Total		686,000	108,000	686,000
Capitalized Contract Cost, Net, Total		0	486,000	0
Capitalized Contract Cost, Amortization			143,000	0
Capitalized Contract Cost, Impairment Loss			0
Retained Earnings (Accumulated Deficit), Ending Balance		(155,385,000)	(197,911,000)	(155,385,000)
Gross Profit, Total			1,016,000	7,320,000
Equity Method Investment, Other than Temporary Impairment		0	$ 0
Series A Preferred Stock [Member]
Convertible Preferred Stock, Shares Issued upon Conversion | shares			1		1
Series B Preferred Stock [Member]
Conversion of Stock Exchange Ratio			653.59
Preferred Stock, Liquidation Preference Per Share | $ / shares			$ 1,000
Conversion of Stock, Conversion Rate | $ / shares			$ 1.53
Accounting Standards Update 2014-09 [Member]
Retained Earnings (Accumulated Deficit), Ending Balance		$ 177,000		177,000
Gross Profit, Total				$ 749,000
Minimum [Member]
Property, Plant and Equipment, Useful Life			3 years
Warranty Period			1 year
Maximum [Member]
Property, Plant and Equipment, Useful Life			7 years
Warranty Period			3 years
Medical Equipment, Sales Demos [Member]
Property, Plant and Equipment, Useful Life			5 years
Customer Concentration Risk [Member] | Revenue Benchmark [Member]
Concentration Risk, Number of Customers			1	1
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | One Customer [Member]
Concentration Risk, Percentage			16.00%	21.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member]
Concentration Risk, Number of Customers			2	3
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Two Customers [Member]
Concentration Risk, Percentage			49.00%
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Three Customers [Member]
Concentration Risk, Percentage				54.00%
Accrued Liabilities and Other Noncurrent Liabilities [Member]
Operating Lease, Liability, Total			$ 400,000			$ 629,000
Reverse Stock Split [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio	100