Note 1 - Organization (Details Textual) - USD ($)				1 Months Ended		6 Months Ended
	Jul. 01, 2022	Jan. 14, 2022	Feb. 02, 2021	Jan. 31, 2022	Feb. 28, 2021	Jun. 30, 2022	May 20, 2022	Dec. 31, 2021
Retained Earnings (Accumulated Deficit), Total						$ (394,107,000)		$ (384,753,000)
Cash and Cash Equivalents, at Carrying Value, Total						$ 16,039,000		$ 19,497,000
Stock Issued During Period, Shares, New Issues (in shares)						326,466
Share Price (in dollars per share)						$ 1.46
Preferred Stock, Par or Stated Value Per Share (in dollars per share)						$ 0.001		$ 0.001
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)						1,006,285		132,265
Class of Warrant or Right, Outstanding (in shares)						43,936,895		26,456,895
Common Stock, Par or Stated Value Per Share (in dollars per share)						$ 0.001		$ 0.001
Common Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)		807,500
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 9.60
Warrants and Rights Outstanding, Term (Year)		5 years
Placement agent warrants issued in the January 2022 financing [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)		66,500				66,500
Class of Warrant or Right, Outstanding (in shares)						1,330,000
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 10.00				$ 10.00
Warrants and Rights Outstanding, Term (Year)		5 years
The Market Offering Agreement (the “ATM Agreement”) [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share)							$ 0.001
Share Offering Agreement, Aggregate Offering							$ 7,000,000
Commission Percentage							3.00%
Series D Preferred Stock [Member]
Preferred Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.001
Series D Preferred Stock [Member] | Common Warrants [Member]
Class of Warrant or Right, Outstanding (in shares)		807,500
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 9.60
Warrants and Rights Outstanding, Term (Year)		5 years
Series D Preferred Stock [Member] | Placement agent warrants issued in the January 2022 financing [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)		66,500
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 10.00
Warrants and Rights Outstanding, Term (Year)		5 years
January 2022 Public Offering [Member]
Proceeds from Issuance or Sale of Equity, Net		$ 6,700,000		$ 6,700,000
January 2022 Public Offering [Member] | Series D Preferred Stock [Member]
Stock Issued During Period, Shares, New Issues (in shares)		7,600
Shares Issued, Price Per Share (in dollars per share)		$ 1,000
Preferred Stock, Convertible, Conversion Price (in dollars per share)		$ 8.00
February 2021 Public Offering [Member]
Proceeds from Issuance or Sale of Equity, Net			$ 13,000,000.0		$ 13,000,000.0
Stock Issued During Period, Shares, New Issues (in shares)			500,000
Share Price (in dollars per share)			$ 28.80
Common Stock in June, 2022 [Member]
Stock Issued During Period, Shares, New Issues (in shares)	259,137
Shares Issued, Price Per Share (in dollars per share)	$ 1.56					$ 1.76
Proceeds from Issuance or Sale of Equity, Total	$ 400,000					$ 600,000
Proceeds from Commissions Received	$ 12,000					$ 17,000