Note 7 - Stockholders' Equity (Details Textual) | | | 3 Months Ended | 6 Months Ended | 12 Months Ended | | |
Jan. 14, 2022 USD ($) $ / shares shares | Feb. 14, 2018 | Jun. 30, 2022 USD ($) $ / shares shares | Jun. 30, 2021 USD ($) | Jun. 30, 2022 USD ($) $ / shares shares | Jun. 30, 2021 USD ($) shares | Dec. 31, 2021 $ / shares shares | Mar. 31, 2022 shares | Feb. 16, 2018 $ / shares |
Preferred Stock, Shares Authorized (in shares) | | | 5,000,000 | | 5,000,000 | | 5,000,000 | | |
Preferred Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares | | | $ 0.001 | | $ 0.001 | | $ 0.001 | | |
Preferred Stock, Shares Issued (in shares) | | | 56,451 | | 56,451 | | 56,451 | | |
Preferred Stock, Shares Outstanding, Ending Balance (in shares) | | | 56,451 | | 56,451 | | 56,451 | | |
Stock Issued During Period, Shares, New Issues (in shares) | | | | | 326,466 | | | | |
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) | | | 1,006,285 | | 1,006,285 | | 132,265 | | |
Preferred Stock Redemption Discount | $ | | | | | $ 5,111,000 | | | | |
Common Stock, Shares Authorized (in shares) | | | 100,000,000 | | 100,000,000 | | 100,000,000 | | |
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares | | | $ 0.001 | | $ 0.001 | | $ 0.001 | | |
Common Stock, Shares, Issued (in shares) | | | 6,081,333 | | 6,081,333 | | 4,778,263 | | |
Common Stock, Shares, Outstanding, Ending Balance (in shares) | | | 6,081,333 | | 6,081,333 | | 4,778,263 | | |
Share Price (in dollars per share) | $ / shares | | | $ 1.46 | | $ 1.46 | | | | |
Share-Based Payment Arrangement, Expense | $ | | | $ 36,000 | $ 303,000 | $ 88,000 | $ 721,000 | | | |
Restricted Stock Units (RSUs) [Member] | | | | | | | | | |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | $ | | | 100,000 | | $ 100,000 | | | | |
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year) | | | | | 3 months 18 days | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Fair Value | $ | | | 100,000 | | $ 100,000 | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value | $ | | | | | 3,000 | 88,000 | | | |
Share-Based Payment Arrangement, Expense | $ | | | $ 36,000 | 300,000 | $ 100,000 | 700,000 | | | |
Restricted Stock Units (RSUs) [Member] | Minimum [Member] | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year) | | | | | 3 years | | | | |
The 2015 Employee Stock Purchase Plan [Member] | | | | | | | | | |
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares) | | | 9,482 | | 9,482 | | | | |
Officer and Director Share Purchase Plan [Member] | | | | | | | | | |
Common Stock, Shares, Issued (in shares) | | | | | | | | 0 | |
Measurement Input, Expected Term [Member] | | | | | | | | | |
Warrants and Rights Outstanding, Measurement Input | 5.5 | | | | | | | | |
Measurement Input, Price Volatility [Member] | | | | | | | | | |
Warrants and Rights Outstanding, Measurement Input | 136.61 | | | | | | | | |
Measurement Input, Discount Rate [Member] | | | | | | | | | |
Warrants and Rights Outstanding, Measurement Input | 1.51 | | | | | | | | |
Measurement Input, Expected Dividend Rate [Member] | | | | | | | | | |
Warrants and Rights Outstanding, Measurement Input | 0 | | | | | | | | |
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) | $ / shares | $ 9.60 | | | | | | | | |
Warrants and Rights Outstanding, Term (Year) | 5 years | | | | | | | | |
Common Stock Warrants, Issued with Series D Convertible Preferred Stock [Member] | | | | | | | | | |
Proceeds from Issuance of Warrants | $ | $ 3,591 | | | | | | | | |
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 | | 66,500 | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares | $ 10 | | $ 10 | | $ 10 | | | | |
Warrants and Rights Outstanding, Term (Year) | 5 years | | | | | | | | |
January 2022 Public Offering [Member] | | | | | | | | | |
Proceeds from Issuance of Convertible Preferred Stock | $ | $ 4,009 | | | | | | | | |
Conversion of Series B Preferred Stock into Common Stock [Member] | | | | | | | | | |
Conversion of Stock, Shares Converted (in shares) | | | | | | | 93 | | |
Conversion of Stock, Shares Issued (in shares) | | | | | | | 18,600 | | |
Series A Preferred Stock [Member] | | | | | | | | | |
Preferred Stock, Shares Outstanding, Ending Balance (in shares) | | | 56,366 | | 56,366 | | | | |
Preferred Stock, Liquidation Preference Per Share (in dollars per share) | $ / shares | | | $ 1,000 | | $ 1,000 | | | | |
Preferred Stock, Convertible, Conversion Price (in dollars per share) | $ / shares | | | $ 400 | | $ 400 | | | | |
Dividends, Preferred Stock, Total | $ | | | $ 1,100,000 | $ 1,000,000 | $ 2,300,000 | $ 2,100,000 | | | |
Series A Preferred Stock [Member] | CRG [Member] | | | | | | | | | |
Preferred Stock Dividends, Shares (in shares) | | | | | | | 4,175 | | |
Series A Preferred Stock [Member] | Conversion of Principal Amount of Senior Secured Loan to Newly Authorized Series A Preferred Stock [Member] | | | | | | | | | |
Preferred Stock, Dividend Rate, Percentage | | 8% | | | | | | | |
Series B Preferred Stock [Member] | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares | | | | | | | | | $ 0.001 |
Preferred Stock, Shares Outstanding, Ending Balance (in shares) | | | 85 | | 85 | | 85 | | |
Preferred Stock, Convertible, Conversion Price (in dollars per share) | $ / shares | | | $ 5 | | $ 5 | | $ 5 | | |
Series D Preferred Stock [Member] | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares | $ 0.001 | | | | | | | | |
Conversion of Stock, Shares Converted (in shares) | | | 2,400 | | 7,600 | | | | |
Conversion of Stock, Shares Issued (in shares) | | | 300,000 | | | 950,000 | | | |
Series D Preferred Stock [Member] | Common Warrants [Member] | | | | | | | | | |
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares | $ 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) | $ / shares | $ 10 | | | | | | | | |
Warrants and Rights Outstanding, Term (Year) | 5 years | | | | | | | | |
Series D Preferred Stock [Member] | January 2022 offering [Member] | | | | | | | | | |
Preferred Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares | $ 0.001 | | | | | | | | |
Preferred Stock, Convertible, Conversion Price (in dollars per share) | $ / shares | $ 8 | | | | | | | | |
Stock Issued During Period, Shares, New Issues (in shares) | 7,600 | | | | | | | | |
Shares Issued, Price Per Share (in dollars per share) | $ / shares | $ 1,000 | | | | | | | | |
Preferred Stock, Convertible, Shares Issuable (in shares) | 950,000 | | | | | | | | |
Series D Preferred Stock [Member] | January 2022 offering [Member] | Common Warrants [Member] | | | | | | | | | |
Conversion of Warrants Allowed Maximum Ownership of Common Stock Percentage | 4.99% | | | | | | | | |
Conversion of Warrants Allowed Maximum Ownership of Common Stock Percentage upon Election | 9.99% | | | | | | | | |
Series D Preferred Stock [Member] | January 2022 Public Offering [Member] | | | | | | | | | |
Preferred Stock, Convertible, Conversion Price (in dollars per share) | $ / shares | $ 8 | | | | | | | | |
Stock Issued During Period, Shares, New Issues (in shares) | 7,600 | | | | | | | | |
Shares Issued, Price Per Share (in dollars per share) | $ / shares | $ 1,000 | | | | | | | | |