Note 6 - Loss Per Share - Shares Used in Basic and Diluted Loss Per Common Share Computations (Details) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Net loss available in basic and diluted calculation		$ (2,373,410)	$ (2,543,670)	$ (4,133,432)	$ (3,885,517)
Weighted average common shares outstanding-basic (in shares)		11,878,490	6,167,689	11,632,221	6,308,554
Effect of diluted stock options, warrants and preferred stock (1) (in shares)	[1]
Loss per common share - basic and diluted (in dollars per share)		$ (0.20)	$ (0.41)	$ (0.36)	$ (0.62)

[1] The number of shares underlying options and warrants outstanding as of June 30, 2018 and June 30, 2017 are 5,693,808 and 3,850,878, respectively. The number of shares underlying the preferred stock as of June 30, 2018 is 79,246. The effect of the shares that would be issued upon exercise of such options, warrants and preferred stock has been excluded from the calculation of diluted loss per share because those shares are anti-dilutive.