Note 5 - Share-based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

Notes Tables

Share-based Compensation, Stock Options, Activity [Table Text Block]

	Six Month Period Ended
	June 30, 2018
				Wtd. Avg.
				Exercise
	Options			Price
Outstanding at beginning of year		2,390,012		$	1.85
Granted		—		$	—
Exercised		(142,914	)	$	1.19
Forfeited		(8,022	)	$	4.30
Expired		—		$	—
Outstanding service vesting-based at June 30, 2018		2,239,076		$	1.89
Service vesting-based options exercisable at June 30, 2018		1,652,714		$	1.80

	Six Month Period Ended
	June 30, 2018
				Wtd. Avg.
				Exercise
	Options			Price
Outstanding at beginning of year		999,997		$	1.64
Granted		—		$	—
Exercised		(35,000	)	$	1.64
Outstanding performance-based at June 30, 2018		964,997		$	1.64
Performance-based options exercisable at June 30, 2018		465,001		$	1.64

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Three Month Period Ended				Six Month Period Ended
	June 30,				June 30,
	2018		2017		2018		2017
Risk free interest rate		N/A		N/A		N/A		2.07	%
Dividend yield		N/A		N/A		N/A		0.0	%
Expected term (in years)		N/A		N/A		N/A		5.18
Volatility		N/A		N/A		N/A		75	%

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

	Six Month Period Ended
	June 30, 2018
	Number of Restricted Shares			Grant-Date Fair Value
Outstanding at beginning of year		237,926		$	1.79
Granted		173,768		$	6.47
Vested		(76,538	)	$	1.79
Forfeited		(13,952	)	$	2.47
Outstanding at June 30, 2018		321,204		$	4.29

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Three Month Period Ended				Six Month Period Ended
	June 30,				June 30,
	2018		2017		2018		2017
Research and development costs	$	64,752	$	58,815	$	130,346	$	118,080
Sales and marketing costs		69,242		58,051		137,755		117,670
General and administrative costs		191,003		154,983		381,953		323,181
Cost of product sales		49,383		42,024		97,751		84,837
Total	$	374,380	$	313,873	$	747,805	$	643,768