Note 5 - Share-based Compensation (Tables)

9 Months Ended

Sep. 30, 2018

Notes Tables

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

	Nine Month Period Ended
	September 30, 2018
				Wtd. Avg.
				Exercise
	Options			Price
Outstanding at beginning of year		2,390,012		$	1.85
Granted		—		$	—
Exercised		(267,055	)	$	1.30
Forfeited		(15,627	)	$	4.34
Expired		—		$	—
Outstanding service vesting-based at September 30, 2018		2,107,330		$	1.90
Service vesting-based options exercisable at September 30, 2018		1,622,980		$	1.83

	Nine Month Period Ended
	September 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 September 30, 2018		964,997		$	1.64
Performance-based options exercisable at September 30, 2018		465,001		$	1.64

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

	Three Month Period Ended				Nine Month Period Ended
	September 30,				September 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]

	Nine Month Period Ended
	September 30, 2018
	Number of Restricted Shares			Grant-Date Fair Value
Outstanding at beginning of year		237,926		$	1.79
Granted		181,268		$	7.02
Vested		(96,593	)	$	1.80
Forfeited		(21,128	)	$	3.32
Outstanding at September 30, 2018		301,473		$	4.82

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

	Three Month Period Ended				Nine Month Period Ended
	September 30,				September 30,
	2018		2017		2018		2017
Research and development costs	$	64,970	$	59,434	$	195,316	$	177,514
Sales and marketing costs		64,152		55,402		201,907		173,072
General and administrative costs		194,764		156,621		576,718		479,803
Cost of product sales		59,254		42,486		157,004		127,322
Total	$	383,140	$	313,943	$	1,130,945	$	957,711