Note 8 - Summary of Stock Options (Tables)

3 Months Ended

Mar. 31, 2016

Notes Tables

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

	Three Months Ended March 31, 2016
						Weighted
				Weighted		Average		Aggregate
	Number			Average		Remaining		Intrinsic
	of			Exercise		Contractual		Value
	Shares			Price		Term (years)		(in thousands)
Options outstanding, beginning of period		1,022,195		$	6.47		9.37	$	-
Options granted		129,267		$	6.35
Options exercised		(1,314	)	$	4.80
Options canceled		(18,380	)	$	8.55
Options outstanding, end of period		1,131,768		$	6.42		9.24	$	414,727
Vested and exercisable and expected to vest, end of period		1,035,338		$	6.48		9.22	$	392,137
Vested and exercisable, end of period		179,832		$	9.86		7.90	$	125,415

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

			Options Outstanding						Options Exercisable
							Weighted
			Number		Weighted		Average		Number		Weighted
			Outstanding		Average		Remaining		Exercisable		Average
Range of			as of		Exercise		Contractual		as of		Exercise
Exercise Prices			March 31, 2016		Price		Term (Years)		March 31, 2016		Price
	$2.64			12,500	$	2.64		9.12		-	$	-
$3.68	-	$3.76		79,376	$	3.75		8.86		21,498	$	3.75
	$4.80			212,300	$	4.80		8.43		81,288	$	4.80
	$6.00			609,003	$	6.00		9.72		29,599	$	6.00
$6.24	-	$6.40		129,267	$	6.35		9.91		-	$	-
$7.12	-	$7.92		41,875	$	7.67		9.35		-	$	-
	$9.92			38,429	$	9.92		6.59		38,429	$	9.92
$56.00	-	$72.00		6,810	$	69.63		1.42		6,810	$	69.63
$96.00	-	$149.04		2,176	$	119.53		1.49		2,176	$	119.53
	$296.00			32	$	296.00		1.48		32	$	296.00
				1,131,768	$	6.42		9.24		179,832	$	9.86

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

	Three Months Ended
	March 31
	2016			2015
Expected term (in years)		5			5
Average volatility		66	%		62	%
Risk-free interest rate		1.55	%		1.32	%
Dividend yield		0	%		0	%

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

	Three Months Ended
	March 31,
	2016		2015
Research and development	$	21	$	4
Selling, general and administrative		167		38
Total	$	188	$	42