Note 7 - Share-based Compensation (Tables)

9 Months Ended

Sep. 30, 2018

Notes Tables

Schedule of Share-based Compensation, Expense [Table Text Block]

	Three months ended September 30,				Nine months ended September 30,
	2018		2017		2018		2017
Cost of goods sold	$	39	$	33	$	105	$	107
Research and development		250		172		711		498
Selling, general and administrative		441		496		1,267		1,394
Share-based compensation expense	$	730	$	701	$	2,083	$	1,999

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

	Number of options outstanding			Weighted average exercise price
Balance, December 31, 2017		4,213,100		$	2.96
Stock options granted		1,698,452			2.41
Stock options exercised		(2,488	)		1.80
Stock options cancelled		(359,958	)		2.93
Balance, September 30, 2018		5,549,106		$	2.80

Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]

	Number of shares			Weighted average grant date fair value per share
Balance, December 31, 2017		97,996		$	8.71
RSUs granted		226,471			1.36
RSUs vested		(57,108	)		7.03
Balance, September 30, 2018		267,359		$	2.84

Non-employee Stock Options [Member]

Notes Tables

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

Risk-free interest rate	2.80%	-	2.84%
Volatility	78%	-	85%
Dividend yield		None
Expected term (in years)	7.9	-	8.8

Employee Stock Option [Member]

Notes Tables

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

Risk-free interest rate	2.66%	-	2.87%
Volatility	81%	-	82%
Dividend yield		None
Expected term (in years)		6.25