Note 10 - Summary of Stock Options (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Nine Months Ended September 30, 2019
						Weighted
				Weighted		Average
	Number			Average		Remaining		Aggregate
	of			Exercise		Contractual		Intrinsic
	Shares			Price		Term (years)		Value
Options outstanding, beginning of period		40,144		$	456.00		7.4	$	-
Options granted		23,344		$	117.91
Options exercised		-
Options canceled		(13,017	)	$	457.34
Options outstanding, end of period		50,471		$	298.99		8.3	$	-
Vested and exercisable and expected to vest, end of period		48,506		$	302.18		8.3	$	-
Vested and exercisable, end of period		21,169		$	397.45		7.4	$	-

Share-based Payment Arrangement, Option, Exercise Price Range [Table Text Block]

			Number		Weighted		Average		Number		Weighted
			Outstanding		Average		Remaining		Exercisable		Average
Range of			as of		Exercise		Contractual		as of		Exercise
Exercise Prices			September 30, 2019		Price		Term (Years)		September 30, 2019		Price
$38.00	-	$58.00		1,650	$	55.42		9.7		-	$	-
$100.00	-	$197.00		25,496	$	138.25		9.1		6,839	$	148.08
$202.00	-	$283.00		775	$	252.06		8.3		305	$	258.36
$311.00	-	$382.00		4,377	$	357.96		8.1		2,318	$	360.44
$430.00	-	$497.00		8,908	$	452.58		7.7		4,576	$	454.70
$501.00	-	$567.00		4,594	$	536.63		6.9		3,126	$	536.17
$600.00	-	$661.00		2,397	$	601.91		5.9		2,236	$	601.42
$700.00	-	$792.00		2,170	$	769.23		6.3		1,665	$	769.86
$992.00	-	$992.00		104	$	992.00		3.3		104	$	992.00
Total:				50,471	$	298.99		8.3		21,169	$	397.45

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

	Three Months Ended					Nine Months Ended
	September 30,					September 30,
	2019		2018			2019			2018
Expected term (in years)		N/A		5			5			5
Average volatility		N/A		70	%		73	%		73	%
Risk-free interest rate		N/A		2.86	%		2.49	%		2.67	%
Dividend yield		N/A		0	%		0	%		0	%

	Three Months Ended					Nine Months Ended
	September 30,					September 30,
	2019		2018			2019			2018
Expected term (in years)		N/A		10			5			10
Average volatility		N/A		66	%		73	%		66	%
Risk-free interest rate		N/A		3.04	%		2.49	%		3.04	%
Dividend yield		N/A		0	%		0	%		0	%

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2019		2018		2019		2018
Cost of revenue	$	25	$	19	$	91	$	47
Research and development		41		79		134		266
Selling, general and administrative		451		667		1,409		1,981
Total	$	517	$	765	$	1,634	$	2,294

2017 Employee Stock Purchase Plan [Member]

Notes Tables

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

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2019			2018			2019			2018
Expected term (in years)		0.25			0.25			0.25			0.25
Average volatility		98	%		67	%		84	%		67	%
Risk-free interest rate		2.21	%		1.93	%		2.40	%		1.71	%
Dividend yield		0	%		0	%		0	%		0	%