Note 5 - Stockholders' Equity, Stock Options and Warrants (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]

	Year Ended December 31,
	2019			2018
	Stock Options
Expected dividend yield		0.0%			0.0 %
Expected stock price volatility	78.6%	-	82.4%		66.0 %
Risk-free interest rate	1.50%	-	2.76%	2.46%	-	3.07%
Expected life of options (in years)		10			10
	Warrants
Expected dividend yield		0.0 %			0.0 %
Expected stock price volatility	78.6%	-	82.4%		59.0 %
Risk-free interest rate	1.39%	-	2.58%	2.33%	-	2.96%
Expected life of options (in years)		5			5

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

	Stock Options					Warrants
	Number of Shares			Average Exercise Price		Number of Shares			Average Exercise Price
Outstanding at December 31, 2017		276,498		$	19.95		195,126		$	237.40
Issued		109,886			10.13		233,615			10.67
Forfeited		(19,456	)		20.00		(1,071	)		1,995.53
Exercised		-			-		(65,006	)		10.00
Outstanding at December 31, 2018		366,928		$	17.03		362,664		$	41.67
Issued		423,295			6.53		1,869,299			9.25
Forfeited		(23,799	)		13.30		(653	)		3,249.28
Exercised		-			-		(59,700	)		0.10
Outstanding at December 31, 2019		766,424		$	11.34		2,171,610		$	15.26

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

Range of Exercise Prices	Shares		Weighted Average Remaining Life
Options:
$2.61 – 6.50		157,848		9.53
$7.324 – 8.491		285,826		9.07
$9.00 – 14.70		310,882		7.50
$21.00 – 51.25		11,045		6.90
$657.50 – 5,962.50		823		4.39
Total		766,424
Warrants:
$0.10 – 8.36		250,145		4.56
$10.00		1,674,088		4.22
$10.71 – 22.50		237,970		3.23
$1,237.50		9,407		0.67
Total		2,171,610

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]

Year	Shares		Price
2011		17			$ 2,812.50
2012		171		1,312.50	–	1,500.00
2013		150		1,481.25	–	5,962.50
2014		84		1,625.00	–	4,312.50
2015		401		657.50	–	862.50
2016		9,617		22.50	–	51.25
2017		235,053		10.10	–	21.00
2018		97,636		6.19	–	13.50
2019		423,295		2.61	–	9.00
Total		766,424		$0.45	–	5962.50

Year	Shares		Price
2015		9,407			$ 1,237.50
2016		25,233			10.00
2017		108,295		10.71	–	22.50
2018		219,076		8.36	–	13.125
2019		1,809,599		2.50	–	11.88
Total		2,171,610		$2.50	–	3,095.00