Statement of Changes in Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total
Begining balance at Dec. 31, 2017	$ 1	$ 81,118	$ (73,597)	$ 7,522
Begining balance (in shares) at Dec. 31, 2017	820,509
Issuance of common stock, sold for cash, net		5,133		5,133
Issuance of common stock, sold for cash, net (in shares)	267,852
Issuance of common stock for services		36		36
Issuance of common stock for services (in shares)	11,060
Stock-based compensation		1,691		1,691
Issuance of warrants		1,693		1,693
Issuance of common stock upon cashless exercise of stock options
Issuance of common stock upon cashless exercise of stock options (in shares)	695
Issuance of common stock upon exercise of warrants		2,214		2,214
Issuance of common stock upon exercise of warrants (in shares)	73,738
Option forfeitures and expirations		(67)		(67)
Payments for employee withholding taxes related to share-based awards
Warrant antidilution price protection adjustment		333	(333)
Warrant revaluation
Net loss			(11,908)	(11,908)
Ending balance at Dec. 31, 2018	$ 1	92,151	(85,838)	6,314
Ending balance (in shares) at Dec. 31, 2018	1,173,854
Issuance of common stock, sold for cash, net		3,631		3,631
Issuance of common stock, sold for cash, net (in shares)	151,838
Issuance of common stock for services		34		34
Issuance of common stock for services (in shares)	7,203
Stock-based compensation		873		873
Issuance of common stock upon exercise of warrants		1,788		1,788
Issuance of common stock upon exercise of warrants (in shares)	80,511
Issuance of common stock upon exercise of stock options
Issuance of common stock upon exercise of stock options (in shares)	1,265
Payments for employee withholding taxes related to share-based awards		(55)		(55)
Warrant revaluation		11		11
Net loss			(10,029)	(10,018)
Ending balance at Dec. 31, 2019	$ 1	$ 98,433	$ (95,867)	$ 2,567
Ending balance (in shares) at Dec. 31, 2019	1,414,671