Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		Total	Preferred Stock	Preferred Stock	Preferred Stock Preferred Stock	Common Stock		Additional Paid-in Capital	Additional Paid-in Capital Preferred Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2019				0		2,486,000	[1]
Beginning balance at Dec. 31, 2019		$ 3,996		$ 0		$ 0		$ 128,873		$ (3)	$ (124,874)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock option and stock purchase plans (in shares)	[1]					60,000
Issuance of common stock under employee stock option and stock purchase plans		100						100
Common stock withheld in lieu of income tax withholding on vesting of restricted stock units		(3)						(3)
Issuance of common stock and warrants (in shares)	[1]					688,000
Issuance of common stock and warrants		2,749						2,749
Offering costs on issuance of common stock and warrants		(510)						(510)
Issuance of common stock upon the exercise of warrants (in shares)	[1]					269,000
Issuance of common stock upon the exercise of warrants		2,235						2,235
Warrant liability - issuance		(1,636)						(1,636)
Warrant liability - modification		1,405						1,405
Conversion of convertible securities (in shares)				112,000	2,709,000	22,000	[1]
Conversion of notes to preferred stock			$ 1,769						$ 1,769
Stock-based compensation		131						131
Net loss		(5,981)									(5,981)
Ending balance at Dec. 31, 2020		4,255		$ 0		$ 0		135,113		(3)	(130,855)
Ending balance (in shares) at Dec. 31, 2020				2,597,000		3,525,000	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under employee stock option and stock purchase plans (in shares)	[1]					79,000
Issuance of common stock under employee stock option and stock purchase plans		80						80
Common stock withheld in lieu of income tax withholding on vesting of restricted stock units		(1)						(1)
Issuance of common stock and warrants (in shares)	[1]					2,183,000
Issuance of common stock and warrants		9,500						9,500
Offering costs on issuance of common stock and warrants		$ (969)						(969)
Issuance of common stock upon the exercise of warrants (in shares)		237,892				237,000	[1]
Issuance of common stock upon the exercise of warrants		$ 801						801
Conversion of convertible securities (in shares)				1,721,000		344,000	[1]
Stock-based compensation		429						429
Net loss		(7,886)									(7,886)
Ending balance at Dec. 31, 2021		$ 6,209		$ 0		$ 0		$ 144,953		$ (3)	$ (138,741)
Ending balance (in shares) at Dec. 31, 2021				876,000		6,368,000	[1]

[1]       *Shares outstanding for prior periods have been restated for the 1-for-5 reverse stock split effective June 11, 2020.