Revenue Recognition, Contract Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Treatment Equipment [Abstract]
Lease term	36 months		36 months
Contract with Customer, Liability [Abstract]
Short-term contract liabilities	$ 51		$ 51
Long-term contract liabilities	18		18
Change in Contract with Customer, Liability [Abstract]
Contract liabilities recognized as revenue	20	$ 53	54	$ 110
Co-pay reimbursements recorded as reduction of revenue	$ (186)	$ (86)	$ (343)	$ (254)
Minimum [Member]
Treatment Equipment [Abstract]
Notice period to cancel contract agreement			30 days
Maximum [Member]
Treatment Equipment [Abstract]
Notice period to cancel contract agreement			60 days
South Korea [Member]
Treatment Equipment [Abstract]
Lease term	48 months		48 months