Commitments and Contingencies, Operating Leases, Gamma Knife and Maintenance Contract (Details) - USD ($)		1 Months Ended			12 Months Ended
	Sep. 01, 2014	Jul. 31, 2018	Aug. 31, 2017	Apr. 30, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2009	Dec. 31, 2008	Oct. 31, 2018	Sep. 30, 2017	Apr. 30, 2016	Dec. 31, 2014	Dec. 31, 2013
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019					$ 42,000
2020					43,000
2021					45,000
2022					46,000
2023					24,000
Total future rental payments					200,000
Rent expense					$ 42,000	$ 46,000
Maintenance Contract [Abstract]
Warrant term of maintenance agreement					1 year
Monthly maintenance agreement cost			$ 26,000	$ 20,000
Maintenance agreement					5 years
Perfexion Gamma Knife [Member]
Gamma Knife [Abstract]
Equipment financed term					7 years
Capital lease obligation					$ 2,387,000	$ 2,638,000
Monthly lease payment													$ 78,000
Perfexion Gamma Knife, Purchase and Replacement [Member]
Gamma Knife [Abstract]
Equipment financed term					24 months
Perfexion Gamma Knife, Leasehold Improvements, New Installation and Related Construction Costs [Member]
Gamma Knife [Abstract]
Equipment financed term					72 months
Gamma Knife Cobalt Reload [Member]
Gamma Knife [Abstract]
Equipment financed term					30 months
Capital lease obligation									$ 833,000
Monthly lease payment									30,000
NYU [Member]
Gamma Knife [Abstract]
Monthly lease payment										$ 50,000
NYU [Member] | Perfexion Gamma Knife [Member]
Gamma Knife [Abstract]
Cost of new equipment installed							$ 3,742,000	$ 3,742,000
Equipment financed term					7 years
NYU [Member] | Perfexion Gamma Knife, Purchase and Replacement [Member]
Gamma Knife [Abstract]
Equipment financed term					6 years
Operating lease amount												$ 4,700,000
Capital lease obligation											$ 879,000
Lease payment due	$ 78,000
Interest on lease	$ 18,000
Monthly lease payment											$ 20,000
NYU [Member] | Perfexion Gamma Knife, Leasehold Improvements, New Installation and Related Construction Costs [Member]
Gamma Knife [Abstract]
Operating lease amount												$ 250,000
NYU [Member] | Gamma Knife Cobalt Reload [Member]
Gamma Knife [Abstract]
Cost of new equipment installed		$ 925,000
Equipment financed term					30 months
Capital lease obligation		$ 833,000							$ 833,000
Monthly lease payment					$ 50,000