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, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2009	Dec. 31, 2008	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2018	Oct. 31, 2018	Sep. 30, 2017	Apr. 30, 2016	Dec. 31, 2014	Dec. 31, 2013
Operating Leases [Abstract]
Operating Lease and Lease Liability							$ 176,000
ROU asset							$ 161,000
Operating lease right-of-use asset					$ 59,000	$ 94,000				$ 68,000	$ 77,000	$ 86,000
Operating lease expense					41,000	42,000
Maturities of operating lease liability [Abstract]
2022					46,000
2023					24,000
Total					70,000
Less interest					(4,000)
Present value of net minimum obligation					66,000	106,000
Gamma Knife [Abstract]
Operating lease amount					$ 66,000	106,000
Maintenance Contract [Abstract]
Warranty 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]
Capital lease obligation					$ 0	$ 0
Monthly lease payment																		$ 78,000
Gamma Knife Cobalt Reload [Member]
Gamma Knife [Abstract]
Monthly lease payment														$ 30,000
NYU [Member]
Gamma Knife [Abstract]
Equipment financed term					7 years
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]
Maturities of operating lease liability [Abstract]
Present value of net minimum obligation																	$ 4,700,000
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]
Maturities of operating lease liability [Abstract]
Present value of net minimum obligation																	250,000
Gamma Knife [Abstract]
Equipment financed term					2 years
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
Monthly lease payment													$ 50,000