Note 10 - Commitments and Contingencies (Details Textual) - USD ($)			12 Months Ended
	Sep. 04, 2022	Sep. 05, 2017	Dec. 31, 2022
Leksell Gamma Knife Icon Systems and Linear Accelerator System [Member]
Long-term Install Service and Purchase Commitment, Amount			$ 13,243,000
Long-term Commitment, Cash on Hand to Fund			12,453,000
Long-term Commitment, Line of Credit to Fund			7,000,000
LINAC System [Member]
Long-Term Service Commitment, Amount			$ 15,374,000
LINAC System [Member] | Maximum [Member]
Long-Term Service Commitment, Period (Year)			9 years
LINAC System [Member] | Minimum [Member]
Long-Term Service Commitment, Period (Year)			5 years
Mevion PBRT Units [Member] | Upgrade and Purchase MEVION Systems [Member]
Long-term Purchase Commitment, Amount			$ 34,000,000
Mevion Medical Systems Inc [Member] | Maintenance And Support Agreement, Mevion Service Agreement [Member]
Purchase Agreement Annual Prepayment	$ 1,800,000
Long-term Purchase Commitment, Period (Year)	1 year	1 year