CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 10,760,000	$ 6,786,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	60,193,000	53,422,000
Amortization of operating lease right-of-use assets	49,948,000
Equity in earnings of joint ventures	(6,072,000)	(9,547,000)
Distributions from joint ventures	3,924,000	21,783,000
Amortization of deferred financing costs and loan discount	3,103,000	2,924,000
Loss (gain) on sale and disposal of equipment and other	1,990,000	(2,204,000)
Stock-based compensation	6,963,000	6,557,000
Other noncash items included in cost of operations	(559,000)	0
Change in fair value of contingent consideration	(1,749,000)	0
Changes in operating assets and liabilities, net of assets acquired and liabilities assumed in purchase transactions:
Accounts receivable	(3,467,000)	(9,641,000)
Other current assets	(1,569,000)	(5,680,000)
Other assets	(5,770,000)	(1,209,000)
Deferred taxes	(4,230,000)	1,531,000
Operating lease liability	(49,721,000)
Deferred rent	0	2,397,000
Deferred revenue	(490,000)	353,000
Accounts payable, accrued expenses and other	19,349,000	20,386,000
Net cash provided by operating activities	82,603,000	87,858,000
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of imaging facilities	(27,150,000)	(17,393,000)
Equity investments at fair value	(143,000)	(2,200,000)
Purchase of property and equipment	(68,269,000)	(62,595,000)
Proceeds from sale of equipment	760,000	2,587,000
Proceeds from the sale of equity interests in a joint venture	132,000	0
Nulogix return of capital	792,000	0
Equity contributions in existing and purchase of interest in joint ventures	(103,000)	(2,000,000)
Net cash used in investing activities	(93,981,000)	(81,601,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Principal payments on notes and leases payable	(4,778,000)	(4,374,000)
Payments on term loan debt	(29,918,000)	(24,810,000)
Proceeds from debt issuance	97,144,000	0
Distributions paid to noncontrolling interests	(1,818,000)	(913,000)
Proceeds from sale of noncontrolling interest	5,275,000	0
Contribution from noncontrolling partner	750,000	0
Proceeds from revolving credit facility	251,200,000	44,000,000
Purchase of noncontrolling interests	0	(200,000)
Payments on revolving credit facility	(279,200,000)	(44,000,000)
Proceeds from issuance of common stock upon exercise of options	50,000	10,000
Net cash provided by (used in) financing activities	38,705,000	(30,287,000)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(28,000)	(65,000)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	27,299,000	(24,095,000)
CASH AND CASH EQUIVALENTS, beginning of period	10,389,000	51,322,000
CASH AND CASH EQUIVALENTS, end of period	37,688,000	27,227,000
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid during the period for interest	36,058,000	27,136,000
Equipment acquired and leasehold improvements	14,100,000	14,200,000
Capital lease debt	$ 0	$ 4,000,000