CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES
Net (loss) income	$ (12,734)	$ 10,760
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	64,536	60,193
Amortization of operating lease right-of-use assets	50,769	49,948
Equity in earnings of joint ventures	530	(2,148)
Amortization of deferred financing costs and loan discount	3,266	3,103
Loss on sale and disposal of equipment and other	543	1,990
Amortization of cash flow hedge	2,204	0
Non-cash change in fair value of interest rate hedge	4,523	0
Stock-based compensation	10,144	6,963
Other non-cash items included in cost of operations	0	(559)
Change in fair value of contingent consideration	(145)	(1,749)
Changes in operating assets and liabilities, net of assets acquired and liabilities assumed in purchase transactions:
Accounts receivable	17,380	(3,467)
Other current assets	13,522	(1,569)
Other assets	(700)	(5,770)
Deferred taxes	(7,640)	(4,230)
Operating lease liability	(43,351)	(49,721)
Deferred revenue	44,530	(490)
Accounts payable, accrued expenses and other	22,966	19,349
Net cash provided by operating activities	170,343	82,603
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of imaging facilities and other acquisitions	(10,125)	(27,150)
Equity investments at fair value	0	(143)
Purchase of property and equipment	(77,303)	(68,269)
Proceeds from sale of equipment	779	760
Proceeds from the sale of equity interests in a joint venture	0	132
Nulogix return of capital	0	792
Equity contributions in existing and purchase of interest in joint ventures	(1,631)	(103)
Net cash used in investing activities	(88,280)	(93,981)
CASH FLOWS FROM FINANCING ACTIVITIES
Principal payments on notes and leases payable	(2,704)	(4,778)
Payments on term loan debt	(32,472)	(29,918)
Additional deferred finance costs on revolving loan amendment	(741)	0
Proceeds from debt issuance, net of issuing costs	0	97,144
Proceeds from Payment Protection Program	4,023	0
Distributions paid to noncontrolling interests	(601)	(1,818)
Proceeds from sale of noncontrolling interest	0	5,275
Contribution from noncontrolling partner	0	750
Proceeds from revolving credit facility	250,900	251,200
Payments on revolving credit facility	(250,900)	(279,200)
Proceeds from issuance of common stock upon exercise of options	0	50
Net cash (used in) provided by financing activities	(32,495)	38,705
EFFECT OF EXCHANGE RATE CHANGES ON CASH	6	(28)
NET INCREASE IN CASH AND CASH EQUIVALENTS	49,574	27,299
CASH AND CASH EQUIVALENTS, beginning of period	40,165	10,389
CASH AND CASH EQUIVALENTS, end of period	89,739	37,688
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid during the period for interest	31,210	36,058
Equipment acquired and leasehold improvements	$ 28,100	$ 14,100