Thank you, Craig. Before I begin my prepared remarks, I would like to call your attention to our third quarter 2018 earnings results we've issued this morning. As the 3 months ended at September 30, 2018, rental income from medical services decreased 3.1% to $4,470,000 compared to rental income from medical services of $4,613,000 for the third quarter of 2017.
Net income attributable to the company for the third quarter was -- of 2018 was $168,000 or $0.03 per share. This compares to net income attributable to the company for the third quarter of 2017 of $99,000 or $0.02 per share. Third quarter revenue for our proton therapy system installed at Orlando Health, increased 11.3% to $1,041,000 compared to revenue for the third quarter of 2017 of $935,000.
Revenue from our Gamma Knife operations decreased 10.4% to $3,194,000 for the third quarter of 2018 compared to $3,564,000 for the third quarter of 2017 due to personnel issues at 3 customer sites, which have been then resolved. Rental income from medical services gross margin for the third quarter of 2018 decreased to $1,634,000 or 36.6% of revenue compared to rental income from medical services gross margin of $1,882,000 or 40.8% of revenues for the third quarter of 2017.
This reflected a decrease in Gamma Knife revenue and an increase in cost of revenue, primarily attributable to the initiation of maintenance and service costs for the company's proton system in Orlando. Non-GAAP pretax income, net of income attributable to the noncontrolling interest, was $250,000 for the third quarter of 2018. This compares to non-GAAP pretax income, net of income attributable to noncontrolling interests of $263,000 for the third quarter of 2017. Adjusted EBITDA, a non-GAAP financial measure, was $2,467,000 for the third quarter of 2018 compared to $2,412,000 for the third quarter of 2017.
A reconciliation of GAAP to non-GAAP financial measures is provided in our release third quarter 2018 results. Cash and cash equivalents and restricted cash was $2,189,000 at September 30, 2018, compared to $2,502,000 at December 31, 2017. Shareholder's equity at September 30, 2018, was $31,023,000 or $5.43 per outstanding share. This compares to shareholders' equity at December 31, 2017 of $29,885,000 or $5.23 per outstanding share.
This concludes the formal part of our presentation. We would like to turn the call back over to you for questions.