An external review of the more than 3,500 mammograms and CT scans at Trillium Health Partners today revealed 11 of those patients had experienced "clinically significant events."

Eight of those 11 cases were caught and corrected by further testing, officials revealed Thursday, but three went unnoticed until the review put the work of Trillium radiologist Dr. Ivo Slezic under the microscope.

Trillium won't comment on the specifics of those cases, or how severe the patients’ health problems may be.

"It has been a difficult time for our patients," Trillium president and CEO Michelle DiEmanuele told CBC News. "And we apologize for the concern and patience they've had to show through this review." 

The review follows the case of Houda Rafle, who died last month after a battle with cancer that started as tiny tumor in her heart. Her test results were allegedly misread by Slezic, leading officials to double-check the 3,500 scans he handled between April 2012 and March 2013 at the Mississauga Hospital and the Queensway Health Centre in Toronto.

Rafle’s family is suing the hospital and Slezic.

Trillium said it will implement a peer review program for its radiology department — echoing a separate announcement by the province, which said Thursday it will put peer review programs in place at all Ontario hospitals that provide diagnostic scans.

A spokeswoman for Health Minister Deb Matthews said a second doctor will look at random samples of diagnostic images after they've been assessed by a radiologist.

Trillium takes other steps to maintain its quality of care, said DiEmanuele. "It's not just one thing we're doing, it's a continuation of many things we're doing. It's a series of initiatives, not just one," she said. 

Trillium Health is made up of the Credit Valley Hospital, Mississauga Hospital, and Queensway Health Centre, and serves a population of 1.15 million people.

With files from CBC's Genevieve Tomney and Canadian Press