In a statement last week, hospital officials said all the patients had been contacted "in the interest of keeping them informed."
"The word 'radiation' never came out of his mouth," said Larry Biggles, who described a brief call he got in late September, a year after he arrived at the emergency room and a scan revealed that he had suffered a stroke.
He said that Dr. Barry D. Pressman, chairman of the imaging department, explained that he was following up on the scan and wanted to know whether Biggles had suffered headaches, blurred vision or hair loss.
Two days after the scan, Biggles had lost clumps of hair in the shower, leaving him bald from the tops of his ears to his neck. The hair had since grown back, he told the doctor, and that was the end of the conversation.
"He never said that we messed up and gave you an overdose of radiation," said Biggles, a 51-year-old dispatcher for a messenger company.
At least now, he said, he knows to be on the alert for any long-term effects.
In a written statement Monday, Pressman said that the radiation was not outside the range used in other medical procedures -- such as angioplasties -- and that his goal in speaking with patients was "to address any side-effects that may occur, without unnecessarily alarming them."
He said that any questions, including those about radiation levels, were addressed. "I sincerely regret if any patient feels that they did not receive the information they needed," he said.
Cedars-Sinai has said the overdoses stemmed from an error made when the hospital reconfigured a scanner to improve doctors' ability to see blood flow in the brain.
The faulty scans began in February 2008 -- after the computerized protocols were modified -- and continued until this August when the hospital discovered the error after learning of a patient's hair loss.
The machine in question was used to perform various types of scans but the problem was limited to CT brain perfusion scans, which are used to diagnose strokes.
Under normal circumstances, the procedure uses more radiation than most other CT scans. It lasts up to a minute as the patient is injected with an iodine solution and a rapid series of X-rays are taken to create a detailed picture of blood flow in the brain.
The most serious risk from the radiation overdose is a brain tumor. Radiation experts said that chance is remote, perhaps 1 in 600 for each scan.
Because the risk from radiation is cumulative and cancers can take decades to develop, younger patients who received multiple scans face the greatest danger. Older patients are likely to die of causes unrelated to the radiation. The median age of those affected at Cedars-Sinai is 70.
If harm was done, the hospital would have a legal obligation to tell patients of any mistake, said George Annas, an ethicist and lawyer at Boston University. But legal responsibility is fuzzy in this case, he said, and comes down to how harm is defined.
From an ethical standpoint, he said, Cedars-Sinai should have fully informed all the patients of the error. "This is part of a trend in patient safety," he said. "Whenever you make an error, you tell the patient."
He dismissed arguments that revealing a small risk would lead to needless worrying, saying that full disclosure fosters trust between doctors and patients.