Ravages of Miscalculation

 
 
By John McCormick  |  Posted 2004-03-08 Email Print this article Print
 
 
 
 
 
 
 


But inside the software, the calculations of appropriate dosages were going awry. The treatment time would be close to correct if Saldaña entered the data for the inner perimeter of the shape going in one direction, say clockwise, and the outer perimeter in the opposite direction, according to the IAEA report. But if she entered the data for the inner and outer perimeters going in the same direction, so that the two loops defining the perimeters crossed, the software essentially locked up. It was not able to accurately recognize the shape and, as a result, miscalculated the treatment times, the report said.

Depending on how many treatments the patients received, they accumulated overdoses ranging from 20 percent more radiation than was prescribed to a double dose of the potentially harmful rays, the IAEA found.

Inspectors from the FDA were dispatched to Multidatas offices after the agency received reports of patient "radiation overexposures." The inspection ran from May 31 to Sept. 21, 2001.

A summary of their findings echoed the IAEA report: "The treatment-planning system miscalculated the dose each patient was to receive due to failure of the software to correctly handle certain types of blocks... This resulted in a much higher dose being calculated for each patient."

Multidatas Conley says the FDAs finding "is wrong." He says that if you read FDA reports, "you find out the FDA isnt always right.

"Given [the input] that was given," he says, "our system calculated the correct amount, the correct dose. It was an unexpected result. And, if [the staff in Panama] had checked, they would have found an unexpected result."

Conley insists his company has done nothing wrong. He says the physicists at the National Cancer Institute never called Multidata asking for advice or support.

The physicists admit they did not always verify the results of the softwares calculations, which Multidatas manual said was "the responsibility of the user."

Saldaña says the hospital was treating more than 100 patients per day using the one Cobalt-60 machine. The IAEA also found that whatever steps the hospital took to ensure the radiation machine was operating properly only addressed the hardware. There was no quality-assurance program for the software-or its results.

In the day-to-day operations of the cancer institute, that meant the physicists were not required to tell anyone they had changed the way they entered data into the cancer-therapy system. As a result, no one on staff questioned the softwares results.

Had the hospital verified the dosages, by manually checking the softwares calculations or by testing the dosages in water before radiating patients, a procedure that Conley argues is standard medical practice in much of the rest of the world-the staff would have caught the overdoses in time to avoid harming anyone.

But independent experts not associated with the case say software that controls medical equipment and other life-critical devices should be designed to pause or shut down if told to execute a task its not programmed to perform.

"If a computer can make a user kill people, its like a loaded gun," says Jack Ganssle, an engineer whose Ganssle Group advises companies and developers on how to create high-quality software. "A user shouldnt be able to do anything that causes a machine to be dangerous."

But the Multidata software continued to operate.

Next Page: Cause of death.



 
 
 
 
 
 
 
 
 
 
 

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