Murphy, who is in charge of neurological testing with the scanner, says the expanded coverage is a "tremendous advantage" over older machines, where images had to be matched and stacked, "like reconstructing layers of a marble statue on top of each other over time," a technologically complex procedure.

Cooling systems, he also notes, will no longer be required to deal with the friction and heat caused by multiple rotations of the gantry, although a cooling system will still be required for the computer hardware. Murphy says the increase in data traffic will range from 5 gigabytes to 10 gigabytes per scan with the 256-CT. With 64-CT, the range is 1gigabyte to 2.5 gigabytes.


However, he does not expect the higher volume of data to slow testing, which is expected to speed up imaging the brain to less than 1 second for the 256-CT, down from 4 or 5 seconds with the 64-CT. Lima says the overall time required for testing the heart will similarly decline to 1 or 2 seconds with the 256-CT, from eight to 10 seconds with the 64-CT.

Lima says the new, faster device will also make it possible to scan patients with arrhythmia, or irregular heartbeats. The 256-CT can acquire a full image in the time it takes for just one beat, whereas the 64-CT takes longer, as much as six or eight heartbeats. Any disturbances between successive beats, he notes, such as those produced in arrhythmia, can lead to distortions in the composite scanned image.

A single scan with the 256-CT device can also perform a full bank of five key diagnostic tests on hearts or single tests in the brain of the most severely ill patients, exposing them to far less radiation, as little as one-eighth to one-third of the dose required in testing with the 64-slice scanner.

Because single scans with the 256-CT should provide a patient's calcium score, to detect hardening of the arteries, along with blood-flow data and strength of the pulse and heartbeat, it is expected to have value in determining more precisely the best candidates for more invasive procedures, such as cardiac catheterization or catheter angiograms of the brain.

The new scanner and nine technicians are on loan to Hopkins from Toshiba America Medical Systems Inc. Installation and renovation costs for its temporary installation at Hopkins were also paid for by Toshiba.


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