New scanner reduces exposure, but at high cost
New scanner reduces exposure, but at high cost
One of the most appealing features in some of the newer, more powerful CT scanning devices is that they can do the job while exposing the patient to less radiation — in some cases significantly less, according to vendors.
For example, the Aquilion One device, made by Tustin, CA-based Toshiba Medical Systems, is the most powerful X-ray imaging machine in its class. The 4,400 pound device, which recently has been approved by the Food and Drug Administration, can perform a cardiac CT exam with 80% less radiation than a standard 64-slice CT device, according to Robb Young, senior manager of Toshiba's CT Business Unit.
This reduction in radiation is possible because with 320 detector rows, the device can complete a cardiac exam with just one rotation, whereas a standard helical exam performed by a 64-slice CT device requires multiple rotations, Young says. Of the 64-slice devices, Young says, "It is like a slinky going around the patient like some sort of spring, and you have to overlap that heavily in the heart because the heart moves so much. When you use the Aquilion One, you can eliminate all of that overlap."
There is not as much overlap required for a standard CT exam of the brain, but Young suggests the Aquilion One still can perform that exam with 25% less radiation than a 64-slice CT. It is a "huge breakthrough" because all the CT devices on the market are looking at dose reduction, but from the standpoint of basic physics, they are still required to do this overlap, he says.
In addition to reducing the amount of radiation required to perform an exam and improving temporal resolution, the approach offers several other advantages, according to Richard George, MD, an assistant professor of medicine in the Division of Cardiology at Johns Hopkins University, which is one of two early users of the Aquilion One device. "The ability to image the heart over one heartbeat or less eliminates the need to reconstruct images over multiple heartbeats into a full cardiac volume. This eliminates step artifacts often seen with other scanners," he says. "Also, shorter scan times require lower contrast doses and fewer opportunities for motion artifacts, secondary to patient movement." George adds that full cardiac coverage over the course of a single heart beat allows for imaging in the setting of arrhythmias.
Device transitions from slices to volume
Another advantage of the technology, according to young, is that it is easier to use because clinicians don't have to worry about table speed, rotations, and making sure they have the right overlap. "It is easy to do in one quick, flash moment and get the image, so we see training as incremental to what [clinicians] already know from their multi-slice CT devices," he says.
Further, unlike the multi-slice devices that capture many slices or images for the clinician to review, the Aquilion One captures one 16 cm volume. "Physicians want to read organ anatomy. They don't want to read slices," says Young. "So this gets them to what they want to look at. They want to look at the whole heart or the whole brain, not just a slice of the heart or a slice of the brain."
The advantages offered by 320 detector rows appear to be substantial for this technology, which carries a $2.5 million price tag. Kieran Murphy, MD, an associate professor of radiology at Johns Hopkins University School of Medicine in Baltimore, MD, says that the technology is capable of reducing costs as well. For example, he points out that it substantially reduces the cost of performing a diagnostic cerebral angiogram. "It takes an $8,000 procedure and reduces it to a $450 procedure, "he says. "And it is perfect for patients because something that would have been frightening to them like a catheter cerebral angiogram is reduced to what will feel like a CT scan."
Murphy also sees the technology as a breakthrough in the way acute stroke patients are examined. "You now have a method of doing CT scans to rule out bleeds," he says. Murphy notes that a CT scan can be used for perfusion to look at stroke volume, and CT angiography can be used to locate the site of a blockage. This all can be done in the space of 3-4 minutes, says Murphy. "That changes how care is delivered and accelerates the onset of therapy," he says.
Currently, there are only three devices in use in the United States at Johns Hopkins, Brigham and Women's Hospital in Boston, and Nevada Imaging Centers in Las Vegas.
(Editor's note: For more information about Toshiba's Aquilion One, or to view images produced by the device, visit www.medical.toshiba.com/Products/CT/DynamicVolume).One of the most appealing features in some of the newer, more powerful CT scanning devices is that they can do the job while exposing the patient to less radiation in some cases significantly less, according to vendors.
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