Toshiba displays first flat-panel CT system

The first in a new generation of CT scanners will be on the market in summer 2008. Aquilion One from Toshiba America Medical Systems debuted at RSNA accompanied by dynamic studies of the brain and heart that demonstrated unprecedented clinical results. Preliminary results indicate that the system can detect subtle changes in blood flow or blockages as small as 1.5 mm in diameter.

"You can do a neuro exam in a single series of rotations. You can do the heart in a single 250-msec rotation or, over a heartbeat, get all your viability and perfusion studies as well," said Doug Ryan, senior director of the Toshiba CT business unit. "The scanner also lowers patient radiation dose and the contrast dose that has to be given."

The specifications of the new scanner took CT users by surprise. Toshiba for years had been talking about a 256-slice CT and had previously shown a prototype detector. It even tested a scanner with such a detector at several beta sites.

"When we got feedback on that initial detector, the physicians said they needed about 25% greater coverage to do a brain or heart in a single rotation," he said. "So our engineering teams over the last two years worked diligently to expand the detector out to 320 elements."

Ryan described Aquilion One as ushering in a new era marked by dynamic volume CT, a type of scanning not defined by the number of slices. No longer would Toshiba engage in the slice wars that had been fought for the past eight years, as the four vendors of multislice scanners tried to outdo or keep up with each other through a succession of eight-, 16-, 32-, 40-, and, most recently, 64-slice systems.

As if reading from the same script, Toshiba's competitors declared the rivalry to be over. All brought to the RSNA meeting works-in-progress that they said made the war comparisons obsolete (see "CT vendors end slice wars").

Toshiba is ahead of the pack. Aquilion One, which received FDA clearance in October, is the first commercial CT to include what can be considered a flat-panel detector. Quantum V, the fifth solid-state detector built by Toshiba for its multislice scanners, is composed of 320 detector elements, each 0.5 mm wide. The detector, which spans a width of 16 cm and rotates once every 350 msec, is huge in comparison to its 64-slice predecessor, which is just 3.2 cm wide.

Just as the new detector dwarfs the size of other detectors, so does its price. Aquilion One lists for between $2.5 million and $2.8 million - more than twice the going rate for 64-slice scanners. The price is intended to help Toshiba recoup its $500 million investment in the underlying technology. Paradoxically, this extraordinarily high-priced scanner could reduce overall healthcare costs, according to Ryan.

"If an exam on this machine can replace a whole series of other tests or modalities by becoming the main point of diagnosis for patients coming through the ER or in follow- up, this lowers healthcare costs," he said.

A single pass of the brain provides the volumetric data to produce a CT angiogram, venogram, digital subtraction angiogram, and whole brain perfusion images, he said. Similarly, a single rotation captures the whole heart, while scanning for a single heartbeat provides all the data needed to complete a functional study.

Underlying these capabilities, in addition to the Quantum V detector, are a redesigned gantry and a new x-ray tube as well as software for reconstructing the data. The names of the tube and gantry indicate the fifth iteration done in lockstep with Toshiba's development of detectors.

The new MegaCool V x-ray tube fires a beam that stretches across the markedly widened detector, incorporating other enhancements deemed necessary on the basis of past multislice experience. The eVolution gantry similarly reflects such changes and the new needs of the 320-element detector. It also offers a green technology that converts kinetic energy generated during braking into electricity rather than heat.

The imaging chain allows not only faster scan time but reduced radiation dose by as much as 80% per exam. This is possible because a single 16-cm swipe of the Aquilion One detector covers five times the distance of a 64-slice detector, which must move back and forth over the heart to capture those data, according to Ryan.

Aquilion One also reduces the amount of contrast medium needed. A complete brain study requires less than 5 mSv of dose--about one-fourth the amount delivered by a typical 64-slice scanner. A single contrast bolus of about 50 mL can gather data for an arteriogram, venogram, DSA, and perfusion study. This replaces multiple administrations of contrast otherwise needed to obtain these data separately.

Following an industry trend, Toshiba beefed up the patient table to handle heavy patients. The table can now support patients weighing as much as 650 pounds.

Johns Hopkins University and Brigham and Women's Hospital are among the U.S. sites where Aquilion One has already been installed. Other potential sites include Fujita Health University in Japan, Humboldt University, Charit Campus Mitte in Germany, and University Health Network in Canada.