A Look Inside: Next-Generation Multidetector CT

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 Multidetector CT scanning is about to take the next step, with major vendors previewing their next-generation systems at radiology’s extravaganza—the Radiological Society of North America meeting in November. The newest innovations in CT scanning promise significant gains ranging from improved temporal and spatial resolution to new applications in stroke evaluation, and for all studies—less contrast media, shorter exam times and, across the board, lower radiation dose.

Four new systems are slated for availability in 2008. Toshiba America Medical Systems dominates on slice count with its AquilionONE 320-slice scanner; Philips Healthcare’s answer is the Brilliance iCT 256-slice scanner. Siemens Medical Solutions touts the SOMATOM Definition Adaptive Scanner (AS), an “adaptive” scanner available in 40-, 64- and 128-count configurations. And GE Healthcare is re-defining CT through High-Definition CT (HDCT) technology.

Health Imaging & IT spoke with a few early adopters of these technologies to gain some insight into the capabilities and see what the next generation has in store.

Clinically meaningful functional CT

Brigham and Women’s Hospital in Boston is an early adopter of Toshiba’s AquilionONE CT scanner. “The new system enables dynamic volume imaging,” says Frank Rybicki, MD, PhD, director of cardiac CT and vascular CT/ MRI. “Using the Aquilion-ONE, we can cover 16 cm in the cranio-caudal direction in a single gantry rotation, [thus] reinventing CT imaging and opening the door to new applications.”

Prior to the introduction of AquilionONE, 64-slice volumetric imaging entailed imaging of separate pieces or sub-volumes. Sub-volumes were stitched together after the scan, a process that produces artifacts, particularly when imaging a moving organ such as in coronary CT angiography (CTA). “Dynamic volume imaging eliminates the need to put the pieces back together and the problems associated with the approach. This is especially important when iodinated contrast is moving through the heart. With a sub-volume CT scanner, iodinated contrast is imaged at a different place in every sub-volume,” explains Rybicki.

Other major AquilionONE applications include CT angiography/venography and CT perfusion of the brain. With 320 x 0.5 mm slices, or 16 cm of coverage, radiologists can image the entire brain parenchyma in a single gantry rotation. The principle is similar to the heart, since whole brain scans capture the exact phase of the iodinated contrast as it tracks from the arteries to the brain parenchyma and then to the veins. “This provides vastly more information for stroke evaluation than current CT scanners,” states Rybicki, who predicts that after the clinical evidence is in, every stroke center will consider an investment in the scanner. Instead of using MRI to assess stroke, centers can potentially use CT in lieu of MRI to avoid the expense, complexity and acquisition time associated with MRI.  “With stroke, physicians constantly battle against the clock to initiate therapy. If time can be shaved from patient imaging, it represents a huge advance in care. Potentially, the entire CT acquisition including the non-contrast, angiography and perfusion maps could take 15 minutes,” notes Rybicki.

“This is clinically relevant functional CT,” continues Rybicki. The difference between 320 and 64 slices is that the new paradigm allows radiologists to view an entire organ rather than a sub-volume. “There are multiple new applications, such as the perfusion of tumors that we are just beginning to explore,” concludes Rybicki.

Deliveries of the AquilionONE are slated to begin this summer.

Cardiac scanning and beyond

MetroHealth in Cleveland, Ohio, deployed Philips Healthcare Brilliance iCT scanner in October and has scanned hundreds of patients with the 256-slice system. The new system produces superior cardiac images as its speed and coverage freezes the motion of the heart and produces a clear snapshot of the coronary arteries. But its benefits extend beyond cardiac and cardiovascular scanning.

“Higher slice [count], higher speed, larger coverage scanner are intended to deliver maximum benefits to cardiovascular and cardiac imaging; however, we’ve seen significant benefits from iCT’s higher resolution and speed in every scan we’ve acquired,” states Pedro Diaz, PhD, vice chair of imaging and informatics. For example, the department turned to iCT to complete a renal stone protocol on an uncooperative patient in tremendous pain. The