CT systems exceed speed limits in pursuit of angiography, bronchoscopy, and other virtual exams

by Linda E. Ketchum

X-ray computed tomography (CT) continues to chase angiography, bronchoscopy, and other invasive procedures with technological advances that provide thinner slices, faster scan times, and improved threedimensional (3D) imaging. Scanning more anatomy in less time, new CT systems continue to sell themselves on speed. The clinical advantages, say manufacturers, include shorter breath holding times-particularly important for pediatric and geriatric patients. Even faster than scanning between breaths, some CT systems claim to capture anatomic cardiac data by scanning fast between heartbeats.

LightSpeed scanner from GE

The latest competitor in this race from GE Medical Systems (Milwaukee) is the LightSpeed ^TM QX/i CT scanner. By the end of 1999, the company expects to install several hundred Light-Speed systems worldwide. Indicating how important this radiology product is to parent company GE, the new CT system was announced in New York by Jack Welch, chairman and chief executive officer (CEO) of GE.

The result of a six-year, $60-million research and development effort, LightSpeed offers the advantage of "acquiring a large number of very thin, high resolution scans quickly" and can "provide data for 3D visualizations such as CT angiography and virtual exams," said Gary M. Glazer, professor and chairman of the Department of Radiology at Stanford University (Stanford, CA).

According to GE, medical centers are using LightSpeed for pulmonary, thoracic, and abdominal arteriography with short breath-holds; enhanced cancer diagnosis and staging; and surgical planning. Whereas most CT scanners use one row of x-ray detectors, LightSpeed's solid-state detector uses 16 rows, allowing for simultaneous scanning of multiple body sections. "A body scan that used to take three minutes now can be completed in approximately 20 seconds," said Carl Ravin, MD, professor and chairman of the Department of Radiology at Duke Medical Center (Durham, NC).

"GE LightSpeed is the world's first scanner that allows doctors to simultaneously capture multiple images of a patient's anatomy six times faster than traditional single-slice scanners," said Jeffrey R. Immelt, president and CEO of GE Medical Systems.

CT detection of coronary artery calcifications

GE also has introduced SmartScore ^TM , a coronary artery calcification (CAC) scoring package used with the company's HiSpeed ^® CT/i system. The package enables a 35-second CT scan to provide data that helps to quantify the calcified plaque in coronary arteries.

CAC scores serve as a marker for atherosclerosis. "An elevated calcium score is an important risk factor for coronary artery disease," said Chris Woodhouse, MD, of the Mount Sinai Medical Center (Miami).

Volume Zoom from Siemens

Siemens Medical Systems, Inc., (Iselin, NJ) introduced its Volume Zoom, an upgrade option for the SOMATOM ^® Plus 4 CT scanner. According to the company, the Volume Zoom can speed up scan times and improve image quality for both two-dimensional (2D) and 3D postprocessing.

"Up until now, performance in CT has been limited by a series of compromises. Large volumes exclude thin slices. Slow scans cause motion artifacts that impair image quality. The question is how to harmonize volume, speed, and detail," explained Siemens. To address these issues, the Volume Zoom features a multislice adaptive array detector with eight detector rows of four different widths to deliver fast results in large volumes and sharp details in sub-millimeter slices.

Cardiac CT closer to clinical reality

According to Picker International (Cleveland), its new Mx8000 ^TM multislice CT system scans 16 times faster than conventional CT and can complete a trauma survey in less than 30 seconds. The company believes that this speed brings cardiac CT scanning close to a clinical reality because the system can capture heart structures during the short time intervals between heartbeats.

As scanning times shrink, so do image reconstruction times and slice thicknesses. Picker states that the Mx8000 reconstructs images in onequarter the time of other conventional CT scanners. The system provides CT slices so thin that "sub-millimeter objects can be seen in all imaging planes," said Mike Sims, product line manager for Picker's CT division. The Mx8000 became a new Picker product when the company completed its acquisition of Elscint's CT division last year.

Diagnosis, intervention, and treatment in "single episode of care"

The multislice scanner can be integrated into Picker's Venue ^TM interventional CT suite, which includes a stereotactic guide for positioning and placement of biopsy needles, drainage devices, and orthopedic devices; and a flat-panel real-time fluoroscopic carm system. The goal of this interventional suite, according to Picker, is to "complete the diagnosis, intervention, and treatment of patients more quickly and accurately in a single episode of care, without moving the patient." The company is working on integrating ultrasound data into this interventional suite.

Low-end, PC-driven, helical CT

It doesn't take long for yesterday's state-of-the-art CT features to get incorporated into the lower-end, more economical systems. Bringing helical CT with slip-ring technology to more patients, Toshiba America Medical Systems, Inc., (Tustin, CA) has introduced the Auklet, a low-end CT scanner driven by a personal computer (PC).

According to Toshiba, the system makes 1.1-second partial scans and 1.8-second routine scans with a low-contrast resolution of 2 mm and a high-contrast resolution of 0.45 mm. The system comprises the gantry, couch, and console, and fits into an area of 18 square meters (about 22 square yards).