Feature | September 15, 2010| Dave Fornell

New CT Technology Lowers the Dose

Left: Users say the image quality from a Toshiba Aquilion One 320-slice scanner provides more accurate diagnoses because the images do not have the artifacts common to stitched 64-slice images. A heart can be scanned in one volume during a single beat.

Advancements in newer 64-slice computed tomography (CT) systems and the introduction of 256- and 320-slice systems are helping to significantly reduce exposure to ionizing radiation.

In 64-slice cardiac imaging, between four and 16 images are taken and stitched together to create a full image of the heart. To create seamless images without gaps, each scan overlaps the previously scanned area by as much as 80 percent, said Michael Poon, M.D., FACC, professor of medicine and radiology, director of advanced cardiac imaging, Stony Brook University Medical Center, Stony Brook, N.Y. He said the number of images that are needed and the required overlap adds up to a lot of additional patient radiation exposure. The number of images and overlap is significantly reduced or eliminated with 256- and 320-slice systems.

The speed of the new high-slice systems and the large area of coverage in each scan also help eliminate motion blur associated with pediatric patients, or patients with fast heart rates or who cannot hold their breath.

320-slice CT
Poon said the single, large volume of the Aquilion One 320-slice system allows for a big reduction in radiation because its 16 cm imaging area can image the whole heart in one scan. This eliminates the need for stitching multiple images together and overlap imaging.

Contrast dose is also reduced with the 320-slice scanner, because only one scan is usually required, instead of several stretched out over several seconds. Poon said an average 80-90 cc contrast agent is used for 64-slice exams, because of the duration and number of images taken. Stony Brook Medical Center reduced this amount to as low as 50 cc with the Aquilion One.

The speed also enables scans of squirmy pediatric or neonates without the need to sedate them, Poon added.

With less radiation, lower contrast usage, fast speed, a patient weight limit of up to 600 pounds and versatility to image any patient for nearly any condition, Poon said he can’t think of any downside to the technology, other than its price.

256-Slice CT
The Brilliance iCT 256-slice scanner can perform a full body scan in less than a minute, and Philips says it exposes patients to 80 percent less radiation than traditional 64-slice CT machines.

The University of Chicago Medical Center’s older 64-slice scanners use retrospective gating. This technique keeps the X-ray source on for the entire scan, and ECG data is used to select the best images to stitch together. However, “You get a whopping dose,” said Michael Vannier, M.D., FACR, professor of medicine at the University of Chicago Medical Center.

The center purchased a Brilliance iCT, which images a larger volume, so only about two images are needed for stitching and there is much less image overlap. The gantry speed is also much faster, helping to reduce motion artifacts. “The doses are reduced dramatically,” Vannier said.
He explained the system also has a setting for 100 kV, which helps lower the dose. The 64-slice systems only have settings for 120 and 140 kV.

Lowering 64-Slice Dose
The GE Healthcare CT750 HD scanner is designed to help reduce dose by up to 83 percent for cardiac scans. That claim was confirmed by James Min, M.D., director of the cardiovascular CT lab at New York Presbyterian Hospital and assistant professor of radiology at Weill Cornell Medical College. He said the system helped lower the average dose among his cardiac patients from an average of 5.5 millisieverts (mSv) to an average of 1.2 mSv. This includes all types of patients. Forty percent of these patients, with a smaller body size, receive doses of less than 1 mSv.

“I think the scanner offers better image quality and increased patient safety,” Min said.

New York Presbyterian will likely purchase a second high-definition CT system later this year for its women’s health center. Min said the system will help promote a lower radiation dose in female patients.

Related Content

Physicians will need to use a CMS-certified appropriate use criteria (AUC) clinical decision support software that documents the appropriateness of an imaging order to receive full reimbursement for Medicare patients starting Jan. 1, 2018.

Feature | Cardiac Imaging| April 18, 2017 | Dave Fornell
As part of U.S. healthcare reform efforts, starting Jan.
University of California Study Searches for Consistent CT Dose Best Practices
News | Radiation Dose Management| April 17, 2017
A new study led by UC San Francisco has found that radiation doses can be safely and effectively reduced – and more...
cardiac CT showing a severe right coronary artery lesion on a Toshiba Aquillion One

A cardiac CT showing a severe right coronary artery lesion on both 3-D and curved multiplanar reconstructions from a Toshiba Aquilion One CT system. The newest generation of CT scanners have very fast gantry speeds to freeze cardiac motion, improved image quality and much lower doses than previous generation scanners from a decade ago.

Feature | CT Angiography (CTA)| April 13, 2017 | Dave Fornell
Cardiac computed tomography (CT) imaging really took off a decade ago with the introduction of 64-slice scanners, whi
Toshiba Medical Launches Aquilion Lightning CT System
News | Computed Tomography (CT)| April 12, 2017
April 12, 2017 — Providers can now offer enhanced care and safe imaging to patients with a compact and economical sol
FDA Clears Siemens Somatom go. CT platform
Technology | Computed Tomography (CT)| April 11, 2017
The U.S. Food and Drug Administration (FDA) has cleared the Somatom go. computed tomography (CT) platform from Siemens...
SCCT, Toshiba Medical, partnership, residents-in-training
News | Computed Tomography (CT)| April 05, 2017
The Society of Cardiovascular Computed Tomography (SCCT) and Toshiba Medical announced a new partnership dedicated to...
tryton side branch stent, dedicated coronary side branch stent

The FDA approval of the Tryton Side Branch Stent was the biggest technology news from March. It is deployed in the side branch artery using a standard single wire balloon-expandable stent delivery system. A conventional drug eluting stent is then placed in the main vessel.

Feature | April 03, 2017 | Dave Fornell
April 3, 2017 — Here is the list of the top 25 most popular pieces of content on the Diagnostic and Interventional Ca
Toshiba, Aquilion One CT, model-based iterative reconstruction, MBIR, ACC 2017, FIRST, RSNA 2017
News | Computed Tomography (CT)| March 21, 2017
March 21, 2017 — Toshiba Medical demonstrated its Forward projected model-based Iterative Reconstruction SoluTion (FI
RESOLVE study, RESOLVE trial, subclinical leaflet thrombosis

A CT study from the RESOLVE Trial showing valve leaflet thrombosis on a TAVR device. The trial examined a range of surgical and transcatheter valves to show thrombosis is found across both types of devices. It also examined if anticoagulation or antiplatelet therapy could reduce thrombosis and allow a greater range of leaflet motion.

Feature | Heart Valve Technology| March 21, 2017
March 21, 2017 — About 12 percent of patients undergoing aortic valve replacement developed non-symptomatic blood clo
CTA, CT angiography, predict heart attacks, Radiology study
News | CT Angiography (CTA)| March 14, 2017
Noninvasive computed tomography (CT) angiography and stress tests can help predict which patients are likely to suffer...
Overlay Init