Reconstruction Software Improves Quality of Low-Dose CT Scans

This article appeared as the introduction to the CT Dose Reduction comparison chart.


Computed tomography (CT) offers a very important, noninvasive diagnostic tool, but the price of high image quality sometimes comes with a cost of high radiation dose. This is especially true of CT angiography (CTA), which may require imaging several cardiac cycles.

CT scans have been a tradeoff, offering a choice between good images using higher doses or lower image quality using lower doses. Advancements in CT image processing software have helped improve the image quality from low-dose scans by eliminating noise. This can help lower patient radiation dose, according to manufacturers, without compromising diagnostic image quality.

The main technique uses iterative image reconstruction. Early versions of the software were slow and required much more time to produce a final image than simply using a higher dose. However, advancements have greatly reduced the processing time.

High-dose CT scans were brought into the public eye last year with mainstream media attention. With radiology associations and the U.S. Food and Drug Administration (FDA) now proposing radiation dose monitoring, registries and procedural limits, dose-lowering technology is playing an increasingly important role.

CT Manufacturers
During the 2010 Radiological Society of North America (RSNA) meeting in December, all the major CT vendors introduced new dose-lowering software or highlighted works-in-progress. Philips introduced its Ingenuity CT, which features the company’s new iDose4 iterative reconstruction software. It is designed to provide equivalent diagnostic image quality at less dose and can also improve spatial resolution with less dose. The platform is available as a standalone or as a hybrid molecular imaging system.

“In the past, because the combination of great image quality, low dose and fast reconstruction times has been a challenge for the industry, CT scanning has often been about tradeoff,” said said Gene Saragnese, Philips imaging systems CEO. However, he said the new system allows both low dose and fast image reconstruction.

At RSNA, Siemens previewed its FAST CARE (Fully Assisting Scanner Technologies - Combined Applications to Reduce Exposure) CT application to assist with dose reduction and faster workflow. It automates many operating procedures, suggests parameter settings for image quality and dose reduction, and standardizes processes. FAST CARE will be available on the Somatom Definition AS and the Somatom Definition Flash scanners. Installed Definition family CT scanners can be upgraded to the new platform.

Toshiba showed its works-in-progress adaptive iterative dose reduction (AIDR) technology, which iterates noise to increase quality and lower radiation dose. The software intuitively improves the image by removing noise until the optimal image is produced. AIDR is pending 510(k) clearance, but will be standard on the Aquilion Premium and Aquilion One.

GE Healthcare showcased its ASiR (adaptive statistical iterative reconstruction) low-dose reconstruction technology, available on the GE Discovery CT750 HD and LightSpeed VCT. The company says it reduces dose while maintaining image quality and can be implemented as a cost-effective upgrade for existing LightSpeed VCT systems. The technology can be used on both helical and axial scans to reduce dose and maintain image quality for patients of all ages. ASiR is now installed on more than 600 CT scanners worldwide.

GE’s newest low-dose technology is a model-based iterative reconstruction (MBIR) technology called Veo. It is currently available in Europe and is pending 510(k) clearance in the United States. When compared to previous GE reconstruction methods, Veo’s new modeling techniques deliver resolution gain, lower noise, improved low-contrast detectability and artifact suppression.

Third-Party Vendors
Medic Vision received FDA clearance to market its add-on SafeCT product in the U.S. in January. The software processes and enhances images on a variety of CT scanners. It enables a dose reduction in CT scans without compromising image quality and diagnostic information. SafeCT, which is compatible with most major CT platforms and picture archiving and communication systems (PACS), can provide low-dose imaging functionality to these scanners.

ContextVision offers OEM image processing solutions as an add-on for CT manufacturers. Its GOPView CT image enhancement software operates on a standard CPU. It can reduce image noise while enhancing fine structures and edges at both standard and low-dose images. The company says clinical studies and current installations demonstrate that exceptional image quality can be achieved in images with a lower dose.

The GOP algorithm is used by OEMs to enhance fine structures and reduce noise across magnetic resonance imaging (MRI), X-ray, ultrasound and CT image data.