Software creates precise 3D models of coronary arteries

Stent placement will be more precise and patient exposure to x-radiation and contrast media reduced if Siemens and Philips make good on promises about two software packages designed to reconstruct coronary lesions in three dimensions.

Philips's Allura 3D-CA generates 3D images of diseased coronary vessels from multiple viewpoints and angles achieved during rotational angiography. Two of these images, both in the same cardiac phase, are chosen as the basis for a 3D reconstruction from a four-second, 110° scan of the patient. The angiographic model may be so precise that the stent can be matched exactly to the blood vessel, leading to a better fit and possibly reducing the chance of restenosis. The patient may also be exposed to less radiation and contrast media.

"With this method, there is less trial and error," said Ernst Wodrada, Philips product manager for Allura 3D-CA. "Otherwise, with 2D imaging, cardiologists tend to use extra puffs of contrast and extra doses of x-ray to get the views they need to assess the lesion."

Siemens Medical Solutions has a similar product called Interventional Cardiac 3D software. IC3D creates a volumetric reconstruction quickly and efficiently

"We've been doing rotational angiography 3D reconstruction for neuro, but it's always been a challenge in the heart because of the fast motion," said Sandy Black, director of the Siemens cardiac business in Malvern, PA. "Here's a new algorithm that is very fast for reconstructing the coronaries in 3D."

Unlike the 3D models of brain vasculature, however, the reconstructions generated using IC3D do not require rotational angiography. The Siemens software uses just two images obtained at different angles.

"A unique benefit of the IC3D product is that the physician does not need to do a 3D rotational spin," Black said. "This product can do the 3D reconstruction from only two single static images."

As with the Siemens software, Philips' Allura 3D-CA needs just two images to produce a volumetric reconstruction. Those images, however, are chosen from hundreds taken as the cardiac cath unit completes a 110° arc around the patient. The software, which runs on a dual processor-equipped PC, selects candidate images in the same cardiac phase as close to 90° from each other as possible. The physician has the final say on which images are picked.

When reconstructed, the model shows the diseased area in 3D. Quantitative measurements of the length and width of the area are figured automatically by the computer. These are used to select the most appropriate stent for placement.

"This software takes 3D modeling and rotational angiography into the next era," Wodrada said.

The product works with Philips' latest digital cardiac cath system, the Allura Xper FD20, but it is also compatible with Philips cardiac equipment built around image intensifiers. Philips executives believe the product will not only improve patient care by ensuring an optimal fit between stent and artery, but cut by as much as 30% the amount of contrast media and x-ray dose given the patient, based on preliminary clinical studies.

Touted as enhancing the diagnostic capabilities of cardiologists, the Siemens' IC3D product is being paired with the company's Axiom Artis digital cardiac cath system. The company makes the same claims for its product as Philips does for the Allura 3D-CA--that the software facilitates greater precision in choosing the stent and decreases the dose of contrast media and x-rays.

Siemens and Philips will showcase their products this week at the Transcatheter Cardiovascular Therapeutics (TCT) conference in Washington, DC. Siemens' IC3D will be shown as a commercial product, having cleared the FDA in July. Just days prior to the conference, Philips' Allura 3D-CA was still in FDA review, but company executives were hoping clearance would be in hand before the conference was over.

Each product addresses the problem of restenosis following stent placement, which is sure to be a major topic of discussion for those attending the TCT meeting. A quarter of the patients treated with a stent for coronary artery disease will need an additional procedure to reopen the coronary artery, according to the American Heart Association. The physician's ability to select and place the appropriate stent is crucial to avoiding restenosis. With 3D visualization, clinicians can see the artery and the stenosis more accurately, and they can therefore size and place the stent more precisely and effectively, Black said.

The IC3D enhances features already available on Siemens' Axiom Artis, improving image quality and ease of use and optimizing radiation dose. Utilizing Siemens' syngo user interface, all patient data can be seamlessly shared, enabling physicians to create a comprehensive patient report during the exam.

Flat projections are a mainstay of cardiac cath procedures, and the 3D software will not replace their use. The 3D models only help make the diagnosis and plan the interventional procedure. The actual placement and assessment of the stent rely heavily on 2D imaging.

In this regard, Philips has developed an algorithm called StentBoost. The product, which will also be highlighted at the TCT conference, uses digital images obtained from the Xper FD20 system to make the verification.

Philips' Allura 3D-CA was developed in collaboration with cardiologists at the University of Colorado Hospital. Philips assigned a software engineer in 2003 to work with Dr. John Carroll, chief of cardiology at the hospital, to create the final version. The software is now in use there, as well as at several sites in Europe.

The company is taking orders for the product but will not ship the package until next summer. It will be available as an option on new Philips cardiac cath systems and as an upgrade for the company's installed base.

Several luminary sites are or will soon be using Siemens' new IC3D software, including Massachusetts General Hospital and the Methodist DeBakey Heart Center, as well as several facilities in Europe.

Siemens plans to begin marketing the product next year as a means for improving accuracy and efficiency. Customers will be contacted via internal promotion, flyers, and the company's sales force.