CT Technology Provides 3D Cardiovascular Imaging

A new computed tomography (CT) application designed for cardiovascular imaging generates CT-like cross-sectional images on an angiographic C-arm system and offers three-dimensional (3D) reconstruction of the aortic root. These 3D images can be overlaid on actual fluoroscopic images and provide a type of three-dimensional roadmap for the examiner. Thus, with the new technology, the cardiologist can position the valve prosthesis more accurate and more quickly than before.

During transfemoral aortic valve replacement, a heart valve prosthesis gets implanted via peripheral artery access. To position aortic valve prostheses accurately, the cardiologist must have very precise knowledge of the individual anatomy of the patient's aorta. For most patients worldwide, open-heart surgery is performed for the placement of an aortic valve prosthesis. The most frequent reason for this intervention is the constriction of the valve, so-called aortic valve stenosis, which occurs primarily in the elderly. In the course of time, the valve loses elasticity and no longer fully opens. This decreases the flow of blood, and the organs no longer receive a sufficient supply of oxygen. Normally, the operation requires opening the sternum. The heart has to be temporarily stopped and its function taken over by a heart-lung machine. Especially for elderly and severely ill patients with accompanying diseases such as heart failure, renal failure, and diabetes, such an intervention is risky.

Recently, new procedures have been developed in which the aortic valve prosthesis is implanted in the heart using a catheter rather than through the usual open-heart surgery. This involves an intervention often performed jointly by the cardiologist and the heart surgeon. First, through a small incision in the groin artery, a special balloon catheter is guided to the heart to dilate the stenosed aortic valve. Then, a collapsed heart valve is also inserted up to the valve level via a balloon catheter; there it is unfolded and attached to the surrounding tissue with a so-called stent.

Prior to such interventions it is imperative that the cardiologist gets a comprehensive image of the heart and vessels. Previously, this normally required imaging with CT scanners or magnetic resonance imaging (MRI) systems, which led to additional costs. For this reason, an application, called the Syngo DynaCT Cardiac, was developed by Siemens Healthcare (Erlangen, Germany) that can generate CT-like 3D images directly on an angiography system. The application has been continually customized and developed, so that it combines the advantages of three-dimensional CT imaging with live X-ray imaging of the beating heart in one examination and on a single system. The CT-like images of the heart are produced by rotating the C-arm at high speed around the patient. In this way, several hundred images are acquired and reconstructed as 3D volumes. If the acquisition is triggered via the patient electrocardiography (ECG), even time-dependent 3D volumes can be generated for visualization of the beating heart.

The complete 3D image is available in less than one minute. Anatomic structure segments are overlaid with the live X-ray image, allowing the physician to navigate with the catheter quickly and confidently without the use of a contrast medium.

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