A Major Advance in CT Angiography, Volumetric Computed Tomography (VCT)

Abstracts & Commentary

Synopsis: VCT substantially improves imaging of vascularization in tumors and offers a promising tool for preclinical studies of tumor angiogenesis and antiangiogenic therapies.

Source: Kiessling F, et al. Volumetric Computed Tomography (VCT): A New Technology For Noninvasive, High-Resolution Monitoring of Tumor Angiogenesis. Nature Med. 2004; 10:1133-1137.

As mentioned in the most recent Neurology Alert, it is likely that advances in CT technology will lead to markedly enhanced ability to assess carotid vascular lesions, as well as small vessels in the brain. This may make it possible to non-invasively monitor cerebral aneurysms. This will be particularly valuable in ruling out mycotic aneurysms. It may also be possible to monitor perfusion in acute stroke to define areas at risk. A major advance in enhancing our ability to do this will be the development of volumetric computed tomography (VCT). This is an extremely high resolution CT scanner which has been recently developed by General Electric. The first report on utilizing this was just published. Detectors are used for imaging large volumes of a subject with isotropic imaging resolution. The prototype VCT scanner used flat-paneled X-ray detectors, and is designed for high-resolution 3-dimensional imaging.

In the present report, Kiessling and colleagues used this technique to study microangiography in xeno-transplanted skin squamous cell carcinomas in nude mice. VCT showed the vessel architecture of the tumors in animals with greater detail and plasticity than has previously been achieved. It was superior to contrast-enhanced magnetic resonance angiography. VCT, and MR images correlated well for larger tumor vessels. However, VCT was clearly superior for smaller vessels. It was demonstrated that it could detect small vessels with a diameter of approximately 30 microns. The scan is exceedingly fast. One scan was done in 16 seconds; an acceptable MR scan time was 28 minutes. Kiessling et al compared VCT and MRI for larger vessels of approximately 50 microns, and found that both techniques would visualize these. However, again the VCT was more sensitive. VCT angiography was optimized using iodine-containing agents. They were able to image small vessel networks inside the tumor tissue, providing improved discrimination of vital and necrotic regions.

Commentary

The development of VCT will provide an extremely advanced tool for imaging vascular lesions in the central nervous system. It will probably also lead to markedly improved identification of carotid artery stenosis. I believe it will also be useful for CT perfusion to identify the penumbra of acute strokes, which are areas that may be salvaged by interventional treatments. The VCT has resolution of 30-50 microns. This is an advance over conventional digital subtraction angiography, as well as MR angiography. It also has the advantage of extremely rapid scanning. —M. Flint Beal

M. Flint Beal, MD Professor and Chairman; Department of Neurology; Cornell University Medical College New York, NY is Editor of Neurology Alert.