BioWorld International Correspondent
LONDON - A prototype imaging technique that is faster and provides better pictures of internal organs of small animals than existing methods has passed one of its first research evaluations with top marks.
The technology could prove useful to companies studying the development of new blood vessels in tumors and the impact of anti-angiogenic drugs on blood vessel growth.
It allows researchers to visualize tumor blood vessels down to a diameter of 50 micrometers - and to see where those vessels originate. The images produced make it easy to discriminate between necrotic and vital tissue within the vessels.
Fabian Kiessling, team leader at the German Cancer Research Center in Heidelberg, Germany, told BioWorld International: "I think the greatest potential of this technique will be in the noninvasive staging of metastasis in small-animal models of cancer. It will allow researchers to focus on how cancer affects the vasculature."
Kiessling, who performed the study with Susanne Greschus of the University of Giessen, also in Germany, predicted that pharmaceutical scientists would find VCT helpful in studying the response of cancers in animal models to new treatments.
"This method also will be used to investigate the internal morphology of transgenic animals - it is possible to see, for example, whether organs such as the liver or the spleen are enlarged," Kiessling added.
He and his colleagues already are expanding their studies to include phenotyping of transgenic animals.
The work is reported in the Sept. 7, 2004, issue of Nature Medicine in a paper titled "Volumetric computed tomography (VCT): a new technology for non-invasive, high-resolution monitoring of tumor angiogenesis."
Kiessling and his group carried out the work using a prototype VCT scanner made by GE Global Research, of Schenectady, N.Y. The scanner detects and processes data from flat-panel X-ray detectors, which were developed to replace X-ray films. It produces high-resolution 3-dimensional images.
Experimenting with a mouse model of squamous-cell carcinoma, the group showed that the images that could be obtained were better than those gained using contrast-enhanced magnetic resonance angiography. Comparison with the histological appearance of the vessels suggested that vessels as small as 50 micrometers could be seen clearly.
Kiessling explained that the type of CT scanners used to scan human patients do not produce good images when used on small animals, due to the size difference. Clear images can be obtained using the technique known as micro-CT scanning, but that requires a long scan time.
VCT, by comparison, makes it possible to scan larger objects, and the vascular system and tumors of a mouse, for example, can be visualized after a short scan lasting 16 seconds.
The team reported that they were able to see the detailed display of the entire vessel architecture in the mice studied, including the cerebral vessels and the organization of vessels around and within the animals' tumors. They wrote: "Some large vessels could be identified as veins by tracking them from the tumors to their confluence with intercostal, subclavian or iliacal veins. Notably, some tumor veins were recruited from the contralateral side of the mouse."
Applying the method to imaging in humans will require further improvements, Kiessling and his colleagues wrote. The resolution of VCT is so high, they pointed out, that vast amounts of data would need to be stored and analyzed if an object the size of a human body were to be scanned. Nevertheless, they predicted that improvements in semiconductor technology and in processing software would, one day, reduce the time taken to acquire the data and to analyse it.
"[This] may facilitate scans with an acceptable X-ray dose for larger organisms, possibly including humans," they wrote.