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Radar technology produces sharper MRT images

PTB scientists have, together with colleagues from TU Ilmenau, developed a method to increase the image quality of magnetic resonance tomographs (MRT) which work with high field strength (3 Tesla to 9.4 Tesla). They use, thereby, ultra-wideband (UWB) radar signals, which can depict the physiological movement of the heart. With it, it is possible to identify those time intervals which correspond to certain cycles of movement of the heart. Thus, the MRT images can be synchronised with the heart beat and image artefacts can be avoided.

Left: Arrangement of a combined MRT/UWB measurement on the opening of the 3-T-MR scanner of PTB. Right: Result of a combined ECG/UWB radar experiment. (top: superposed ECG epochs, bottom: superposed corresponding myocardial deformation, reconstructed from the signals of the UWB radar. The red line indicates the mean value of the signals.)

In order to produce images of the moving heart, an MRT requires more detailed information about the various positions of the heart. In the case of clinical standard MRT devices (with a field strength of 1.5 Tesla), they are provided by an electrocardiogram, which is not suitable for high field systems, however. Here, ultra-wideband techniques (up to 10 GHz) are suitable. They do not interfere with narrow band systems, such as the MRT, and penetrate the materials to be examined with only a small emission performance of less than one milliwatt. A further advantage of such sensors is their high temporal and spatial resolution. With them, it is possible to detect body or organ movement, whose perturbing influence can then be eliminated in a subsequent statistical analysis of the MRT data.

At PTB, a combined MRT/UWB radar technique was developed in cooperation with TU Ilmenau and tested on phantoms as well as on volunteers. Results of the analytical and model-based tests document that the new method is principally suitable as navigator technique. Comparisons with an ECG/UWB method on patients have shown that the UWB radar displays the movement of those parts of the heart which are also detected by the MRT. These results confirm the suitability of the UWB radar to follow physiological processes directly to their place of origin inside the body and to identify in these signals characteristic points with which an MR scanner can be controlled. In a next step, the data acquisition is further optimized with focused UWB antenna arrays.

Contact at PTB:

Phone: +49-531-592-0