• Testing of quality of NMR images using physical and electro-magnetic phantoms

• Noninvasive localization of ischemic lesions based on stress test ECG mapping

Result 1: Testing of quality of NMR images using physical and electro-magnetic phantoms

Projects: VEGA 2/0142/08

Authors: I. Frollo, P. Szomolányi, V. Juráš, P. Andris, J. Přibil, L. Vojtíšek, Z. Holúbeková, T. Dermek

A unique technique using the nuclear magnetic resonance (NMR) has been developed for testing quality of NMR images on measured data from the point of view of interpolation and homogeneity of the static and radio-frequency magnetic fields and linearity of the gradient magnetic fields. Three types of physical phantoms and series of electro-magnetic phantoms have been developed. Weighed images in multi-slice mode have been acquired for each phantom. Conditions of imaging , dimensions of the depicted matrix, setting the smoothing the data, change of positions of imaging planes and variations of imaging sequences were defined. Different types of planar and electro-magnetic phantoms: rectangular, meander, helical were developed and tested. The phantoms were placed into a homogeneous background. Deformation of the magnetic field were depicted using a special technique of processing the phase data. The suggested technique improves quality of NMR images and is suitable for testing the imaging equipment and techniques with high versatility, stability and repeatability. Verification of the technique were performed on a group of in-vitro samples. The technique can be utilized on clinical working places focused on liver and other organs diagnostics, equipped by NMR systems.

Partner abroad: Univ.-Prof. Dr. Siegfried Trattnig, MR Center, Highfield MR, Department of Radiology, Medical University of Vienna, Austria. Scientific co-operation agreements to 28.8.2006 and 24.8.2009.

Left: NMR images of three types of physical circle phantoms (diameter 1 to 3 mm) in images from 16x16 to 256x256 pixels, base magnetic field 3 Tesla. Right: NMR image of magnetic field of a meander phantom (50 x 50 mm), 128 x 128 pixels, base magnetic field 0.1 Tesla.

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Result 2:  Noninvasive localization of ischemic lesions based on stress test ECG mapping

Projects: VEGA 2/7092/27

Authors: J. Švehlíková, M. Tyšler, M. Turzová, E. Hebláková

Within the international cooperation with IBIB (Institute of Biocybernetics and Biomedical Engineering) PAN Warsaw, Poland, we obtained averaged ECG signals from 10 patients measured in 64 leads during the stress test at Dept. of Cardiology, Warsaw hospital. The data were used for the study of heart rhythm changes compensation. Furthermore, the data were used for experimental verification of the suggested method for identification of one or two ischemic lesions in myocardium by the inverse solution with two dipoles from difference integral maps and for evaluation of the use of 4 available heart cycle time intervals of integration in the suggested method. From the results it implied that the most suitable ECG interval was QRST. For 8 patients the difference integral maps fulfilled criteria for using the suggested method (suspicion of local ischemia). Comparison of the inverse results with the results from the usual imaging diagnostic methods - coronarography and SPECT - showed that for 5 patients (3 with 2-vessels disease, 2 with 1 lesion) the localization of the lesions agreed with medical documentation. For remaining 3 patients the type of lesion was correctly assessed (1 lesion) but its localization was not correct, which could have been caused by the use of the only one general standard torso model in the inverse solution.

Figure: Example of localization of one and two ischemic lesions. Comparison of results from coronarography and from SPECT (at rest and after load).

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