Pengembangan Elektroda Flat Base dan Gel Konduktif Sebagai Pengganti Elektroda Konvensional

Pengembangan elektroda flat base dengan menggunakan gel konduktif telah dilakukan dalam pengukuran data geolistrik di lapangan. Pengembangan elektroda flat base bertujuan untuk mengganti penggunaan elektroda konvensional berupa elektroda tancap (spike electrode) yang memiliki keterbatasan pada area yang berbeton atau tidak memiliki ruang tancap ke tanah. Ukuran flat base 7 x 7 cm dengan gel konduktif, gel A (campuran tepung gula, garam, dan air), gel B (campuran MgSO4, tepung gula, air), dan gel C (campuran CuSO4, tepung gula, air), telah dibuat. Perbandingan hasil pengukuran dilakukan terhadap hasil pengukuran menggunakan ketiga jenis gel untuk menentukan gel konduktif yang terbaik yang dapat menggantikan penggunaan elektroda tancap. Dari hasil pengukuran diperoleh, arus listrik yang mengalir pada elektroda flat base dengan ukuran 7 x 7 cm dan gel A lebih baik dibandingkan penggunaan gel yang lain. Selain itu dari hasil inversi data pengukuran, hasil pengolahan data yang menggunakan elektroda dan gel tersebut cukup merepresentasikan kondisi bawah permukaan daerah pengukuran. The development of flat base electrodes using conductive gel has been done in measuring geoelectric data in the field. The development of flat base electrode aims to replace the use of conventional electrodes in the form of spike electrode which has limitedness in the area which is concrete or does not have a tap space to the ground. The size of a 7 x 7 cm flat base with a conductive gel, gel A (a mixture of sugar, salt, and water flour), gel B (mixture MgSO4, sugar powder, water), and gel C (CuSO4 mixture, created. A comparison of the measurement results has made to the measurements using the three types of gels to determine the best conductive gel that can replace the use of the stepped electrode. From the measurement results obtained, the electric current flowing on the flat base electrode with a size of 7 x 7 cm and gel A is better than the use of another gel. In addition from the inversion of measurement data, the results of data processing using electrodes and the gel is quite representative of the subsurface condition of the measurement area.

Invisible Base Electrode Coordinates Approximation for Simultaneous SPECT and EEG Data Visualization

This work was performed as part of a larger research concerning the feasibility of improving the localization of epileptic foci, as compared to the standard SPECT examination, by applying the technique of EEG mapping. The presented study extends our previous work on the development of a method for superposition of SPECT images and EEG 3D maps when these two examinations are performed simultaneously. Due to the lack of anatomical data in SPECT images it is a much more difficult task than in the case of MRI/EEG study where electrodes are visible in morphological images. Using the appropriate dose of radioisotope we mark five base electrodes to make them visible in the SPECT image and then approximate the coordinates of the remaining electrodes using properties of the 10-20 electrode placement system and the proposed nine-ellipses model. This allows computing a sequence of 3D EEG maps spanning on all electrodes. It happens, however, that not all five base electrodes can be reliably identified in SPECT data. The aim of the current study was to develop a method for determining the coordinates of base electrode(s) missing in the SPECT image. The algorithm for coordinates approximation has been developed and was tested on data collected for three subjects with all visible electrodes. To increase the accuracy of the approximation we used head surface models. Freely available model from Oostenveld research based on data from SPM package and our own model based on data from our EEG/SPECT studies were used. For data collected in four cases with one electrode not visible we compared the invisible base electrode coordinates approximation for Oostenveld and our models. The results vary depending on the missing electrode placement, but application of the realistic head model significantly increases the accuracy of the approximation.