Quantification of magnetic nanocomposites in biological tissue through a cross-calibration of X-ray and Magnetic Resonance Imaging with the help of a uniform phantom
Biomedical Systems Technology
Measurement Systems
Final Report Abstract
A calibration of XµCT/XCT and MRI equipment with these three different phantom systems was shown as feasible. A co-registration of the MRI and XµCT data sets is possible. The calibration can be applied to data sets of biological tissues enriched with MNC. And the MNC distribution as well as their content can be examined 3-dimensionally. The performed study of a long-term phantom for MRI and X-Ray imaging of body tissues enriched with magnetic nanocomposites has shown that synthetic rubber EcoFlex™ (EF) is suitable for 3-dimensional and quantitative imaging of tissues after, for example, magnetically assisted cancer treatments. These phantoms consist of a synthetic rubber with different concentrations of multi-core magnetic nanocomposites. The produced phantoms are shaped as cylindrical discs stacks with D=30 mm and H~80 mm (EF-MNC) and as bigger cylinder discs (D=60 mm and H~25 mm) with 3 inclusions of MNC enriched cylinder discs (EF-3-MNC). This phantoms have been proved of being long-term stable and can be applied to various MRI and XCT equipments. The obtained calibration equation enables a 3-D examination of the MNC content. Based on this, a cross-calibration and data co-registration were performed. The results are a 3-dimensional study of the MNC distribution on the one hand, and on the other one a quantification of the MNC content within the tissue sample. The 3-D MNC distribution and quantification were performed on two tumour samples after MDT. Here, the MNC content was calculated with deviation of 9.03 - 43.44 % in comparison to the absolute MRX value. This deviation leads to a further investigation. The most probable solution is an extended study of the XµCT experimental conditions. This was not possible within the time frame of the research project. A cross-calibration of XµCT and MRI was performed, followed by data co-registration, and a 3-D study of MNC biodistribution as well as MNC quantification. Although feasible to act as substitutes for body tissue enriched with MNC, the EF-MNC phantom system has to be analysed further with regard to its sensitivity for X-Ray contrast at lower MNC concentrations to extend the common sensitivity range for cross-calibration of XCT and MRI. In case of the 3MNC phantoms it could be shown that the EF-3-MNC phantom has a high potential to replace 12 separate MNC concentrations with 5-6 MNC concentrations. This would result in much shorter production times as well as in XµCT measuring time thereby reducing X-Ray exposure and costs. Here, has been figured out, that an adapted choice of the included MNC concentrations need to be performed, to enable a more precise detection of the threshold. Additionally, two phantom systems based on gelatin (LTSG-MNC), and on gelatin and raw biological tissue (LTSG-CB-MNC) have been presented and compared to the EF-MNC phantom. These phantoms were also shaped as cylinder disc stacks and as more tumour like shaped cylinder discs with 3 MNC loaded regions LTSG-MNC phantom system has shown easy handling and great ability of MNC dispersion and purity. A time dependent stability of 5.5 months has been observed with a shrinkage of 3.11 % to 9.59 %. Whereas, the LTSG-CB-MNC phantom needs an improvement with respect to the homogeneous MNC distribution and purity (air bubbles). Due to the included isopropanol the life time of LTSG-CB-MNC phantoms could be extended to 5.5 months compared to raw biological tissue, where decomposition occurs after 1 to 2 days usually. Furthermore, hydrogels based on alginic acid and agarose gel have been considered as matrix components for immobilisation of MNC and raw tissue. After tests with NMR, VSM, XCT, and MRI, these two matrix components have been excluded as phantom systems, due to the lack of reproducibility and long-term stability (shrinkage). The next steps towards clinical applications are adjustments of experimental conditions during the XCT measurements for all phantoms systems to provide a more precise MNC quantification in tissue sample as tumours after MDT or MHT.
