Improved sensitivity and limit-of-detection using a receive-only coil in magnetic particle imaging. (2nd July 2018)

• Record Type: Journal Article
• Authors: Paysen, Hendrik; Wells, James; Kosch, Olaf; Steinhoff, Uwe; Franke, Jochen; Trahms, Lutz; Schaeffter, Tobias; Wiekhorst, Frank
• Is Part Of: Physics in medicine & biology. Volume 63:Number 13(2018:Jul.)
• Publication Date: 2018-07-02
• Subjects: magnetic particle imaging -- magnetic nanoparticles -- MPI -- MNP -- gradiometer; Biophysics -- Periodicals; Medical physics -- Periodicals; 610.153
• DOI: 10.1088/1361-6560/aacb87
• Languages: English
• ISSNs: 0031-9155

Abstract

Abstract: Magnetic particle imaging (MPI) is an imaging modality capable of quantitatively determining the 3D distribution of a magnetic nanoparticle (MNP) ensemble. In this work, we present a method for reducing the MNP limit of detection by employing a new receive-only coil (Rx-coil) for signal acquisition. The new signal detector is designed to improve the sensitivity and thus quality of reconstructed images. We present characterization measurements conducted with the prototype Rx-coil installed in a preclinical MPI scanner. The gradiometric design of the Rx-coil attenuates the unwanted signal contributions arising from the excitation field, leading to a 17 dB lower background level compared to the conventional dual-purpose coil (TxRx-coil), which is crucial for detecting low amounts of MNP. Network analyzer measurements of the frequency-dependent coil sensitivity, as well as spectral analysis of recorded MPI data demonstrate an overall increase of the coil sensitivity of about +12 dB for the Rx-coil. Comparisons of the sensitivity distributions revealed no significant degradations in terms of homogeneity for the Rx-coil compared to the TxRx-coil in an imaging volume of 6 × 3 × 3 cm 3 . Finally, the limit of detection was determined experimentally for each coil type using a serial dilution of MNPs, resulting in values of 133 ng of iron for the conventional TxRx-coil and 20 ng for the new Rx-coil, using an acquisition time of 2 s. A linear relationship between the reconstructed signal intensities and the iron mass in the samples was observed with coefficients of determination (R 2 ) of above 99% in the range of the limit of detection to 3 10 3 ng(Fe). These results open the way for improved image quality and faster acquisition time in pre-clinical MPI scanners.