Improved Detection of Molecularly Targeted Iron Oxide Particles in Small Animals with High Resolution MRI

Abstract

Authors: Paul Kinchesh, Stuart Gilchrist, Niloufar Zarghami, Alexandre A Khrapitchev, Nicola R Sibson, Veerle Kersemans, Sean C Smart. High resolution multi-gradient echo (MGE) scanning is typically used for detection of molecularly targeted iron oxide particles. The images of individual echoes are often combined to generate a composite image with improved SNR from the early echoes and boosted contrast from later echoes. In 3D implementations prolonged scanning at high gradient duty cycles induces a B0 shift that predominantly affects image alignment in the slow phase encoding dimension of 3D MGE images. The effect corrupts the composite echo image and limits the image resolution that is realised. A real-time adaptive B0 stabilisation during respiration gated 3D MGE scanning reduces image misalignment and improves detection of molecularly targeted iron oxide particles in composite images of the mouse brain. Respiration gated MGE 3D scans were performed to visualise molecularly targeted MPIO in a BALB/c mouse model of acute neuroinflammation. Data were acquired with and without B0 stabilisation for comparison. The slow phase encode image dimension runs in the left-right direction of the brain. It is particularly instructive to inspect the registration of image data by selecting an axial slice and scrolling through the acquired echoes. The echoes can be summed to form a simple composite image. The data in this archive demonstrate that high resolution imaging for the detection of molecularly targeted iron oxide particles in the mouse brain requires good stabilisation of the main B0 field so that the composite image resolution reflects the prescribed image resolution. Data were acquired on a 9.4 T 160 mm horizontal bore VNMRS preclinical imaging system equipped with 100 mm bore gradient insert (Varian Inc, CA) and are available for 6 mice. The *.nii files are NIfTI-1 formatted image files, http://nifti.nimh.nih.gov/ ImageJ is a suitable viewer, http://imagej.nih.gov/ij/ M#_compensatedXXX.nii: Mouse #, B0 stabilisation of a XXX Hz frequency drift. M#_uncompensatedYYY.nii: Mouse #, a YYY Hz frequency drift without B0 compensation. # = [1,6