Development, integration and use of an ultra-high-strength gradient system on a human-size 3 T magnet for small animal MRI

Abstract

This study aims to integrate an ultra-high-strength gradient coil system on a clinical 3 T magnet and demonstrate its preclinical imaging capabilities. Dedicated phantoms were used to qualitatively and quantitatively assess the performance of the gradient system. Advanced MR imaging sequences, including diffusion tensor imaging (DTI) and quantitative susceptibility mapping (QSM), were implemented and executed on an ex vivo specimen as well as in vivo rats. The DTI and QSM results on the phantom agreed well with those in the literature. Furthermore, studies on ex vivo specimens have demonstrated the applicability of DTI and QSM on our system to probe microstructural changes in a mild traumatic brain injury rat model. The feasibility of in vivo rat DTI was also demonstrated. We showed that the inserted ultra-high-strength gradient coil was successfully integrated on a clinically used magnet. After careful tuning and calibration, we verified the accuracy and quantitative preclinical imaging capability of the integrated system in phantom and in vivo rat brain experiments. This study can be essential to establish dedicated animal MRI platform on clinical MRI scanners and facilitate translational studies at clinical settings.

White and gray matter integrity evaluated by MRI-DTI can serve as noninvasive and reliable indicators of structural and functional alterations in chronic neurotrauma

“…For the acquisition of MR signals, a single-loop transmit/receive surface coil with a diameter of 35 mm (Doty Scientific, Columbia, SC, USA) was utilized. Further information regarding the integration, calibration, and validation of this 3 T MRI system can be found in our previous publication 27 .…”

“…The regions of interest (ROIs) were manually outlined based on rat brain atlas maps 29 , 30 by two of the authors (Dr. Li-Wei Kuo and Dr. Kuan-Hung Cho) with extensive experience in neuroanatomy, both in histologic preparation and MRI. They have developed a proprietary code that has been successfully employed for DTI reconstruction in previous publications 27 , 31 . In this study, the white matter regions were selected by reference to the paper of Laitinen et al 8 and were manually outlined on FA maps (Supplementary Fig.…”

White Matter Pathology in Alzheimer’s Transgenic Mice With Chronic Exposure to Low-Level Ambient Fine Particulate Matter

“…Brain image acquisition was performed on a 3T MRI system (Achieva, Philips Health care, Best, Netherlands) with an ultrahigh-strength gradient coil of 675 mT/m in maximal intensity. Scheduled brain MRI scan sequencing was available for every sample, including high-resolution axial T2weighted imaging (TR/TE = 4000/34, slice thickness = 0.5 mm, slice number = 35), for volumetric analysis of the region of interest [37]. Diffusion tensor imaging (DTI) was performed with the following parameters: TR = 2000 ms, TE = 37 ms, difference between diffusion gradient pair (Δ) = 20 ms, diffusion gradient pulse duration (δ) = 4.5 ms, diffusion gradient strength = 19.87 G/cm, and b-values = 1000 s/mm 2 .…”

A 5‐channel local B0 shimming coil combined with a 3‐channel RF receiver coil for rat brain imaging at 3 T

“…1 The use of clinical scanners to conduct preclinical research can facilitate a more direct comparison with clinical studies, accelerate the development of clinically applicable imaging protocols, improve the matching of field strength-related mechanisms such as relaxation, and provide evidence to support the clinical relevance of functional MRI data/biomarkers. [2][3][4][5][6][7] The use of clinical scanners to conduct preclinical research also benefits from the hardware and software advancements continuously being made in modern clinical MRI systems, such as RF coil technology, 1 gradient coil technology, 8 deep-brain stimulation technology, 9 and molecular imaging technology. 10 Moreover, many laboratories and clinical research groups struggle to access dedicated animal systems, whereas clinical whole-body scanners are often more readily available.…”