Unambiguous identification of superparamagnetic iron oxide particles through quantitative susceptibility mapping of the nonlinear response to magnetic fields

Abstract

Superparamagnetic iron oxide (SPIO) particles generate signal void regions on gradient echo images due to their strong magnetization. In practice, the signal void region might be indistinguishable from that generated by air. However, the response of SPIO to an externally applied magnetic field is nonlinear. Magnetization of SPIO saturates at around 1 Tesla while magnetization of water and air increase linearly with field strength. Phantom experiment and mice experiments demonstrated the feasibility of a non-ambiguous identification of superparamagnetic contrast agents.

Cerebral Microbleeds: Burden Assessment by Using Quantitative Susceptibility Mapping

“…Liu et al (nonferromagnetic), then the total susceptibility measurement should be independent of fi eld strength ( 30 ). The susceptibility changes within cerebral microbleeds are primarily due to hemosiderin deposits and refl ect the amount of iron that is recognized as an important factor for brain injury in intracerebral hemorrhage ( 31,32 ).…”

Phase-corrected bipolar gradients in multi-echo gradient-echo sequences for quantitative susceptibility mapping

“…The field of the induced magnetization can be measured using MRI signal phases and can be deconvolved to yield quantitative susceptibility maps (QSMs) [1-9]. QSMs provide a noninvasive means of assessing iron deposition [5,8,10-17], blood oxygen saturation [6,10,18,19], the myelin in white matter tracts [7,20,21], cortical and deep gray matter structures and substructures [17,22-25], and the biodistribution of contrast agents for clinical and preclinical investigations [26,27]. Because of its promising potential, QSM has recently received increased scientific and clinical attention [28-30].…”

Gradient Echo Plural Contrast Imaging — Signal model and derived contrasts: T2*, T1, Phase, SWI, T1f, FST2*and T2*-SWI

“…The clinical applications for SWI continue to expand steadily (Haacke 2011). Other techniques, some of which rely exclusively on the phase data of the GRE signal have also been intensely explored for uniquely characterizing anatomical structures that are especially evident at high field MRI (Duyn et al 2007; Marques et al 2009; Rauscher et al 2005; Zhong et al 2008), and even for creating maps of tissue magnetic susceptibility – the so called Quantitative Susceptibility Mapping (QSM) (de Rochefort et al 2008; de Rochefort et al 2010; Liu 2010; Liu et al 2010; Schweser et al 2010; Schweser et al 2011; Shmueli et al 2009). The information obtained from these techniques reveals image features complimentary to that obtained from traditional magnitude-based imaging and could improve our understanding of both normal tissue anatomy as well as changes in tissue in various pathological conditions.…”