SNRRelaxivity and Stability of Agarose-based MRI Phantoms with Iron (III) Chloride and Gadolinium (III) Chloride as Relaxation Modifier: A Longitudinal Study

Abstract

Magnetic resonance imaging (MRI) quality control (QC) relies heavily on phantom relaxation to maintain image consistency. Current research indicates that many laboratory-fabricated phantoms often fall short of image uniformity and stability over time. This study aimed to assess the signal-to-noise ratio (SNR) relaxivity and stability of agarose gel phantoms added with relaxation modifiers against time. A total of twenty-two agarose gel phantoms added with different volumes of gadolinium (III) chloride (GdCl3) and iron (III) chloride (FeCl3) were prepared. The phantoms were scanned using a 3-T Siemens Magnetom Skyra MRI system at an interval of 30 days apart. A Turbo Spin Echo (TSE) pulse sequence was used in acquiring T1 and T2 measurement images. The SNR of all the T1 and T2 images acquired were calculated, analyzed, and compared. The GdCl3 and FeCl3 added agarose gel phantoms showed a decreasing T1 SNR value when the relaxation modifier content increased and a gradually decreasing T1 SNR value in the range of TR used. The prepared phantoms displayed an unstable T1 SNR over an interval of time after preparation. The T2 curves for all phantoms appear the same at all time points (TP) indicating the very small influence of TP on T2 relaxation. While the T1 values for the phantoms were undetermined in this study, their T2 values show an inconsistent trend with increasing relaxation modifier content and at different TP. The use of FeCl3 and GdCl3 as relaxation modifiers seemed promising especially for the quality control of a fast imaging sequence due to their ability to reduce T1 relaxation time markedly. In addition, the consistency of T2 relaxation over time indicates the T2 SNR stability of the phantoms.