Technical Note: Human tissue‐equivalent MRI phantom preparation for 3 and 7 Tesla

Abstract

While test objects (phantoms) in MRI are crucial for sequence development, protocol validation and quality control, studies on the preparation of phantoms has been scarce, particularly at fields exceeding 3 Tesla. Here we present a framework for the preparation of phantoms with well-defined T 1 and T 2 times at 3 and 7 Tesla. MethodsPhantoms with varying concentrations of agarose and Gd-DTPA were prepared and measured at 3 and 7 Tesla using T 1 and T 2 mapping techniques. An empirical, polynomial model was constructed that best represents the data at both field strengths, enabling the preparation of new phantoms with specified combinations of both T 1 and T 2 . Instructions for three different tissue types (brain grey matter, brain white matter, and renal cortex) are presented and validated. ResultsT 1 times in the samples ranged from 698ms to 2820ms and from 695ms to 2906ms, whereas T 2 times ranged from 39ms to 227ms and from 34ms to 235ms for 3 and 7 Tesla scans, respectively. Models for both relaxation times used six parameters to represent the data with an adjusted R² of 0.998 and 0.997 for T 1 and T 2 , respectively. ConclusionBased on the equations derived from the current study, it is now possible to obtain accurate weight specifications for a test object with desired T 1 and T 2 relaxation times. This will spare researchers the laborious task of trail-and-error approaches in test object preparation attempts.

MRI and Ultrasound Visualization of a Nerve Repair Implant Containing Nitinol

“…13 Agarose doped with gadolinium was utilized, with the concentrations of agarose and gadolinium needed to achieve these target T1 and T2 values. 14 The nerve-mimicking samples were prepared in a glass beaker by combining a 0.05% NaN 3 solution (Sigma-Aldrich; Milwaukee, Wis.), 2% agarose (Sigma-Aldrich), and 50 µmol/kg of gadobutrol (Gadovist, Bayer AG, Leverkusen, Germany). The compound was mixed at room temperature continuously and heated to 75°C, with deionized water added to maintain the original mixture mass to account for evaporation.…”

Silicone‐based materials with tailored MR relaxation characteristics for use in reduced coil visibility and in tissue‐mimicking phantom design

“…Phantoms used in magnetic resonance imaging (MRI) applications should be fabricated with precise T 1 (longitudinal) and T 2 (transverse) relaxation times that can vary significantly depending on the tissue of interest, and the field strength of the MRI scanner. [13][14][15] The choice of phantom material depends on many factors, such as mechanical strength, material cost, preparation time,toxicity,shelf life,thermal behavior,etc.Some widely used materials include agarose and gelatin due to their availability, low cost, and ease of fabrication. 1,3,16,17 However,they are both fragile,and provide limited optical opacity, with a shelf life that is compromised without the use of toxic preservatives.…”

“…Phantoms used in magnetic resonance imaging (MRI) applications should be fabricated with precise T 1 (longitudinal) and T 2 (transverse) relaxation times that can vary significantly depending on the tissue of interest, and the field strength of the MRI scanner 13–15 . The choice of phantom material depends on many factors, such as mechanical strength, material cost, preparation time, toxicity, shelf life, thermal behavior, etc.…”