A USPIO doped gel phantom for R2 relaxometry

• Published in: Magma (New York, N.Y.) N.Y.), 2017-02, Vol.30 (1), p.15-27
• Main Authors: Brown, Gregory C., Cowin, Gary J., Galloway, Graham J.
• Format: Article
• Language: English
• Subjects: Algorithms; Assessments; Axons - pathology; Biomedical Engineering and Bioengineering; Calibration; Carrageenan - chemistry; Computer Appl. in Life Sciences; Computer Simulation; Contrast Media - chemistry; Diffusion Magnetic Resonance Imaging; Durability; Estimates; Ferric Compounds - chemistry; Gels; Health Informatics; Humans; Image Processing, Computer-Assisted; Imaging; Internet resources; Iron - chemistry; Liver - diagnostic imaging; Liver - pathology; Magnetic resonance; Magnetic Resonance Spectroscopy; Medicine; Medicine & Public Health; Nonlinearity; Phantoms, Imaging; Radiology; Regression; Regression Analysis; Reproducibility of Results; Research Article; Sepharose - chemistry; Solid State Physics; Water - chemistry
• ISSN: 0968-5243; 1352-8661
• DOI: 10.1007/s10334-016-0576-x

Objective This work describes a phantom containing regions of controlled R 2* (1/ T 2*) values to provide a stable reference object for testing implementations of R 2* relaxometry commonly used for liver and heart iron assessments. Materials and methods A carrageenan-strengthened gadolinium DTPA doped agarose gel was used to enclose nine gels additionally doped with ultra-small superparamagnetic iron oxide. R 2* values were determined at 1.5 T using multi-echo GRE sequences and exponential regression of pixel values from a region of interest against echo time using non-linear regression algorithms. We measured R 2*, R 2 and R 1 values and the inter-scan and inter-operator reproducibility. Results The phantom reliably demonstrated R 2* values in seven steps between 22.4 s −1 (SE 1.98) and 441.9 s −1 (SE 6.76), with an R 2* relaxivity ( r 2*) of 792 (SE 5.6) mM −1  s −1 . The doped gels displayed a concentration-dependent R 2ʹ component of R 2* phantom, indicating superparamagnetic enhancement effects. We observed no significant change in relaxivity ( r 2*) over 12 months, and estimate a useful life of 3 years. Detailed descriptions of the production process and calculators are been provided as Online Resources. Conclusion The phantom provides a durable test object with controlled R 2* relaxation behaviour, useful for a range of R 2* relaxometry reference work.