Biomimetic phantom for cardiac diffusion MRI

Abstract

PurposeDiffusion magnetic resonance imaging (MRI) is increasingly used to characterize cardiac tissue microstructure, necessitating the use of physiologically relevant phantoms for methods development. Existing phantoms are generally simplistic and mostly simulate diffusion in the brain. Thus, there is a need for phantoms mimicking diffusion in cardiac tissue.Materials and MethodsA biomimetic phantom composed of hollow microfibers generated using co-electrospinning was developed to mimic myocardial diffusion properties and fiber and sheet orientations. Diffusion tensor imaging was carried out at monthly intervals over 4 months at 9.4T. 3D fiber tracking was performed using the phantom and compared with fiber tracking in an ex vivo rat heart.ResultsThe mean apparent diffusion coefficient and fractional anisotropy of the phantom remained stable over the 4-month period, with mean values of 7.53 ± 0.16 × 10−4 mm2/s and 0.388 ± 0.007, respectively. Fiber tracking of the 1st and 3rd eigenvectors generated analogous results to the fiber and sheet-normal direction respectively, found in the left ventricular myocardium.ConclusionA biomimetic phantom simulating diffusion in the heart was designed and built. This could aid development and validation of novel diffusion MRI methods for investigating cardiac microstructure, decrease the number of animals and patients needed for methods development, and improve quality control in longitudinal and multicenter cardiac diffusion MRI studies.

Phantoms for diffusion-weighted imaging and diffusion tensor imaging quality control: a review and new perspectives

“…Moreover, smaller air bubbles may not be detected and their removal is not easy. In addition, MD and FA values of these phantoms differ significantly from those obtained from biological tissues in most cases, because when phantom structures have dimensions lower than the scanner spatial resolution, bias in MD and FA values may occur (Teh et al, 2016). It is also worth mentioning that the pattern of magnetic field distortion due to the patient's head and to the phantom in the scanner is different from that seen in images of one or the other independently (Kim et al, 2015).…”

“…In the reviewed studies, the range of B 0 goes from 0.5T to 9.4T. Most studies apply SE-EPI sequences or their clinical/research routines (Lorenz et al, 2006;Teh et al, 2016). New sequences, such as d-PSGE, are being proposed and tested (Komlosh et al, 2008;Lorenz et al, 2008).…”

“…2017 June;33(2): 156-165 Researchers suggest different kinds of phantoms for DWI and DTI QC, as well as different compounds and solutions to fill them (Madsen and Fullerton, 1982;Pierpaoli et al, 2009;Tofts et al, 2000). There are phantoms of isotropic diffusion for DWI (typically spheres or cylinders filled by liquid) (Laubach et al, 1998;Lavdas et al, 2013;Pierpaoli et al, 2009); fiber phantoms to simulate axonal tracts or cardiac muscle (Fieremans et al, 2008;Lorenz et al, 2008;Teh et al, 2016); phantoms made of capillary or microcapillary arrays permeated by liquid with diffusion properties and/or relaxation times similar to biological tissues (Ebrahimi et al, 2010) test tubes with different solutions (Pierpaoli et al, 2009;Tofts et al, 2000); biological phantoms, such as green asparagus inside a water container (Latt et al, 2007); or animal tissues (axons of pigs or mice) (Chen et al, 2014;Komlosh et al, 2008). There are gels, for isotropic or anisotropic diffusion studies, whose magnetic properties are similar to healthy or pathological tissue (Hellerbach et al, 2013;Kato et al, 2005).…”

“…The setup remained stable for 1 month; however, it was a small phantom, incompatible with clinical scanners (Hubbard et al, 2015). The co-electrospinning technique was also used to develop an anisotropic phantom to simulate cardiac muscle tissue (Teh et al, 2016). Phantoms made using lithography and other microfabrication techniques also been reported to be useful for DTI QC and pulse-sequence tests (Ebrahimi et al, 2010;Komlosh et al, 2011).…”

“…In other words, changes in the MRI scanner tend to degrade DWI and DTI images before they compromise T1, T2 and PD-weighted scans. Recent studies have suggested phantoms for QC of diffusion acquisitions, based on different kinds of materials and a variety of geometries (Fieremans et al, 2008;Hellerbach et al, 2013;Hubbard et al, 2015;Teh et al, 2016). This work provides an overview of current literature related to this issue, highlighting the progress made and the main challenges to overcome, as well as prospects to standardization of diffusion images' QC.…”