Quantitative anatomy mimicking slice phantoms

Abstract

To present a reproducible methodology for building an anatomy mimicking phantom with targeted T 1 and T 2 contrast for use in quantitative magnetic resonance imaging. Methods: We propose a reproducible method for creating high-resolution, quantitative slice phantoms. The phantoms are created using gels with different concentrations of NiCl 2 and MnCl 2 to achieve targeted T 1 and T 2 values. We describe a calibration method for accurately targeting anatomically realistic relaxation pairs.In addition, we developed a method of fabricating slice phantoms by extruding 3D printed walls on acrylic sheets. These procedures are combined to create a physical analog of the Brainweb digital phantom. Results: With our method, we are able to target specific T 1 /T 2 values with less than 10% error. Additionally, our slice phantoms look realistic since their geometries are derived from anatomical data. Conclusion: Standardized and accurate tools for validating new techniques across sequences, platforms, and different imaging sites are important. Anatomy mimicking, multi-contrast phantoms designed with our procedures could be used for evaluating, testing, and verifying model-based methods. K E Y W O R D S3D printing, digital manufacturing, phantom, quantitative F I G U R E 1 Process flow of converting an image of a brain slice into a phantom. A,B, Solutions of paramagnetic ions NiCl 2 and MnCl 2 are prepared with agar and salt to calibrate the influence of their concentrations on T 1 /T 2 . C, A slice of a brain is acquired, 14 segmented into compartments, and labeled. The compartment boundaries are 3D printed onto an acrylic sheet. D, Premixed gels are blended following different linear combinations to target specific R1 and R2 values. Different blend compositions are used to fill each compartment according to the anatomy. E, Finally, the phantom is scanned for verification and visualized here with a T 1 -weighted image

Vendor‐neutral sequences and fully transparent workflows improve inter‐vendor reproducibility of quantitative MRI

“…For future work, we plan to develop a double‐angle VENUS prescan using the same excitation pulses as the qMRI sequences that follow, to determine a global RF scaling factor. Coupled with the use of anatomy‐mimicking quantitative MRI phantoms, 70 this would offer qMRI‐ready adaptive prescan routines and help investigate the effect of standardizing calibration measurements on multicenter accuracy and agreement.…”

3D Extrusion Printing of Biphasic Anthropomorphic Brain Phantoms Mimicking MR Relaxation Times Based on Alginate-Agarose-Carrageenan Blends

“…Toward Large-Scale Fabrication in Anatomical Dimensions. Many approaches have been developed for phantom fabrication over the years: Altermatt and colleagues presented a casted biphasic phantom based on agar and MnCl 2 with silicone molds mimicking the brain folding pattern, 19 while Gopalan and co-workers demonstrated the possibility of a partly (GM-) printed biphasic phantom based on agar and MnCl 2 as well 18,26 and later suggested breaking down the brain pattern into phantom slices. 18 With nonprintable hydrogels fully characterized for T 1 or T 2 impacts before, 16,21,23 reproducing real GM and WM relaxation times was better achieved compared to our approach.…”

“…Techniques of additive manufacturing (AM) still play a minor role, as AM is merely used for the fabrication of casting molds: Yunker and co-workers have evaluated the relevance and suitability of materials for the 3D printing of MRI phantoms, while Gopalan et al 3D printed a cast that can be manually filled up with a low viscosity hydrogel for biphasic structures. , Another study suggested a 3D-printed, PLA-based shell for filling up the phantom structure in order to simulate transcranial magnetic stimulation . Other popular alternative materials are silicones, while other approaches describe the casting or printing of hydrogel phases consisting of polysaccharides such as gelatin to match the mechanical properties of brain tissue, , or their combination with polymers such as poly vinyl alcohol (PVA), or different types of silicone. ,− …”

“…17 However, for the advancement of quantitative methods with a high spatial resolution in anatomic geometries, novel anthropomorphic phantoms will be indispensable. So far, such structures have required the usage of casting molds with walls in between different compartments representing the anthropomorphic shape 18 as approaches without separating layers lacked stability of the spin-relaxation times. 19 For fast, easy hardening and long-term stability, the materials filled into such objects are mainly based on biopolymer hydrogel networks with different gelling mechanism.…”

Vendor-neutral sequences and fully transparent workflows improve inter-vendor reproducibility of quantitative MRI

“…For future work, we plan to develop a double-angle VENUS prescan using the same excitation pulses as the qMRI sequences that follow, to determine a global RF scaling factor. Coupled with the use of anatomy-mimicking quantitative MRI phantoms 71 , this would offer qMRI-ready adaptive prescan routines and help investigate the effect of standardizing calibration measurements on multicenter accuracy and agreement.…”