Imagine you’re a baker creating a cake that looks and tastes like a real cactus. To achieve this, you need a recipe that accurately replicates the texture, color, and complexity of a cactus. Similarly, scientists studying white matter microstructure need realistic substrates to validate their models. That’s where CACTUS comes in! CACTUS is like a customizable cake decorator for researchers, allowing them to generate synthetic white matter substrates that closely resemble real tissue. It can create substrates with high packing density and larger voxel sizes, making it more versatile than existing methods. With its ability to mimic important features of tissue, such as bundle crossings and variations in radii, CACTUS improves the accuracy of simulations and opens up new possibilities for microstructure imaging. If you’re eager to learn more about this exciting computational framework and its potential applications, dig into the full article!

Monte-Carlo diffusion simulations are a powerful tool for validating tissue microstructure models by generating synthetic diffusion-weighted magnetic resonance images (DW-MRI) in controlled environments. This is fundamental for understanding the link between micrometre-scale tissue properties and DW-MRI signals measured at the millimetre-scale, optimizing acquisition protocols to target microstructure properties of interest, and exploring the robustness and accuracy of estimation methods. However, accurate simulations require substrates that reflect the main microstructural features of the studied tissue. To address this challenge, we introduce a novel computational workflow, CACTUS (Computational Axonal Configurator for Tailored and Ultradense Substrates), for generating synthetic white matter substrates. Our approach allows constructing substrates with higher packing density than existing methods, up to 95% intra-axonal volume fraction, and larger voxel sizes of up to 500μm3 with rich fibre complexity. CACTUS generates bundles with angular dispersion, bundle crossings, and variations along the fibres of their inner and outer radii and g-ratio. We achieve this by introducing a novel global cost function and a fibre radial growth approach that allows substrates to match predefined targeted characteristics and mirror those reported in histological studies. CACTUS improves the development of complex synthetic substrates, paving the way for future applications in microstructure imaging.

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