CAD-ASTRA: a versatile and efficient mesh projector for X-ray tomography with the ASTRA-toolbox.

Accurate and fast simulation of X-ray projection data from mesh models has many applications in academia and industry, ranging from 3D X-ray computed tomography (XCT) reconstruction algorithms to radiograph-based object inspection and quality control. While software tools for the simulation of X-ray projection data from mesh models are available, they lack either performance, public availability, flexibility to implement non-standard scanning geometries, or easy integration with existing 3D XCT software. In this paper, we propose CAD-ASTRA, a highly versatile toolbox for fast simulation of X-ray projection data from mesh models. While fully functional as standalone software, it is also compatible with the ASTRA toolbox, an open-source toolbox for flexible tomographic reconstruction. CAD-ASTRA provides three specialized GPU projectors based on state-of-the-art algorithms for 3D rendering, implemented using the NVIDIA CUDA Toolkit and the OptiX engine. First, it enables X-ray phase contrast simulations by modeling refraction through ray tracing. Second, it allows the back-propagation of projective errors to mesh vertices, enabling immediate application in mesh reconstruction, deep learning, and other optimization routines. Finally, CAD-ASTRA allows simulation of polychromatic X-ray projections from heterogeneous objects with a source of finite focal spot size. Use cases on a CAD-based inspection task, a phase contrast experiment, a combined mesh-volumetric data projection, and a mesh reconstruction demonstrate the wide applicability of CAD-ASTRA.

Towards storage of cells and gametes in dry form.

We review published data on cell/gamete lyophilization. Most studies have utilized the same established protocols for cryopreservation (storage in liquid nitrogen) as for cell lyophilization (dehydration of frozen samples by water sublimation). Surveying natural lyoprotectants, we suggest trehalose and late embryogenesis abundant (LEA) proteins as ideal candidates for the reversible desiccation of mammalian cells/gametes. We find that despite the numerous water subtraction techniques, scientists have relied almost exclusively on lyophilization. There is thus room for improvement in both medium formulation and water subtraction strategies for dry cell/gamete storage. We believe the development of dry processing protocols for use in biobanks of cells/gametes, at reduced cost and with minimal carbon footprint, is within our grasp.