Silver nitrate (AgNO₃) as an alternative contrast agent for X-ray imaging of wheat tissue samples

One of the challenges in using X-ray computed tomography (CT) for plant imaging is lack of contrast in anatomical structures and tissues due to similar density. Iodine is the most commonly used contrast agent and studies on additional contrast agents are scarce. In the present study, we describe the successful application of silver nitrate (AgNO 3 ) as a novel contrast agent in synchrotron-based CT of wheat. The lower K-edge of silver (25.514 keV) is more optimal for plant imaging than a high atomic number contrast agent, such as iodine (33.164 keV), for which the below- and above-edge images would have poorer absorption contrast (due to reduced ratio of absorption coefficients from plants). Particularly, this is applicable for studies at the Biomedical Imaging and Therapy beamline (BMIT-BM) at the Canadian Light Source due to the peak flux of the beamline being proximal to the K-edge of silver in comparison to iodine (leading to decreased image noise, increased contrast, and a better signal-to-noise ratio).