Evaluation of tri-signature X-ray computed tomography for larvae-in-fruit infestation inspection

Detection of invasive insect pest internally infesting plant commodities is challenging. Currently, imported fruits are manually dissected for labor-intensive inspection. X-ray imaging may provide a way to detect concealed pests.  Many insects and their host fruits have high water content (70-96%).  Traditional attenuation-based X-ray imaging cannot decern differences between high-water-content insects and high-water-content fruits, making this methodimpractical.  We tested a grating-based X-ray phase contrast imaging system, which enables measuring traditional absorption-contrast, differential phase-contrast, and dark-field images simultaneously.  We showed that fruit fly pupae in waterthat were invisible in absorption-contrast images were unveiledusing differential phase-contrast and dark-field images. We are now using computed tomography (CT) of the phase-contrast imaging system to create a detailed larvae-in-fruit image. Larvae are often hidden behind fruit tissues in projection images, which makes it challenging to find larvae among fruit backgrounds.  However, the traces of the larva’s features are present on theimage. We used CT to reconstruct a detailed image of the larvae. In addition, we evaluated quantitative tri-signature CT data to differentiate the properties of the larva from the fruit soft tissues.  Our results indicate that tri-signature X-ray CT may prove afeasible way to detect pests otherwise found only through dissection. We continue to explore the capabilities of this technology to detect other species in their host fruits. Ultimately, we aim to utilize the X-ray phase-contrast imaging technology to improve detection and increase the speed of inspections at US customs borders and in the food industry.