Soft X-ray and susceptibility based magnetic resonance imaging to map iron distribution in apples: initial results to model iron storage in water-deficient or dehydrated biological tissue

Abstract

Abstract Radiology departments have contributed significantly to greenhouse gases including release of toxic imaging contrast media to environment. We feel Radiology also has several spectroscopy and imaging tools that may apply to monitor and support cleaner environmental goals. The current manuscript is one of the firsts to prompt Radiology to move in that direction by non-invasive imaging of bio metals that are less abundant in biological tissues but play key roles as co-factors in tissue structure and function. Conventional analytical tools are mostly invasive and cannot characterize the native oxidation states of bio metals. We chose carbohydrate matrix of metal-rich fruits and optimized two non-invasive imaging methods to detect changes in bio metal distribution as the samples were allowed to dry over time. It complements our prior work in Tomography Journal that demonstrated breakdown of specific radiological contrast media causing inflow of lanthanides and iodinated compounds to agricultural products and alter homeostasis by chelation and transmetallation. We observed that in the 20–30 keV range, that is at low end of clinical X-ray, commercial mammography detectors can detect alkali, alkaline earth, and transition metals in fruit samples irrespective of their oxidation states with appropriate X-ray filters utilizing preferential photoelectric absorption while high field magnetic resonance imagers (MRI) can localize paramagnetic states of certain minerals due to their ability to accelerate proton T2* decay and was used here to study biological tissues at different stages of dehydration. We also observed a central, radial shift of iron distribution from cortex toward the core for partially dried Apples indicative of porosity changes with de-moisturization. However, at this time our approach is unable to convincingly separate the susceptibility effects of paramagnetic bio metals from susceptibility effects of porosity changes during dehydration. We believe this work has two novel aspects: first, that MRI and X-ray could be used for complementary roles to map distribution of paramagnetics rich species, and secondly, ionic transport during heat processing of agricultural products or crops grown in arid land can be monitored for altered bio metal distribution by low energy X-ray as well as by high field MRI. In vivo applications may be possible to exploit MR susceptibility of native bio metals to localize abnormal iron distribution in neurodegeneration.