Monitoring the postharvest ripening of tomato fruit using quantitative MRI and NMR relaxometry

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceMagnetic Resonance Imaging (MRI) was performed on tomato fruit during two 3-week periods of postharvest ripening. Different image types were acquired to study macroscopic and microscopic structural changes. Air spaces were identified close to seeds and their shrinkage during the ripening period was estimated from the spin echo images. The development of the bubbles in the outer pericarp during ripening was estimated from the ratio of the long- and short-echo time gradient echo MRI images and supported by the macrovision imaging. Variations in the transverse (T2) and longitudinal (T1) relaxation times were determined from quantitative MRI images. They depended on the tissue type and matched fairly well between fruit. In the core, placenta, radial and outer pericarp, T2 decreased by about 25% from the initial values and T1 by about 25-30% from the initial values during postharvest ripening. In the locular tissue the relaxation times had less marked trends than in other tissues: both T2 and T1 increased slightly until the eighth or ninth measurement day and after that it returned to its approximate initial value. Multi-component characteristics of T2 and T1 decay were investigated by Nuclear Magnetic Resonance (NMR) relaxometry. They provided information about all major sub-cellular compartments and showed there was water redistribution among compartments during ripening. In addition to the relaxometry measurements, water content, weight loss and concentration of neutral sugars and acids were measured on some of the tomato fruit. Cell size and organization were investigated by macrovision experiments. Although the overall dependence of the relaxation time on tissue type was to some extent explained by chemical composition and cell dimension, no relationships between trends in MR data and tissue properties were established

An investigation of the structural aspects of the tomato fruit by means of quantitative nuclear magnetic resonance imaging

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceIn this study, magnetic resonance imaging (MRI) was applied to study the structural aspects of the tomato fruit. The main study was performed on tomatoes (cv. Tradiro) using a 0.2-T electromagnet scanner. Spin-echo images were acquired to visualize the tomato macrostructure. The air bubble content in tissues was evaluated by exploiting susceptibility effects using multiple gradient echo images. The microstructure was further studied by measuring spin-spin (T2) and spin-lattice (T1) relaxation time distributions. Nuclear magnetic resonance relaxometry, macro vision imaging and chemical analysis were used as complementary and independent experimental methods in order to emphasize the MRI results. MRI images showed that the air bubble content varied between tissues. The presence of gas was attested by macro vision images. Quantitative imaging showed that T2 and T1 maps obtained by MRI reflected the structural differences between tomato tissues and made it possible to distinguish between them. The results indicated that cell size and chemical composition contribute to the relaxation mechanism

Rapid quantification of muscle fat content and subcutaneous adipose tissue in fish using MRI

International audienceThe potentiality of MRI to quantify fat content in flesh and subcutaneous fat in fish cutlets was investigated. Low measurement time was aimed at in a view to handling large number of samples needed in selective breeding programs for example. Results on fresh and frozen-thawed cutlets were compared to assess this way of conservation. As MRI generates unwanted spatial variations of the signal, a correction method was developed enabling the measurement on several cutlets simultaneously in less than 3 min per sample. For subcutaneous fat, the results were compared with vision measurements. High correlations between both techniques were found (R2 = 0.77 and 0.87 for the ventral and dorsal part). Fat in flesh was validated vs NMR measurements. No statistical difference was found between fresh and frozen-thawed cutlets. RMSE was respectively 0.8% and 0.89%. These results confirmed the potentiality of MRI for fat measurement in fish particularly for a large number of samples

MRI investigation of internal defects in potato tubers with particular attention to rust spots induced by water stress

International audiencePotato quality is a major concern for both producers and customers. However, potato tubers are affected by various forms of internal damage with no external symptoms, leading to substantial economic losses. MRI was used as a non-invasive and quantitative method to evaluate internal defects in potato tubers and their evolution during storage. Rust spots, induced by water stress, were considered in particular. To this end, potato plants were cultivated both in the field and in pots and their water uptake was controlled. Following harvest and throughout the storage period, 3D images of tubers were recorded on a 1.5 T MRI scanner using a fast spin echo sequence. In parallel, the multi-exponential transverse relaxation times (T2) of the tubers were mapped in order to provide information on changes in water status and distribution at the subcellular level in rust spots and in healthy perimedullary regions. The occurrence of rust spots correlated with water conditions in greenhouse where water intake was carefully controlled. The number and individual volume of rust spots did not change during storage period, but they significantly increased with tuber size. Bi-exponential transverse relaxation revealed differences between healthy and damaged tissue

High-throughput phenotyping of health biomarkers in Crassostrea gigas by magnetic resonance imaging

High-throughput phenotyping of shellfish’s traits constitutes a challenge due to the specificities of aquatic animals. Appropriate measuring tools have often to be developed or adapted, in order to continuously and automatically acquire data of biomarkers of interest. IMAGIGAS project aimed to explore a non-destructive and non-invasive approach by using magnetic resonance imaging (MRI) to monitor at high-throughput two biomarkers (body weight and temperature) of the pacific oyster, before and during infectious challenges by Ostreid Herpesvirus type 1 (OsHV-1). Pacific oysters and OsHV-1 suspension and contaminated seawater were produced at Ifremer facilities. The experiments were conducted in 2016-2017 by three staffs (Ifremer LGPMM, Irstea IRM Food, Université de La Rochelle LIENSs) at PRISM platform of Irstea at Rennes who provided a Siemens Avanto 1,5 T MRI. One objective was to monitor body weight of numerous individuals. Protocols were inspired by previous Ifremer / Irstea collaborative works and allowed to increase the throughput of measure to 69 oysters every 45 minutes. The estimation of body weight is based on a relation established between the sum of pixels whose grey level is greater than a particular value in pictures taken by MRI and the weight of drained then lyophilized flesh of oysters measured by precision balance. Each development experiments were completed by application experiments with infection of oysters by OsHV-1 and measures of body weight

"Qualitytruite" : l'IRM comme méthode de quantification rapide du gras intramusculaire et du tissu adipeux sous cutané des darnes de truite arc-en-ciel (Oncorhynchus mykiss)

Le but du projet était d’évaluer chez la truite arc-en-ciel la faisabilité du dosage de la teneur en lipides intramusculaires et de la surface de gras sous cutané par Imagerie en Résonance Magnétique (IRM) sur des darnes entières après décongélation. La possibilité d’analyser plusieurs darnes simultanément dans l’IRM a été validée en utilisant un support spécifique pour disposer les darnes au sein de l’imageur. Un modèle de correction du signal permet de pallier l’inhomogénéité du signal dans l’espace de mesure. La comparaison de la teneur en lipides de darnes fraîches et décongelées avec un dosage RMN met en évidence de très bonnes corrélations avec une erreur moyenne de 0.8 et 0.89% respectivement. Ce qui démontre que la congélation ne dégrade pas la précision du dosage. La surface de gras sous cutané mesurée en IRM et en vision numérique présente de bonnes corrélations R²=0.77 et 0.87 respectivement pour les tissus adipeux ventraux et dorsaux

Characterization of the Water Shortage Effects on Potato Tuber Tissues during Growth Using MRI Relaxometry and Biochemical Parameters

International audienceThe potato is one of the most cultivated crops worldwide, providing an important source of food. The quality of potato tubers relates to their size and dry matter composition and to the absence of physiological defects. It depends on the spatial and temporal coordination of growth and metabolic processes in the major tuber tissues: the cortex, flesh and pith. In the present study, variations in the biochemical traits of each of these tissues were investigated during tuber growth under optimal and water-deficit conditions. MRI relaxometry was used as a non-invasive and quantitative method to access information on cellular water status. The presence of slight but significant variations in organic compound contents quantified in the cortex and flesh revealed a tissue-dependent metabolic pattern. The T2 and relative I0 of the bi-exponential relaxation signal allowed a distinction to be made between the pith and the cortex, whereas the flesh could be differentiated from these tissues only through its relative I0. T2 values did not vary significantly during tuber development, in accordance with the typical growth pattern of tubers, but were shown to be sensitive to water stress. The interpretation of the multi-exponential transverse relaxation times is discussed and could be further developed via microscopic analysis