Spurious phase correction in rapid metabolic imaging

International audienceIDEAL-type magnetic resonance spectroscopic imaging (MRSI) sequences require the acquisition of several datasets using optimized sampling in the time domain to reconstruct metabolite maps. Each unitary scan consists of a selective slice (2D) or slab (3D) excitation followed by an evolution time and then the acquisition of the spatially encoded signal. It is critical that the phase variation during the evolution time for each scan is only dependent on chemical shifts. In this paper, we described the apparition of spurious phase due to either the transmit or the receive frequency. The presence of this unwanted phase depends on (i) where the commutation between these two frequencies is performed and (ii) how it is done, as there are two phase commutation modes: continuous and coherent. We present the correction needed in function of the different cases. It appears that some solutions are universal. However, it is critical to know which case is implemented on the MRI scanner, which is not always easy information to have. We illustrated several cases with our preclinical MRI by using the IDEAL spiral method on a 13C phantom. © 2021 Elsevier Inc

Correction to : MRSI vs CEST MRI to understand tomato metabolism in ripening fruit: is there a better contrast ?

ABSTRACT Background Processed meat intake is associated with a higher risk of colorectal and stomach cancers, coronary artery disease, and type 2 diabetes and with higher mortality, but the estimation of intake of different processed meat products in this heterogeneous food group in epidemiological studies remains challenging. Objective This work aimed at identifying novel biomarkers for processed meat intake using metabolomics. Methods An untargeted, multi-tiered metabolomics approach based on LC-MS was applied to 33 meat products digested in vitro and secondly to urine and plasma samples from a randomized crossover dietary intervention in which 12 volunteers consumed successively 3 processed meat products (bacon, salami, and hot dog) and 2 other foods used as controls, over 3 consecutive days. The putative biomarkers were then measured in urine from 474 subjects from the European Prospective Investigation into Cancer and Nutrition (EPIC) cross-sectional study for which detailed 24-h dietary recalls and FFQs were available. Results Syringol and 4 derivatives of syringol were found to be characteristic of in vitro digests of smoked meat products. The same compounds present as sulfate esters in urine increased at 2 and 12 h after consumption of smoked meat products (hot dog, bacon) in the intervention study. The same syringol sulfates were also positively associated with recent or habitual consumption of smoked meat products in urine samples from participants of the EPIC cross-sectional study. These compounds showed good discriminative ability for smoked meat intake with receiver operator characteristic areas under the curve ranging from 0.78 to 0.86 and 0.74 to 0.79 for short-term and habitual intake, respectively. Conclusions Four novel syringol sulfates were identified as potential biomarkers of smoked meat intake and may be used to improve assessment of smoked meat intake in epidemiological studies. This trial was registered at clinicaltrials.gov as NCT03354130

Characterization of the sodium binding state in several food products by 23 Na nuclear magnetic resonance spectroscopy

International audienceIn food, salt has several key roles including conservative and food perception. For this latter, it is well-known that the interaction of sodium with the food matrix modifies the consumer perception. It is then critical to characterize these interactions in various real foods. For this purpose, we exploited the information obtained on both single and double quantum 23Na nuclear magnetic resonance (NMR) spectroscopies. All salted food samples studied showed strong interactions with the food matrix leading to quadrupolar interactions.However, for some of them, the single quantum analysis did not match the theoretical prediction. This was explained by the presence of another type of sodium population, which did not produce quadrupolar interactions. This finding is of critical importance to perform quantitative magnetic resonance imaging (MRI) and to understand the consumer salty taste perception

Towards portable MRI in the plant sciences

International audienceAbstract Plant physiology and structure are constantly changing according to internal and external factors. The study of plant water dynamics can give information on these changes, as they are linked to numerous plant functions. Currently, most of the methods used to study plant water dynamics are either invasive, destructive, or not easily accessible. Portable magnetic resonance imaging (MRI) is a field undergoing rapid expansion and which presents substantial advantages in the plant sciences. MRI permits the non-invasive study of plant water content, flow, structure, stress response, and other physiological processes, as a multitude of information can be obtained using the method, and portable devices make it possible to take these measurements in situ, in a plant’s natural environment. In this work, we review the use of such devices applied to plants in climate chambers, greenhouses or in their natural environments. We also compare the use of portable MRI to other methods to obtain the same information and outline its advantages and disadvantages

Tumor microenvironment imaging: Benefits of multimodality to study chondrosarcoma

International audienceSwarm rat CHSs were implanted subcutaneously in NMRI nude mice (n=10). When tumors were measurable (12-16 days post-transplant), mice were imaged by CEST MRI (Dou W et al., Quant Imaging Med Surg, 2019). Proteoglycans, the main component of chondrogenic extracellular matrix, were quantified by GAG CEST contrast. Guanidyl-and APT CEST contrasts were combined to characterize acidic pH, as hypoxia reflect. ☢ These two features, proteoglycans and hypoxia, were assessed in parallel by nuclear imaging with [ 99m Tc]Tc-NTP 15-5 SPECT imaging (Peyrode C et al., Sarcoma, 2011) and [ 18 F]-FMISO PET imaging (Rajendran JG et al., Clin Cancer Res, 2004), respectively. Data were also completed by ex vivo analyses of tumor and muscle proteoglycans (Alcian blue stain and biochemical assay with dimethylmethylene blue) and hypoxia (pimonidazole immunofluorescence). CONCLUSION: The results from CEST MRI, nuclear imaging and ex vivo analyses were in agreement and highlighted a rich proteoglycan extracellular matrix and a heterogeneous hypoxic tumoral microenvironment for Swarm rat CHS xenograft in mice. This study emphasizes the role of multimodal imaging to characterize tumor phenotypes resistant to treatments and allows a better understanding of the relationship between tumor cells and their environment. Grants: "La Ligue contre le Cancer Auvergne-Rhône-Alpes". All imaging experiments were performed at In Vivo Imaging Auvergne (IVIA) facilit