In Vivo Quantitative Microimaging of Rat Spinal Cord at 7T

International audienceIn vivo T(2), ADC, and MT properties of the GM and WM of the rat spinal cord were measured at 7T in the cervical region. The GM T(2), T(2GM) = 43.2 +/- 1.0 msec is significantly reduced compared to the WM T(2), T(2WM) = 57.0 +/- 1.6 msec. Diffusion is anisotropic for both GM and WM, with a larger ADC value along the cord axis (ADC(GM//) = 1.05 +/- 0.09 10(-9) m(2)sec(-1) and ADC(WM//) = 1.85 +/- 0.18 10(-9) m(2)sec(-1)) than perpendicular to this plane (ADC(GM)( perpendicular) approximately 0.50 * 10(-9) m(2)sec(-1) and ADC(WM)( perpendicular) approximately 0.18 * 10(-9) m(2)sec(-1)). The MT properties do not significantly differ between the WM and the GM, but allow one to distinguish the thin CSF layer from the WM. DWI with the sensitizing gradient perpendicular to the cord axis leads to the best contrast between GM and WM in the cervical region

Diffusion imaging with a multi-echo MISSTEC sequence

An imaging method is presented to measure the water-diffusion coefficient. The sequence (MISSTEC) uses the simultaneous acquisition of a spin echo and several stimulated echoes with the same intensity except for diffusion weighting. The optimal number of stimulated echoes was calculated to minimize the diffusion coefficient error (D). D values obtained in vitro and in vivo were in good agreement with those from the spin-echo sequence (IntraVoxel Incoherent Motion [IVIM] method). The total acquisition time is half that of the classic IVIM method

Quantitative MR renography using a calibrated internal signal (ERETIC)

To measure MR renograms, cortical and medullary kidney signal intensity evolution is followed after contrast agent injection. To obtain an accurate quantitative signal measurement, the use of a reference signal is necessary to correct the potential MRI system variations in time. The ERETIC method (Electronic Reference To access In vivo Concentrations) provides an electronic reference signal. It is synthesized as an amplitude modulated RF pulse applied during the acquisition. The ERETIC method was as precise as the external tube reference method but presents major advantages like its free adjustability (shape, location and magnitude) to the characteristics of the organ studied as well as its not taking room inside the magnet. Even though ERETIC showed a very good intrinsic stability, systems’ variations still affect its signal in the same way as real NMR signals are affected. This method can be easily implemented on any imaging system with two RF channels

In vitro expansion of U87-MG human glioblastoma cells under hypoxic conditions affects glucose metabolism and subsequent in vivo growth

Hypoxia is a characteristic feature of solid tumors leading to the over expression of hypoxia-inducible factor (HIF)-1α protein and therefore to a specific cellular behavior. However, even though the oxygen tension in tumors is low (<5 %), most of the cell lines used in cancer studies are grown under 21 % oxygen tension. This work focuses on the impact of oxygen conditions during in vitro cell culture on glucose metabolism using 1-13C-glucose. Growing U87-MG glioma cells under hypoxic conditions leads to a two- to threefold reduction of labeled glutamine and an accumulation of fructose. However, under both hypoxic and normoxic conditions, glucose is used for de novo synthesis of pyrimidine since the 13C label is found both in the uracil and ribose moieties. Labeling of the ribose ring demonstrates that U87-MG glioma cells use the reversible branch of the non-oxidative pentose phosphate pathway. Interestingly, stereotactic implantation of U87-MG cells grown under normoxia or mild hypoxia within the striatum of nude mice led to differential growth; the cells grown under hypoxia retaining an imprint of the oxygen adaptation as their development is then slowed down

Rapid and Accurate Identification of Nontuberculous Mycobacteria Directly from Positive Primary MGIT Cultures by MALDI-TOF MS

Over the last years, nontuberculous mycobacteria (NTM) have emerged as important human pathogens. Accurate and rapid mycobacterial species identification is needed to successfully diagnose, treat, and manage infections caused by NTM. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry, MALDI-TOF MS, was demonstrated to effectively identify mycobacteria isolates subcultured from solid or liquid media rather than new positive cultures. The present study aims to develop a new extraction protocol to yield rapid and accurate identification of NTM from primary MGIT cultures by MALDI-TOF MS. A total of 60 positive MGIT broths were examined by the Bruker Biotyper system with Mycobacteria Library v. 2.0 (Bruker Daltonics GmbH & Co. KG., Bremen, Germany). The results were compared with those obtained by the molecular method, line probe assay GenoType Mycobacterium CM/AS/NTM-DR. All samples were concordantly identified by MALDI-TOF MS and the molecular test for all the tested mycobacteria. Fifty-seven (95%) MGIT positive cultures for NTM from clinical samples had a MALDI-TOF MS analysis score S ≥ 1.8. Although a small number of strains and a limited diversity of mycobacterial species were analysed, our results suggest that MALDI-TOF MS could represent a promising routine diagnostic tool for identifying mycobacterial species directly from primary liquid culture

Gender Differences among Sardinians with Alcohol Use Disorder

Sardinia is an Italian island in the Mediterranean characterized by secular isolation and the singular genetic characteristics of its inhabitants. Findings obtained in populations with diverse genetic make-up and cultural background indicate gender differences and/or similarities in drinking characteristics of patients with alcohol use disorder (AUD). Knowledge of these characteristics in AUD patients is useful to improve access to treatments. This paper investigated the drinking characteristics of 66 female and 282 male outpatients with AUD, born from 1937 to 1991, living in Sardinia, and compared their characteristics with those of AUD patients living in other countries. Most Sardinian patients were men, approximately 3 years younger than women; women consumed lower amounts of alcohol than men but did not differ from men in the severity of AUD. Men were more often single than women, while a higher proportion of women reported that their mother or spouse was affected by AUD. Anxiety and depression were more prevalent among women while a higher proportion of men were affected by substance use disorders. Women were older than men at the age of first drink, regular drinking, and onset of AUD, and progressed faster than men from regular use to AUD onset. Women did not differ from men in age at first request for care, and in the lapse from AUD onset to first request for care. Women and men waited for more than 8 and 9 years, respectively, before receiving medical treatment. Gender differences progressively decreased among younger patients. Although the scarce number of women in some cohorts limits the strength of these findings, drinking characteristics of Sardinian patients did not vary significantly from those of AUD patients living in other countries. These results suggest that the number of Sardinian women with AUD is increasing and services for treatment of AUD should (a) consider women’s specific needs, and (b) realize effective policies to reduce latency prior to accessing medical treatment for both men and women with AUD

Susceptibility gradient quantization by MRI signal response mapping (SIRMA) to dephaser

Purpose: Susceptibility effects are a very efficient source of contrast in magnetic resonance imaging. However, detection is hampered by the fact the induced contrast is negative. In this work, the SIgnal Response MApping (SIRMA) to dephaser method is proposed to map susceptibility gradient to improve visualization. Methods: In conventional gradient echo acquisitions, the echo formation of susceptibility affected spins is shifted in k -space, the shift being proportional to the susceptibility gradient. Susceptibility gradients map can be produced by measuring this induced shifts. The SIRMA method measures these shifts from a series of dephased images collected with additional incremental dephasers. These additional dephasers correspond either to a slice refocusing gradient offset or to a reconstruction window off-centering. The signal intensity profile as a function of the additional dephaser was determined on a pixel-by-pixel basis from the ensemble of dephased images. Susceptibility affected voxels presented a signal response profile maximum shifted compared to nonaffected voxels ones. Shift magnitude and sign were measured for each pixel to determine susceptibility gradients and produce a susceptibility gradient map. Results: In vitro experiments demonstrated the ability of the method to map gradient inhomogeneities induced by a cylinder. Quantization accuracy was evaluated comparing SIRMA images and simulations performed on the well-characterized air filled cylinder model. Performances of the SIRMA method, evaluated in vitro on cylinders filled with various superparamagnetic iron oxide SPIO concentrations, showed limited influence of acquisition parameters. Robustness of the method was then assessed in vivo after an infusion of SPIO-loaded nanocapsules into the rat brain using a convection-enhanced drug delivery approach. The region of massive susceptibility gradient induced by the SPIO-loaded nanocapsules was clearly delineated on SIRMA maps and images were compared to T 2 weighted images, Susceptibility Gradient Map (SGM), and histological Perl\u27s staining slice. The potential for quantitative evaluation of SPIO distribution volume was demonstrated. Conclusions: The proposed method is a promising technique for a wide range of applications especially in molecular or cellular imaging with respect to its quantitative nature and its computational simplicity