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PURPOSE: To demonstrate the feasibility of 3D echo-planar spectroscopic imaging (EPSI) technique with rapid volumetric radial k-space sampling for hyperpolarized (HP) 13C magnetic resonance spectroscopic imaging (MRSI) in vivo. METHODS: A radial EPSI (rEPSI) was implemented on a 3 T clinical PET/MR system. To enable volumetric coverage, the sinusoidal shaped readout gradients per k-t-spoke were rotated along the three spatial dimensions in a golden-angle like manner. A distance-weighted, density-compensated gridding reconstruction was used, also in cases with undersampling of spokes in k-space. Measurements without and with HP 13C-labeled substances were performed in phantoms and rats using a double-resonant 13C/1H volume resonator with 72 mm inner diameter. RESULTS: Phantom measurements demonstrated the feasibility of the implemented rEPSI sequence, as well as the robustness to undersampling in k-space up to a factor of 5 without advanced reconstruction techniques. Applied to measurements with HP [1-13C]pyruvate in a tumor-bearing rat, we obtained well-resolved MRSI datasets with a large matrix size of 123 voxels covering the whole imaging FOV of (180 mm)3 within 6.3 s, enabling to observe metabolism in dynamic acquisitions. CONCLUSION: After further optimization, the proposed rEPSI method may be useful in applications of HP 13C-tracers where unknown or varying metabolite resonances are expected, and the acquisition of dynamic, volumetric MRSI datasets with an adequate temporal resolution is a challenge.
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31P MRSI allows for the non-invasive mapping of pH and magnesium ion content (Mg) in vivo, by translating the chemical shifts of inorganic phosphate and adenosine-5'-triphosphate (ATP) to pH and Mg via suitable calibration equations, such as the modified Henderson-Hasselbalch equation. However, the required constants in these calibration equations are typically only determined for physiological conditions, posing a particular challenge for their application to diseased tissue, where the biochemical conditions might change manyfold. In this article, we propose a multi-parametric look-up algorithm aiming at the condition-independent determination of pH and Mg by employing multiple quantifiable 31P spectral properties simultaneously. To generate entries for an initial look-up table, measurements from 114 model solutions prepared with varying chemical properties were made at 9.4 T. The number of look-up table entries was increased by inter- and extrapolation using a multi-dimensional function developed based on the Hill equation. The assignment of biochemical parameters, that is, pH and Mg, is realized using probability distributions incorporating specific measurement uncertainties on the quantified spectral parameters, allowing for an estimation of most plausible output values. As proof of concept, we applied a version of the look-up algorithm employing only the chemical shifts of γ- and ß-ATP for the determination of pH and Mg to in vivo 3D 31P MRSI data acquired at 7 T from (i) the lower leg muscles of healthy volunteers and (ii) the brains of patients with glioblastoma. The resulting volumetric maps showed plausible values for pH and Mg, partly revealing differences from maps generated using the conventional calibration equations.
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Algoritmos , Magnésio , Magnésio/análise , Magnésio/química , Concentração de Íons de Hidrogênio , Humanos , Imageamento por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Fósforo/química , Isótopos de FósforoRESUMO
OBJECTIVE: First implementation of dynamic oxygen-17 (17O) MRI at 7 Tesla (T) during neuronal stimulation in the human brain. METHODS: Five healthy volunteers underwent a three-phase 17O gas (17O2) inhalation experiment. Combined right-side visual stimulus and right-hand finger tapping were used to achieve neuronal stimulation in the left cerebral hemisphere. Data analysis included the evaluation of the relative partial volume (PV)-corrected time evolution of absolute 17O water (H217O) concentration and of the relative signal evolution without PV correction. Statistical analysis was performed using a one-tailed paired t test. Blood oxygen level-dependent (BOLD) experiments were performed to validate the stimulation paradigm. RESULTS: The BOLD maps showed significant activity in the stimulated left visual and sensorimotor cortex compared to the non-stimulated right side. PV correction of 17O MR data resulted in high signal fluctuations with a noise level of 10% due to small regions of interest (ROI), impeding further quantitative analysis. Statistical evaluation of the relative H217O signal with PV correction (p = 0.168) and without (p = 0.382) did not show significant difference between the stimulated left and non-stimulated right sensorimotor ROI. DISCUSSION: The change of cerebral oxygen metabolism induced by sensorimotor and visual stimulation is not large enough to be reliably detected with the current setup and methodology of dynamic 17O MRI at 7 T.
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Encéfalo , Imageamento por Ressonância Magnética , Humanos , Encéfalo/diagnóstico por imagem , Encéfalo/fisiologia , Isótopos de Oxigênio , Imageamento por Ressonância Magnética/métodos , Mapeamento Encefálico/métodos , OxigênioRESUMO
PURPOSE: The non-invasive determination of the free magnesium ion concentration ([Mg2+free ]) using 31 P MRSI in vivo is of interest in research on various pathologies, e.g. diabetes. The purpose of this study was to demonstrate the potential of 31 P MRSI at 7 T to enable volumetric, high-resolution mapping of [Mg2+free ]. METHODS: 3D 31 P MRSI datasets from the lower leg of three healthy volunteers were acquired at B0 = 7 T with a nominal spatial resolution of (8 × 8 × 16) mm3 in 56 min. Volumetric [Mg2+free ] maps were calculated based on the quantified local chemical shift difference between the α- and ß-resonance of adenosine triphosphate (ATP) considering also local pH values. Mean [Mg2+free ] values from three different muscle groups were compared. To demonstrate the potential of reducing the measurement time, the analysis was repeated on the acquired MRSI data retrospectively reconstructed with fewer averages. RESULTS: The generated [Mg2+free ] maps revealed local differences, and mean [Mg2+free ] values of (1.08 ± 0.03) mM were found in the tibialis anterior, (0.91 ± 0.04) mM in the soleus and (0.98 ± 0.03) mM in the gastrocnemius medialis. The time-reduced 28-min scan resulted in comparable [Mg2+free ] maps, and mean values being in agreement with the values from the 56-min scan. CONCLUSION: 31 P MRSI at 7 T enables volumetric, high-resolution mapping of free magnesium ion content in human lower leg muscles. The measurement time of the 31 P MRSI acquisition can be reduced to 28 min, opening the potential to apply volumetric [Mg2+free ] mapping for the investigation of pathologies with altered magnesium homeostasis.
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Perna (Membro) , Magnésio , Encéfalo , Humanos , Perna (Membro)/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Músculo Esquelético/diagnóstico por imagem , Estudos RetrospectivosRESUMO
PURPOSE: In principle, non-invasive mapping of the intracellular pH (pHi ) in vivo is possible using endogenous chemical exchange saturation transfer (CEST)-MRI of the amide and guanidyl signals. However, the application for cancer imaging is still impeded, as current state-of-the-art approaches do not allow for simultaneous compensation of concomitant effects that vary within tumors. In this study, we present a novel method for absolute pHi mapping using endogenous CEST-MRI, which simultaneously compensates for concentration changes, superimposing CEST signals, magnetization transfer contrast, and spillover dilution. THEORY AND METHODS: Compensation of the concomitant effects was achieved by a ratiometric approach (i.e. the ratio of one CEST signal at different B1 ) in combination with the relaxation-compensated inverse magnetization transfer ratio MTRRex and a separate first-order polynomial-Lorentzian fit of the amide and guanidyl signals at 9.4 T. Calibration of pH values was accomplished using in vivo-like model suspensions from porcine brain lysates. Applicability of the presented method in vivo was demonstrated in n = 19 tumor-bearing mice. RESULTS: In porcine brain lysates, measurement of pH was feasible over a broad range of physiologically relevant pH values of 6.2 to 8.0, while being independent of changes in concentration. A median pHi of approximately 7.2 was found in the lesions of 19 tumor-bearing mice. CONCLUSION: The presented method enables non-invasive mapping of absolute pHi values in tumors using CEST-MRI, which was so far prevented by concomitant effects. Consequently, pre-clinical studies on pHi changes in tumors are possible allowing the assessment of pHi in vivo as a biomarker for cancer diagnosis or treatment monitoring.
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Amidas , Glioblastoma , Animais , Encéfalo , Concentração de Íons de Hidrogênio , Imageamento por Ressonância Magnética/métodos , Camundongos , SuínosRESUMO
The situation of nurses in hospitals during the second wave of the COVID-19 pandemic: an online survey Abstract. Background: The COVID-19 pandemic has an impact on stress and wellbeing of nurses. Anxiety of infection, lack of protective equipment and insufficient expertise in care of these patients were described as reasons of burnout. Aim: The influence of work-related sense of coherence as well as perceived organizational support on the burnout level and the intention to leave the job will be explored. Method: In December 2020 and January 2021, staff of 81 hospitals in Hessia, Germany were invited to participate in an online survey using the BAT (Burnout-Assessment-Tool), work-SoC (work-related - Sence of Coherence), the POS-s (perceived organizational Support - short version) and items based on a literature review. Results: Of 595 nurses, 47.6% showed a moderate or high burnout level, 20.7% want to leave the job after the pandemic. The higher the work-SoC (ß = -0.467; p < 0.001) and the higher the POS-s (ß = -0.178; p < 0.001), the lower the burnout level. Trainings in the organization were mentioned by 24.7% of the nurses as a positive factor. They missed support in mindfulness and resilience training, in child care and health-related topics. 55.1% did not agree that the employer does everything to support them. Conclusions: Regardless of the pandemic, salutogenic leadership is required, which deals with "moral injuries" of employees as a result of implicit rationing and foster health-related support.
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Esgotamento Profissional , COVID-19 , Esgotamento Profissional/prevenção & controle , COVID-19/epidemiologia , Estudos Transversais , Hospitais , Humanos , Satisfação no Emprego , Pandemias , Inquéritos e QuestionáriosRESUMO
Malignant tumors commonly exhibit a reversed pH gradient compared with normal tissue, with a more acidic extracellular pH and an alkaline intracellular pH (pHi). In this prospective study, pHi values in gliomas were quantified using high-resolution phosphorous 31 (31P) spectroscopic MRI at 7.0 T and were used to correlate pHi alterations with histopathologic findings. A total of 12 participants (mean age, 58 years ± 18 [SD]; seven male, five female) with histopathologically proven, newly diagnosed glioma were included between September 2018 and November 2019. The 31P spectroscopic MRI scans were acquired using a double-resonant 31P/1H phased-array head coil together with a three-dimensional (3D) 31P chemical shift imaging sequence (5.7-mL voxel volume) performed with a 7.0-T whole-body system. The 3D volumetric segmentations were performed for the whole-tumor volumes (WTVs); tumor subcompartments of necrosis, gadolinium enhancement, and nonenhancing T2 (NCE T2) hyperintensity; and normal-appearing white matter (NAWM), and pHi values were compared. Spearman correlation was used to assess association between pHi and the proliferation index Ki-67. For all study participants, mean pHi values were higher in the WTV (7.057 ± 0.024) compared with NAWM (7.006 ± 0.012; P < .001). In eight participants with high-grade gliomas, pHi was increased in all tumor subcompartments (necrosis, 7.075 ± 0.033; gadolinium enhancement, 7.075 ± 0.024; NCE T2 hyperintensity, 7.043 ± 0.015) compared with NAWM (7.004 ± 0.014; all P < .01). The pHi values of WTV positively correlated with Ki-67 (R2 = 0.74, r = 0.78, P = .001). In conclusion, 31P spectroscopic MRI at 7.0 T enabled high-resolution quantification of pHi in gliomas, with pHi alteration associated with the Ki-67 proliferation index, and may aid in diagnosis and treatment monitoring. Keywords: 31P MRSI, pH, Glioma, Glioblastoma, Ultra-High-Field MRI, Imaging Biomarker, 7 Tesla Supplemental material is available for this article. © RSNA, 2023.
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Neoplasias Encefálicas , Glioma , Masculino , Humanos , Feminino , Pessoa de Meia-Idade , Meios de Contraste , Estudos Prospectivos , Gadolínio , Antígeno Ki-67 , Neoplasias Encefálicas/diagnóstico por imagem , Glioma/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Encéfalo/patologia , Necrose , Concentração de Íons de HidrogênioRESUMO
BACKGROUND: The SARS-CoV-2 pandemic has an impact on the wellbeing of health care workers. The influence of a work-related sense of coherence as well as perceived organizational support on the level of burnout and the intention to leave the job is largely unknown, especially for physicians in German hospitals. METHOD: In December 2020 and January 2021, physicians of 81 hospitals in Hessian (Germany) participated in an online survey using the BAT (Burnout Assessment Tool), Work-SoC (Work-related Sense of Coherence), the POS-s (Perceived Organizational SUPPORT - short version) and literature-based items based. RESULTS: Of 181 physicians, 34% showed a moderate or high burnout level, 21% would leave the job after the pandemic. The higher the work-SoC (ßâ¯=â¯-0.560; pâ¯<â¯0.001) and the higher the POS-s (ßâ¯=â¯-0.125; pâ¯<â¯0.05), the lower the burnout level. Not being able to care sufficiently for their patients has a negative impact on the sense of coherence. 46.4% reported that they did not feel sufficiently prepared by their employer during the pandemic. They wished to have support in the form of the mindfulness and resilience trainings (45%), emergency childcare (41%) and a crisis counselor in their team (32%). CONCLUSION: Regardless of the pandemic, health-promoting work conditions have to be developed that facilitate coherent work and prevent "moral injuries" or enable physicians to deal with them.
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Esgotamento Profissional , COVID-19 , Humanos , SARS-CoV-2 , Alemanha , COVID-19/epidemiologia , Pandemias , Esgotamento Profissional/epidemiologia , Inquéritos e Questionários , HospitaisRESUMO
Phosphorus magnetic resonance spectroscopic imaging (31P MRSI) is of particular interest for investigations of patients with brain tumors as it enables to non-invasively assess altered energy and phospholipid metabolism in vivo. However, the limited sensitivity of 31P MRSI hampers its broader application at clinical field strengths. This study aimed to identify the additional value of 31P MRSI in patients with glioma at ultra-high B 0 = 7T, where the increase in signal-to-noise ratio may foster its applicability for clinical research. High-quality, 3D 31P MRSI datasets with an effective voxel size of 5.7 ml were acquired from the brains of seven patients with newly diagnosed glioma. An optimized quantification model was implemented to reliably extract an extended metabolic profile, including low-concentrated metabolites such as extracellular inorganic phosphate, nicotinamide adenine dinucleotide [NAD(H)], and uridine diphosphoglucose (UDPG), which may act as novel tumor markers; a background signal was extracted as well, which affected measures of phosphomonoesters beneficially. Application of this model to the MRSI datasets yielded high-resolution maps of 12 different 31P metabolites, showing clear metabolic differences between white matter (WM) and gray matter, and between healthy and tumor tissues. Moreover, differences between tumor compartments in patients with high-grade glioma (HGG), i.e., gadolinium contrast-enhancing/necrotic regions (C+N) and peritumoral edema, could also be suggested from these maps. In the group of patients with HGG, the most significant changes in metabolite intensities were observed in C+N compared to WM, i.e., for phosphocholine +340%, UDPG +54%, glycerophosphoethanolamine -45%, and adenosine-5'-triphosphate -29%. Furthermore, a prominent signal from mobile phospholipids appeared in C+N. In the group of patients with low-grade glioma, only the NAD(H) intensity changed significantly by -28% in the tumor compared to WM. Besides the potential of 31P MRSI at 7T to provide novel insights into the biochemistry of gliomas in vivo, the attainable spatial resolutions improve the interpretability of 31P metabolite intensities obtained from malignant tissues, particularly when only subtle differences compared to healthy tissues are expected. In conclusion, this pilot study demonstrates that 31P MRSI at 7T has potential value for the clinical research of glioma.