Time-domain EPR imaging with slice selection

Synopsis: The slice selection imaging has advantages of reducing imaging time and obtaining optimum dynamic range in image for EPR imaging as well as for MRI. However, the slice selection using a selective pulse, which is used in MRI, is difficult to implement in EPR imaging because of ultra-fast relaxation time compared to gradient settling time. Therefore, we used a modulated gradient field to achieve slice selection in pulsed EPR imaging in this study. We demonstrated the slice selection imaging with tubes and a living mouse to show the effect of slice selection in pulsed EPR imaging. Introduction: In MRI, slice-selection is accomplished using a selective pulse in presence of a slice selective gradient. The spatial encoding and other functional properties of the spins in the selected slice are carried out by the subsequent refocusing pulses and phase or frequency encoding gradients. Such slice selection is difficult in pulsed EPR imaging, due the ~microsecond relaxation times of unpaired electrons which are shorter than gradient settling times. An alternative mode of slice-selection however is feasible by applying a modulated gradient along one of the directions1,2. The selected slice is located at the ‘zero-crossing’ of the modulated gradient. Its thickness depends on the modulation amplitude and frequency. Such slice selection can reduce the imaging time by an order of magnitude since only 2D images are measured, and the slice location can be changed by physically translating the resonator or electrically off-setting the center of the oscillatory gradient. Phantom and in vivo results are shown. Modalities which image a small number of m slices We have incorporated this approach of slice-selection using sinusoidally modulated gradients to generate a set of 2D images of slices that can greatly reduce the measurement time and can thus allow improvement in the SNR and resolution in the selected slices without additional measurement time. Methods: We employ the single point imaging (SPI) scheme, by which two and three dimensional in vivo EPR imaging and relaxation based oximetry have been carried out routinely in our laboratory. In this development, we use the same imaging equipment operating at 300 MHz, with an additional provision of applying a low frequency (100 Hz) sinusoidal field along one of the gradient axes at nominal AC amplitude of about 10 mT/m. The modulation of the gradient along a particular axis introduces inhomogeneity along that axis everywhere except around the midpoint at which the amplitude is zero. A two-dimensional phase encoding in a plane perpendicular to the axis of the modulated gradient retains coherent phase information only from the narrow slice at the center with spin distribution on either side of the slice undergoing total loss of coherence and does not contribute to the detected signal (Fig. 1). As proof of principle we made a phantom consisting of three tubes(4 mm i.d) filled to different levels with 3 mM Oxo633 (a stable trityl radical with a narrow single ESR absorption) and placed at a spacing interval of 10 mm as shown in Fig. 2A. Two dimensional images were obtained by single point imaging with a maximum gradient of 15 mT/m along the three planes.In addition to above phantom experiment, we performed in vivo experiments to investigate how dynamic range was improved using a mouse hind leg. Along with the mouse leg, we placed a TCNQ tube which produces strong signal as shown in Fig. 3A. The mouse was injected 75 mM oxo63 intravenously. Two dimensional images were obtained by single point imaging with a maximum gradient of 8 mT/m. In order to investigate the minimum slice thickness that can be achieved, we filled a 14 mm glass cuvette (the ones used in optical spectroscopy) with 2 mM Oxo63 and placed the cuvette at the center of the resonator along Y-direction. The EPR spectra were obtained when the Z-gradient was modulated at 100 Hz with a gradual increase in amplitude from 0 to 2 volt. Results and Discussion: When we carried out the 2D phase encoding in the XY plane with the Z-gradient being modulated at 100 Hz at amplitude of 1.4 volt, we saw only the tube centered at z-coordinate of zero (Fig. 2D). The other two tubes did not produce any signal due to the inhomogeneity imposed by the modulated Z-gradient. By shifting the resonator such that the other tubes were brought to the center sequentially, we could get slices showing exclusive images of each tube. Figure 3B and 3C shows the comparison between images acquired with conventional 2D projection and slice-selection methods. The distribution of Oxo63 acquired by 2D projection imaging was interfered by strong signal of TCNQ, while the slice selection image showed only the distribution of Oxo63. This suggested the optimum dynamic range in signal intensity was achieved by slice selection technique. The minimum slice thickness that could be achieved was around 1.7 mm at and above 1.8 volt. Conclusion: With modulation gradient, we have demonstrated the slice selection in pulsed EPR imaging and succeeded to obtain slice selected images with optimum dynamic range in signal intensity. The method will also enable the study functional dynamics in the images with improved temporal resolution.References:1. Hinshaw WS. Spin mapping:application of moving gradients to NMR. Phys Lett A. 1974; 48: 87–88. 2.Sato-Akaba H, Abe H, Fujii H, Hirata H. Slice-selective images of free radicals in mice with modulated field gradient electron paramagnetic resonance (EPR) imaging. Magn Reson Med. 2008; 59: 885-890. 3.Ardenkjaer-Larsen JH, Laursen I, Leunbach I, Ehnholm G, Wistrand LG, Petersson JS, Golman K. EPR and DNP properties of certain novel single electron contrast agents intended for oximetric imaging. J Magn Reson 1998; 133: 1–12.Joint Annual Meeting ISMRM-ESMRMB 201

Pulsed electron paramagnetic resonance imaging: Applications in the studies of tumor physiology

Significance:Electron Paramagnetic Resonance imaging (EPRI) is a powerful technique capable of generating images of tissue oxygenation using exogenous paramagnetic probes such as trityl radicals and nitroxyl radicals. Using principles similar to Magnetic Resonance Imaging (MRI) with field gradients, the spatial distribution of the paramagnetic probecan be generated and from its spectral features, spatial maps of oxygen can be obtained from live objects. In this review, the two methods of signal acquisition, image formation/reconstruction will be described. The probes used and its application to study tumor physiology and monitor treatment response with chemotherapy drugs in mouse models of human cancer will be summarized.Recent Advances: By implementing phase encoding/Fourier reconstruction in EPRI in time-domain mode, the frequency contribution to the spatial resolution was avoided and improved images can be obtained. The highresolution EPRI revealed the pO2 change in tumor, which was useful to detect and evaluate the effects of various antitumor therapies. The coregistration with other imaging modalities provided a better understanding of hypoxia related alteration in physiology.Critical Issues: The high power of EPR irradiation and toxicity profile of radical probes are the main obstacles for clinical application. The improvement of pulse sequence may lower the risk.Future Directions:Pulsed EPR oximetry will be a powerfultool to research various disease involving hypoxia such as cancer, ischemic heart diseases, stroke, and diabetes. By optimizing radical probes, it can also be applied for various other purposes such as detecting local acid-base balance or oxidative stress

Immunomodulatory and Metabolic Changes after Gnetin-C Supplementation in Humans

Gnetin-C is a naturally occurring stilbene derived from the seeds of Gnetum gnemon L., an edible plant native to Southeast Asia that is called melinjo. Although the biological properties and safety of G. gnemon extract, which contains nearly 3% Gnetin-C, have been confirmed in various human studies, whether or not pure Gnetin-C is safe for humans is unclear at present. We conducted a randomized, double-blind, placebo-controlled trial. Healthy subjects were randomly divided into two groups. The interventional group (n = 6) was given Gnetin-C, and the control group (n = 6) was provided a placebo, for 14 days. Lipid profiles, biomarkers of oxidative stress and circulating blood cells were assessed before and after the intervention. All subjects completed the study, with no side effects reported across the study duration. Gnetin-C supplementation demonstrated a statistically significant increase in the absolute number of circulating natural killer (NK) cells expressing the activating receptors NKG2D and NKp46. NK cells derived from subjects who received Gnetin-C for two weeks showed higher cytotoxicity against K562 target cells than those before receiving Gnetin-C. In addition, Gnetin-C also resulted in a significant decrease in the absolute neutrophil count in the blood compared with the placebo. Furthermore, Gnetin-C significantly reduced the levels of uric acid, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, total adiponectin, and high-molecular-weight adiponectin. These data indicate that Gnetin-C has biological effects of enhancing the NK activity on circulating human immune cells. The immunomodulatory effects are consistent with a putative improvement in cancer immunosurveillance via the upregulation of the NKG2D receptor. The study was registered with UMIN-CTR, number 000030364, on 12 December 2017

Favorable prognostic phenotype in myelodysplastic syndrome with der(1;7)(q10;p10)

Abstract Unbalanced translocation der(1;7)(q10;p10) is a characteristic chromosomal abnormality in myelodysplastic syndrome (MDS). The current study revealed that among 13 MDS patients with der(1;7)(q10;p10), seven cases with no apparent dysplasia also had low numbers of myeloblasts in the bone marrow and a 3‐year survival rate of 86%; in contrast, the remaining six cases had a 3‐year survival rate of 0% (P = .003). It was therefore suggested that MDS patients with der(1;7)(q10;p10) are classified into a distinct group with a favorable prognosis and another distinct group with a very poor prognosis

Cytopenia associated with copper deficiency

Abstract Introduction Due to an increased incidence of copper deficiency, we investigated adult patients who had low serum levels of copper with cytopenia at our hospital from March 2014 to March 2021. Methods We retrospectively reviewed the clinical data of patients who had been diagnosed with cytopenia due to copper deficiency at the Aichi Medical University Hospital from March 2014 to March 2021. Results In the 15 patients with cytopenia secondary to low serum copper level, 11 had cytopenia of two to three lineages; three (27%) had pancytopenia, and eight (73%) had bicytopenia. Of the 15 patients, nine (60%) underwent bone marrow examinations; three (30%) showed typical morphologic features associated with copper deficiency, such as multiple clear cytoplasmic vacuoles in erythroblasts and myeloid cells, and three (30%) showed dysplastic features as observed in myelodysplastic syndrome. Among the 14 (93%) patients who were treated with copper supplements, had cessation of zinc supplements, or both, 11 (73%) and eight (53%) showed normal copper levels and hematological improvement, respectively. Conclusion Copper deficiency is more common than expected and should be considered in patients with unexplained cytopenia

Rivaroxaban with or without aspirin in stable cardiovascular disease

BACKGROUND: We evaluated whether rivaroxaban alone or in combination with aspirin would be more effective than aspirin alone for secondary cardiovascular prevention. METHODS: In this double-blind trial, we randomly assigned 27,395 participants with stable atherosclerotic vascular disease to receive rivaroxaban (2.5 mg twice daily) plus aspirin (100 mg once daily), rivaroxaban (5 mg twice daily), or aspirin (100 mg once daily). The primary outcome was a composite of cardiovascular death, stroke, or myocardial infarction. The study was stopped for superiority of the rivaroxaban-plus-aspirin group after a mean follow-up of 23 months. RESULTS: The primary outcome occurred in fewer patients in the rivaroxaban-plus-aspirin group than in the aspirin-alone group (379 patients [4.1%] vs. 496 patients [5.4%]; hazard ratio, 0.76; 95% confidence interval [CI], 0.66 to 0.86; P<0.001; z=−4.126), but major bleeding events occurred in more patients in the rivaroxaban-plus-aspirin group (288 patients [3.1%] vs. 170 patients [1.9%]; hazard ratio, 1.70; 95% CI, 1.40 to 2.05; P<0.001). There was no significant difference in intracranial or fatal bleeding between these two groups. There were 313 deaths (3.4%) in the rivaroxaban-plus-aspirin group as compared with 378 (4.1%) in the aspirin-alone group (hazard ratio, 0.82; 95% CI, 0.71 to 0.96; P=0.01; threshold P value for significance, 0.0025). The primary outcome did not occur in significantly fewer patients in the rivaroxaban-alone group than in the aspirin-alone group, but major bleeding events occurred in more patients in the rivaroxaban-alone group. CONCLUSIONS: Among patients with stable atherosclerotic vascular disease, those assigned to rivaroxaban (2.5 mg twice daily) plus aspirin had better cardiovascular outcomes and more major bleeding events than those assigned to aspirin alone. Rivaroxaban (5 mg twice daily) alone did not result in better cardiovascular outcomes than aspirin alone and resulted in more major bleeding events