Evaluation of apparent diffusion coefficient of two-dimensional BLADE turbo gradient- and spin-echo diffusion-weighted imaging with a breast phantom.

This study aimed to evaluate the reliability of apparent diffusion coefficient (ADC) values generated with two-dimensional turbo gradient- and spin-echo with BLADE trajectory diffusion-weighted imaging (TGSE-BLADE-DWI) sequence using a breast diffusion phantom. TGSE-BLADE-DWI and single-shot spin-echo echo-planar imaging (SS-EPI-DWI) were performed using a 3.0 T magnetic resonance imaging scanner. Concordance rates of ADC values and the signal-to-noise ratio (SNR) were compared between TGSE-BLADE-DWI and SS-EPI-DWI. TGSE-BLADE-DWI provided a higher concordance rate for ADC values than SS-EPI-DWI when b-values > 2000s/mm2 and a slice thickness of 1 mm were used. TGSE-BLADE-DWI showed less image distortion than SS-EPI-DWI. The SNR of TGSE-BLADE-DWI was higher than that of SS-EPI-DWI, except at a number of excitations of 7 and a slice thickness of 1 mm. In conclusion, TGSE-BLADE-DWI can offer a better SNR, less distortion, and more reliable ADC measurements than SS-EPI-DWI in a breast phantom.

Evaluation of Temozolomide Treatment for Glioblastoma Using Amide Proton Transfer Imaging and Diffusion MRI.

This study aimed to evaluate tumor changes due to chemotherapy with temozolomide (TMZ) in terms of quantitative values measured by APT imaging and NODDI. We performed TMZ treatment (administered orally by gavage to the TMZ-40 mg and TMZ-60 mg groups) on 7-week-old male Wistar rats with rat glioma C6 implanted in the right brain. T2WI, APT imaging, diffusion tensor imaging (DTI), and NODDI were performed on days 7 and 14 after implantation using 7T-MRI, and the calculated quantitative values were statistically compared. Then, HE staining was performed on brain tissue at day 7 and day 14 for each group to compare the results with the MR images. TMZ treatment inhibited tumor growth and necrotic area formation. The necrotic areas observed upon hematoxylin and eosin (HE) staining were consistent with the MTR low-signal areas observed upon APT imaging. The intracellular volume fraction (ICVF) map of the NODDI could best show the microstructure of the tumor, and its value could significantly highlight the difference in treatment effects at different TMZ doses. APT imaging and NODDI can be used to detect the microstructural changes caused by TMZ-induced tumor growth inhibition. The ICVF may be useful as a parameter for determining the effect of TMZ.

Evaluation of liver T1rho and T2 values in acute liver inflammation models using 7T-MRI.

PURPOSE: We measured the T1rho and T2 values the liver of acute liver inflammation model mice administered carbon tetrachloride (CCl4) after 3 days and 6 days after dispensed, and we compared and examined whether each relaxation time can be used for detect acute liver inflammation. METHODS: To create an acute liver inflammation model, a mixture of 0.2 ml / 100 g of CCl4 with an equal amount of Sesame Oil was administered once intraperitoneally to C57BL / 6JJmsSlc mice (n = 15). On the 3 days and 6 days after administration, we acquired T1rho mapping images and T2 mapping images of the liver under respiratory synchronization using for preclinical 7T-MRI, and we measured T1rho and T2 values and compared statistically. RESULTS: The liver T1rho value of control mice was 33.9 ± 2.5 ms before CCl4 administration, 43.2 ± 4.9 ms (p < 0.01) on the 3 days post CCl4 injection, and 41.0 ± 1.2 ms (p < 0.001) on the 6 days post CCl4 injection. The rate showed a significant increase of 27% on the 3 days after, as well as significant increase of 21% on the 6 days after. On the other hand, the liver T2 value of control mice was 26.7 ± 1.9 ms before CCl4 administration, 31.5 ± 3.4 ms (p < 0.05) 3 days post CCl4 injection, and 29.0 ± 2.0 ms (p = 0.06) 6 days post CCl4 injection. The rate 3 days after CCl4 administration showed a significant increase of 18%, after 6 days rate increased 9%, but no significant difference was confirmed compared with normal mice. CONCLUSIONS: The T1rho value changed significantly compared to the T2 value, and a continuous change was observed even after 6 days. T1rho mapping can diagnose acute liver inflammation.

Magnetic resonance imaging of umbilical cord stem cells labeled with superparamagnetic iron oxide nanoparticles: effects of labelling and transplantation parameters.

Cell tracking with magnetic resonance imaging (MRI) is important for evaluating the biodistribution of transplanted cells. Umbilical cord-derived mesenchymal stem cells (UC-MSCs) have emerged as a promising therapeutic tool in regenerative medicine. We examined the UC-MSCs labeled with superparamagnetic (SPIO) and ultrasmall superparamagnetic iron oxide (USPIO) in terms of cell functioning and imaging efficiency in vitro and in vivo. The UC-MSCs were co-incubated with SPIO or USPIO at a concentration of 50 or 100 µg/mL of label. Viability and proliferation were assessed by Trypan blue dye exclusion and MTT assay, respectively. Differentiation (chondrogenesis, osteogenesis, and adipogenesis) was induced to examine the impact of labelling on stemness. For in vitro experiments, we used 7-T MRI to assess the T2 values of phantoms containing various concentrations of cell suspensions. For in vivo experiments, nine neonatal rats were divided into the control, SPIO, and USPIO groups. The UC-MSCs were injected directly into the rat brains. MRI images were obtained immediately and at 7 and 14 days post injection. The UC-MSCs were successfully labeled with SPIO and USPIO after 24 h of incubation. Cell viability was not changed by labelling. Nevertheless, labelling with 100 µg/mL USPIO led to a significant decrease in proliferation. The capacity for differentiation into cartilage was influenced by 100 µg/mL of SPIO. MRI showed that labeled cells exhibited clear hypointense signals, unlike unlabeled control cells. In the USPIO-labeled cells, a significant (P < 0.05) decrease in T2 values (= improved contrast) was observed when compared with the controls and between phantoms containing the fewest and the most cells (0.5 × 106 versus 2.0 × 106 cells/mL). In vivo, the labeled cells were discernible on T2-weighted images at days 0, 7, and 14. The presence of SPIO and USPIO particles at day 14 was confirmed by Prussian blue staining. Microscopy also suggested that the regions occupied by the particles were not as large as the corresponding hypointense areas observed on MRI. Both labels were readily taken up by the UC-MSCs and identified well on MRI. While SPIO and USPIO provide improved results in MRI studies, care must be taken while labelling cells with high concentrations of these agents.

Comparison of Chemical Exchange Saturation Transfer Imaging with Diffusion-weighted Imaging and Magnetic Resonance Spectroscopy in a Rat Model of Hypoxic-ischemic Encephalopathy.

PURPOSE: This study aimed to evaluate the effect of chemical exchange saturation transfer (CEST) on the ischemic regions in hypoxic-ischemic encephalopathy (HIE) in comparison with diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS) using a 7T-MRI. METHODS: We used neonatal rats (n = 8), aged 8 days, to clarify the progression of HIE. The rat model of HIE was developed by ligating and severing the left common carotid artery, followed by 45 minutes of recovery, and 60 minutes of hypoxia (8% O2/92% N2; 34°C). At 0-2 and 24 hours after the onset of HIE, CEST imaging, DWI, and MRS were performed with a 7T-MRI. The magnetization transfer ratio (MTR) asymmetry curves and four MTR asymmetry maps at 0.5, 1.0, 2.0, and 3.5 ppm were calculated using the CEST images. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) maps were calculated by DWI, and brain metabolites were assessed by MRS. RESULTS: In the ischemic regions of neonatal rats, FA was significantly increased at 0-2 hours and decreased at 24 hours after the onset of HIE. ADC in the ipsilateral side was significantly lower than that of contralateral side. All rats with HIE showed hypointense areas on MTR asymmetry maps (2.0 and 3.5 ppm), that did not correspond with the hyperintense areas on DWI. In addition, a significant increase in lactate levels was observed at 0-2 and 24 hours after the onset of HIE. CONCLUSION: CEST MTR maps did not correspond with the hyperintense areas on DWI at 0-2 and 24 hours after the onset of HIE. The change of multi offset CEST signal may be primarily related to the brain metabolites and pH alterations, such as that caused by lactate, after the onset of HIE.

Neurite orientation dispersion and density imaging for evaluating the severity of neonatal hypoxic-ischemic encephalopathy in rats.

PURPOSE: To evaluate the utility of neurite orientation dispersion and density imaging (NODDI) for longitudinally assessing neonatal hypoxic-ischemic (HI) encephalopathy severity with 7.0 T magnetic resonance imaging. METHODS: Thirteen 8-day-old Wistar rats underwent unilateral ligation of the left common carotid artery followed by mild (1 h; n = 6) or severe (2 h; n = 7) hypoxic exposure (8% O2, 34 °C). Diffusion-weighted, T2-weighted (T2W), and flow-sensitive alternating inversion recovery images were obtained with a horizontal 7.0 T scanner at 1, 24, 72, and 168 h after HI insult. The fractional anisotropy (FA), apparent diffusion coefficient (ADC), intracellular volume fraction (ICVF), isotropic volume fraction (ISO), orientation dispersion index (ODI), and cerebral blood flow (CBF) values were calculated for each group (mild and severe) at each time point (1, 24, 72, and 168 h). ICVF, ISO, and ODI were the NODDI parameters. RESULTS: Left hemisphere brain damage was identified as slight hyperintensity on T2W images after 1 h in both groups. In the severe group only, the signal hyperintensity increased time-dependently over 168 h. The ADC and CBF were not significantly different between the groups within any region. The ICVF and ODI were significantly higher in the severe vs. mild group at various points between 1 and 168 h (cortex, striatum, or white matter), whereas the FA was significantly higher in the mild vs. severe group at 168 h (cortex and white matter). The ISO was higher in the severe vs. mild group at 72 h (striatum) and 168 h (all regions), while the ISO was significantly higher in the mild vs. severe group at 24 h (all regions). CONCLUSION: Here, ODI, a NODDI metric, identified early differences between mild and severe HI injuries. Our findings support the potential utility of NODDI for determining neonatal HI encephalopathy severity in rats.

Detection of increased intracerebral lactate in a mouse model of Leigh syndrome using proton MR spectroscopy.

PURPOSE: To establish a brain proton magnetic resonance spectroscopy (1H MRS) experimental system using a mouse model of Leigh syndrome for monitoring intracerebral lactate levels as a biomarker of mitochondrial disease progression. MATERIALS AND METHODS: Brain 1H MRS was performed in the Ndufs4 homozygous knockout (KO) mice, a mouse model of Leigh syndrome, and control mice on a horizontal 7.0-T magnetic resonance imaging system at age 5-9 weeks. In a subset of KO mice, survival analysis was performed according to the median of the intracerebral lactate levels. In addition, in KO mice alive until 9 weeks of age, both 1H MRS and T2-weighted imaging (T2WI) were longitudinally performed in the same individuals at 5, 7, and 9 weeks of age. RESULTS: Brain 1H MRS demonstrated increased lactate levels in KO mice compared with control mice (6.4 ±â€¯1.2 mM vs. 3.3 ±â€¯0.8 mM, p < 0.0001). The increased intracerebral lactate levels were already observed at 5 weeks of age, while no obvious abnormal findings were detected in T2WI. Notably, an increased lactate level of >5.94 mM at week 5 was associated with a poor prognosis (median survival days: 24.5 vs. 42 days, log-rank p = 0.03). Longitudinal 1H MRS experiments revealed temporal increase of intracerebral lactate levels, peaking at week 7 (mean change: 2.6 ±â€¯0.7 mM, p = 0.001), followed by decrease at week 9 (mean change: -3.8 ±â€¯2.5 mM, p = 0.03), along with further disease progression, with brain lesions being detected on T2WI. CONCLUSION: Using brain 1H MRS, we demonstrated significant increase in intracerebral lactate levels in a mouse model of Leigh syndrome. Additionally, we demonstrated that intracerebral lactate is a useful biomarker of mitochondrial disease progression at stages preceding the development of brain lesions.

Early detection of elevated lactate levels in a mitochondrial disease model using chemical exchange saturation transfer (CEST) and magnetic resonance spectroscopy (MRS) at 7T-MRI.

This study aimed to use chemical exchange saturation transfer (CEST) and magnetic resonance spectroscopy (MRS) at 7T-MRI for early detection of intracerebral lactate in a mitochondrial disease model without brain lesions. We considered Ndufs4-knockout (KO) mice as Leigh syndrome models and wild-type (WT) mice as control mice. Brain MRI and 1H-MRS were performed. T2WI data acquired with the Rapid Acquisition with Refocused Echoes (RARE) sequence were used for evaluation of brain lesions. CEST imaging of mice brains was performed using RARE with a magnetization transfer (MT) pulse. The MT ratio (MTR) asymmetry curves and five MTR asymmetry maps at 0.5, 1.0, 2.0, 3.0, and 3.5 ppm were calculated using these CEST images. Metabolite concentrations were measured by MRS. T2WI MRI revealed no obvious abnormal findings in KO and WT mice brains at 6 weeks of age. The MTR asymmetry maps at 0.5 ppm, 1.0 ppm, and 2.0 ppm of the KO mice were higher than those of the control mice. Brain 1H MRS revealed a significant increase in lactate levels in all KO mice in comparison with those in the control mice. Additionally, creatine levels in the KO mice were slightly higher than those in the control mice. The levels of the other four metabolites-mIns, NAA + NAAG, GPC + PCh, and Glu + Gln-did not change significantly. We propose that CEST imaging can be used as a biomarker of intracerebral elevated lactate levels in mitochondrial disease.

In vitro cytotoxicity of zoledronate (nitrogen-containing bisphosphonate: NBP) and/or etidronate (non-NBP) in tumour cells and periodontal cells.

OBJECTIVE: Nitrogen-containing bisphosphonates (NBPs), the first-choice drugs for diseases that cause enhanced bone resorption, may injure jawbones and gastrointestinal tissues. In rodents, NBPs cause necrosis at injection sites. Bisphosphonates accumulate within bones, especially where there is inflammation. We hypothesized that if jawbone-accumulated NBPs are released, they may directly injure cells around the jawbones. To examine this hypothesis, we compared the direct effects of zoledronate (NBP) and/or etidronate (non-NBP) on various cells, including periodontal cells. DESIGN: Various human tumour cells (such as squamous carcinoma cells and prostate adenocarcinoma cells) and periodontal cells (such as gingival fibroblasts and periodontal ligament cells) were incubated with or without zoledronate and/or etidronate. Cell viability and cytotoxicity were determined by tetrazolium dye assay and by FITC-Annexin V/propidium iodide assay, respectively. RESULTS: Zoledronate, at 100µM, was toxic to all types of cells tested, while its toxicity varied among cells at both 1 and 10µM. There was no clear difference between tumour cells and non-tumour cells in sensitivity to the cytotoxicity of zoledronate. In contrast, etidronate was not toxic at 1-100µM in any of the cells tested. Interestingly, etidronate reduced the cytotoxicity of zoledronate in many cell-types, including gingival fibroblasts. CONCLUSIONS: These results, together with those reported by others and those from our previous in vivo experiments, suggest that NBPs, upon release from jawbones (e.g., during dental surgery or bone infection), may directly injure various cells located around the jawbones, and that etidronate may be protective against the cytotoxicity of NBPs in periodontal tissues.