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This study aimed to evaluate an intracerebral hemorrhage (ICH) model using quantitative susceptibility mapping (QSM) and chemical exchange saturation transfer (CEST) with preclinical 7T-magnetic resonance imaging (MRI) and determine the potential of amide proton transfer-CEST (APT-CEST) for use as a biomarker for the early detection of ICH. Six Wistar male rats underwent MRI, and another six underwent histopathological examinations on postoperative days 0, 3, and 7. The ICH model was created by injecting bacterial collagenase into the right hemisphere of the brain. QSM and APT-CEST MRI were performed using horizontal 7T-MRI. Histological studies were performed to observe ICH and detect iron deposition at the ICH site. T2-weighted images (T2WI) revealed signal changes associated with hemoglobin degeneration in red blood cells, indicating acute-phase hemorrhage on day 0, late-subacute-phase hemorrhage on day 3, and chronic-phase hemorrhage on day 7. The susceptibility alterations in each phase were detected using QSM. QSM and Berlin blue staining revealed hemosiderin deposition in the chronic phase. APT-CEST revealed high magnetization transfer ratios in the acute phase. Abundant mobile proteins and peptides were observed in early ICH, which were subsequently diluted. APT-CEST imaging may be a reliable noninvasive biomarker for the early diagnosis of ICH.

Herein, 4D-flow MRI was performed on the bilateral carotid arteries in a rat model of unilateral carotid artery injury to analyze changes in flow velocity, flow rate, wall shear stress (WSS), and cross-sectional area due to endothelial injury. MR images of the rat carotid artery were acquired using 7T-MRI. Seven control rats and 16 rats with right endothelial injury (VED) were used. For five of the VED models where blood flow in both the right and left common carotid arteries was confirmed, 4D-flow MRI was performed after obtaining 3D images using the time of flight method. MRI was performed to calculate the flow velocity, flow rate, WSS, and cross-sectional area of the proximal, middle, and distal carotid arteries. In all five VED models, blood flow rate and WSS were predominantly decreased at the proximal injured side compared to the ipsilateral control side ( p  < 0.05). The cross-sectional area of the vessel distal to the injured side of the VED model was reduced compared to that of the non-injured side ( p  < 0.05). A comparison of the proximal part of the uninjured side between the control group and VED model showed that the vascular cross-sectional area was predominantly increased in the VED model ( p  < 0.05). 4D-flow MRI with 7T-MRI enabled analysis of changes in flow velocity, flow rate, WSS, and cross-sectional area due to vascular endothelial injury.

We aimed to assess tumor growth and cell density in colon cancer-bearing mouse models using CEST and diffusion-weighted imaging (DWI). Mouse carcinoma models were created by transplanting the mouse colon cancer cell line colon-26. They were divided into three groups at 6, 8, and 10 days after transplantation and underwent T 2 WI, CEST, and DWI using 7T-MRI. The Magnetization Transfer Ratio asymmetry (MTR) of 1.2 ppm reflecting hydroxyl metabolite in CEST imaging and the apparent diffusion coefficient (ADC) of the same region were statistically analyzed for each group. The MTR and ADC values were 6.51 ± 3.47% and 1.14 ± 0.34 × 10 − 3 mm 2 /s, 3.65 ± 1.65% and 0.77 ± 0.20 × 10 − 3 mm 2 /s, and 2.84 ± 0.82%, and 0.54 ± 0.02 × 10 − 3 × mm 2 /s on days 6, 8, and 10, respectively. The MTR and ADC values were high at 6 days after cell transplantation, and both values tended to decrease with tumor growth. These results indicate that hydroxyl metabolism was high on the sixth day, and both values decreased after the eighth day. CEST imaging and DWI may be useful markers of cell proliferation and metabolism in tumors.

This study aimed to evaluate cardiac function in a young mouse model of Duchenne muscular dystrophy (mdx) using cardiac magnetic resonance imaging (MRI) with feature tracking and self-gated magnetic resonance cine imaging. Cardiac function was evaluated in mdx and control mice (C57BL/6JJmsSlc mice) at 8 and 12 weeks of age. Preclinical 7-T MRI was used to capture short-axis, longitudinal two-chamber view and longitudinal four-chamber view cine images of mdx and control mice. Strain values were measured and evaluated from cine images acquired using the feature tracking method. The left ventricular ejection fraction was significantly less (p < 0.01 each) in the mdx group at both 8 (control, 56.6 ± 2.3% mdx, 47.2 ± 7.4%) and 12 weeks (control, 53.9 ± 3.3% mdx, 44.1 ± 2.7%). In the strain analysis, all strain value peaks were significantly less in mdx mice, except for the longitudinal strain of the four-chamber view at both 8 and 12 weeks of age. Strain analysis with feature tracking and self-gated magnetic resonance cine imaging is useful for assessing cardiac function in young mdx mice.

Late gadolinium enhancement (LGE) is a widely used magnetic resonance imaging method for assessing cardiac disease. However, the relationship between different LGE signal thresholds and microscopic tissue staining images is unclear. In this study, we performed cardiovascular MRI on myocardial infarction (MI) model rats and evaluated the relationship between LGE with different signal thresholding methods and tissue staining images. We prepared 16 rats that underwent MRI 14–18 days following a surgery to create an MI model. We captured cine and LGE images of the cardiac short-axis and longitudinal two- and four-chamber views. The mean ± 2SD, ± 3SD, and ± 5SD of the pixel values in the non-infarcted area were defined as the LGE area. We compared areas of Sirius red staining, determined by the color tone, with their respective LGE areas at end-diastole and end-systole. We observed that the LGE area calculated as the mean ± 2SD of the non-infarcted area at end-diastole demonstrated a significant positive correlation with the area of Sirius red staining (Pearson’s correlation coefficient in both: 0.81 [ p  < 0.01]). Therefore, the LGE area calculated as the mean ± 2SD of the non-infarcted area at end-diastole best reflected the MI area in tissue staining.

Objectives: Acute kidney injury (AKI), characterized by a rapid decline in renal function, affects approximately 13 million new patients annually. Adverse drug reactions have increasingly contributed to renal injury, underscoring the need for methods to directly and quantitatively evaluate renal injury. Methods: We utilized a drug-induced AKI model using gentamicin overdose, combining 7T magnetic resonance imaging (MRI) relaxation time measurements and blood tests to evaluate pathophysiological changes from multiple perspectives. Ten-week-old Wistar rats received intraperitoneal administration of gentamicin (80 mg/kg) for 7 days. Under respiratory synchronization, T1, T1rho, T2, and T2* maps were obtained in six control and five disease model rats. Relaxation times in the cortex and medulla were measured separately and compared between groups. Results: Blood tests evaluated Na, K, Cl, blood urea nitrogen, creatinine, and hematocrit levels. Renal tissue damage was evaluated via hematoxylin and eosin (HE) staining. Relaxation time showed significant changes in the cortex, especially in the T1 (control: 1156.7 ± 140.0, gentamicin: 1550.4 ± 162.1, p < 0.05) and T2 (control: 42.9 ± 3.4, gentamicin: 53.4 ± 4.8, p < 0.05) maps. Blood tests revealed significant increases in Na, blood urea nitrogen, creatinine, and hematocrit levels in the disease model. A correlation was observed between the T1 map of the renal cortex and each substance. HE staining revealed tissue damage due to renal injury. Conclusions: Multiparametric MRI facilitates quantitative and multidimensional evaluation of renal pathological changes caused by drug-induced AKI.

Background/Objectives: The Glutamate Chemical Exchange Saturation Transfer (GluCEST) technique is an advanced imaging modality that enables non-invasive glutamate quantification using MRI. Methods: This study evaluated glutamate dynamics in Parkinson’s disease (PD) using a unilateral PD rat model, in which Wistar rats received 6-hydroxydopamine (6-OHDA) injections into the medial forebrain bundle, selectively eliminating dopaminergic neurons in the substantia nigra–striatum pathway. Results: The PD rat model exhibited a significant GluCEST increase (MTR Values: 3.0 ppm) compared to the sham-operated group, which was suppressed by administration of L-DOPA, a dopamine precursor drug (Sham: 0.9 ± 0.4%, PD: 2.0 ± 0.2%, Sham L-DOPA: 0.9 ± 0.5%, PD_L-DOPA: 0.8 ± 0.7%, p < 0.01). Additionally, magnetic resonance spectroscopy-derived glutamate data were consistent with GluCEST findings (Sham: 1.4 ± 0.03, PD: 1.7 ± 0.06, Sham_L-DOPA: 1.4 ± 0.12, PD_L-DOPA: 1.4 ± 0.10, p < 0.01). Conclusions: These findings suggest that GluCEST and magnetic resonance spectroscopy are valuable for assessing abnormal glutamate dynamics in the 6-OHDA-induced rat PD model. Furthermore, GluCEST may detect suppressed glutamate secretion following L-DOPA treatment, underscoring its potential for monitoring disease progression and therapeutic responses in PD.

Background/Objectives: This study aimed to examine the changes in brain metabolites and water molecule diffusion using chemical exchange saturation transfer (CEST) imaging and diffusion-weighted imaging (DWI) after 15 Gy of X-ray irradiation in a rat model of glioma. Methods: The glioma-derived cell line, C6, was implanted into the striatum of the right brain of 7-week-old male Wistar rats. CEST imaging and DWI were performed on days 8, 10, and 17 after implantation using a 7T-magnetic resonance imaging. X-ray irradiation (15 Gy) was performed on day 9. Magnetization transfer ratio (MTR) and apparent diffusion coefficient (ADC) values were calculated for CEST and DWI, respectively. Results: On day 17, the MTR values at 1.2 ppm, 1.5 ppm, 1.8 ppm, 2.1 ppm, and 2.4 ppm in the irradiated group decreased significantly compared with those of the control group. The standard deviation for the ADC values on a pixel-by-pixel basis increased from day 8 to day 17 (0.6 ± 0.06 → 0.8 ± 0.17 (×10−3 mm2/s)) in the control group, whereas it remained nearly unchanged (0.6 ± 0.06 → 0.8 ± 0.11 (×10−3 mm2/s)) in the irradiated group. Conclusions: This study revealed the effects of 15 Gy X-ray irradiation in a rat model of glioma using CEST imaging and DWI.

This study investigated a method for improving the quality of images with a low number of excitations (NEXs) based on deep learning using T2-weighted magnetic resonance imaging (MRI) of the heads of normal Wistar rats to achieve higher image quality and a shorter acquisition time. A 7T MRI was used to acquire T2-weighted images of the whole brain with NEXs = 2, 4, 8, and 12. As a preprocessing step, non-rigid registration of the acquired low NEX images (NEXs = 2, 4, 8) and NEXs = 12 images was performed. A residual dense network (RDN) was used for training. A low NEX image was used as the input to the RDN, and the NEX12 image was used as the correct image. For quantitative evaluation, we measured the signal-to-noise ratio (SNR), peak SNR, and structural similarity index measure of the original image and the image obtained by RDN. The NEX2 results are presented as an example. The SNR of the cortex was 10.4 for NEX2, whereas the SNR of the image reconstructed with RDN for NEX2 was 32.1. (The SNR NEX12 was 19.6) In addition, the PSNR in NEX2 was significantly increased to 35.4 ± 2.0 compared to the input image and to 37.6 ± 2.9 compared to the reconstructed image (p = 0.05). The SSIM in NEX2 was 0.78 ± 0.05 compared to the input image and 0.91 ± 0.05 compared to the reconstructed image (p = 0.0003). Furthermore, NEX2 succeeded in reducing the shooting time by 83%. Therefore, in preclinical 7T MRI, supervised learning between the NEXs using RDNs can potentially improve the image quality of low NEX images and shorten the acquisition time.

This study used a rat model of coronary artery reperfusion imaged with preclinical 7-tesla magnetic resonance imaging (7T-MRI) to evaluate cardiac function, myocardial deformation, and the impact of infarction-to-reperfusion time. Wistar rats were assigned to control (n = 6), 20 min infarction (n = 10), 30 min infarction (n = 6), and 40 min infarction (n = 6) groups. Myocardial infarction occurred in all infarction groups but not in controls. Imaging included short- and long-axis slices. Cardiac function was assessed using end-diastolic volume, end-systolic volume, and left-ventricular ejection fraction. Myocardial deformation was analyzed by circumferential strain, radial strain (RS), and longitudinal strain (LS, four-chamber and two-chamber) using feature tracking. The 30 and 40 min infarction groups showed significant reductions in cardiac function and strain compared to the controls. RS decreased significantly between the control and 20 min infarction groups (40.6 ± 4.7% and 34.0 ± 4.1%, p < 0.05). No significant LS difference was observed between 30 and 40 min. Consequently, RS detects early myocardial changes (20 min), whereas LS may reflect compensatory contractility in severe infarction. Preclinical 7T-MRI provides valuable insights into the impact of infarction duration on cardiac function and myocardial deformation.