Blood Oxygen Level-dependent Magnetic Resonance Research Articles

Linking renal hypoxia and oxidative stress in chronic kidney disease: Based on clinical subjects and animal models.

This study aims to explore the relationships between renal function, hypoxia, and oxidative stress in chronic kidney disease (CKD). Seventy-six non-dialysis patients with CKD stages 1-5 and eight healthy subjects were included in the clinical research. They were divided into three groups: healthy subjects, CKD stages 1-3, and CKD stages 4-5. In the animal study, 16 rat models of CKD were established through 5/6 renal ablation/infarction (A/I) surgery, and 8 normal rats were split into 3 groups: Sham, CKD, and losartan groups. Blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) was used to measure cortical and medullary T2* values (COT2* and MET2*) in all subjects and rats to evaluate renal oxygenation. Biochemical indicators were used to assess renal function and antioxidant capacity. Furthermore, the effects of losartan on renal fibrosis, hypoxia, and oxidative stress were examined using immunoblotting, colorimetric, and fluorometric assays. The results demonstrated significant positive associations between COT2* and MET2* with estimated glomerular filtration rate (eGFR). Patients with CKD stages 4-5 showed significantly lower serum superoxide dismutase (SOD) levels, which also had positive correlations with eGFR, COT2*, and MET2*. Furthermore, losartan treatment resulted in improved renal function and fibrosis, leading to increased levels of COT2*, MET2*, and SOD levels in 5/6 A/I rats. This was accompanied by reduced levels of hypoxia-inducible factor-1 alpha (HIF-1α) and malondialdehyde. Furthermore, losartan restored the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), and suppressed the expression of Kelch-like ECH-associated protein 1 (Keap1) in 5/6 A/I kidneys. The study indicates that decline in renal oxygenation and antioxidant capacity is associated with the severity of renal failure in CKD. Losartan can potentially alleviate renal hypoxia and oxidative stress in the treatment of CKD via Keap1-Nrf2/HO-1 pathway.

Magnetic resonance imaging-based approaches for detecting the efficacy of combining therapy following VEGFR-2 and PD-1 blockade in a colon cancer model

BackgroundAngiogenesis inhibitors have been identified to improve the efficacy of immunotherapy in recent studies. However, the delayed therapeutic effect of immunotherapy poses challenges in treatment planning. Therefore, this study aims to explore the potential of non-invasive imaging techniques, specifically intravoxel-incoherent-motion diffusion-weighted imaging (IVIM-DWI) and blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI), in detecting the anti-tumor response to the combination therapy involving immune checkpoint blockade therapy and anti-angiogenesis therapy in a tumor-bearing animal model.MethodsThe C57BL/6 mice were implanted with murine MC-38 cells to establish colon cancer xenograft model, and randomly divided into the control group, anti-PD-1 therapy group, and combination therapy group (VEGFR-2 inhibitor combined with anti-PD-1 antibody treatment). All mice were imaged before and, on the 3rd, 6th, 9th, and 12th day after administration, and pathological examinations were conducted at the same time points.ResultsThe combination therapy group effectively suppressed tumor growth, exhibiting a significantly higher tumor inhibition rate of 69.96% compared to the anti-PD-1 group (56.71%). The f value and D* value of IVIM-DWI exhibit advantages in reflecting tumor angiogenesis. The D* value showed the highest correlation with CD31 (r = 0.702, P = 0.001), and the f value demonstrated the closest correlation with vessel maturity (r = 0.693, P = 0.001). While the BOLD-MRI parameter, R2* value, shows the highest correlation with Hif-1α(r = 0.778, P < 0.001), indicating the capability of BOLD-MRI to evaluate tumor hypoxia. In addition, the D value of IVIM-DWI is closely related to tumor cell proliferation, apoptosis, and infiltration of lymphocytes. The D value was highly correlated with Ki-67 (r = − 0.792, P < 0.001), TUNEL (r = 0.910, P < 0.001) and CD8a (r = 0.918, P < 0.001).ConclusionsThe combination of VEGFR-2 inhibitors with PD-1 immunotherapy shows a synergistic anti-tumor effect on the mouse colon cancer model. IVIM-DWI and BOLD-MRI are expected to be used as non-invasive approaches to provide imaging-based evidence for tumor response detection and efficacy evaluation.

Value of blood oxygenation level-dependent magnetic resonance imaging in early evaluation of the response and prognosis of esophageal squamous cell carcinoma treated with definitive chemoradiotherapy: a preliminary study

BackgroundTo find a useful hypoxia non-invasive biomarker for evaluating early treatment response and prognosis to definitive chemoradiotherapy (dCRT) in patients with esophageal squamous cell carcinoma (ESCC), using blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI).MethodsThe R2* values were obtained pre- and 2–3 weeks post-dCRT in 28 patients with ESCC using BOLD MRI. Independent samples t-test (normality) or Mann-Whitney U test (non-normality) was used to compare the differences of R2*-related parameters between the complete response (CR) and the non-CR groups. Diagnostic performance of parameters in predicting response was tested with receiver operating characteristic (ROC) curve analysis. The 3-year overall survival (OS) was evaluated using Kaplan Meier curve, log rank test, and Cox proportional hazards regression analysis.ResultsThe post-R2*, ∆R2*, and ∆%R2* in the CR group were significantly higher than those in the non-CR group (P = 0.002, 0.003, and 0.006, respectively). The R2*-related parameters showed good prediction of tumor response, with AUC ranging from 0.813 to 0.829. The 3-year OS rate in patients with ∆R2* >-7.54 s− 1 or CR were significantly longer than those with ∆R2* ≤ -7.54 s− 1 (72.37% vs. 0.00%; Hazard ratio, HR = 0.196; 95% confidence interval, 95% CI = 0.047–0.807; P = 0.024) or non-CR (76.47% vs. 29.27%; HR = 0.238, 95% CI = 0.059–0.963; P = 0.044).ConclusionsThe preliminary results demonstrated that the R2* value might be a useful hypoxia non-invasive biomarker for assessing response and prognosis of ESCC treated with dCRT. BOLD MRI might be used as a potential tool for evaluating tumor oxygenation metabolism, which is routinely applied in clinical practice and beneficial to clinical decision-making. A large sample size was needed for further follow-up studies to confirm the findings.

Functional MRI evaluation of blood oxygen dependent (BOLD) in renal allograft dysfunction: a prospective study.

Blood oxygen level dependent-magnetic resonance imaging (BOLD-MRI) is a non-invasive functional imaging technique that can be used to assess renal allograft dysfunction. To evaluate the diagnostic performance of BOLD-MRI using a 3-T scanner in discriminating causes of renal allograft dysfunction in the post-transplant period. This prospective study was conducted on 112 live donor-renal allograft recipients: 53 with normal graft function, as controls; 18 with biopsy-proven acute rejection (AR); and 41 with biopsy-proven acute tubular necrosis (ATN). Multiple fast-field echo sequences were performed to obtain T2*-weighted images. Cortical R2* (CR2*) level, medullary R2* (MR2*) level, and medullary over cortical R2* ratio (MCR) were measured in all participants. The mean MR2* level was significantly lower in the AR group (20.8 ± 2.8/s) compared to the normal group (24 ± 2.4/s, P <0.001) and ATN group (27.4 ± 1.7/s, P <0.001). The MCR was higher in ATN group (1.47 ± 0.18) compared to the AR group (1.18 ± 0.17) and normal functioning group (1.34 ± 0.2). Both MR2* (area under the curve [AUC] = 0.837, P <0.001) and MCR (AUC = 0.727, P = 0.003) can accurately discriminate ATN from AR, however CR2* (AUC = 0.590, P = 0.237) showed no significant difference between both groups. In early post-transplant renal dysfunction, BOLD-MRI is a valuable non-invasive diagnostic technique that can differentiate between AR and ATN by measuring changes in intra-renal tissue oxygenation.

Association of Baseline Cerebrovascular Reactivity and Longitudinal Development of Enlarged Perivascular Spaces in the Basal Ganglia.

Increasing evidence suggests that enlarged perivascular spaces (ePVS) are associated with cognitive dysfunction in aging. However, the pathogenesis of ePVS remains unknown. Here, we tested the possibility that baseline cerebrovascular dysfunction, as measured by a magnetic resonance imaging measure of cerebrovascular reactivity, contributes to the later development of ePVS. Fifty cognitively unimpaired, older adults (31 women; age range, 60-84 years) underwent magnetic resonance imaging scanning at baseline and follow-up separated by ≈2.5 years. ePVS were counted in the basal ganglia, centrum semiovale, midbrain, and hippocampus. Cerebrovascular reactivity, an index of the vasodilatory capacity of cerebral small vessels, was assessed using carbon dioxide inhalation while acquiring blood oxygen level-dependent magnetic resonance images. Low baseline cerebrovascular reactivity values in the basal ganglia were associated with increased follow-up ePVS counts in the basal ganglia after controlling for age, sex, and baseline ePVS values (estimate [SE]=-3.18 [0.96]; P=0.002; [95% CI, -5.11 to -1.24]). This effect remained significant after accounting for self-reported risk factors of cerebral small vessel disease (estimate [SE]=-3.10 [1.00]; P=0.003; [CI, -5.11 to -1.09]) and neuroimaging markers of cerebral small vessel disease (estimate [SE]=-2.72 [0.99]; P=0.009; [CI, -4.71 to -0.73]). Our results demonstrate that low baseline cerebrovascular reactivity is a risk factor for later development of ePVS.

COVID-19 during pregnancy could potentially affect placental function

Objective COVID-19 is an ongoing pandemic and has been extensively studied. However, the effects of COVID-19 during pregnancy, particularly on placental function, have not been verified. In this study, we used blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) to evaluate whether COVID-19 incidence during pregnancy has any lasting effects with respect to placental oxygenation. Methods This is a case-control study, in which eight cases of singleton pregnancies before 30 weeks gestation with COVID-19 mothers were included. Placental oxygenation was evaluated using BOLD-MRI after 32 weeks of gestation. BOLD-MRI was consecutively performed under normoxia (21% O2), hyperoxia (100% O2), and normoxia for 4 min each. Individual placental time–activity curves were evaluated to calculate the peak score (peakΔR2*) and the time from the start of maternal oxygen administration to the time of peakΔR2* (time to peakΔR2*). Eighteen COVID-19-free normal pregnancies from a previous study were used as the control group. Results No significant differences were found between the two groups regarding maternal background, number of days of delivery, birth weight, and placental weight. The parameter peakΔR2* was significantly decreased in the COVID-19 group (8 ± 3 vs. 5 ± 1, p < .001); however, there was no significant difference in time to peakΔR2* (458 ± 74 s vs. 471 ± 33 s, p = .644). Conclusions In this study, BOLD-MRI was used to evaluate placental oxygenation during pregnancy in COVID-19-affected patients. COVID-19 during pregnancy decreased placental oxygenation even post-illness, but had no effect on fetal growth; further investigation of the possible effects of COVID-19 on the fetus and mother is warranted.

Convolutional Neural Networks to Assess Steno-Occlusive Disease Using Cerebrovascular Reactivity.

Cerebrovascular Reactivity (CVR) is a provocative test used with Blood oxygenation level-dependent (BOLD) Magnetic Resonance Imaging (MRI) studies, where a vasoactive stimulus is applied and the corresponding changes in the cerebral blood flow (CBF) are measured. The most common clinical application is the assessment of cerebral perfusion insufficiency in patients with steno-occlusive disease (SOD). Globally, millions of people suffer from cerebrovascular diseases, and SOD is the most common cause of ischemic stroke. Therefore, CVR analyses can play a vital role in early diagnosis and guiding clinical treatment. This study develops a convolutional neural network (CNN)-based clinical decision support system to facilitate the screening of SOD patients by discriminating between healthy and unhealthy CVR maps. The networks were trained on a confidential CVR dataset with two classes: 68 healthy control subjects, and 163 SOD patients. This original dataset was distributed in a ratio of 80%-10%-10% for training, validation, and testing, respectively, and image augmentations were applied to the training and validation sets. Additionally, some popular pre-trained networks were imported and customized for the objective classification task to conduct transfer learning experiments. Results indicate that a customized CNN with a double-stacked convolution layer architecture produces the best results, consistent with expert clinical readings.

Can the apparent transverse relaxation rate (R2*) evaluate the efficacy of concurrent chemoradiotherapy in locally advanced nasopharyngeal carcinoma? a preliminary experience

BackgroundThe use of the apparent transverse relaxation rate (R2*) in nasopharyngeal carcinoma (NPC) has not been previously reported in the literature. The aim of this study was to investigate the role of the R2* value in evaluating response to concurrent chemoradiotherapy (CCRT) in patients with NPC.MethodsForty-one patients with locoregionally advanced NPC confirmed by pathology were examined by blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) before and after CCRT, and conventional MRI was performed 3 months after the completion of CCRT. All patients were divided into a responding group (RG) and a nonresponding group (NRG), according to MRI findings 3 months after the end of treatment. The R2* values before (R2*preT) and after (R2*postT) CCRT and the ΔR2* (ΔR2*=R2*postT – R2*preT) were calculated in the tumor.ResultsAmong the 41 patients, 26 were in the RG and 15 were in the NRG. There was no statistical difference in the R2*preT between RG and NRG (P = 0.307); however, there were significant differences in R2*postT and ΔR2* (P < 0.001). The area under the curve of R2*postT and ΔR2* for predicting the therapeutic response of NPC was 0.897 and 0.954, respectively, with cutoff values of 40.95 and 5.50 Hz, respectively.ConclusionThe R2* value can be used as a potential imaging indicator to evaluate the therapeutic response of locoregionally advanced NPC.

Effects of alfaxalone, propofol and isoflurane on cerebral blood flow and cerebrovascular reactivity to carbon dioxide in dogs: A pilot study.

Propofol total intravenous anesthesia is a common choice to anesthetize patients with increased intracranial pressure, reducing cerebral blood flow while maintaining cerebrovascular reactivity to CO2. Propofol and alfaxalone are commonly used for total intravenous anesthesia in dogs, but the effects of alfaxalone on cerebral blood flow and cerebrovascular reactivity to CO2 are unknown. Our hypothesis was that alfaxalone would not be significantly different to propofol, while isoflurane would increase cerebral blood flow and decrease cerebrovascular reactivity to CO2. Six healthy hound dogs were evaluated in this randomized crossover trial. Dogs were anesthetized with 7.5mg/kg propofol, 3mg/kg alfaxalone or 8% sevoflurane, mechanically ventilated and maintained with propofol (400µg/kg/min), alfaxalone (150µg/kg/min) or 1.7% end-tidal isoflurane, respectively, with one week washout between treatments. Cerebral blood flow and cerebrovascular reactivity to CO2 during hypercapnic and hypocapnic challenges were measured using arterial spin labelling and blood oxygen level-dependent magnetic resonance imaging sequences, respectively. Median (interquartile range, IQR) normocapnic cerebral blood flow was significantly lower (P=0.016) with alfaxalone compared to isoflurane, in the whole brain 15.39mL/min/100g (14.90-19.90mL/min/100g) vs. 34.10mL/min/100g (33.35-43.17mL/min/100g), the grey matter 14.57mL/min/100g (13.66-18.72mL/min/100g) vs. 32.37mL/min/100g (31.03-42.99mL/min/100g), the caudal brain 15.47mL/min/100g (13.37-21.45mL/min/100g) vs. 36.85mL/min/100g (32.50-47.18mL/min/100g) and the temporal lobe grey matter 18.80mL/min/100g (15.89-20.84mL/min/100g) vs. 43.32 (36.07-43.58mL/min/100g). Median (IQR) hypocapnic cerebrovascular reactivity to CO2 was significantly higher (P=0.016) for alfaxalone compared to isoflurane 8.85%S/mm Hg (6.92-10.44%S/mm Hg) vs. 3.90%S/mm Hg (3.80-4.33%S/mm Hg). Alfaxalone maintained lower cerebral blood flow and higher hypocapnic cerebrovascular reactivity to CO2 than isoflurane.

Correlation of Renal Oxygenation with Renal Function in Chronic Kidney Disease: A Preliminary Prospective Study

Introduction: Chronic hypoxia is prevalent in chronic kidney disease (CKD), and blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) provides noninvasive evaluation of renal oxygenation. This study aimed to explore the correlation of renal oxygenation evaluated by BOLD-MRI with renal function. Methods: 97 non-dialysis patients with CKD stages 1–5 and healthy volunteers (HVs) were recruited in the study, all participants without diabetes. Based on their estimated glomerular filtration rate (eGFR), the patients were divided into two groups: CKD stages 1–3 (CKD 1–3) and CKD stages 4–5 (CKD 4–5). We measured cortical and medullary T2* (COT2* and MET2*) values in all participants by BOLD-MRI. Physiological indices were also recorded and compared among three groups. Correlation of T2* values with clinical characteristics was determined. Results: The COT2* values were significantly higher than MET2* values in all participants. The COT2* and MET2* values of three groups were ranked as HV > CKD 1–3> CKD 4–5 (p r > 0.4, p rs = −0.2301, p = 0.0265) and no correlation with the MET2* value (p > 0.05). Urinary microprotein, including urinary alpha1-microglobulin, urinary beta2-microglobulin (β2-MG), and urinary retinol-binding protein (RBP), showed strong correlation with COT2* and MET2* values. According to the analysis of receiver operating characteristic curve, the optimal cut-points between HV and CKD 1–3 were “Conclusion: The decline of renal oxygenation reflected on T2* values, especially in cortex, may be an effective diagnostic marker for early detection of CKD.

The value of magnetic resonance blood oxygen level-dependent imaging in evaluating the efficacy of advanced cervical cancer combined with radiotherapy and chemotherapy.

Blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) is an imaging method used to analyze oxygenation status of the tumor. To investigate the feasibility of BOLD-MRI in evaluating the efficacy of advanced cervical cancer combined with radiotherapy and chemotherapy. This prospective study included 85 patients with advanced cervical cancer who received BOLD-MRI examination before and after concurrent chemoradiotherapy from October 2020 to December 2021. To investigate the changes of baseline R2* values and △R2* values of cervical cancers before and after treatment. 29 cases were complete response, 34 cases were partial response, and 22 cases showed progression. The baseline R2* values of the tumors were lower than that of the normal cervical muscle (P < 0.0001). After oxygen stimulation, the baseline R2* values of the tumors decreased (P = 0.012). After treatment, the baseline R2* values of the tumors increased (P = 0.007), and the dynamic △R2* values of the tumors decreased (P = 0.025). The baseline R2* value of the complete response was the highest (P = 0.000), the dynamic △R2* value of the complete response was the lowest (P = 0.017). BOLD-MRI can evaluate the efficacy of concurrent chemoradiotherapy for advanced cervical cancer.

Evaluating renal iron overload in diabetes mellitus by blood oxygen level-dependent magnetic resonance imaging: a longitudinal experimental study

BackgroundIron overload plays a critical role in the pathogenesis of diabetic nephropathy. Non-invasive evaluation of renal iron overload in diabetes in the management and intervention of diabetic nephropathy is of great significance. This study aimed to explore the feasibility of blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) in evaluating renal iron overload in diabetes using a rabbit model.MethodsThe rabbits were randomly divided into control, iron-overload (I), diabetes (D), and diabetes with iron-overload (DI) groups (each n = 19). The diabetes models were generated by injecting intravenous alloxan solution, and the iron-overload models were generated by injecting intramuscular iron-dextran. BOLD MRI was performed immediately (week 0) and at week 4, 8, and 12 following modeling. The differences in renal cortex (CR2*) and outer medulla R2* (MR2*) and the ratio of MR2*–CR2* (MCR) across the different time points were compared.ResultsIron was first deposited in glomeruli in the I group and in proximal tubular cells in renal cortex in the D group. In the DI group, there was iron deposition in both glomeruli and proximal tubular cells at week 4, and the accumulation increased subsequently. The degree of kidney injury and iron overload was more severe in the DI group than those in the I and D groups at week 12. At week 8 and 12, the CR2* and MR2* in the DI group were higher than those in the I and D groups (all P < 0.05). The MCR in the I, D, and DI groups decreased from week 0 to 4 (all P < 0.001), and that in the I group increased from week 8 to 12 (P = 0.034). CR2* and MR2* values displayed different trends from week 0–12. Dynamic MCR curves in the D and DI groups were different from that in the I group.ConclusionIt presents interactions between diabetes and iron overload in kidney injury, and BOLD MRI can be used to evaluate renal iron overload in diabetes.

Cyclic changes in T2* relaxometry of human uterus during the menstrual cycle using BOLD MR imaging

PurposeTo evaluate dynamic changes of T2* values within the endometrium, junctional zone and myometrium during the menstrual cycle using blood oxygen level-dependent (BOLD) magnetic resonance imaging. MethodVolunteers underwent MRI scans on menstrual phase, ovulatory phase and luteal phase, including T2-weighted imaging and BOLD MR imaging. Multi-gradient-recalled echo (MGRE) sequence was used to obtain BOLD MR images. T2* values of different uterine layers, including endometrium, junctional zone and myometrium, on sagittal images were analyzed quantitatively. ResultsTwenty-four subjects calculated T2* values successfully. The T2* values of each zonal structure during menstruation were significantly lower than those during ovulatory phase (P < 0.05) and luteal phase (P < 0.001). The T2* value of junctional zone was significantly lower than that of the myometrium over all three menstrual phases (P = 0.000, menstrual; P = 0.000, ovulatory; P = 0.001, luteal). The mean T2* value in endometrium during the ovulatory phase was the highest of the uterine zones over menstrual cycle. During menstrual phase, there was no statistical difference between endometrium and junctional zone (P > 0.05). Conversely, the comparison of the T2* values between endometrium and myometrium, junctional zone and myometrium both showed significant difference (P = 0.000). The mean T2* values within endometrium during ovulatory phase and luteal phase were significantly higher than those within junctional zone and myometrium (P < 0.05). ConclusionsCyclic changes of T2* values in each zonal structure of the uterus were revealed during the menstrual cycle by means of BOLD technique, which may be potentially beneficial in investigating dysmenorrhea, guiding assisted reproductive technologies and monitoring hypoxia in gynecological tumors.

Correlation between Blood Oxygen Level-Dependent Magnetic Resonance Imaging Images and Prognosis of Patients with Multicenter Diabetic Nephropathy on account of Artificial Intelligence Segmentation Algorithm.

This study was aimed to analyze the correlation between blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) images and prognosis of patients with diabetic nephropathy (DN) based on artificial intelligence (AI) segmentation algorithm, so as to provide references for diagnosis and treatment as well as prognosis analysis of patients DN. In this study, a kernel function-based fuzzy C-means algorithm (KFCM) model was proposed, and the FCM algorithm based on neighborhood pixel information (BCFCM) and the FCM algorithm based on efficiency improvement (EnFCM) were introduced for comparison to analyze the image segmentation effects of three algorithms. The results showed that the partition coefficient (Vpc) and partition entropy (Vpe) of the KFCM algorithm were 0.801 and 0.602, respectively, which were better than those of the traditional FCM, BCFCM, and EnFCM algorithm. At the same time, the effects of correlation between renal cortex R2∗ (RC-R2∗), renal medulla R2∗ (RM-R2∗), renal cortex D (RC-D), renal medulla D (RM-D) and renal function on the prognosis were compared. The results showed that the correlation coefficients between RC-R2∗, RM-R2∗, RC-D, RM-D and renal function were 0.57, 0.62, 0.49, and 0.38, respectively; among them, RC-R2∗ and RM-R2∗ were negatively correlated to the estimated glomerular filtration rate (eGFR), and the difference between the groups was statistically significant (P <0.05). Among the factors affecting the prognosis of DN patients, the GFR, hemoglobin (Hb), RC-R2∗, RM-R2∗, and RC-D were all related to the prognosis of DN, and the difference between groups was statistically obvious (P <0.05). It suggested that the KFCM algorithm proposed in this study showed the relatively best segmentation effect on BOLD-MRI images for DN patients; an increase in R2∗ indicated a poor prognosis, and an increase in the RC-D value indicated a better prognosis.

Evaluation of renal oxygenation by BOLD-MRI in high-risk patients with type 2 diabetes and matched controls.

Diabetic kidney disease (DKD) accounts for ∼50% of end-stage kidney disease. Renal hypoxia is suggested as a main driver in the pathophysiology underlying chronic DKD. Blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) has made noninvasive investigations of renal oxygenation in humans possible. Whether diabetes per se contributes to measurable changes in renal oxygenation by BOLD-MRI remains to be elucidated. We investigated whether renal oxygenation measured with BOLD-MRI differs between people with type 2 diabetes (T2DM) with normal to moderate chronic kidney disease (CKD) (Stages 1-3A) and matched controls. The repeatability of the BOLD-MRI method was also assessed. In this matched cross-sectional study, 20 people with T2DM (age 69.2 ± 4.7 years, duration of diabetes 10.5 ± 6.7 years, male 55.6%) and 20 matched nondiabetic controls (mean age 68.8 ± 5.4 years, male 55.%) underwent BOLD-MRI analysed with the 12-layer concentric object method (TLCO). To investigate the repeatability, seven in the T2DM group and nine in the control group were scanned twice. A significant reduction in renal oxygenation from the cortex to medulla was found in both groups (P<.01) but no intergroup difference was detected [0.71/s (95% confidence interval -0.28-1.7), P=.16]. The median intraindividual coefficient of variation (CV) varied from 1.2% to 7.0%. T2DM patients with normal to moderate CKD do not seem to have lower renal oxygenation when measured with BOLD-MRI and TLCO. BOLD-MRI has a low intraindividual CV and seems like a reliable method for investigation of renal oxygenation in T2DM.

Brain Activation During Processing of Depression Emotion in College Students With Premenstrual Syndrome in China: Preliminary Findings.

BackgroundThis study aimed to investigate the neural substrates of processing depression emotion in premenstrual syndrome (PMS) and healthy subjects of college students using blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI).MethodsDuring BOLD-fMRI scanning, 13 PMS patients and 15 healthy controls (HC) performed a picture visual stimulation task during luteal and follicular phases, in which participants and HC were asked to see pictures containing depression and non-depression emotions. Simultaneously, self-rating depression scales (SDS) were employed to evaluate the emotional status of participants.ResultsCompared to HC, right inferior occipital gyrus, right middle occipital gyrus, right lingual gyrus, right fusiform gyrus, right inferior temporal gyrus, cerebelum_crus1_R, cerebelum_6_R, culmen, the cerebellum anterior lobe, tuber, and cerebellar tonsil of PMS patients showed enhanced activation. In contrast, sub-lobar, sub-gyral, extra-nuclear, right orbit part of superior frontal gyrus, right middle temporal gyrus, right orbit part of inferior frontal gyrus, limbic lobe, right insula, bilateral anterior and adjacent cingulate gyrus, bilateral caudate, caudate head, bilateral putamen, and left globus pallidus exhibited decreased activation.ConclusionThe findings indicate that abnormal functional regulation of brain regions such as occipital lobe and cerebellum leads to abnormal changes in emotional regulation, cognitive ability, and attention distribution in PMS patients, implying significant central pathogenesis.

Evaluation of placental oxygenation in fetal growth restriction using blood oxygen level-dependent magnetic resonance imaging

IntroductionAbnormalities in placental function can lead to fetal growth restriction (FGR), but there is no consensus on their evaluation. Using blood oxygen level-dependent magnetic resonance imaging (BOLD MRI), we compared placental oxygenation between FGR cases and previously reported normal pregnancies. MethodsEight singleton pregnant women (>32 weeks of gestation) diagnosed with fetal growth failure during pregnancy were recruited. BOLD MRI was consecutively performed under normoxia (21% O2), hyperoxia (100% O2), and normoxia for 4 min each. Each placental time-activity curve was evaluated to calculate the peak score (peakΔR2*) and the time from the start of maternal oxygen administration to the time of peakΔR2* (time to peakΔR2*). In six of the eight FGR cases, placental FGR-related pathological findings were evaluated after delivery. ResultsThe parameter peakΔR2* was significantly decreased in the FGR group (8 ± 3 vs 6 ± 1, p < 0.001), but there was no significant difference in time to peakΔR2* (458 ± 74 s vs 468 ± 57 s, p = 0.750). The findings in the six FGR cases assessed for placental pathologies included chorangiosis in two cases, avascular chorions in two cases, placental infarction in two cases, and syncytial knot formation in one case. DiscussionThe peakΔR2* values were lower in the FGR group than in the normal pregnancy group. This suggests that oxygenation of the placenta is decreased in the FGR group compared to the normal group, and this may be related to FGR. Placental pathology also revealed findings possibly related to FGR, suggesting that low peakΔR2* values in the FGR group may reflect placental dysfunction.

Myocardial Tissue Oxygenation and Microvascular Blood Volume Measurement Using a Contrast Blood Oxygenation Level-Dependent Imaging Model.

We propose a method of quantitatively measuring drug-induced microvascular volume changes, as well as drug-induced changes in blood oxygenation using calibrated blood oxygen level-dependent magnetic resonance imaging (MRI). We postulate that for MRI signals there is a contribution to R2* relaxation rates from static susceptibility effects of the intravascular blood that scales with the blood volume/magnetic field and depends on the oxygenation state of the blood. These may be compared with the effects of an intravascular contrast agent. With 4 R2* measurements, microvascular blood volume (MBV) and tissue oxygenation changes can be quantified with the administration of a vasoactive drug. The protocol examined 12 healthy rats in a prospective observational study. R2* maps were acquired with and without infusion of adenosine, which increases microvascular blood flow, or dobutamine, which increases myocardial oxygen consumption. In addition, R2* maps were acquired after the intravenous administration of a monocrystalline iron oxide nanoparticle, with and without adenosine or dobutamine. Total microvascular volume was shown to increase by 10.8% with adenosine and by 25.6% with dobutamine ( P < 0.05). When comparing endocardium versus epicardium, both adenosine and dobutamine demonstrated significant differences between endocardial and epicardial MBV changes ( P < 0.05). Total myocardial oxygenation saturation increased by 6.59% with adenosine and by 1.64% with dobutamine ( P = 0.27). The difference between epicardial and endocardial oxygenation changes were significant with each drug (adenosine P < 0.05, dobutamine P < 0.05). Our results demonstrate the ability to quantify microvascular volume and oxygenation changes using calibrated blood oxygen level-dependent MRI, and we demonstrate different responses of adenosine and dobutamine. This method has clinical potential in examining microvascular disease in various disease states without the administration of radiopharmaceuticals or gadolinium-based contrast agents.

Toward an integrative neurovascular framework for studying brain networks.

.Brain functional connectivity based on the measure of blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signals has become one of the most widely used measurements in human neuroimaging. However, the nature of the functional networks revealed by BOLD fMRI can be ambiguous, as highlighted by a recent series of experiments that have suggested that typical resting-state networks can be replicated from purely vascular or physiologically driven BOLD signals. After going through a brief review of the key concepts of brain network analysis, we explore how the vascular and neuronal systems interact to give rise to the brain functional networks measured with BOLD fMRI. This leads us to emphasize a view of the vascular network not only as a confounding element in fMRI but also as a functionally relevant system that is entangled with the neuronal network. To study the vascular and neuronal underpinnings of BOLD functional connectivity, we consider a combination of methodological avenues based on multiscale and multimodal optical imaging in mice, used in combination with computational models that allow the integration of vascular information to explain functional connectivity.

Fluctuation of R2* values in blood oxygenation level-dependent MRI during acute and remission phases of IgA vasculitis with nephritis in children.

Noninvasive assessment of the kidney using blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) has progressed remarkably; indications have expanded to include the evaluation of glomerulonephritis. However, no longitudinal measurements from acute to post-treatment remission phases have been reported. Hence, this study aimed to investigate spin relaxation rate (R2*) values during acute and remission phases in children with glomerulonephritis. All pediatricpatients with IgA vasculitis with nephritis (IgAVN) diagnosed between January 2014 and October 2021 and requiring renal biopsy were retrospectively reviewed; four patients who were observed from onset to remission were included in this study. In total, eight MRIs were performed in the acute and remission phases, and R2* values and fluctuations induced by low-dose oxygen administration were determined from 10 echoes using a 1.5T MRI system with 4.76-47.6ms echo times and a 153ms repetition time. The median age of patients undergoing MRI was 8.5years in the acute phase and 13.9years in the remission phase. R2* values of the acute phase were higher than those of the remission phase; however, the difference was not significant (cortex; p = 0.32 and medulla; p = 0.052). Oxygen administration did not cause fluctuations in the R2* values in the cortex or medulla during the acute phase (cortex; p = 0.67 and medulla; p = 0.76); however, in the remission phase, the R2* values in the cortex and medulla significantly decreased due to low-dose oxygen administration (cortex; p < 0.01 and medulla; p < 0.01). The fluctuation in R2* values observed during different phases of IgAVN indicates that BOLD MRI may be used to assess disease activity. Therefore, we propose BOLD MRI with low-dose oxygen administration as a noninvasive method to evaluate the activity of glomerulonephritis.