Purpose: We evaluated the utility of arterial spin labeling (ASL) imaging of tumor blood flow (TBF) for grading non-enhancing astrocytic tumors.
Materials and Methods: Thirteen non-enhancing astrocytomas were divided into high-grade (n = 7) and low-grade (n = 6) groups. Both ASL and conventional sequences were acquired using the same magnetic resonance machine. Intratumoral absolute maximum TBF (TBFmax), absolute mean TBF (TBFmean), and corresponding values normalized to cerebral blood flow (TBFmax and TBFmean ratios) were measured. The Mann-Whitney U test and receiver operating characteristic (ROC) curve analysis were used to assess the accuracy of TBF variables for tumor grading.
Results: Compared with low-grade astrocytoma, high-grade astrocytoma exhibited significantly greater absolute TBFmax (90.93 ± 24.96 vs 46.94 ± 20.97 ml/100 g/min, P < 0.001), TBFmean (58.75 ± 19.89 vs 31.16 ± 17.63 ml/100 g/min, P < 0.001), TBFmax ratio (3.34 ± 1.22 vs 1.35 ± 0.5, P < 0.001), and TBFmean ratio (2.15 ± 0.94 vs 0.88 ± 0.41, P < 0.001). The TBFmax ratio yielded the highest diagnostic accuracy (sensitivity 100%, specificity 86.3%), while absolute TBFmean yielded the lowest accuracy (sensitivity 85.7%, specificity 70.1%) by ROC analysis.
Conclusion: Parameters from ASL perfusion imaging, particularly TBFmax ratio, may be useful for distinguishing high-grade from low-grade astrocytoma in cases with equivocal conventional MRI findings.
Purpose: To test the feasibility of the phase difference enhanced (PADRE) imaging for differentiation between Alzheimer disease (AD) patients and control subjects on 3T MR imaging.
Materials and Methods: Fifteen patients with AD and 10 age-matched control subjects underwent two-dimensional fast field echo imaging to obtain PADRE images on a 3T MR scanner. A double Gaussian distribution model was used to determine the threshold phase value for differentiation between the physiologic and non-physiologic iron in the cerebral cortices, and PADRE images were processed with the threshold. Using a 4-point grading system, two readers independently assessed the signal of the four cerebral cortices on PADRE images: the cuneus, precuneus, superior frontal gyrus, and superior temporal gyrus. The difference in the signals in each cortex between the AD patients and age-matched control subjects was determined by using Mann–Whitney U test. Inter-rater reliability was determined by Kappa analysis. We also evaluated the correlation between Mini-Mental State Examination (MMSE) score and the hypointense grade, and between disease duration and the hypointense grade using the Spearman rank correlation test.
Results: The threshold phase value for differentiation between the physiologic and non-physiologic iron was −4.6% π (radian). The mean grades of the cuneus, precuneus, and superior temporal gyrus were significantly higher for the AD patients than for the control subjects (P = 0.002). Excellent inter-rater reliability was seen in the precuneus (kappa = 0.93), superior temporal gyrus (kappa = 0.94), and superior frontal gyrus (kappa = 0.93); good inter-rater reliability was observed in the cuneus (kappa = 0.75). We found a statistical correlation between MMSE score and the hypointense grade in superior temporal gyrus (STG) (P = 0.008), and no correlation between disease duration and the hypointense grade in any gyrus.
Conclusion: Our results suggest the feasibility of PADRE imaging at 3T for differentiation between AD patients and control subjects.
Purpose: To evaluate the error in segmented tissue images and to show the usefulness of the brain image in voxel-based morphometry (VBM) using Statistical Parametric Mapping (SPM) 12 software and 3D T1-weighted magnetic resonance images (3D-T1WIs) processed to simulate idiopathic normal pressure hydrocephalus (iNPH).
Materials and Methods: VBM analysis was performed on sagittal 3D-T1WIs obtained in 22 healthy volunteers using a 1.5T MR scanner. Regions of interest for the lateral ventricles of all subjects were carefully outlined on the original 3D-T1WIs, and two types of simulated 3D-T1WI were also prepared (non-dilated 3D-T1WI as normal control and dilated 3D-T1WI to simulate iNPH). All simulated 3D-T1WIs were segmented into gray matter, white matter, and cerebrospinal fluid images, and normalized to standard space. A brain image was made by adding the gray and white matter images. After smoothing with a 6-mm isotropic Gaussian kernel, group comparisons (dilated vs non-dilated) were made for gray and white matter, cerebrospinal fluid, and brain images using a paired t-test.
Results: In evaluation of tissue volume, estimation error was larger using gray or white matter images than using the brain image, and estimation errors in gray and white matter volume change were found for the brain surface.
Conclusion: To our knowledge, this is the first VBM study to show the possibility that VBM of gray and white matter volume on the brain surface may be more affected by individual differences in the level of dilation of the lateral ventricles than by individual differences in gray and white matter volumes. We recommend that VBM evaluation in patients with iNPH should be performed using the brain image rather than the gray and white matter images.
Purpose: To elucidate differences between the perivascular space (PVS) in the basal ganglia (BG) versus that found in white matter (WM) using heavily T2-weighted FLAIR (hT2-FL) in terms of 1) signal intensity on non-contrast enhanced images, and 2) the degree of contrast enhancement by intravenous single dose administration of gadolinium based contrast agent (IV-SD-GBCA).
Materials and Methods: Eight healthy men and 13 patients with suspected endolymphatic hydrops were included. No subjects had renal insufficiency. All subjects received IV-SD-GBCA. MR cisternography (MRC) and hT2-FL images were obtained prior to and 4 h after IV-SD-GBCA. The signal intensity of the PVS in the BG, subinsular WM, and the cerebrospinal fluid (CSF) in Ambient cistern (CSFAC) and CSF in Sylvian fissure (CSFSyl) was measured as well as that of the thalamus. The signal intensity ratio (SIR) was calculated by dividing the intensity by that of the thalamus. We used 5% as a threshold to determine the significance of the statistical test.
Results: In the pre-contrast scan, the SIR of the PVS in WM (Mean ± standard deviation, 1.83 ± 0.46) was significantly higher than that of the PVS in the BG (1.05 ± 0.154), CSFSyl (1.03 ± 0.15) and the CSFAC (0.97 ± 0.29). There was no significant difference between the SIR of the PVS in the BG compared to the CSFAC and CSFSyl. For the evaluation of the contrast enhancement effect, significant enhancement was observed in the PVS in the BG, the CSFAC and the CSFSyl compared to the pre-contrast scan. No significant contrast enhancement was observed in the PVS in WM.
Conclusion: The signal intensity difference between the PVS in the BG versus WM on pre-contrast images suggests that the fluid composition might be different between these PVSs. The difference in the contrast enhancement between the PVSs in the BG versus WM suggests a difference in drainage function.
Purpose: Fetal cardiac MRI has the potential to play an important role in the assessment of fetal cardiac pathologies, but it is up to now not feasible due to a missing gating method. The purpose of this work was the evaluation of Doppler ultrasound (DUS) for external fetal cardiac gating with regard to compatibility, functionality, and reliability. Preliminary results were assessed performing fetal cardiac MRI.
Methods: An MRI conditional DUS device was developed to obtain a gating signal from the fetal heart. The MRI compatibility was evaluated at 1.5T and 3T using B1 field maps and gradient echo images. The quality and sensitivity of the DUS device to detect the fetal heart motion for cardiac gating were evaluated outside the MRI room in 15 fetuses. A dynamic fetal cardiac phantom was employed to evaluate distortions of the DUS device and gating signal due to electromagnetic interferences at 1.5T and 3T. In the first in vivo experience, dynamic fetal cardiac images were acquired in four-chamber view at 1.5T and 3T in two fetuses.
Results: The maximum change in the B1 field and signal intensity with and without the DUS device was <6.5% for 1.5T and 3T. The sensitivity of the DUS device to detect the fetal heartbeat was 99.1%. Validation of the DUS device using the fetal cardiac phantom revealed no electromagnetic interferences at 1.5T or 3T and a high correlation to the simulated heart frequencies. Fetal cardiac cine images were successfully applied and showed good image quality.
Conclusion: An MR conditional DUS gating device was developed and evaluated revealing safety, compatibility, and reliability for different field strengths. In a preliminary experience, the DUS device was successfully applied for in vivo fetal cardiac imaging at 1.5T and 3T.
Purpose: Chronic cerebral hypoperfusion model mice were created by unilateral common carotid artery occlusion (UCCAO) surgery, which does not cause cerebral infarction, but which does cause long-term reduction in cerebral blood flow (CBF) to the occluded side. Cognitive dysfunction in this mouse model has been demonstrated in behavioral experiments, but neuron density change was not found in a previous positron emission tomography (PET) study. As a next step, in this study we investigated the injury of neuronal fibers in chronic cerebral hypoperfusion model mice using diffusion tensor imaging (DTI).
Methods: In diffusion-weighted imaging (DWI), not only the diffusion of water but also the capillary flow in the voxel, i.e., intravoxel incoherent motion (IVIM), contributes to the signal. Thus, we used DTI to evaluate DWI signal changes in the brains of chronic hypoperfusion model mice at 4 weeks after UCCAO while monitoring the possible influence of CBF change using arterial spin-labeling (ASL) MRI.
Results: Simple t-tests indicated that there were significant differences in CBF between the control and occluded sides of the brain, but there was no significant difference for the mean diffusivity (MD) or fractional anisotropy (FA). However, as Pearson correlation analysis showed that MD was strongly correlated with CBF, analysis-of-covariance (ANCOVA) was then performed using CBF as a covariate and a significant difference in MD between the contra- and ipsilateral sides was found. Performing a similar procedure for the FA found no significant differences.
Conclusion: The results suggest the injury of neuronal fibers due to chronic hypoperfusion. It is also suggested that CBF-related signal changes should be considered when DWI-based information is used for pathological diagnosis.
Purpose: To assess the clinical importance in the feature change in giant cell tumors of the bone (GCTB) after denosumab treatment, detected by MRI.
Methods: In 12 patients, MRI and CT of GCTB obtained before and after the treatment retrospectively compared. The tumor size, the signal intensity (SI) ratio between the solid part of the GCTB and muscle, cystic part size, gadolinium enhancement and apparent diffusion coefficient (ADC) value were measured on MRI. The bone formation in the tumor was observed on CT and X-ray.
Results: The mean number of denosumab injections was 19 ± 10. The follow-up period was up to 2 years. One case showed partial remission, while the other 11 cases were stable. A mean SI ratio on T2-weighted image statistically significantly decreased from 3.9 to 1.9 after the treatment. A cystic component in the tumor was observed in five cases before the treatment, and the diameter of the cystic part decreased after the treatment in 80% of cases (4/5). All the tumors showed contrast enhancement on T1-weighted image pre- and post-treatment (11/11). The averaged ADC values were 1.52 × 10−3 mm2/s before and 1.44 × 10−3 mm2/s after the treatment (P = 0.63). Bone formation in the tumor was observed in 58% of cases (7/12).
Conclusion: The decrease of SI ratio on T2-weighted image, shrinkage of cystic part and bone formation should be regarded as the effectiveness of denosumab treatment despite of no substantial change in the tumor size.
Purpose: High Mobility Group Box1 (HMGB1), which is one of the damage-associated molecular pattern molecules relating to various inflammatory diseases, has gained interest as a therapeutic target because of its involvement in wound healing processes. In the present study, we investigated HMGB1 as a potential therapeutic target in a model of lung fibrosis using a preclinical hyperpolarized 129Xe (HPXe) MRI system.
Methods: Lung injury was induced by intra-peritoneal injection of bleomycin (BLM) in 19 mice. Three weeks post-injection (when fibrosis was confirmed histologically), administration of ethyl pyruvate (EP) and alogliptin (ALG), which are down- and up-regulators of HMGB1, respectively, was commenced in six and seven of the 19 mice, respectively, and continued for a further 3 weeks. A separate sham-instilled group was formed of five mice, which were administered with saline for 6 weeks. Over the second 3-week period, the effects of disease progression and pharmacological therapy in the four groups of mice were monitored by HPXe MRI metrics of fractional ventilation and gas-exchange function.
Results: Gas-exchange function in BLM mice was significantly reduced after 3 weeks of BLM challenge compared to sham-instilled mice (P < 0.05). Ethyl pyruvate was found to improve HPXe MRI metrics of both ventilation and gas exchange, and repair tissue damage (assessed histologically), to a similar level as sham-instilled mice (P < 0.05), whilst ALG treatment caused no significant improvement of pulmonary function.
Conclusion: This study demonstrates the down-regulator of HMGB1, EP, as a potential therapeutic agent for pulmonary fibrosis, as assessed by a non-invasive HPXe MRI protocol.
Techniques for testis immobilization can facilitate high-resolution MR imaging applications for testicular diseases by assuring good positioning of the testis on small radiofrequency coils and reducing motion artifacts. We tested negative pressure suction to immobilize the testis of rats during MR image acquisitions. Suction pressure between −5 and −10 kPa assured good positioning, suppressed motion artifacts, and allowed the observation of blood vessels and seminiferous tubules.
The purpose was to evaluate the feasibility of quantitative MRI T2 mapping based on the quantitative MRI (QRAPMASTER) sequence for the quantitative assessment of knee cartilage. The T2 values from the phantom study showed excellent correlation between the two techniques (r2 = 0.998). The cartilage T2 values exhibited strong correlations (r2 = 0.867–0.982). Quantitative MRI (qMRI) T2 mapping can be used as an alternative to multi-echo T2 mapping, with relatively short scan time.
To obtain objective and concrete data by physically assessing the quality of breast magnetic resonance images based on the fat-suppression effect by the modified Dixon method (mDixon) and frequency-selective fat suppression (e-Thrive) using an original lipid-content breast phantom that could easily reveal the influence of non-uniform fat suppression in breast magnetic resonance imaging. The fat-suppression uniformity was approximately seven times superior when using mDixon compared with when using e-Thrive. mDixon appears to have a significant advantage.