Magnetic resonance imaging (MRI)-based semi-quantitative (SQ) methods applied to knee osteoarthritis (OA) have been introduced during the last decade and have fundamentally changed our understanding of knee OA pathology since then. Several epidemiological studies and clinical trials have used MRI-based SQ methods to evaluate different outcome measures. Interest in MRI-based SQ scoring system has led to continuous update and refinement. This article reviews the different SQ approaches for MRI-based whole organ assessment of knee OA and also discuss practical aspects of whole joint assessment.
Pseudoprogression is regarded as a subacute form of treatment-related change with a reported incidence of 20–30%, occurring predominantly within the first three months after the completion of concurrent chemoradiotherapy (CCRT) in glioblastoma multiforme (GBM) patients. Occurrence of progressive lesions on conventional contrast-enhanced MR imaging may also accompany clinical deterioration, posing considerable diagnostic challenges to clinicians and radiologists. False interpretation of treatment-related change as true progression may lead to the cessation of effective first-line therapy (i.e., adjuvant temozolomide) and unnecessary surgery. Increasing awareness of the diagnostic challenge of the phenomenon has underscored the need for better imaging techniques that may aid in differentiating the treatment-related change from true progression. In this review, we discuss the recent applications of advanced MR imaging such as diffusion-weighted and perfusion-weighted imaging in the evaluation of treatment response in high-grade glioma patients and highlight their potential role in differentiating pseudoprogression from true progression.
Resting-state functional magnetic resonance imaging (RS-fMRI) is used to investigate brain functional connectivity at rest. However, noise from human physiological motion is an unresolved problem associated with this technique. Following the unexpected previous result that group differences in head motion between control and patient groups caused group differences in the resting-state network with RS-fMRI, we reviewed the effects of human physiological noise caused by subject motion, especially motion of the head, on functional connectivity at rest detected with RS-fMRI. The aim of the present study was to review head motion artifact with RS-fMRI, individual and patient population differences in head motion, and correction methods for head motion artifact with RS-fMRI. Numerous reports have described new methods [e.g., scrubbing, regional displacement interaction (RDI)] for motion correction on RS-fMRI, many of which have been successful in reducing this negative influence. However, the influence of head motion could not be entirely excluded by any of these published techniques. Therefore, in performing RS-fMRI studies, head motion of the participants should be quantified with measurement technique (e.g., framewise displacement). Development of a more effective correction method would improve the accuracy of RS-fMRI analysis.
Purpose: To investigate temporal changes in brain metabolites during the first year of life in preterm infants using multivoxel proton magnetic resonance spectroscopy (1H-MRS). Methods: Seventeen infants born at 29 (25–33) gestational week (median, range) weighing 1104 (628–1836) g underwent 1.5-T multivoxel 1H-MRS at 42 postconceptional week (PCW) and at 3, 6, 9, and 12 months after. We measured N-acetyl aspartate (NAA)/creatine (Cr), choline (Cho)/Cr, myo-inositol (Ins)/Cr, NAA/Cho, and Ins/Cho ratios in the frontal lobe (FL) and basal ganglia and thalamus (BG + Th). Linear regression analyses were performed to identify longitudinal changes in infants showing normal imaging findings and normal development. We also evaluated ratios of subjects with abnormal imaging findings and/or development using the 95% confidence intervals (CIs) of regression equations in normal subjects. Results: In the 13 infants with normal development, NAA/Cr and NAA/Cho ratios showed significant positive correlations with PCWs in the FL (r = 0.64 and 0.83, respectively, both P < 0.01) and BG + Th (r = 0.79 and 0.87, respectively, both P < 0.01), while Cho/Cr and Ins/Cr ratios revealed significant negative correlations with PCWs in the FL (r =−0.69 and −0.58, respectively, both P < 0.01) and BG + Th (r =−0.74 and −0.72, respectively, both P < 0.01). Ins/Cho ratios in the FL did not significantly correlate with PCWs (r =−0.19, P = 0.18), while those in the BG + Th showed significant negative correlation with PCWs (r =−0.44, P < 0.01). The metrics in the abnormal group were within the normal group 95% CIs in all periods except a few exceptions. Conclusions: Longitudinal multivoxel MRS is able to detect temporal changes in major brain metabolites during the first year of life in preterm infants.
Purpose: Institutional Review Board (IRB)-approved prospective study was conducted to test whether objective and quantitative hemodynamic markers wall shear stress (WSS) and oscillatory shear index (OSI) measured by three-dimensional (3D) cine phase-contrast (PC) can reflect pulmonary arterial hypertension (PAH). Patients and Methods: Seventeen consecutive patients of suspected secondary PAH were examined for pulmonary artery pressures (PAPs) with right heart catheterization (RHC) and three-dimensional (3D) cine PC MR. Based on the RHC data, patients were subdivided into two groups of 12 non-PAH (median age of 74.5 years) and 5 PAH (median age of 77 years) patients. Based on 3D cine PC magnetic resonance (MR), hemodynamic parameters including spatially averaged systolic WSS (sWSS), diastolic WSS (dWSS), mean WSS (mWSS), OSI and blood vessel section area (BVSA) at the pulmonary arterial trunk were calculated. Streamline images in the pulmonary arteries were also assessed. All the parameters were compared between non-PAH and PAH groups. Results: sWSS (N/m2) and mWSS (N/m2) of PAH group was lower than that of non-PAH group (0.594 ± 0.067 vs. 0.961 ± 0.590, P = 0.001), (0.365 ± 0.035 vs. 0.489 ± 0.132, P = 0.027). OSI of PAH group was higher than that of non-PAH (0.214 ± 0.026 vs. 0.130 ± 0.046, P = 0.001). sWSS, mWSS, and dWSS were inversely correlated and OSI was positively correlated to mean PAP or systolic PAP with r values of −0.638 (P = 0.005), −0.643 (P = 0.005), −0.485 (P = 0.049), and 0.625 (P = 0.007); or −0.622 (P = 0.008), −0.629 (P = 0.007), −0.484 (P = 0.049), and 0.594 (P = 0.012), respectively. sWSS was also inversely correlated to BVSA with r value of −0.488 (P = 0.049), and OSI was correlated to BVSA with r value of 0.574 (P = 0.016). Vortex or helical flows were observed more frequently in PAH patients. Conclusions: The low sWSS and mWSS as well as high OSI measured with 3D cine PC MR could be potential hemodynamic markers for the increased PAP in suspected secondary PAH patients.
Purpose: To compare the signal increase in cochlear lymph fluid on three-dimensional fluid-attenuated inversion recovery (3D-FLAIR) in patients with sudden sensorineural hearing loss (SNHL) between regular contrast 3D-FLAIR (FL) and heavily T2-weighted 3D-FLAIR (HF). Methods: Twenty-five patients with unilateral sudden SNHL and eight healthy volunteers were included. Patients were divided into two groups: the mild group consisted of 9 patients, with an average hearing level of 60 dB or less; the severe group consisted of 16 patients, with an average hearing level of more than 60 dB. All patients and healthy volunteers underwent magnetic resonance (MR) cisternography for anatomical reference of the fluid space with FL and HF at 3 T. The region of interest (ROI) was manually drawn on the mid-modiolar section of the MR cisternography around the cochlea. The ROI for noise was drawn within the air space. ROIs were copied onto the FL and HF images. The contrast-to-noise ratio (CNR) between the affected and non-affected ear was measured in the patient group and the CNR between the right and left ear was also measured in the control group. Differences in the CNR on FL and HF images among the three groups were tested by one-way analysis of variance (ANOVA). Results: There was a statistically significant difference in mean CNR on HF among the three groups (P < 0.001). Furthermore, based on pairwise comparisons, there was a statistically significant difference between them in mean CNR on HF (P < 0.05). There was no statistically significant difference in mean CNR on FL among the three groups (P = 0.074). Conclusions: HF is more sensitive to signal alterations in cochleae with sudden SNHL than FL.
Purpose: To evaluate morphological and signal intensity (SI) changes of placental insufficiency on magnetic resonance imaging (MRI) and to assess morphological changes and decreased flow voids (FVs) on T2-weighted rapid acquisition with relaxation enhancement (RARE) images for diagnosing placental insufficiency. Methods: Fifty singleton fetuses underwent MRI using a 1.5-T MR scanner. Placental thickness, area, volume, SI, amniotic fluid SI, and size of FVs between the uterus and the placenta were measured on MR images. Two radiologists reviewed T2-weighted RARE images for globular appearance of the placenta and FVs between the uterus and the placenta. Data were analyzed using t-tests, McNemar’s tests, and areas under the receiver operating characteristic curve (AUCs) at 5% level of significance. Results: Twenty-five of the 50 pregnancies were categorized as having an insufficient placenta. Significant differences were observed between insufficient and normal placentas in mean placental thickness, area, volume, placenta to amniotic fluid SI ratio, and size of FVs (49.0 mm vs. 36.9 mm, 1.62 × 104 mm2 vs. 2.67 × 104 mm2, 5.13 × 105 mm3 vs. 6.56 × 105 mm3, 0.549 vs. 0.685, and 3.4 mm vs. 4.3 mm, respectively). The sensitivity and accuracy using globular appearance plus decreased FVs were greater than those using decreased FVs (P < 0.01). There was no significant difference among AUCs using globular appearance and decreased FVs, and globular appearance plus decreased FVs. Conclusions: Placental insufficiency was associated with placental thickness, area, volume, placenta to amniotic fluid SI ratio, and size of FVs. Evaluating FVs on T2-weighted RARE images can be useful for detecting placental insufficiency, particularly in placentas without globular appearance on MR images.
Objectives: To assess the detectability of a low-signal-intensity line within adenomyosis lesions adjacent to the endometrium on apparent diffusion coefficient (ADC) maps, and to establish correlations between these lesions and their possible causes, and more particularly the hormonal changes and magnetic resonance (MR) factors. Materials and methods: MR images were obtained from 110 patients with adenomyosis (age 30–57 y.o.) using 3.0 T or 1.5 T MR units. Recognition of the low-signal-intensity line on ADC map was scored using confidence level. The correlation between recognition of the line and the following factors were examined: magnetic field strength, age group, menstrual cycle phases, history of delivery, and hormonal treatments. Presence of the structure corresponding to the low-signal-intensity line on ADC map was evaluated pathologically in the cases that underwent surgery. Results: The low-signal-intensity line visible on ADC map was recognized in 55/110 patients. The visibility of the line was not significantly related to hormonal status, age, history of delivery, or magnetic resonance imaging (MRI) magnet strength. There were no corresponding pathological structures. Conclusion: One half of the adenomyosis patients showed discrepant appearances in T2-weighted (T2WI) vs. ADC map, but no significant relationship with hormonal changes was found in this study. This result may suggest that the low-signal-intensity line within the junctional zone may be related to a functional phenomenon.
Purpose: Gadobutrol 1.0 M is macrocyclic gadolinium-based contrast agent for magnetic resonance imaging (MRI). This multicenter, open-label, phase 3 study aimed to investigate the efficacy and safety of gadobutrol-enhanced versus unenhanced MRI in the visualization and diagnosis of central nervous system (CNS) lesions in Japanese patients.
Methods: A total of 223 patients referred for contrast-enhanced MRI of the CNS underwent unenhanced and gadobutrol-enhanced (0.1 mmol/kg body weight) MRI. The unenhanced and combined (unenhanced and enhanced) images were evaluated by three independent readers in a blinded manner for degree of contrast enhancement, border delineation, internal morphology, and number of detected lesions (primary variables), and for primary diagnosis and diagnostic confidence. Final clinical diagnoses were established by an independent truth committee consisting of two neurosurgeons. Sensitivity, specificity, and accuracy were calculated for the detection of malignancy and the preciseness of diagnoses (secondary variables) by comparing the results obtained by the blinded readers and the truth committee. Results: Gadobutrol enhancement significantly improved three visualization parameters in MR images: contrast enhancement, border delineation, and internal morphology (P < 0.0001). Non-inferiority was achieved for mean number of lesions detected. Gadobutrol-enhanced imaging provided significant improvements in sensitivity and accuracy for the detection of malignant disease with no loss in specificity, and also improvements in accuracy of exact match diagnosis and diagnostic confidence. Drug-related adverse events were reported in 6 out of 223 patients (2.7%); all were non-serious. Conclusion: Gadobutrol is an effective and well-tolerated contrast agent for MR imaging of the CNS.
Purpose: To determine the appropriateness of statistical models using the truncated Gaussian distribution and gamma distribution for diffusion signal decay, and to assess the correlation between the parameters obtained from the statistical models and estimated glomerular filtration rate (eGFR). Methods: Twenty-nine patients with chronic kidney disease and 21 healthy volunteers were included and classified in four groups according to eGFR (ml/min/1.73 m2): group 1 (90 ≤ eGFR, n = 10), group 2 (eGFR 60–90, n = 15), group 3 (eGFR 30–60, n = 17), and group 4 (eGFR < 30, n = 8). Diffusion-weighted imaging using five b-values (0, 500, 1000, 1500, and 2000 s/mm2) was performed. Truncated Gaussian and gamma models were compared for goodness of fit. Area fractions for the diffusion coefficient D < 1.0 × 10−3 mm2/s (Frac < 1.0) and D > 3.0 × 10−3 mm2/s (Frac > 3.0) obtained from the statistical model were compared among four groups. Correlation between proposed parameters and conventional apparent diffusion coefficient (ADC) with eGFR was calculated. Results: There was no significant difference in goodness of fit between the truncated Gaussian and gamma models. Frac < 1.0 and Frac > 3.0 showed good correlation with eGFR, as did ADC. Comparison between groups 1 and 2 showed that only Frac < 1.0 in both distribution models had significant differences. Conclusion: Statistical models yield robust interpretation of diffusion magnetic resonance (MR) signals with relevance to histological changes in the kidney. The parameters of the statistical models, particularly Frac < 1.0, strongly correlated with eGFR.
In the present study, we have performed a statistical analysis to investigate damages in magnetic resonance (MR) scanners caused by the Great East Japan Earthquake (GEJE, magnitude 9.0) and evaluated whether these disaster-prevention technologies contributed to the reduction of damages in the GEJE or not. It was confirmed that the extent of damage was significantly different between seismic scale (SS) 5 and SS over 6. Our survey study demonstrated that anchoring of MR facilities reduced damages due to quakes and demonstrated that anchoring is an efficient method for quake-induced damage prevention. The odds ratio revealed that base isolation was very useful to prevent damages in MR scanners.
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