Magnetic resonance in medical sciences : MRMS : an official journal of Japan Society of Magnetic Resonance in Medicine最新文献

Purpose: To reduce motion artifacts (MA) and noise in brain MRI using deep learning to promote clinical utility.

Methods: T1-weighted (T1W), T2-weighted (T2W), and fluid attenuated inversion recovery (FLAIR) images of the brain (including sagittal, coronal, and axial sections) of 20 healthy volunteers were collected using a 3.0T MR system. Simulated images with horizontal and vertical phase directions exhibiting varying white noise and MA (n = 115200) were created for each sequence and trained in deep learning (36000 pairs), validation (200 pairs), and testing (200 pairs, 2000 pairs) datasets. Images with MA and noise and images without MA and noise were included. A training model was constructed to remove noise and MA. The model's ability to remove noise and MA was evaluated by the structural similarity index (SSIM) and peek signal to noise ratio (PSNR). The SSIM and PSNR between the ground-truth and output images were calculated (SSIMout, PSNRout), and the SSIM and PSNR between the ground-truth and input images were calculated (SSIMinp, PSNRinp). The ratio of SSIMinp to SSIMout was then evaluated as the improvement ratio of SSIM (IMPRs) and the ratio of PSNRinp to PSNRout as the improvement ratio of PSNR (IMPRp). In addition, 10 radio technologists performed visual evaluation.

Results: The SSIMout were >0.95 and 33 dB, respectively, for T1W, T2W, and FLAIR images with different contrasts. The mean value of SSIMinp was 0.72. Noise and MA removal effects were observed in images, with an average value of 72 dB. Visual evaluation revealed that the reduction effect in the output image was higher than that observed in the input image.

Conclusion: The method proposed herein, which uses separate training models for the T1W, T2W, and FLAIR sequences, is a valuable approach for removing MA and noise, independent of the imaging direction and artifact orientation. An improvement in image quality was achieved by generating a large amount of training data through simulation.

Purpose: To investigate whether significant differences exist in labyrinthine lymph fluid signal intensities on non-contrast-enhanced 3D real inversion recovery (3D-real IR) images between patients with and without significant endolymphatic hydrops (EH), potentially enabling the non-contrast detection of EH.

Methods: Thirty-nine patients suspected of having EH underwent 3D-real IR MRI before and 4 hours after intravenous administration of a single dose of gadobutrol. Signal intensities of the cerebrospinal fluid (CSF), perilymph, and endolymph were manually measured on pre-contrast images using ROIs. Patients were categorized into 2 groups based on post-contrast imaging: those with significant EH and those without. Normalized signal intensities (nSIs) of the endolymph were calculated and compared between the groups using the Mann-Whitney U test.

Results: The nSIs of the vestibular endolymph on non-contrast 3D-real IR images were significantly lower in the group with significant EH compared to the group without EH (P  < 0.05), suggesting T1 prolongation in the vestibular endolymph of patients with significant EH. However, considerable overlap was observed in the nSIs between the 2 groups, and significant EH did not always result in T1 prolongation. No significant differences were found in the nSIs of the perilymph or CSF between the groups.

Conclusion: The study suggests that T1 prolongation occurs in the vestibular endolymph in cases of significant EH. This finding indicates the potential for developing non-contrast MRI methods to detect EH and underscores the importance of understanding the mechanisms behind T1 changes in the endolymph. Further research with larger patient cohorts and inclusion of healthy control subjects is necessary to validate these results and to elucidate the pathophysiology of EH in Ménière's disease.

Purpose: To compare diagnostic reliability between an intravoxel incoherent motion (IVIM) imaging and an arterial spin labeling (ASL) in assessment of renal blood flow in rodents.

Methods: We first evaluated 3 different fitting methods on 5 datasets of diffusion-weighted imaging (DWI) with 10 b-values (0-1000 s/mm²) for bi-exponential analysis in IVIM imaging to calculate pseudo-diffusion parameters. Coefficient of variation (CV) for each parameter and correlation among the parameters was assessed to test the robustness of the 3 fitting methods. Subsequently, DWI and ASL methods were performed before and 14 days after onset of acute kidney injury (AKI) in a rat model. Temporal change before and after AKI onset in the pseudo-diffusion parameters in 3 fitting methods was compared with that in the renal blood flow (RBF) derived in the ASL method.

Results: The CVs in all IVIM parameters were the lowest in the fitting method that estimated pseudo-diffusion parameters after a fixed true-diffusion was determined where the pseudo- and true-diffusion coefficients had no correlation. The RBF substantially reduced (~50%, P < 0.001) due to the AKI onset; however, no pseudo-diffusion parameters in any of 3 fitting methods could not detect the change. Further, any pseudo-diffusion parameters showed no correlation with the RBF.

Conclusion: Pseudo-diffusion parameters in the IVIM concept were not reliable to estimate RBF in the study. Since the kidney has a unique profile in the "tissue flow", our data indicate that study design and interpretation of results needs to be carefully considered when IVIM imaging is used for evaluation of blood flow in tissue, especially in the kidney.

Purpose: The purpose of this study was to assess the extent to which improvement in sleep with lemborexant contributed to changes in interstitial fluid dynamics.

Methods: The 3 methods including diffusion tensor image analysis along the perivascular space (DTI-ALPS), dynamic contrast-enhanced method to assess tissue vascular permeability (Ktrans), and choroid plexus volume (CPV) were used. Correlations between these imaging indices and sleep parameters (latency to persistent sleep [LPS], wake after sleep onset [WASO], total sleep time [TST], and sleep efficiency [SE]) were evaluated using Pearson correlation analysis. Additionally, multiple regression analysis and linear mixed model analysis were employed to assess the relationship between baseline sleep status and imaging parameter changes. MRI and sleep assessments were performed before treatment initiation (week 0, w0) and at 12 weeks after lemborexant administration (week 12, w12).

Results: The ALPS-index was inversely correlated with LPS and positively correlated with TST and SE at w0. In multiple regression analysis, ALPS-index was lower when sleep parameters other than LPS were poor at w0. A linear mixed model analysis suggested that poor sleep status in LPS and SE at w0 may have an effect on greater ALPS-index. In the evaluation of Ktrans measurement, the single regression analysis showed a statistically significant correlation between the reduction in Ktrans and the shortening in LPS. Examination of CPV and sleep parameters showed a significant negative correlation between TST and CPV at w0 and w12. Multiple regression analysis also showed that TST of w12 had a significant effect on CPV at w12.

Conclusion: Our results suggested that poor sleep status is related to the greater change of ALPS-index and CPV improvement after lemborexant administration may be related to in part to sleep parameter improvement.

Purpose: To investigate the potential of 4D flow MRI-derived pulmonary hemodynamic parameters as sensitive markers for chronic obstructive pulmonary disease (COPD) patients with right ventricular dysfunction (RVD).

Methods: We enrolled 15 COPD patients combined with RVD and 43 non-RVD participants, all of them underwent pulmonary function tests, thoracic CT and cardiac MR examinations, and the image post-processing analysis was completed. After comparing the 2 groups, the average flow velocity of the main pulmonary artery (Vavg-MPA) and the right pulmonary artery (Vavg-RPA) were identified as statistically significant confounding factors, propensity score matching was used to pair patients controlling for these 2 parameters. Univariate and multivariate logistic regression analyses were performed to assess the pulmonary hemodynamic parameters obtained from 4D flow MRI that could serve as sensitive markers for identifying COPD patients with RVD based on the matched participants dataset.

Results: Fourteen COPD patients combined with RVD and 29 non-RVD participants were successfully matched. Logistic regression analysis showed that the decreased systolic pressure drop along the MRA-RPA tract (odds ratio [OR]: 0.31; 95% confidence interval [CI]: 0.12-0.78; P =0.013) and the presence of vortex (OR: 8.82; 95% CI: 1.11-70.36; P =0.040) were identified as independent risk factors for RVD in COPD patients.

Conclusion: Pulmonary hemodynamic parameters derived from 4D flow MRI, specifically the systolic pressure drop along the MPA-RPA tract and the presence of vortex in the main pulmonary artery, can serve as sensitive indicators for predicting right ventricular dysfunction in COPD patients.

Purpose: This study aimed to quantitatively evaluate whether non-echoplanar diffusion-weighted MRI (non-EP DWI) lesion size and detectability can predict mastoid extension and complications such as labyrinthine fistula and dural exposure in middle ear cholesteatoma.

Methods: This retrospective study included 120 lesions with surgically confirmed middle ear cholesteatoma. Non-EP DWI was performed within 6 months preoperatively and evaluated for lesion detectability and size measurements, including maximum axial diameter, maximum axial area, and volume. Surgical findings were used to assess mastoid extension, labyrinthine fistula, and dural exposure.

Results: Of the 120 lesions, 30 were undetectable and 90 were detectable on non-EP DWI. Undetectable lesions had significantly less mastoid extension or labyrinthine fistula compared to detectable lesions (P < 0.001 - P = 0.006). The undetectable finding on non-EP DWI for identifying mastoid extension-negative lesions showed a sensitivity of 0.59, specificity of 0.95, and for labyrinthine fistula-negative lesions showed a sensitivity of 0.29, specificity of 1.00. Among the 90 detectable lesions, all size parameters (maximum axial diameter, maximum axial area, and volume) were significantly larger in cases with positive mastoid extension and positive labyrinthine fistula compared to negative cases (P < 0.001 - P = 0.005). For dural exposure, the maximum axial diameter and maximum axial area were significantly larger in positive cases (P = 0.002), but volume did not differ significantly. Optimal diagnostic cut-off values were determined for mastoid extension (8.9 mm diameter and 56 mm² area, both with sensitivity 0.89 and specificity 0.97), labyrinthine fistula (82 mm² area, sensitivity 0.47, specificity 1.00), and dural exposure (14.3 mm diameter, sensitivity 0.59, specificity 0.87; 112 mm² area, sensitivity 0.68, specificity 0.73).

Conclusion: Non-EP DWI lesion size and detectability can predict important operative findings in middle ear cholesteatoma. Undetectable lesions on non-EP DWI indicate a lack of mastoid extension or labyrinthine fistula, while larger detectable lesions correlate with increased risks of extension and complications.

Purpose: This study aims to evaluate the predictive value of MRI features for pathologic complete response (pCR) and survival outcomes in patients with breast cancer (BC) undergoing neoadjuvant chemotherapy (NAC).

Methods: A retrospective analysis was conducted on 168 BC patients treated with NAC between 2018 and 2022. Pre-NAC breast MRI scans were evaluated for enhancement patterns, time-intensity curve (TIC), peritumoral edema, and background enhancement. Both pre- and post-NAC MRIs were assessed for Epeak %, mean apparent diffusion coefficient (ADC) value, and ADC ratio (mean ADC of lesion/contralateral normal breast parenchyma). Survival outcomes were analyzed using Kaplan-Meier and Cox regression models.

Results: pCR was achieved in 34% of patients. MRI demonstrated a sensitivity of 74% and a specificity of 86% in predicting pCR, with an overall accuracy of 82%. The post-NAC percentage of initial peak enhancement (Epeak) was significantly lower in the pCR group (P < 0.001). Multivariate analysis identified a pre-NAC Epeak ≤ 96 (hazard ratio [HR]: 6.26, P < 0.001) and a post-NAC Epeak > 188 (HR: 18.40, P < 0.001) as independent risk factors for disease-free survival. Additionally, a lower pre-NAC ADC ratio (≤0.65) was associated with poorer overall survival (HR: 2.8, P: 0.041). Pre-NAC peritumoral edema, background enhancement, and TIC were not significant predictors of survival outcomes.

Conclusion: MRI features, including Epeak % and ADC ratio, are important predictors of pCR and survival outcomes in BC patients undergoing NAC. Incorporating these biomarkers into clinical practice may improve treatment planning and optimize patient outcomes.

Purpose: A cyst-like structure near superior sagittal sinus (Arachnoid Cuff Exit Site cysts: ACES cysts) has been reported in MRI. The purpose of this study was to investigate the association between presence of ACES cysts and cognitive function, as assessed using mini-mental state examination (MMSE) scores.

Methods: We retrospectively analyzed patients who underwent head MRI for dementia screening. Differences in patient ages and MMSE scores between patients with and without ACES cysts were examined using the Mann-Whitney U test. Correlations between patient ages and MMSE scores were examined for patients with and without ACES cysts using Spearman's rank correlation coefficient. Multivariate logistic regression analysis was performed to examine the influence of presence or absence of ACES cysts on MMSE score.

Results: A total of 112 patients (male: 28, female: 84) were included for the analysis. The patient ages ranged from 66 to 94 years (median: 83 years). MMSE scores ranged from 6 to 30 (median: 24). ACES cysts were detected in 57 patients (50.9%). There was no significant difference in patient ages between the patients with and without ACES cysts (P = 0.058). The patients with ACES cysts showed significantly lower MMSE scores compared to the patients without ACES cysts (P < 0.001). In the patients with ACES cysts, there was no significant correlation between patient ages and MMSE scores (ρ = -0.178, P = 0.185), whereas a significant negative correlation was observed in the patients without ACES cysts (ρ = -0.347, P = 0.001). The presence of ACES cysts was determined as an independent predictor for the lower MMSE score (odds ratio = 15.2, 95% confidence interval = 5.59-41.4, P < 0.001).

Conclusion: The presence of the ACES cysts showed significant association with lower MMSE score. ACES cysts might be involved in the pathological processes affecting cognitive function.

Purpose: Hyperthermia is a treatment that applies heat to damage or kill cancer cells and can be also used for drug deliveries. It is important to apply the heat into the specific area in order to target the cancer tissue and avoid damaging healthy tissue. For this reason, the development of heat applicators that have the capability to deliver the heat to the target area is vital. In this study, we present an optimization of an array coil for brain hyperthermia that can be used in combination with MRI, such that the heat can be delivered to the cancer area.

Methods: The array coils were based on optimizing loop coils by varying the capacitor's position along the perimeter. The optimization was performed using electromagnetic simulations, by computing the electric field (E) and temperature inside of the brain and targeting tumor tissues for focus temperature application. The coils were compared with a general-use symmetric coil array for head heating.

Results: The optimization of the coil array was able to focus electric field and make temperature rise at the cancer areas. The temperature in Tumor 1 before and after standard and the proposed method optimization was 43.6°C, 48.3°C, and 42.5°C and for Tumor 2 the temperatures were 44.2°C, 43.1°C, and 42.9°C, respectively. Although the standard optimization method exhibits higher temperatures, it also had higher temperatures outside the tumors area.

Conclusion: We demonstrated the optimization of array coils with different capacitor positions to obtain focused heating temperatures.

Purpose: This study aims to assess thalamocortical tract fiber injury using diffusion-tensor imaging (DTI) and to characterize metabolic alterations in the dorsal thalamus with proton magnetic resonance spectroscopy (MRS) in patients with cervical spondylotic myelopathy (CSM).

Methods: A prospective study involved 98 CSM patients and 66 age-matched controls without neurological disease, recruited from May 2021 to December 2021. Neurological function was evaluated using the modified Japanese Orthopaedic Association (mJOA) score. DTI and MRS were analyzed by 2 experienced radiologists, with statistical analysis performed via SPSS (v.26), including t-tests, chi-square tests, and Pearson's correlation.

Results: DTI revealed significantly lower fractional anisotropy (FA) and higher radial and axial diffusivity in the bilateral postcentral gyrus of CSM patients compared to controls (P < 0.001). MRS showed decreased ratios of N-acetylaspartate (NAA)/creatinine (Cr), choline (Cho)/Cr, and myo-inositol (mI)/Cr in the dorsal thalamus of CSM patients (P < 0.001). Correlation analysis indicated a moderate association between mJOA scores and NAA/Cr and mI/Cr ratios, and a weaker correlation with FA and Cho/Cr.

Conclusion: CSM patients exhibit significant thalamocortical disruptions and metabolic changes in the dorsal thalamus, correlating with clinical severity. These findings suggest that DTI and MRS could provide valuable insights into the extent of neural damage in CSM.