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

Purpose: Peritumoral enhancement (PTE) on dynamic contrast-enhanced MRI is a highly specific imaging feature of muscle-invasive bladder cancer (MIBC). However, the histopathological basis of PTE remains unclear. This study aimed to elucidate the pathological substrates underlying PTE, by correlating MRI findings with quantitative histopathological analysis.

Methods: This retrospective cross-sectional study included 14 patients with pathologically confirmed MIBC who underwent preoperative multiparametric MRI followed by radical cystectomy. PTE was assessed on preoperative dynamic contrast-enhanced MRI by 4 experienced radiologists, and its thickness was measured. Postoperatively, histopathological evaluation was performed in 3 regions: intratumoral area (ITA), peritumoral area (PTA), and non-tumoral muscularis propria (MP). Fibrosis was quantified using Masson trichrome staining, T-lymphocytes using CD8 immunohistochemistry, and microvessels using CD31 immunostaining. Quantitative spot-based analysis and continuous ROI-based spatial analysis were performed along the invasive front of the tumor. Regional comparisons were conducted using the Wilcoxon signed-rank test with Bonferroni correction.

Results: PTE thickness on MRI ranged from 1 to 2 mm (median, 1.5 mm), spatially corresponding to the histologically defined PTA. The fibrosis area fraction was significantly higher in the PTA than the ITA and MP (all P < 0.001), with continuous spatial analysis demonstrating a distinct peak immediately outside the tumor invasive margin. T-lymphocyte counts and area fractions were significantly higher in both the ITA and PTA than in the MP, with no significant differences between the ITA and PTA. The number of microvessels was significantly higher in the PTA than in the MP, but did not differ significantly between the PTA and ITA. Microvessel density was significantly higher in the PTA than in both the ITA and MP.

Conclusion: PTE reflects localized stromal remodeling at the tumor invasive front, characterized predominantly by marked peritumoral fibrosis accompanied by increased microvessel density.

Purpose: Cranial nerve imaging with 3T MRI commonly uses 3D fast imaging employing steady-state acquisition (3D-FIESTA); however, this sequence has limitations in achieving higher spatial resolution and provides poor tissue contrast between cranial nerves and adjacent vascular structures. We evaluated 3D T2-weighted imaging (T2-CUBE) with deep learning-based reconstruction (DLR) for cranial nerve visualization, focusing on the trochlear nerve, the smallest cranial nerve with the longest intracranial course, and compared it with T2-CUBE without DLR and 3D-FIESTA.

Methods: Ten healthy male volunteers (age, 23-40 years; mean age, 32 years) underwent T2-CUBE with and without DLR, and 3D-FIESTA at 3T. Two neuroradiologists independently evaluated trochlear nerve visualization in 4 anatomical segments (origin from the midbrain, cisternal, tentorial, and anterior portion of its cavernous segments) using a 3-point scale, and SNR of the pons (SNR_PONS) and cerebrospinal fluid (SNR_CSF) were calculated.

Results: T2-CUBE with DLR achieved a 100% visualization across all trochlear nerve segments and demonstrated significantly better visualization than both T2-CUBE without DLR and 3D-FIESTA (P < 0.025). T2-CUBE without DLR showed 67.5%-100% visualization across the 4 segments. 3D-FIESTA showed 32.5%-80% visualization of the origin from the midbrain, cisternal, and tentorial segments, with no visualization of the cavernous segments. DLR increased SNR_PONS and SNR_CSF by factors of 1.8-2.5 (SNR_PONS: 14.1 vs 5.7; SNR_CSF: 31.8 vs 17.5, respectively; P < 0.001). T2-CUBE with DLR demonstrated significantly higher SNR_PONS than 3D-FIESTA (14.1 vs 6.4, P < 0.001), while SNR_CSF was comparable (31.8 vs 36.3, P = 0.20).

Conclusion: T2-CUBE with DLR at 3T provided a significantly better trochlear nerve visualization than T2-CUBE without DLR and 3D-FIESTA. This technique may extend beyond the trochlear nerve to other cranial nerves and to the evaluation of neurovascular compression in the cistern, with the potential to become the new standard for cisternal imaging.

Whole-body MRI (WB-MRI) has evolved over the past 2 decades as a noninvasive imaging technique for detecting distant metastases in prostate cancer. Since the introduction of diffusion-weighted imaging with background body signal suppression by Takahara et al. in 2004, its clinical use has expanded rapidly, particularly in the detection of bone metastases. WB-MRI offers whole-body coverage without radiation exposure and can be completed within approximately 30 minutes, making it suitable for repeated examinations. Consequently, it is now applied not only for metastasis detection but also for treatment response evaluation. Diffusion-weighted imaging further enables semi-quantitative assessment of tumor burden by measuring total tumor diffusion volume. Nevertheless, manual processing and interinstitutional standardization remain limitations that hinder widespread clinical adoption. Recent advances in deep learning and quantitative imaging are expected to overcome these issues through automated lesion extraction and volumetric analysis. Moreover, comparative studies have shown that WB-MRI and prostate-specific membrane antigen positron emission tomography can serve as complementary modalities. The integration of both techniques will enhance diagnostic accuracy, facilitate individualized treatment strategies, and contribute to establishing WB-MRI as a next-generation imaging standard in prostate cancer management.

Purpose: To evaluate the monitoring value of T1 and T2 mapping in assessing kidney injury associated with chronic liver disease and the therapeutic efficacy of bone marrow mesenchymal stem cells (BMSCs) treatment.

Methods: Thirty-six rats were divided into 6 subgroups (n = 6/group) and underwent MRI scanning at 0, 2, 4, 6, 8, and 12 weeks, respectively, followed by biochemical and histological analyses. Seven rats underwent continuous MRI scanning to monitor changes in imaging parameters. Twenty-four rats divided into BMSC and control group. Six rats per group were subjected to serial MRI scans at weeks 13, 14, 15, and 16, another six rats per group were scanned at week 14 and then sacrificed for biochemical and renal histological analysis.

Results: From baseline to 12 weeks, renal hematoxylin and eosin (HE) scores and α-smooth muscle actin (α-SMA) levels increased significantly, and similar trends were found in renal T1 and T2 values. Following BMSCs injection, both BMSC and control groups exhibited reductions in HE scores and α-SMA levels, with BMSC group demonstrating more substantial decreases. Renal T1 and T2 values declined in both groups, with the BMSC group showing significantly lower T2 values than the control group. Strong correlations were found between renal T1/T2 values and HE scores, α-SMA levels (|r|=0.419-0.724). The area under the curve values for T1 and T2 in differentiating renal injury severity across different renal strips were from 0.793 to 0.930.

Conclusion: T1 and T2 mapping can effectively monitor renal injury progression in chronic liver disease, with T2 values demonstrating greater potential for assessing the therapeutic efficacy of BMSCs.

Purpose: This study aimed to assess the potential enhancement of image quality in fast-spin-echo T2-weighted images (FSE-T2WI) with respiratory-gating compared to conventional FSE-T2WI and to clarify how abdominal wall motion affects uterine displacement and consequently impacts image quality.

Methods: One hundred and three women who underwent pelvic MRI using a 3T-MRI scanner were enrolled. FSE-T2WI with and without respiratory-gating was visually assessed for motion-related artifacts, and the image quality was categorized as poor, moderate, or excellent. The uterus was classified as type 1 (on the bladder), type 2 (not on the bladder and not retroflexed), or type 3 (uterus contacting the vertebrae or a retroflexed uterus). The relationships (1) between the abdominal wall and uterine displacements, (2) between the quality of FSE-T2WI with and without respiratory-gating and uterine displacement, and (3) between uterine displacement and types were investigated.

Results: Respiratory-gated FSE-T2WI achieved better overall image quality, with poor, moderate, and excellent ratings observed in 27, 44, and 32 patients, respectively, compared with 53, 34, and 16 patients for conventional FSE-T2WI. Improvement with respiratory-gating was observed in 43 patients, particularly in those with type 1 and type 2 uteri, whereas only 8 patients showed decreased image quality. A strong correlation was found between abdominal wall and uterine displacements (P < 0.001), indicating that uterine motion is largely driven by respiration. The amplitude of uterine displacement was significantly smaller in type 3 uteri (P < 0.05), consistent with fewer motion-related artifacts.

Conclusion: Respiratory-gated FSE-T2WI effectively reduces motion artifacts caused by respiratory-induced uterine displacement, particularly in type 1 and type 2 uteri where displacement is pronounced.

Purpose: This work aims to overcome an assumption of conventional MR simulators: Individual isochromats should be simulated individually.

Methods: To reduce the computational times of MR simulation, a new simulation method using grouped isochromats is proposed. When multiple isochromats are grouped before simulations, some parts of the simulation can be shared in each group. For a certain gradient type, the isochromats in the group can be easily chosen for ensuring that they behave the same. For example, the group can be defined as the isochromats whose locations along x-axis, T1, T2 and magnetic field inhomogeneity values are the same values. In such groups, simulations can be combined when a pulse sequence with the magnetic field gradient along x-axis only are processed. The processing times of the conventional and proposed methods were evaluated with several sequences including echo-planar imaging (EPI) and spiral sequences.

Results: The simulation times of the proposed method were 1.7 to 161 times faster than those of the conventional methods. In the cases of 2.3 billion isochromats using single instruction, multiple data (SIMD) instructions and multi-threading, the conventional method simulated the EPI and spiral sequences in 5526.7 and 15678.4 seconds, respectively. In the same cases, the proposed method simulated these sequences in 652.2 and 8046.2 seconds, respectively.

Conclusion: The proposed method using grouped isochromats was efficient for reducing the computational times of the simulations.

This study evaluated the utility of deep learning reconstruction (DLR) in vessel wall imaging (VWI) for visualizing the entire cerebral arterial system, including cortical arteries. Seventeen patients underwent post-contrast 3D T1WI-CUBE VWI with 0.5 mm isotropic resolution. Images with and without DLR were compared using qualitative and quantitative assessments. Qualitative image quality was rated on a 4-point scale across 29 arterial segments, including the internal carotid, vertebral, basilar, and the 1st to 4th segments of the major cerebral arteries. Quantitative evaluation of the vertebral artery wall assessed SNR and contrast-to-noise ratio (CNR). DLR significantly improved overall image quality compared to the without-DLR group, with cortical arteries rated as optimal in all cases with DLR (all P < 0.001). SNR and CNR were also significantly higher with DLR (P = 0.004). These results suggest that DLR enables high-resolution VWI of intracranial cortical arteries within a clinically acceptable scan time.

Purpose: To evaluate the clinical utility of macromolecular proton fraction mapping for early osteoarthritis detection and compare its effectiveness with T₂* mapping in evaluating cartilage degeneration.

Methods: Eleven controls and 29 patients with osteoarthritis underwent 3.0T magnetic resonance imaging. Patients were classified based on the Kellgren-Lawrence grading system into mild osteoarthritis (KL 1-2, n = 9) and severe (KL 3-4, n = 20) osteoarthritis. Macromolecular proton fraction maps were generated from proton density-, T₁-, and magnetization transfer-weighted images using a single-point synthetic reference algorithm. T₂* maps were derived from multi-echo sequences. Macromolecular proton fractions and T₂* values were measured in 6 subregions of the femoral cartilage. Statistical analyses were conducted to compare values among the control, mild osteoarthritis, and severe osteoarthritis groups.

Results: Macromolecular proton fraction values decreased with increasing osteoarthritis severity. Compared to controls, both the mild and severe osteoarthritis groups exhibited significantly lower macromolecular proton fraction in the medial anterior and medial posterior regions. Additionally, the severe osteoarthritis group demonstrated significantly lower macromolecular proton fraction values in the medial central and lateral posterior regions compared to controls. In contrast, T₂* values generally increased with osteoarthritis severity. The mild and severe osteoarthritis groups had significantly elevated T₂* values in the medial anterior region compared to controls. Furthermore, the mild osteoarthritis group exhibited increased T₂* in the medial central region, whereas the severe osteoarthritis group had significantly higher T₂* in the medial anterior, medial posterior, and lateral posterior regions compared to controls.

Conclusion: Macromolecular proton fraction mapping demonstrated sensitivity to early-stage cartilage degeneration in osteoarthritis, suggesting its potential as a biomarker for early osteoarthritis detection. The combination of macromolecular proton fraction and T₂* mapping could enhance the biochemical assessment of cartilage integrity, providing valuable insights for early diagnosis and monitoring treatment effects in osteoarthritis.

Purpose: To evaluate whether periodically rotated overlapping parallel lines with enhanced reconstruction-diffusion-weighted imaging (PROPELLER-DWI) combined with deep learning-based reconstruction (DLR) improves head and neck DWI, we conducted a primary comparison of PROPELLER-DWI with DLR at varying strengths and without DLR, and a secondary comparison of DLR-processed PROPELLER-DWI with DLR-processed single-shot echo-planar imaging (EPI)-DWI.

Methods: Ten healthy adults (8 males, 2 females) participated in the study. PROPELLER-DWI and single-shot EPI-DWI images were acquired using a 3-Tesla MRI system (Discovery MR750w; GE Healthcare, Waukesha, WI, USA) with various recon deep-learning strength (DLS) values: off (DLS-Off), low (DLS-L), medium (DLS-M), and high (DLS-H). We measured the SNR and contrast ratio on DWI images and value of coefficient of variation (CV) on apparent diffusion coefficient (ADC) maps for a quantitative evaluation. For a qualitative evaluation, we visually evaluated the overall image quality, degree of geometric distortion, and magnetic susceptibility artifacts.

Results: The SNRs for PROPELLER and EPI-DWI improved with the increase in the DLS level, with DLS-H showing a significantly higher SNR than DLS-Off. ADC maps demonstrated lower CVs at higher DLS levels, significantly lower in DLS-H than DLS-Off. The qualitative evaluation revealed that PROPELLER-DWI with DLR (at all DLS levels: -L, -M, and -H) provided significantly better overall image quality than that without DLR. In addition, PROPELLER-DWI demonstrated significantly higher qualitative scores across all evaluation items (i.e., overall image quality, geometric distortion, and magnetic susceptibility artifacts) compared with EPI-DWI.

Conclusion: In head and neck DWI, PROPELLER-based acquisition with DLR enabled the acquisition of visually superior image quality. This approach is clinically useful for the head and neck radiology.