Single-shot Diffusion-weighted Imaging Research Articles

Improved Value of Multiplexed Sensitivity Encoding DWI with Reversed Polarity Gradients in Diagnosing Prostate Cancer: A Comparison Study with Single-Shot DWI and MUSE DWI

This study aimed to investigate the value of multiplexed sensitivity encoding with reversed polarity gradients in improving the quality of diffusion-weighted imaging (DWI) images of the prostate and the diagnostic efficacy of prostate cancer. Seventy-three patients with prostate disease underwent multiplexed sensitivity encoding with reversed polarity gradients (RPG-MUSE), multiplexed sensitivity encoding (MUSE), and single-shot echo-planar imaging (ssEPI) DWI. Three radiologists performed a qualitative image analysis of the three DWI sequences. Qualitative image analysis included artifact minimization, anatomical detail, and sharpness of prostate edges. Two radiologists measured the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), geometric distortion rate, and the apparent diffusion coefficient (ADC) values of the prostate disease tissue. Two radiologists jointly performed Prostate Imaging Reporting and Data System scoring of prostate lesions and compared the diagnostic efficacy of the three DWI sequences for prostate cancer. There was good agreement among radiologists in the evaluation and measurement of the three DWI sequence images (intraclass correlation coefficient >0.75, P<0.05). The RPG-MUSE DWI images were rated higher than those of MUSE and ssEPI in terms of artifact minimization, anatomical details, and sharpness of prostate edges (P<0.05). The SNR and CNR of the RPG-MUSE DWI images were higher than those of MUSE and ssEPI (P<0.05), and the geometric distortion rate was lower than that of the other two sequences (P<0.05). There were no statistical differences in ADC values between the three DWI sequences (P>0.05). The diagnostic efficacy of RPG-MUSE and MUSE DWI was higher than that of ssEPI (P<0.017). RPG-MUSE can reduce the artifacts and geometric distortion in DWI images of the prostate, improve the SNR and CNR of the images, improve the clarity of anatomical details and boundaries without affecting the measurement of ADC values, has the potential to improve the diagnostic efficacy of prostate lesions, and facilitates the clear display and accurate assessment of prostate lesions.

MRI: Evaluating the Application of FOCUS-MUSE Diffusion-Weighted Imaging in the Pancreas in Comparison With FOCUS, MUSE, and Single-Shot DWIs.

Diffusion-weighted imaging (DWI) is a useful technique to detect pancreatic lesion. In DWIs, field-of-view optimized and constrained undistorted single-shot (FOCUS) can improve the spatial resolution and multiplexed sensitivity-encoding (MUSE) can gain a high signal-to-noise ratio (SNR). Based on the advantage of FOCUS and MUSE, a new DWI sequence-named FOCUS-MUSE DWI (FOCUS combined with MUSE)-was developed to delineate the pancreas. To investigate the reliability of FOCUS-MUSE DWI compared to FOCUS, MUSE and single-shot (SS) DWI via the systematical evaluation of the apparent diffusion coefficient (ADC) measurements, SNR and image quality. Prospective. A total of 33 healthy volunteers and 9 patients with pancreatic lesion. A 3.0 T scanner. FOCUS-MUSE DWI, FOCUS DWI, MUSE DWI, SS DWI. For volunteers, ADC and SNR were measured by two readers in the pancreatic head, body, and tail. For all subjects, the diagnostic image quality score was assessed by three other readers on above four DWIs. Paired-sample T-test, intraclass correlation (ICC), Bland-Altman method, Friedman test, Dunn-Bonferroni post hoc test and kappa coefficient. A significance level of 0.05 was used. FOCUS-MUSE DWI had the best intersession repeatability of ADC measurements (head: 59.53, body: 101.64, tail: 42.30) among the four DWIs, and also maintained the significantly highest SNR (reader 1 [head: 19.68 ± 3.23, body: 23.42 ± 5.00, tail: 28.85 ± 4.96], reader 2 [head: 19.93 ± 3.52, body: 23.02 ± 5.69, tail: 29.77 ± 6.33]) except for MUSE DWI. Furthermore, it significantly achieved better image quality in volunteers (median value: 4 score) and 9 patients (most in 4 score). FOCUS-MUSE DWI improved the reliability of pancreatic images with the most stable ADC measurement, best image quality score and sufficient SNR among four DWIs. 2 TECHNICAL EFFICACY: Stage 2.

Role of diffusion-weighted imaging in carotid plaque vulnerability assessment

BackgroundMR plaque imaging is a valuable tool in characterizing carotid atherosclerotic plaque and identifying high-risk features. There are limited data on the role of the widely available single-shot diffusion-weighted imaging (DWI) in plaque characterization along with histological correlation. This study aimed to correlate the plaque characteristics identified by MR imaging in vivo at the level of maximum stenosis with histological plaque characteristics in the postoperative specimen.MethodsPatients who underwent carotid endarterectomy in a tertiary care center during one and half years were prospectively recruited for non-contrast MR carotid plaque imaging (including single-shot EPI-DWI sequence) in a 3 Tesla MRI using a dedicated carotid coil. An experienced radiologist correlated DWI sequence findings with histopathology of postsurgical sections to confirm the high-risk features.ResultsTwenty-three patients (mean age 66.1 years ± SD 6.25) were evaluated, of which 65% were males and 96% were symptomatic. Apparent diffusion coefficient (ADC) values in location of plaques could differentiate histopathological unstable from stable plaques (0.83 × 10–3 mm2/s vs 1.7 × 10–3 mm2/s; p 0.001), with a sensitivity and specificity of 75% and 79%, respectively, at an ADC cutoff of 1.24 × 10–3 mm2/s. Plaques with and without lipid-rich necrotic core (0.86 × 10–3 mm2/s vs 1.44 × 10–3 mm2/s; p = 0.042) as well as intraplaque hemorrhage could be differentiated (0.751 × 10–3 mm2/s vs 1.352 × 10–3 mm2/s; p 0.037) using the apparent diffusion coefficients.ConclusionThe widely available single-shot EPI-DWI in assessing plaque characteristics in carotid stenosis is promising and correlated with histopathological features. Diffusion-weighted imaging will be a helpful adjunct in patients when contrast administration is intolerable.

Multi-shot Diffusion-Weighted MRI With Multiplexed Sensitivity Encoding (MUSE) in the Assessment of Active Inflammation in Crohn's Disease.

Single-shot diffusion-weighted imaging (ssDWI) has been shown useful for detecting active bowel inflammation in Crohn's disease (CD) without MRI contrast. However, ssDWI suffers from geometric distortion and low spatial resolution. To compare conventional ssDWI with higher-resolution ssDWI (HR-ssDWI) and multi-shot DWI based on multiplexed sensitivity encoding (MUSE-DWI) for evaluating bowel inflammation in CD, using contrast-enhanced MR imaging (CE-MRI) as the reference standard. Prospective. Eighty nine patients with histological diagnosis of CD from previous endoscopy (55 male/34 female, age: 17-69 years). FIELD STRENGTH/SEQUENCES: ssDWI (2.7 mm × 2.7 mm), HR-ssDWI (1.8 mm × 1.8 mm), MUSE-DWI (1.8 mm × 1.8 mm) based on echo-planar imaging, T2-weighted imaging, and CE-MRI sequences, all at 1.5 T. Five raters independently evaluated the tissue texture conspicuity, geometry accuracy, minimization of artifacts, diagnostic confidence, and overall image quality using 5-point Likert scales. The diagnostic performance (sensitivity, specificity and accuracy) of each DWI sequences was assessed on per-bowel-segment basis. Inter-rater agreement for qualitative evaluation of each parameter was measured by the intra-class correlation coefficient (ICC). Paired Wilcoxon signed-rank tests were performed to evaluate the statistical significance of differences in qualitative scoring between DWI sequences. A P value <0.05 was considered to be statistically significant. Tissue texture conspicuity, geometric distortions, and overall image quality were significantly better for MUSE-DWI than for ssDWI and HR-ssDWI with good agreement among five raters (ICC: 0.70-0.89). HR-ssDWI showed significantly poorer performance to ssDWI and MUSE-DWI for all qualitative scores and had the worst diagnostic performance (sensitivity of 57.0% and accuracy of 87.3%, with 36 undiagnosable cases due to severe artifacts). MUSE-DWI showed significantly higher sensitivity (97.5% vs. 86.1%) and accuracy (98.9% vs. 95.1%) than ssDWI for detecting bowel inflammation. MUSE-DWI was advantageous in assessing bowel inflammation in CD, resulting in improved spatial resolution and image quality. 2 TECHNICAL EFFICACY STAGE: 2.

Multishot Diffusion-Weighted MRI of the Breast With Multiplexed Sensitivity Encoding (MUSE) and Shot Locally Low-Rank (Shot-LLR) Reconstructions.

Diffusion-weighted imaging (DWI) has shown promise to screen for breast cancer without a contrast injection, but image distortion and low spatial resolution limit standard single-shot DWI. Multishot DWI methods address these limitations but introduce shot-to-shot phase variations requiring correction during reconstruction. To investigate the performance of two multishot DWI reconstruction methods, multiplexed sensitivity encoding (MUSE) and shot locally low-rank (shot-LLR), compared to single-shot DWI in the breast. Prospective. A total of 45 women who consented to have multishot DWI added to a clinically indicated breast MRI. Single-shot DWI reconstructed by parallel imaging, multishot DWI with four or eight shots reconstructed by MUSE and shot-LLR, 3D T2 -weighted imaging, and contrast-enhanced MRI at 3T. Three blinded observers scored images for 1) general image quality (perceived signal-to-noise ratio [SNR], ghosting, distortion), 2) lesion features (discernment and morphology), and 3) perceived resolution. Apparent diffusion coefficient (ADC) of the lesion was also measured and compared between methods. Image quality features and perceived resolution were assessed with a mixed-effects logistic regression. Agreement among observers was estimated with a Krippendorf's alpha using linear weighting. Lesion feature ratings were visualized using histograms, and correlation coefficients of lesion ADC between different methods were calculated. MUSE and shot-LLR images were rated to have significantly better perceived resolution (P < 0.001), higher SNR (P < 0.005), and a lower level of distortion (P < 0.05) with respect to single-shot DWI. Shot-LLR showed reduced ghosting artifacts with respect to both MUSE (P < 0.001) and single-shot DWI (P < 0.001). Eight-shot DWI had improved perceived SNR and perceived resolution with respect to four-shot DWI (P < 0.005). Multishot DWI enables increased resolution and improved image quality with respect to single-shot DWI in the breast. Shot-LLR reconstructs multishot DWI with minimal ghosting artifacts. The improvement of multishot DWI in image quality increases with an increased number of shots. 2 TECHNICAL EFFICACY STAGE: 2.

Minimizing the echo time in diffusion imaging using spiral readouts and a head gradient system.

Diffusion weighted imaging (DWI) is commonly limited by low signal-to-noise ratio (SNR) as well as motion artifacts. To address this limitation, a method that allows to maximize the achievable signal yield and increase the resolution in motion robust single-shot DWI is presented. DWI was performed on a 3T scanner equipped with a recently developed gradient insert (gradient strength: 200 mT/m, slew rate: 600 T/m/s). To further shorten the echo time, Stejskal-Tanner diffusion encoding with a single-shot spiral readout was implemented. To allow non-Cartesian image reconstruction using such strong and fast gradients, the characterization of eddy current and concomitant field effects was performed based on field-camera measurements. An echo time of only 19 ms was achieved for a b-factor of 1000 s/mm2 . An in-plane resolution of 0.68 mm was encoded by a single-shot spiral readout of 40.5 ms using 3-fold undersampling. The resulting images did not suffer from off-resonance artifacts and blurring that are common to single-shot images acquired with regular gradient systems. Spiral diffusion imaging using a head gradient system, together with an accurate characterization of the encoding process allows for a substantial reduction of the echo time, and improves the achievable resolution in motion-insensitive single-shot DWI.

High-Spatial-Resolution Multishot Multiplexed Sensitivity-encoding Diffusion-weighted Imaging for Improved Quality of Breast Images and Differentiation of Breast Lesions: A Feasibility Study.

Multishot multiplexed sensitivity-encoding diffusion-weighted imaging is a feasible and easily implementable routine breast MRI protocol that yields high-quality diffusion-weighted breast images.Purpose: To compare multiplexed sensitivity-encoding (MUSE) diffusion-weighted imaging (DWI) and single-shot DWI for lesion visibility and differentiation of malignant and benign lesions within the breast.Materials and Methods: In this prospective institutional review board-approved study, both MUSE DWI and single-shot DWI sequences were first optimized in breast phantoms and then performed in a group of patients. Thirty women (mean age, 51.1 years ± 10.1 [standard deviation]; age range, 27-70 years) with 37 lesions were included in this study and underwent scanning using both techniques. Visual qualitative analysis of diffusion-weighted images was accomplished by two independent readers; images were assessed for lesion visibility, adequate fat suppression, and the presence of artifacts. Quantitative analysis was performed by calculating apparent diffusion coefficient (ADC) values and image quality parameters (signal-to-noise ratio [SNR] for lesions and fibroglandular tissue; contrast-to-noise ratio) by manually drawing regions of interest within the phantoms and breast tumor tissue. Interreader variability was determined using the Cohen κ coefficient, and quantitative differences between MUSE DWI and single-shot DWI were assessed using the Mann-Whitney U test; significance was defined at P < .05.Results: MUSE DWI yielded significantly improved image quality compared with single-shot DWI in phantoms (SNR, P = .001) and participants (lesion SNR, P = .009; fibroglandular tissue SNR, P = .05; contrast-to-noise ratio, P = .008). MUSE DWI ADC values showed a significant difference between malignant and benign lesions (P < .001). No significant differences were found between MUSE DWI and single-shot DWI in the mean, maximum, and minimum ADC values (P = .96, P = .28, and P = .49, respectively). Visual qualitative analysis resulted in better lesion visibility for MUSE DWI over single-shot DWI (κ = 0.70).Conclusion: MUSE DWI is a promising high-spatial-resolution technique that may enhance breast MRI protocols without the need for contrast material administration in breast screening.Keywords: Breast, MR-Diffusion Weighted Imaging, OncologySupplemental material is available for this article.© RSNA, 2020.

Prediction of skull base osteomyelitis in necrotising otitis externa with diffusion-weighted imaging.

To predict skull base osteomyelitis in patients with necrotising otitis externa using diffusion-weighted imaging. A retrospective analysis was conducted of 25 necrotising otitis externa patients with skull base osteomyelitis (n = 10) or without skull base involvement (n = 14) who underwent a single-shot diffusion-weighted imaging of the skull base. The respective mean apparent diffusion coefficient values of the skull base, as determined by two reviewers, were 0.851 ± 0.15 and 0.841 ± 0.14 ×10-3mm2/s for the skull base osteomyelitis patients, and 1.065 ± 0.19 and 1.045 ± 0.20 ×10-3mm2/s for the necrotising otitis externa patients without skull base involvement. The difference in apparent diffusion coefficients between the groups was significant, for both reviewers (p = 0.008 and 0.012). The optimal threshold apparent diffusion coefficient for predicting skull base osteomyelitis in necrotising otitis externa patients was 0.945 ×10-3mm2/s and 0.915 ×10-3mm2/s, with an area under the curve of 0.825 and 0.800, accuracy of 87.5 and 83.3 per cent, sensitivity of 85.7 and 90.0 per cent, and specificity of 90.0 and 78.6 per cent, for each reviewer respectively. Apparent diffusion coefficient is a non-invasive imaging parameter useful for predicting skull base osteomyelitis in necrotising otitis externa patients.

Phase-constrained reconstruction of high-resolution multi-shot diffusion weighted image

Diffusion weighted imaging (DWI) is a unique examining method in tumor diagnosis, acute stroke evaluation. Single-shot echo planar imaging is currently conventional method for DWI. However, single-shot DWI suffers from image distortion, blurring and low spatial resolution. Although multi-shot DWI improves image resolution, it brings phase variations among different shots at the same time. In this paper, we introduce a smooth phase constraint of each shot image into multi-shot navigator-free DWI reconstruction by imposing the low-rankness of Hankel matrix constructed from the k-space data. Furthermore, we exploit the partial sum minimization of singular values to constrain the low-rankness of Hankel matrix. Results on brain imaging data show that the proposed method outperforms the state-of-the-art methods in terms of artifacts removal and our method potentially has the ability to reconstruct high number of shot of DWI.

Diffusion-weighted imaging in acute pulmonary embolism: a feasibility study.

BackgroundMagnetic resonance imaging (MRI) can be an alternative method to computed tomography angiography (CTA) for pulmonary embolism.PurposeTo evaluate the feasibility of diffusion-weighted imaging (DWI) detecting acute pulmonary embolism (PE) in free-breathing humans.Material and MethodsTwenty patients with PE verified by CTA and 20 controls were investigated with MRI (1.5 Aera, Siemens Healthcare). All sequences were performed in the transversal plane using free-breathing without gating. The protocol consisted of a two-dimensional steady-state free precession (SSFP) and a single-shot DWI echo-planar imaging sequence with a voxel resolution of 2 × 2 × 5 mm. Three b values were used: 50, 400, and 800 s/mm2. Images were analyzed in two orders: an open source analysis (OSA); and a blinded only DWI analysis (BDA) simulating clinical work.ResultsOSA of corresponding images showed 370 findings on CTA (i.e. one elongated emboli could be represented in multiple images). SSFP identified 237 of those (64%). DWI with b values of 50, 400, and 800 identified 327 (88%), 245 (66%), and 138 (37%), respectively. In BDA we found 160 true emboli (according to CTA) on b50, 78 on b400, and 54 on b800. Fifty-two of these findings at the subsegmental level could be correlated to PE on CTA but were not visible on SSFP.ConclusionsDWI has a high sensitivity for detecting PE but suffers from poor specificity. It could potentially be used as an eye catcher, i.e. where to look for PE in other MRI sequences.

Magnetic resonance diffusion‐weighted imaging: reproducibility of regional apparent diffusion coefficients for the normal fetal brain

To evaluate the reproducibility of regional apparent diffusion coefficient (ADC) measurements of the normal fetal brain in the second and third trimesters of pregnancy. Fifty normal singleton fetuses from healthy pregnant women between 19 and 37 weeks' gestation were studied without sedation. Single-shot diffusion-weighted images of the fetal brain were obtained using a 1.5-Tesla magnetic resonance scanner and a six-channel body array coil. ADC maps were created using 0 and 1000 b-values along three orthogonal directions. Two examiners independently measured ADC values in the cerebellar hemispheres (CH), pons, thalamus, basal ganglia (BG), centrum semiovale (CSO), and frontal (FWM), parietal (PWM), temporal (TWM) and occipital (OWM) white matter. Correlation between ADC values and menstrual age was assessed by linear regression analysis. The bias and agreement of ADC measurements were determined using Bland-Altman plots. ADC values either remained constant (BG, FWM, PWM, TWM, OWM, CSO) or decreased (CH, pons, thalamus) with advancing menstrual age. Mean intraobserver bias for ADC measurements was not significantly different from zero. Small interobserver differences in mean ADC measurements (i.e. a small mean bias) were detected for CH (1.26 ± 0.20 vs 1.20 ± 0.18 μm(2) /ms, P = 0.006), PWM (1.37 ± 0.29 vs 1.33 ± 0.26 μm(2) /ms, P = 0.02) and CSO (1.36 ± 0.29 vs 1.33 ± 0.28 μm(2) /ms, P < 0.0001). Measurement agreement was acceptable. ADC measurements in normal unsedated fetuses in the second and third trimesters are reproducible except for small differences for PWM, CH and CSO between examiners.

On the application of a non-CPMG single-shot fast spin-echo sequence to diffusion tensor MRI of the human brain.

The strong sensitivity of Carr-Purcell-Meiboom-Gill (CPMG) fast spin-echo (FSE) sequences, such as rapid acquisition with relaxation enhancement (RARE), to the phase of the prepared transverse magnetization means that artifact-free single-shot diffusion-weighted images can currently only be obtained with a 30-50% reduction in the signal-to-noise ratio (SNR). However, this phase sensitivity and signal loss can be addressed in FSE sequences that use quadratic phase modulation of the radiofrequency (RF) refocusing pulses to generate a sustained train of stable echoes. Here the first application of such a non-CPMG single-shot FSE (ssFSE) sequence to diffusion tensor MR imaging (DT-MRI) of the human brain is described. This approach provides high SNR diffusion-weighted images that have little or no susceptibility to poor B(0) magnetic field homogeneity and the strong eddy currents typically present in DT-MRI experiments.