Ultra-high B-value Research Articles

Alterations of apparent diffusion coefficient from ultra high b-values in the bilateral thalamus and striatum in MRI-negative drug-resistant epilepsy.

Subcortical nuclei such as the thalamus and striatum have been shown to be related to seizure modulation and termination, especially in drug-resistant epilepsy. Enhance diffusion-weighted imaging (eDWI) technique and tri-component model have been used in previous studies to calculate apparent diffusion coefficient from ultra high b-values (ADCuh). This study aimed to explore the alterations of ADCuh in the bilateral thalamus and striatum in MRI-negative drug-resistant epilepsy. Twenty-nine patients with MRI-negative drug-resistant epilepsy and 18 healthy controls underwent eDWI scan with 15 b-values (0-5000 s/mm2). The eDWI parameters including standard ADC (ADCst), pure water diffusion (D), and ADCuh were calculated from the 15 b-values. Regions-of-interest (ROIs) analyses were conducted in the bilateral thalamus, caudate nucleus, putamen, and globus pallidus. ADCst, D, and ADCuh values were compared between the MRI-negative drug-resistant epilepsy patients and controls using multivariate generalized linear models. Inter-rater reliability was assessed using the intra-class correlation coefficient (ICC) and Bland-Altman (BA) analysis. False discovery rate (FDR) method was applied for multiple comparisons correction. ADCuh values in the bilateral thalamus, caudate nucleus, putamen, and globus pallidus in MRI-negative drug-resistant epilepsy were significantly higher than those in the healthy control subjects (all p < 0.05, FDR corrected). The alterations of the ADCuh values in the bilateral thalamus and striatum in MRI-negative drug-resistant epilepsy might reflect abnormal membrane water permeability in MRI-negative drug-resistant epilepsy. ADCuh might be a sensitive measurement for evaluating subcortical nuclei-related brain damage in epilepsy patients. This study aimed to explore the alterations of apparent diffusion coefficient calculated from ultra high b-values (ADCuh) in the subcortical nuclei such as the bilateral thalamus and striatum in MRI-negative drug-resistant epilepsy. The bilateral thalamus and striatum showed higher ADCuh in epilepsy patients than healthy controls. These findings may add new evidences of subcortical nuclei abnormalities related to water and ion hemostasis in epilepsy patients, which might help to elucidate the underlying epileptic neuropathophysiological mechanisms and facilitate the exploration of therapeutic targets.

Evaluating Biliary Malignancy with Measured and Calculated Ultra-high b-value Diffusion-weighted MR Imaging at 3T.

Although diffusion-weighted imaging (DWI) with ultra-high b-values is reported to be advantageous in the detection of some tumors, its applicability is not yet known in biliary malignancy. Therefore, this study aimed to evaluate the impact of measured b = 1400 s/mm2 (M1400) and calculated b = 1400 s/mm2 (C1400) DWI on image quality and quality of lesion discernibility using a modern 3T MR system compared to conventional b = 800 s/mm2 DWI (M800). We evaluated 56 patients who had pathologically proven biliary malignancy. All the patients underwent preoperative or baseline 3T MRI using DWI (b = 50, 400, 800, and 1400 s/mm2). The calculated DWI was obtained using a conventional DWI set (b = 50, 400, and 800). The tumor-to-bile contrast ratio (CR) and tumor SNR were compared between the different DWI images. Likert scores were given on a 5-point scale to assess the overall image quality, overall artifacts, ghost artifacts, misregistration artifacts, margin sharpness, and lesion discernibility. Repeated-measures analysis of variance with post hoc analyses was used for statistical evaluations. The CR of the tumor-to-bile was significantly higher in both M1400 and C1400 than in M800 (Pa < 0.01). SNRs were significantly higher in M800, followed by C1400 and M1400 (Pa < 0.01). Lesion discernibility was significantly improved for M1400, followed by C1400 and M800 for both readers (Pa < 0.01). Using a 3T MRI, both measured and calculated DWI with an ultra-high b-value offer superior lesion discernibility for biliary malignancy compared to the conventional DWI.

A Paired Phase and Magnitude Reconstruction for Advanced Diffusion-Weighted Imaging.

Multi-shot interleaved echo planer imaging (Ms-iEPI) can obtain diffusion-weighted images (DWI) with high spatial resolution and low distortion, but suffers from ghost artifacts introduced by phase variations between shots. In this work, we aim at solving the ms-iEPI DWI reconstructions under inter-shot motions and ultra-high b-values. An iteratively joint estimation model with paired phase and magnitude priors is proposed to regularize the reconstruction (PAIR). The former prior is low-rankness in the k-space domain. The latter explores similar edges among multi-b-value and multi-direction DWI with weighted total variation in the image domain. The weighted total variation transfers edge information from the high SNR images (b-value = 0) to DWI reconstructions, achieving simultaneously noise suppression and image edges preservation. Results on simulated and in vivo data show that PAIR can remove inter-shot motion artifacts very well (8 shots) and suppress the noise under the ultra-high b-value (4000 s/mm2) significantly. The joint estimation model PAIR with complementary priors has a good performance on challenging reconstructions under inter-shot motions and a low signal-to-noise ratio. PAIR has potential in advanced clinical DWI applications and microstructure research.

Identifying potential imaging markers for diffusion property changes in a mouse model of amyotrophic lateral sclerosis: Application of the continuous time random walk model to ultrahigh b-value diffusion-weighted MR images of spinal cord tissue.

Diffusion MRI (dMRI) explores tissue microstructures by analyzing diffusion-weighted signal decay measured at different b-values. While relatively low b-values are used for most dMRI models, high b-value diffusion-weighted imaging (DWI) techniques have gained interest given that the non-Gaussian water diffusion behavior observed at high b-values can yield potentially valuable information. In this study, we investigated anomalous diffusion behaviors associated with degeneration of spinal cord tissue using a continuous time random walk (CTRW) model for DWI data acquired across an extensive range of ultrahigh b-values. The diffusion data were acquired in situ from the lumbar level of spinal cords of wild-type and age-matched transgenic SOD1G93A mice, a well-established animal model of amyotrophic lateral sclerosis (ALS) featuring progressive degeneration of axonal tracts in this tissue. Based on the diffusion decay behaviors at low and ultrahigh b-values, we applied the CTRW model using various combinations of b-values and compared diffusion metrics calculated from the CTRW model between the experimental groups. We found that diffusion-weighted signal decay curves measured with ultrahigh b-values (up to 858,022 s/mm2 in this study) were well represented by the CTRW model. The anomalous diffusion coefficient obtained from lumbar spinal cords was significantly higher in SOD1G93A mice compared with control mice (14.7 × 10-5 ± 5.54 × 10-5 vs. 7.87 × 10-5 ± 2.48 × 10-5 mm2 /s, p = 0.01). We believe this is the first study to illustrate the efficacy of the CTRW model for analyzing anomalous diffusion regimes at ultrahigh b-values. The CTRW modeling of ultrahigh b-value dMRI can potentially present a novel approach for noninvasively evaluating alterations in spinal cord tissue associated with ALS pathology.

Objective Value of the Apparent Diffusion Coefficient (ADC) Map from Ultrahigh b-value Diffusion-weighted Imaging (DWI) in 3T MRI could be a Non-invasive Specific Biomarker for Prostate Cancer.

This article aims to explore the ADC value of ultrahigh b-value DWI and the diagnostic cutoff point in prostate cancer. A total of 78 patients were included in this study. T2 weighted imaging (T2WI), conventional diffusion-weighted imaging (DWI) (1000 s/mm2), and DWI with ultrahigh b-values of 2000 s/mm2 and 3000 s/mm2 were performed in each patient. With reference biopsy as the gold standard, the apparent diffusion coefficient (ADC)s of each b-value DWI image were analyzed. According to different b-value receiver operating characteristic (ROC) curves, the ADC diagnostic cutoff point for prostate cancer was determined. A total of 154 lesions were identified as prostate cancer. The ADC values for conventional DWI and ultrahigh b-value DWI with 2000 s/mm2 and 3000 s/mm2 were 1.097×10-3 mm2/s (1.040-1.153), 0.809×10-3 mm2/s (0.766-0.851) and 0.622×10-3 mm2/s (0.591-0.652), respectively, in the peripheral zone and 1.085×10-3 mm2/s (1.022-1.147), 0.815×10-3 mm2/s (0.770-0.861) and 0.651×10-3 mm2/s (0.617-0.685) in the transition zone. The area under the curve (AUC)s of the ADC values from ultrahigh b-value DWI (2000 s/mm2 and 3000 s/mm2) were 0.824 and 0.852 in the peripheral zone and 0.905 for the ADC values from ultrahigh b-value DWI (3000 s/mm2) in the transition zone. In the peripheral zone, the ADC diagnostic cutoff values for prostate cancer were 0.75×10-3 mm2/s and 0.685×10-3 mm2/s in DWI at 2000 s/mm2 and 3000 s/mm2, respectively, and the diagnosis of transition zone cancer was 0.8×10-3 mm2/s and 0.634×10-3 mm2/s, respectively. The ADC values from ultrahigh b-value DWI demonstrated better consistency and diagnostic efficacy in the diagnosis of prostate cancer.

Advanced Diffusion-Weighted Imaging Sequences for Breast MRI: Comprehensive Comparison of Improved Sequences and Ultra-High B-Values to Identify the Optimal Combination

This study investigated the image quality and choice of ultra-high b-value of two DWI breast-MRI research applications. The study cohort comprised 40 patients (20 malignant lesions). In addition to s-DWI with two m-b-values (b50 and b800) and three e-b-values (e-b1500, e-b2000, and e-b2500), z-DWI and IR m-b1500 DWI were applied. z-DWI was acquired with the same measured b-values and e-b-values as the standard sequence. For IR m-b1500 DWI, b50 and b1500 were measured, and e-b2000 and e-b2500 were mathematically extrapolated. Three readers used Likert scales to independently analyze all ultra-high b-values (b1500-b2500) for each DWI with regards to scan preference and image quality. ADC values were measured in all 20 lesions. z-DWI was the most preferred (54%), followed by IR m-b1500 DWI (46%). b1500 was significantly preferred over b2000 for z-DWI and IR m-b1500 DWI (p = 0.001 and p = 0.002, respectively). Lesion detection was not significantly different among sequences or b-values (p = 0.174). There were no significant differences in measured ADC values within lesions between s-DWI (ADC: 0.97 [±0.09] × 10-3 mm2/s) and z-DWI (ADC: 0.99 [±0.11] × 10-3 mm2/s; p = 1.000). However, there was a trend toward lower values in IR m-b1500 DWI (ADC: 0.80 [±0.06] × 10-3 mm2/s) than in s-DWI (p = 0.090) and z-DWI (p = 0.110). Overall, image quality was superior and there were fewer image artifacts when using the advanced sequences (z-DWI + IR m-b1500 DWI) compared with s-DWI. Considering scan preferences, we found that the optimal combination was z-DWI with a calculated b1500, especially regarding examination time.

Linear multi-scale modeling of diffusion MRI data: A framework for characterization of oriented structures across length scales.

Diffusion-weighted magnetic resonance imaging (DW-MRI) has evolved to provide increasingly sophisticated investigations of the human brain's structural connectome in vivo. Restriction spectrum imaging (RSI) is a method that reconstructs the orientation distribution of diffusion within tissues over a range of length scales. In its original formulation, RSI represented the signal as consisting of a spectrum of Gaussian diffusion response functions. Recent technological advances have enabled the use of ultra-high b-values on human MRI scanners, providing higher sensitivity to intracellular water diffusion in the living human brain. To capture the complex diffusion time dependence of the signal within restricted water compartments, we expand upon the RSI approach to represent restricted water compartments with non-Gaussian response functions, in an extended analysis framework called linear multi-scale modeling (LMM). The LMM approach is designed to resolve length scale and orientation-specific information with greater specificity to tissue microstructure in the restricted and hindered compartments, while retaining the advantages of the RSI approach in its implementation as a linear inverse problem. Using multi-shell, multi-diffusion time DW-MRI data acquired with a state-of-the-art 3T MRI scanner equipped with 300 mT/m gradients, we demonstrate the ability of the LMM approach to distinguish different anatomical structures in the human brain and the potential to advance mapping of the human connectome through joint estimation of the fiber orientation distributions and compartment size characteristics.

Acutely Inhibiting AQP4 With TGN-020 Improves Functional Outcome by Attenuating Edema and Peri-Infarct Astrogliosis After Cerebral Ischemia

BackgroundIschemic stroke is one of the leading causes of human death and disability. Brain edema and peri-infarct astrocyte reactivity are crucial pathological changes, both involving aquaporin-4 (AQP4). Studies revealed that acute inhibition of AQP4 after stroke diminishes brain edema, however, its effect on peri-infarct astrocyte reactivity and the subacute outcome is unclear. And if diffusion-weighted imaging (DWI) could reflect the AQP4 expression patterns is uncertain.MethodsRats were subjected to middle cerebral artery occlusion (MCAO) and allocated randomly to TGN 020-treated and control groups. One day after stroke, brain swelling and lesion volumes of the rats were checked using T2-weighted imaging (T2-WI). Fourteen days after stroke, the rats successively underwent neurological examination, T2-WI and DWI with standard b-values and ultra-high b-values, apparent diffusion coefficient (ADC) was calculated correspondingly. Finally, the rats’ brains were acquired and used for glial fibrillary acidic protein (GFAP) and AQP4 immunoreactive analysis.ResultsAt 1 day after stroke, the TGN-020-treated animals exhibited reduced brain swelling and lesion volumes compared with those in the control group. At 14 days after stroke, the TGN-020-treated animals showed fewer neurological function deficits and smaller lesion volumes. In the peri-infarct region, the control group showed evident astrogliosis and AQP4 depolarization, which were reduced significantly in the TGN-020 group. In addition, the ultra-high b-values of ADC (ADCuh) in the peri-infarct region of the TGN-020 group was higher than that of the control group. Furthermore, correlation analysis revealed that peri-infarct AQP4 polarization correlated negatively with astrogliosis extent, and ADCuh correlated positively with AQP4 polarization.ConclusionWe found that acutely inhibiting AQP4 using TGN-020 promoted neurological recovery by diminishing brain edema at the early stage and attenuating peri-infarct astrogliosis and AQP4 depolarization at the subacute stage after stroke. Moreover, ADCuh could reflect the AQP4 polarization.

The value of multi-parameter diffusion and perfusion magnetic resonance imaging for evaluating epithelial-mesenchymal transition in rectal cancer

PurposeEpithelial-mesenchymal transition (EMT) is characterized by a decreased expression of E-cadherin and an increased expression of vimentin, which is associated with poor prognosis in rectal cancer. This study aimed to explore the feasibility of using multi-parameter diffusion and perfusion magnetic resonance imaging (MRI) to evaluate the expression of E-cadherin and vimentin. MethodsOne hundred and ten patients with rectal cancer, who underwent preoperative multi-parameter diffusion and perfusion MRI and subsequent radical resection of rectal carcinoma, were included in this prospective study. The expression of E-cadherin, vimentin, vascular endothelial growth factor (VEGF), and Ki67 was identified by immunohistochemical test and MRI morphology features; quantitative parameters were analyzed and combined diagnostic models were created by binary logistic regression. The receiver operating characteristics curve with area under the curve (AUC) was used to evaluated diagnostic performance. Interobserver agreement for MRI parameters was evaluated by intraclass correlation coefficient. ResultsIn the low expression E-cadherin group, the VEGF expression was significantly higher than the high expression group (60.5% vs 37.3%, P < 0.05), and the Ki67 expression had no significant difference (P > 0.05). In the high expression vimentin group, the Ki67 expression was significantly higher than the low expression group (77.3% vs 56.1%, P < 0.05), and the VEGF expression was not significantly significant (P > 0.05). MRI morphological features had no significant diagnostic efficacy for E-cadherin and vimentin expression in rectal cancer (P > 0.05). There were positive and negative correlations between apparent diffusion coefficient (ADC) values with E-cadherin and vimentin expression (P < 0.05), the Ktrans and Kep values were negatively and positively correlated with the expression of E-cadherin and vimentin (P < 0.05). The ADC value (b = 3000 s/mm2) had mild significant diagnostic efficiencies for low E-cadherin expression and high vimentin expression (AUC = 0.63 and 0.644, P < 0.05), the Ktrans and Kep values had significant diagnostic efficiencies (AUC = 0.801 and 0.724, P < 0.05; AUC = 0.722 and 0.628, P < 0.05, respectively). The combined model of ADC, Ktrans, and Kep values had good diagnostic efficiencies for low E-cadherin expression and high vimentin expression (AUC = 0.814 and 0.728, P < 0.05). ConclusionThe quantitative parameters of diffusion (with ultra-high b-values) and perfusion MRI can assess the major biomarkers of EMT in rectal cancer, and the combined diagnostic model could further improve the evaluating efficiency for EMT, which possibly can provide valuable information for non-invasive and preoperative assessment of the tumor microenvironment.

Diffusion MRI With High to Ultrahigh b-Values: How It Will Benefit the Discovery of Brain Microstructure and Pathological Changes

Diffusion MRI With High to Ultrahigh b-Values: How It Will Benefit the Discovery of Brain Microstructure and Pathological Changes

Accuracy and precision in super-resolution MRI: Enabling spherical tensor diffusion encoding at ultra-high b-values and high resolution

Diffusion MRI (dMRI) can probe the tissue microstructure but suffers from low signal-to-noise ratio (SNR) whenever high resolution is combined with high diffusion encoding strengths. Low SNR leads to poor precision as well as poor accuracy of the diffusion-weighted signal; the latter is caused by the rectified noise floor and can be observed as a positive bias in magnitude signal. Super-resolution techniques may facilitate a beneficial tradeoff between bias and resolution by allowing acquisition at low spatial resolution and high SNR, whereafter high spatial resolution is recovered by image reconstruction. In this work, we describe a super-resolution reconstruction framework for dMRI and investigate its performance with respect to signal accuracy and precision. Using phantom experiments and numerical simulations, we show that the super-resolution approach improves accuracy by facilitating a more beneficial trade-off between spatial resolution and diffusion encoding strength before the noise floor affects the signal. By contrast, precision is shown to have a less straightforward dependency on acquisition, reconstruction, and intrinsic tissue parameters. Indeed, we find a gain in precision from super-resolution reconstruction is substantial only when some spatial resolution is sacrificed. Finally, we deployed super-resolution reconstruction in a healthy brain for the challenging combination of spherical b-tensor encoding at ultra-high b-values and high spatial resolution—a configuration that produces a unique contrast that emphasizes tissue in which diffusion is restricted in all directions. This demonstration showcased that super-resolution reconstruction enables a vastly superior image contrast compared to conventional imaging, facilitating investigations that would otherwise have prohibitively low SNR, resolution or require non-conventional MRI hardware.

Single shot zonal oblique multislice SE-EPI diffusion-weighted imaging with low to ultra-high b-values for the differentiation of benign and malignant vertebral spinal fractures

PurposeTo investigate the diagnostic yield of low to ultra-high b-values for the differentiation of benign from malignant vertebral fractures using a state-of-the-art single-shot zonal-oblique-multislice spin-echo echo-planar diffusion-weighted imaging sequence (SShot ZOOM SE-EPI DWI). Materials and Methods66 patients (34 malignant, 32 benign) were examined on 1.5 T MR scanners. ADC maps were generated from b-values of 0,400; 0,1000 and 0,2000s/mm2. ROIs were placed into the fracture of interest on ADC maps and trace images and into adjacent normal vertebral bodies on trace images. The ADC of fractures and the Signal-Intensity-Ratio (SIR) of fractures relative to normal vertebral bodies on trace images were considered quantitative metrics. The appearance of the fracture of interest was graded qualitatively as iso-, hypo-, or hyperintense relative to normal vertebrae. ResultsADC achieved an area under the curve (AUC) of 0.785/0.698/0.592 for b = 0,400/0,1000/0,2000s/mm2 ADC maps respectively. SIR achieved an AUC of 0.841/0.919/0.917 for b = 400/1000/2000s/mm2 trace images respectively. In qualitative analyses, only b = 2000s/mm2 trace images were diagnostically valuable (sensitivity:1, specificity:0.794). Machine learning models incorporating all qualitative and quantitative metrics achieved an AUC of 0.95/0.98/0.98 for b-values of 400/1000/2000s/mm2 respectively. The model incorporating only qualitative metrics from b = 2000s/mm2 achieved an AUC of 0.97. ConclusionBy using quantitative and qualitative metrics from SShot ZOOM SE-EPI DWI, benign and malignant vertebral fractures can be differentiated with high diagnostic accuracy. Importantly qualitative analysis of ultra-high b-value images may suffice for differentiation as well.

PI-RADS 2.1 - Image Interpretation: The Most Important Updates andTheir Clinical Implications.

Multiparametric magnetic resonance imaging (MRI) of the prostate plays a central role in the diagnosis of patients with suspected prostate cancer. The increasing distribution and application of the guideline for the standardization of image acquisition, evaluation, and reporting (Prostate Imaging - Reporting and Data System, PI-RADS), which was updated in 2019 to version 2.1, contributes to the success of the technique. The most important updates of PI-RADS version 2.1 presented in 2019 compared to the previous version PI-RADS 2.0 are highlighted and interpreted with regard to their clinical implications. PI-RADS version 2.1 aims to simplify the application of the scoring scheme without changing the basic concept of dominant sequences (DWI in the peripheral zone, T2 in the transition zone). Of particular importance are the increasing role of diffusion-weighted imaging in the transition zone, the now mandatory high b-value of at least 1400 s/mm2, and new information on the assessment of the central zone and the anterior fibromuscular stroma. PI-RADS version 2.1 published in 2019 addresses a number of changes to the previous version, including both the examination technique and image interpretation. Prospective clinical studies have yet to prove the extent to which the goals of reducing interreader variability and increasing the detection rate in the transition zone will be achieved. · The new PI-RADS version 2.1. includes changes regarding image interpretation and examination technique. · The role of diffusion-weighted imaging is strengthened in the transition zone. · An ultra-high b-value of at least 1400 s/mm2 is mandatory according to PI-RADS 2.1. · Biparametric MRI is not recommended for general application. · Beyer T, Schlemmer H, Weber M et al. PI-RADS 2.1 - Image Interpretation: The Most Important Updates and Their Clinical Implications. Fortschr Röntgenstr 2021; 193: 787 - 795.

Whole-Body MRI with an Ultrahigh b-Value of 2000 s/mm2 Improves the Specificity of Diffusion-Weighted Imaging in Patients with Plasma Cell Dyscrasias

Our study compared sensitivity, specificity, and accuracy of whole-body diffusion-weighted imaging (WB-DWI) using a b-value of 2000 s/mm2 with that of the commonly used b-value of 800 s/mm2 for depiction of active tumor sites in patients with plasma cell diseases. We introduced an ultrahigh b-value to reduce interfering signals from benign and post-therapeutic inactive lesions by suppressing T2-shine-through effects. The prospective single-center study included patients when they went through a whole-body MRI (WB-MRI) staging or response evaluation procedure. The apparent diffusion coefficient (ADC) and morphologic appearance served as reference for classifying focal lesions on WB-DWI as vital or post-therapeutic. Additionally, we compared our classification with patients' serological markers of disease activity. One hundred participants (65 ± 10 years, 58 men) underwent WB-DWI between June and October 2019. The detection rate of vital focal lesions was similar for both b-values with a sensitivity of 0.99 using b = 800 s/mm2 and 0.98 using b = 2000 s/mm2. By contrast, specificity and accuracy were 0.09 and 0.71 when using a b-value of 800 s/mm2, and 0.96 and 0.98 when using a b-value of 2000 s/mm2, respectively. The difference in specificity and accuracy was statistically significant (p < 0.001). Using a b-value of 2000 s/mm2 significantly improved the specificity of lesion detection with WB-DWI as compared to the commonly used b-value of 800 s/mm2. The high b-value significantly reduced signal intensities of post-therapeutic or benign lesions and provided a significantly more accurate representation of active tumor load.

Measured Multipoint Ultra-High b-Value Diffusion MRI in the Assessment of MRI-Detected Prostate Lesions.

The aim of this study was to assess quantitative ultra-high b-value (UHB) diffusion magnetic resonance imaging (MRI)-derived parameters in comparison to standard clinical apparent diffusion coefficient (SD-ADC-2b-1000, SD-ADC-2b-1500) for the prediction of clinically significant prostate cancer, defined as Gleason Grade Group greater than or equal to 2. Seventy-three patients who underwent 3-T prostate MRI with diffusion-weighted imaging acquired at b = 50/500/1000/1500s/mm2 and b = 100/500/1000/1500/2250/3000/4000 s/mm2 were included. Magnetic resonance lesions were segmented manually on individual sequences, then matched to targeted transrectal ultrasonography/MRI fusion biopsies. Monoexponential 2-point and multipoint fits of standard diffusion and of UHB diffusion were calculated with incremental b-values. Furthermore, a kurtosis fit with parameters Dapp and Kapp with incremental b-values was obtained. Each parameter was examined for prediction of clinically significant prostate cancer using bootstrapped receiver operating characteristics and decision curve analysis. Parameter models were compared using Vuong test. Fifty of 73 men (age, 66 years [interquartile range, 61-72]; prostate-specific antigen, 6.6 ng/mL [interquartile range, 5-9.7]) had 64 MRI-detected lesions. The performance of SD-ADC-2b-1000 (area under the curve, 0.82) and SD-ADC-2b-1500 (area under the curve, 0.82) was not statistically different (P = 0.99), with SD-ADC-2b-1500 selected as reference. Compared with the reference model, none of the 19 tested logistic regression parameter models including multipoint and 2-point UHB-ADC, Dapp, and Kapp with incremental b-values of up to 4000 s/mm2 outperformed SD-ADC-2b-1500 (all P's > 0.05). Decision curve analysis confirmed these results indicating no higher net benefit for UHB parameters in comparison to SD-ADC-2b-1500 in the clinically important range from 3% to 20% of cancer threshold probability. Net reduction analysis showed no reduction of MR lesions requiring biopsy. Despite evaluation of a large b-value range and inclusion of 2-point, multipoint, and kurtosis models, none of the parameters provided better predictive performance than standard 2-point ADC measurements using b-values 50/1000 or 50/1500. Our results suggest that most of the diagnostic benefits available in diffusion MRI are already represented in an ADC composed of one low and one 1000 to 1500 s/mm2 b-value.

Abnormalities of aquaporin-4 in the cerebellum in bipolar II disorder: An ultra-high b-values diffusion weighted imaging study

BackgroundCumulative evidence indicated the cerebellum is involved in the pathophysiology of bipolar disorder (BD). It was reported that the apparent diffusion coefficient from ultra-high b-values (ADCuh) could reflect the function of aquaporin-4 (AQP4) which was involved in neurological disorders. However, no studies have reported the AQP4 alteration in the cerebellum in BD. Therefore, this study aimed to investigate the ADCuh and AQP4 in the cerebellum in BD-II. MethodsFifty patients with BD-II as well as 43 healthy controls underwent enhance diffusion weighted imaging (eDWI) with ultra-high b-values. The eDWI parameters including ADCuh , pure water diffusion (D) and pseudodiffusion (D*) was measured using regions-of-interest analysis in the superior cerebellar peduncles (SCP), middle cerebellar peduncles (MCP) , cerebellar hemisphere, dentate nuclei, tonsil and vermis of the cerebellum. ResultsBD-II exhibited increased ADCuh values in the bilateral SCP, cerebellar hemisphere, tonsil and right dentate nuclei, and increased D* and D in the bilateral SCP, and decreased D* in the tonsil. Additionally, there were positive correlations between Hamilton Rating Scale for Depression-24 scores and bilateral ADCuh values in the SCP and cerebellar hemisphere. ConclusionsThe alteration of the ADCuh values in the cerebellum may reflect the changes of the AQP4, especially the abnormality of eDWI parameters in the SCP may be a key neurobiological feature of BD-II. The current results provide a novel insight to look into the pathophysiology mechanisms underlying BD-II.

Advanced Diffusion-Weighted Abdominal Imaging: Qualitative and Quantitative Comparison of High and Ultra-High b-Values for Lesion Detection and Image Quality.

Magnetic resonance imaging (MRI) of the abdomen increasingly incorporates diffusion-weighted imaging (DWI) sequences. Whereas DWI can substantially aid in detecting and characterizing suspicious findings, it remains unclear to what extent the use of ultra-high b-value DWI might further be of aid for the radiologist especially when using DWI sequences with advanced processing. The target of this study was therefore to compare high and ultra-high b-value DWI in abdominal MRI examinations. This institutional review board-approved, prospective study included abdominal MRI examinations of 70 oncologic patients (mean age, 58 years; range, 21-90 years) examined with a clinical 1.5 T MRI scanner (MAGNETOM Aera, Siemens Healthcare, Erlangen, Germany) with an advanced echo planar DWI sequence (b = 0, 50, 900, and 1500 s/mm) after ex vivo phantom and in vivo volunteer investigations. High b900 and ultra-high b1500 DWIs were compared by a qualitative reading for image quality and lesion conspicuity using a 5-point Likert scale with 2 radiologists as readers. The ratios of apparent signal intensities of suspicious lesions/normal tissue of the same organ (LNTRs) were calculated. Appropriate methods were used for statistical analysis, including Wilcoxon signed-rank test and κ statistic for interreader agreement analysis (P < 0.05/0.0125/0.005 after Bonferroni correction). Image quality was significantly increased with b900 as compared with b1500 DWI (P < 0.001) despite using an advanced DWI sequence. A total of 153 suspicious lesions were analyzed. Overall reader confidence for characterization/detection of malignant lesions and, correspondingly, the LNTR (mean, 2.7 ± 1.8 vs 2.4 ± 1.6) were significantly higher with b900 than with b1500 DWI (P < 0.001 and P < 0.001). The increased confidence of lesion recognition and LNTR in the b900 DWI remained significant qualitatively in lymphatic and hepatic lesions and quantitatively in lymphatic, pulmonal, and osseous lesions. Using high b-value DWI (900 s/mm) provided an improved image quality and also lesion conspicuity as compared with ultra-high b-value DWI (1500 s/mm) in oncologic abdominal examinations despite using advanced processing. Consequently, the value for additional ultra-high b-value DWI in oncologic examinations should be critically evaluated in future studies.

Multicomponent diffusion analysis reveals microstructural alterations in spinal cord of a mouse model of amyotrophic lateral sclerosis ex vivo.

The microstructure changes associated with degeneration of spinal axons in amyotrophic lateral sclerosis (ALS) may be reflected in altered water diffusion properties, potentially detectable with diffusion-weighted (DW) MRI. Prior work revealed the classical mono-exponential model fails to precisely depict decay in DW signal at high b-values. In this study, we aim to investigate signal decay behaviors at ultra-high b-values for non-invasive assessment of spinal cord alterations in the transgenic SOD1G93A mouse model of ALS. A multiexponential diffusion analysis using regularized non-negative least squares (rNNLS) algorithm was applied to a series of thirty DW MR images with b-values ranging from 0 to 858,022 s/mm2 on ex vivo spinal cords of transgenic SOD1G93A and age-matched control mice. We compared the distributions of measured diffusion coefficient fractions between the groups. The measured diffusion weighted signals in log-scale showed non-linear decay behaviors with increased b-values. Faster signal decays were observed with diffusion gradients applied parallel to the long axis of the spinal cord compared to when oriented in the transverse direction. Multiexponential analysis at the lumbar level in the spinal cord identified ten subintervals. A significant decrease of diffusion coefficient fractions was found in the ranges of [1.63×10−8,3.70×10−6] mm2/s (P = 0.0002) and of [6.01×10−6,4.20×10−5] mm2/s (P = 0.0388) in SOD1G93A mice. Anisotropic diffusion signals persisted at ultra-high b-value DWIs of the mouse spinal cord and multiexponential diffusion analysis offers the potential to evaluate microstructural alterations of ALS-affected spinal cord non-invasively.

Insight into the fundamental trade-offs of diffusion MRI from polarization-sensitive optical coherence tomography in ex vivo human brain

In the first study comparing high angular resolution diffusion MRI (dMRI) in the human brain to axonal orientation measurements from polarization-sensitive optical coherence tomography (PSOCT), we compare the accuracy of orientation estimates from various dMRI sampling schemes and reconstruction methods. We find that, if the reconstruction approach is chosen carefully, single-shell dMRI data can yield the same accuracy as multi-shell data, and only moderately lower accuracy than a full Cartesian-grid sampling scheme. Our results suggest that current dMRI reconstruction approaches do not benefit substantially from ultra-high b-values or from very large numbers of diffusion-encoding directions. We also show that accuracy remains stable across dMRI voxel sizes of 1 ​mm or smaller but degrades at 2 ​mm, particularly in areas of complex white-matter architecture. We also show that, as the spatial resolution is reduced, axonal configurations in a dMRI voxel can no longer be modeled as a small set of distinct axon populations, violating an assumption that is sometimes made by dMRI reconstruction techniques. Our findings have implications for in vivo studies and illustrate the value of PSOCT as a source of ground-truth measurements of white-matter organization that does not suffer from the distortions typical of histological techniques.

Synthetic Apparent Diffusion Coefficient for High b-Value Diffusion-Weighted MRI in Prostate.

Purpose It has been reported that diffusion-weighted imaging (DWI) with ultrahigh b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher Materials and Methods. Fifteen patients (7 malignant and 8 benign) were included in this study retrospectively with the institutional ethical committee approval. All images were acquired at a 3T MR scanner. The ADC values were calculated using a monoexponential model. Synthetic ADC (sADC) for higher b-value increases the diagnostic power of prostate cancer. DWI with higher Results No significant difference was observed between actual ADC and sADC for b-value increases the diagnostic power of prostate cancer. DWI with higher p=0.002, paired t-test) in sDWI as compared to DWI. Malignant lesions showed significantly lower sADC as compared to benign lesions (p=0.002, paired t-test) in sDWI as compared to DWI. Malignant lesions showed significantly lower sADC as compared to benign lesions (Discussion/Conclusion Our initial investigation suggests that the ADC values corresponding to higher b-value can be computed using log-linear relationship derived from lower b-values (b ≤ 1000). Our method might help clinicians to decide the optimal b-value for prostate lesion identification.b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher b-value increases the diagnostic power of prostate cancer. DWI with higher