Diffusion-Tensor MR Imaging of Cortical Lesions in Multiple Sclerosis: Initial Findings

BackgroundCortical multiple sclerosis lesions are clinically relevant butinconspicuous at conventional clinical MRI. Double inversion recovery(DIR) and phase-sensitive inversion recovery (PSIR) are more sensitivebut often unavailable. In the past 2 years, artificial intelligence (AI)was used to generate DIR and PSIR from standard clinical sequences (eg,T1-weighted, T2-weighted, and fluid-attenuated inversion-recoverysequences), but multicenter validation is crucial for furtherimplementation.PurposeTo evaluate cortical and juxtacortical multiple sclerosis lesiondetection for diagnostic and disease monitoring purposes on AI-generatedDIR and PSIR images compared with MRI-acquired DIR and PSIR images in amulticenter setting.Materials and MethodsGenerative adversarial networks were used to generate AI-based DIR(n = 50) and PSIR (n = 43) images.The number of detected lesions between AI-generated images andMRI-acquired (reference) images was compared by randomized blindedscoring by seven readers (all with >10 years of experience inlesion assessment). Reliability was expressed as the intraclasscorrelation coefficient (ICC). Differences in lesion subtype weredetermined using Wilcoxon signed-rank tests.ResultsMRI scans of 202 patients with multiple sclerosis (mean age, 46 years± 11 [SD]; 127 women) were retrospectively collected from sevencenters (February 2020 to January 2021). In total, 1154 lesions weredetected on AI-generated DIR images versus 855 on MRI-acquired DIRimages (mean difference per reader, 35.0% ± 22.8;P < .001). On AI-generated PSIR images, 803lesions were detected versus 814 on MRI-acquired PSIR images (98.9%± 19.4; P = .87). Reliability was good for bothDIR (ICC, 0.81) and PSIR (ICC, 0.75) across centers. Regionally, morejuxtacortical lesions were detected on AI-generated DIR images than onMRI-acquired DIR images (495 [42.9%] vs 338 [39.5%]; P< .001). On AI-generated PSIR images, fewer juxtacortical lesionswere detected than on MRI-acquired PSIR images (232 [28.9%] vs 282[34.6%]; P = .02).ConclusionArtificial intelligence–generated double inversion-recovery andphase-sensitive inversion-recovery images performed well compared withtheir MRI-acquired counterparts and can be considered reliable in amulticenter setting, with good between-reader and between-centerinterpretative agreement.Published under a CC BY 4.0 license.Supplemental material is available for thisarticle.See also the editorial by Zivadinov and Dwyer in this issue.

Global White Matter Changes and Associations with Cognition in Pediatric Sickle Cell Disease

Signal abnormalities of the substantia nigra and the olfactory tract detected either by diffusion tensor imaging, including measurements of mean diffusivity, a parameter of brain tissue integrity, and fractional anisotropy, a parameter of neuronal fibre integrity, or transcranial sonography, were recently reported in the early stages of Parkinson's disease. In this study, changes in the nigral and olfactory diffusion tensor signal, as well as nigral echogenicity, were correlated with clinical scales of motor disability, odour function and putaminal dopamine storage capacity measured with 6-[(18)F] fluorolevodopa positron emission tomography in early and advanced stages of Parkinson's disease. Diffusion tensor imaging, transcranial sonography and positron emission tomography were performed on 16 patients with Parkinson's disease (mean disease duration 3.7 ± 3.7 years, Hoehn and Yahr stage 1 to 4) and 14 age-matched healthy control subjects. Odour function was measured by the standardized Sniffin' Sticks Test. Mean putaminal 6-[(18)F] fluorolevodopa influx constant, mean nigral echogenicity, mean diffusivity and fractional anisotropy values of the substantia nigra and the olfactory tract were identified by region of interest analysis. When compared with the healthy control group, the Parkinson's disease group showed significant signal changes in the caudate and putamen by 6-[(18)F] fluorolevodopa positron emission tomography, in the substantia nigra by transcranial sonography, mean diffusivity and fractional anisotropy (P < 0.001, P < 0.01, P < 0.05, respectively) and in the olfactory tract by mean diffusivity (P < 0.05). Regional mean diffusivity values of the substantia nigra and the olfactory tract correlated significantly with putaminal 6-[(18)F] fluorolevodopa uptake (r = -0.52, P < 0.05 and r = -0.71, P < 0.01). Significant correlations were also found between nigral mean diffusivity values and the Unified Parkinson's Disease Rating Scale motor score (r = -0.48, P < 0.01) and between mean putaminal 6-[(18)F] fluorolevodopa uptake and the total odour score (r = 0.58; P < 0.05) as well as the Unified Parkinson's Disease Rating Scale motor score (r = -0.53, P < 0.05). This study reports a significant association between increased mean diffusivity signal and decreased 6-[(18)F] fluorolevodopa uptake, indicating that microstructural degradation of the substantia nigra and the olfactory tract parallels progression of putaminal dopaminergic dysfunction in Parkinson's disease. Since increases in nigral mean diffusivity signal also correlated with motor dysfunction, diffusion tensor imaging may serve as a surrogate marker for disease progression in future studies of putative disease modifying therapies.

Differentiation of high-grade-astrocytomas from solitary-brain-metastases: Comparing diffusion kurtosis imaging and diffusion tensor imaging

To investigate the diffusion characteristics of water of optic nerve and optic radiation in healthy adults and its related factors by diffusion tensor imaging (DTI) at 3T. A total of 107 healthy volunteers performed head conventional MRI and bilateral optic nerve and optic radiation DTI. The primary data of DTI was processed by post-processing software of DTI studio 2.3, obtaining fractional anisotropy value, mean diffusivity value, principal engine value, orthogonal engine value by measuring, and analyzed by the SPSS13.0 statistical software. The bilateral optic nerve and optic radiation fibers presented green color in directional encoded color (DEC) maps and presented high signal in fractional anisotropy (FA) maps. The FA value of the left optic nerve was 0.598±0.069 and the right was 0.593±0.065; the mean diffusivity (MD) value of the left optic nerve was (1.324±0.349)×10(-3)mm(2)/s and the right was (1.312±0.350)×10(-3)mm(2)/s; the principal engine value (λ‖) of the left optic nerve was (2.297±0.522)×10(-3)mm(2)/s and the right was (2.277±0.526)×10(-3)mm(2)/s; the orthogonal engine value (λ⊥) of the left optic nerve was (0.838±0.285)×10(-3)mm(2)/s and the right was (0.830±0.280)×10(-3)mm(2)/s; the FA value of the left optic radiation was 0.636±0.057 and the right was 0.628±0.056; the mean diffusivity (MD) value of the left optic radiation was (0.907±0.103)×10(-3)mm(2)/s and the right was (0.889±0.125)×10(-3)mm(2)/s; the principal eigenvalue (λ‖) of the left optic radiation was (1.655±0.210)×10(-3)mm(2)/s and the right was (1.614±0.171)×10(-3)mm(2)/s; the orthogonal enginvalue (λ⊥) of the left optic radiation was (0.531±0.103)×10(-3)mm(2)/s and the right was (0.524±0.152)×10(-3)mm(2)/s. There was no obvious difference between the FA, MD, λ‖, λ⊥ of the bilateral optic radiation and the bilateral optic nerve (P>0.05) and no obvious difference between male and female group. The FA, MD, λ‖, λ⊥ of the bilateral optic radiation and the bilateral optic nerve had no obvious correlations to the age. DTI is sensitive to the optic nerve and radiation and the relevant DTI parameters of the optic nerve and radiation are established preliminarily in this study.

To investigate the clinical usefulness of diffusion tensor imaging (DTI) in demonstrating between gliomas and surrounding fibers. 24 patients of glioma (WHO grade: grade I - II 16 cases; grade III - IV 8 cases) were examined using DTI and conventional contrast-enhanced MRI of 3.0 T MRI scanner (GE company, America). After the initial data acquisition introduced into workstation, image analysis was performed with the use of functool software. Mean diffusivity (MD) and fractional anisotropy (FA) values were measured in regions of solid tumor, surrounding edema and normal white matter of the high grade cerebral gliomas. Differences in these values among the tissues were assessed on the high grade cerebral gliomas. Anatomic relationship between intracranial tumors and surrounding fibers was analysed on fractional anisotropic (FA) map, color-coded directional map, three-dimensional white matter tractography. All patients' symptoms were evaluated preoperative and postoperative respectively. The DTI patterns altered by the tumor were categorized as follows: displacement, infiltration and destruction. The tractography showed that the main influence in 16 cases of grade I - II glioma on adjacent white matter tracts was displacement, but infiltration and destruction were also revealed. The patients have definite improvement in symptoms. The destruction and infiltration of fiber tracts could be seen in all edema regions around grade III - IV gliomas in 8 cases. The patients have not definite improvement in symptoms. Apparently significant differences of MD were found in solid tumor, surrounding edema, compared with normal white matter regions (P < 0.05). But there was no significant difference among solid tumor and surrounding edema region (P > 0.05). There were significant differences of FA between solid tumor, surrounding edema and normal white matter region (P < 0.05). The DTI offered the optimal visualization of white matter tracts. DTI plays an important role in demonstrating relationship between gliomas and neighboring fibers. MD and FA values could be used to distinguish normal white matter from solid tumor and surrounding edema region of high grade glioma. The application of DTI in preoperation plays an guidance role in making microsurgery plans and the evaluation of brain functional recovery in postoperation. DTI should be of great value in the microsurgical planning as well as estimation and reduction of potential postoperative neurological deficits for the cerebral gliomas resection.

IntroductionLate gadolinium enhancement (LGE) imaging with cardiovascular magnetic resonance (CMR) is considered the non-invasive gold standard for identifying and quantifying myocardial scar. The diagnostic and prognostic importance of myocardial scar...

Diffusion tensor imaging of rectal carcinoma: Clinical evaluation and its correlation with histopathological findings

BackgroundSpoken discourse (language beyond single words or sentences) performance can be used to detect cognitive impairment in cerebrovascular disease (CVD) [Roberts A, et al. (2021). Top Lang Disord 41(1):73‐98]. However, the neurological basis for altered spoken discourse in CVD is poorly defined. This study examined the association between spoken discourse and indicators of white matter microstructural integrity provided by diffusion tensor imaging (DTI) to better define the link between CVD‐related neurodegeneration and altered spoken discourse.MethodSpoken discourse and 3T DTI data (30‐32 directions, b=1000) were obtained from the CVD cohort of the Ontario Neurodegenerative Disease Research Initiative (n=133). Spoken discourse analyses were completed previously [Roberts, 2021]. A DTI analysis pipeline [Hassan SMH, et al. (2019) PLoS One 14(12):e0226715] was used to generate brain maps of fractional anisotropy (FA) and mean diffusivity (MD) and calculate mean FA and MD values for the inferior longitudinal fasciculus (ILF), superior longitudinal fasciculus – parietal (SLFp) and temporal (SLFt) endings, and uncinate fasciculi (UNC) in each hemisphere. Canonical correlation analyses examined associations between DTI metrics and 10 spoken discourse measures separately for FA in left hemisphere, MD in left hemisphere, FA in right hemisphere, MD in right hemisphere.ResultCanonical correlations were significant in the left hemisphere (FA: r=0.47, p&lt;0.05; MD: r=0.51, p&lt;0.01) but not the right (FA: r=0.34, p=0.90; MD: r=0.40, p=0.15)(Figure 1). Among the white matter tracts, the strongest canonical loadings were seen for the SLFp (FA: 0.81; MD: ‐0.59) and SLFt (FA: 0.71; MD: ‐0.40) compared to the ILF (FA: 0.44; MD: 0.03) and UNC (FA: ‐0.34; MD: 0.10). Higher FA in the SLFp and SLFt was associated with better performance on measures of fluency and information content. Lower MD in these tracts was associated with better performance on measures of fluency, information content, and syntax.ConclusionSpoken discourse performance was associated with white matter microstructural integrity in the left hemisphere of the brain. Of the white matter tracts investigated in this study, impaired spoken discourse performance in CVD was most strongly linked to altered tissue microstructure in the parietal and temporal endings of the superior longitudinal fasciculus.

Fractional anisotropy and tumor cell density of the tumor core show positive correlation in diffusion tensor magnetic resonance imaging of malignant brain tumors

Diffusion tensor imaging (DTI) of the breast may provide a powerful new approach for the detection of intraductal processes. The aim of this investigation was to characterize the relation between diffusion tensor parameters [fractional anisotropy (FA), mean diffusivity (MD)] in normal breast tissue to obtain information on the microenvironment of the diffusing water molecules and to provide a systematic approach for DTI analysis. Seven female, healthy volunteers underwent prospective double-spin-echo prepared echo-planar diffusion-weighted sequence (TR/TE 8,250 ms/74 ms, b values 0 and 500 s/mm (2), six encoding directions, 12 averages, 35 slices) in 4 consecutive weeks (3.0 T). Quantitative maps of diffusion tensor parameters were computed offline with custom routines. The interdependence of MD and FA in different voxels was analysed by linear and exponential regression. All MD and FA maps were of excellent quality. A consistent pattern was observed in that lower fractional anisotropy values were more likely associated with higher mean diffusivity values. The dependence exhibited an exponential behavior with a correlation coefficient R = 0.60 (R linear = 0.57). The likelihood with which FA and MD values are observed in a voxel within normal breast tissue is characterized by a specific pattern, which can be described by an exponential model. Moreover, we could show that the proposed technique does not depend on the menstrual cycle.

Background and purposeSynthetic MR imaging (SyMRI) allows the reconstruction of various contrast images, including double inversion recovery (DIR), from a single scan. This study aimed to investigate the advantages of SyMRI by comparing synthetic DIR images with synthetic T2-weighted fluid-attenuated inversion recovery (T2W-FLAIR) and conventional DIR images.Materials and methodsWe retrospectively reviewed the imaging data of 100 consecutive patients who underwent brain MRI between December 2018 and March 2019. Synthetic DIR, T2W-FLAIR, T1-weighted, and phase-sensitive inversion recovery (PSIR) images were generated from SyMRI data. For synthetic DIR, the two inversion times required to suppress white matter and cerebrospinal fluid (CSF) were manually determined by two radiologists. Quantitative analysis was performed by manually tracing the region of interest (ROI) at the sites of the lesion, white matter, and CSF. Synthetic DIR, synthetic T2W-FLAIR, and conventional DIR images were compared on the basis of using the gray matter-to-white matter, lesion-to-white matter, and lesion-to-CSF contrast-to-noise ratios.ResultsThe two radiologists showed no differences in setting inversion time (TI) values, and their evaluations showed excellent interobserver agreement. The mean signal intensities obtained with synthetic DIR were significantly higher than those obtained with synthetic T2W-FLAIR and conventional DIR.ConclusionSynthetic DIR images showed a higher contrast than synthetic T2WFLAIR and conventional DIR images.

This thesis aimed to investigate the feasibility of two diffusion imaging techniques, Diffusion Tensor Imaging (DTI) and Diffusion Kurtosis Imaging (DKI), on detecting subtle physiological or pathological microstructural changes in normal-appearing neural tissues of human central nervous system. &#13;\n At first, ten patients with neuromyelitis optica (NMO) and twelve age- and gender-matched healthy subjects were recruited. DTI-derived indices including fractional anisotropy (FA), mean diffusivity (MD), axial and radial diffusivities were quantified in the lateral and dorsal columns of cervical spinal cord. Based on the regions of interest (ROIs) measurement, NMO patients showed reduced FA, increased MD and radial diffusivity compared to control subjects, while axial diffusivity did not show any significant difference. The three former DTI metrics also showed significant correlations with disability scores, and especially FA was found to be sensitive to mild NMO. Our results show that DTI-derived indices can quantitatively assess the white matter (WM) abnormalities with seemingly normal appearance in conventional MRI, and are associated with the level of clinical disability, suggesting that DTI may have great potential as a useful diagnostic tool in the clinical setting.&#13;\n DKI is an extension of conventional DTI to probe the non-Gaussian diffusion property in biological tissues. Besides the four conventional DTI-derived metrics, DKI also provide three additional kurtosis metrics (mean kurtosis (MK), axial and radial kurtosis). In the second study, ROI-based analysis was used to characterize age-related microstructural changes in WM, cortical and subcortical gray matter (GM) of 27 healthy adults (21~59 yrs). Though the volumes of GM and WM were still preserved, DTI-derived metrics can detect the subtle changes in WM and GM. Meanwhile, MK and radial kurtosis significantly increased in both caudate nucleus and putamen while Thalamus showed little aging effect in the diffusivity and kurtosis metrics but significantly decreased only in FA. Our results demonstrated that DKI is sensitive to detect the age-related alterations in neural microstructures at the stage of early aging.&#13;\n In addition, DKI has been applied to detect the pathological changes in the normal-appearing neural tissues of 18 patients with multiple sclerosis (MS), compared to 22 healthy controls. Diffuse WM abnormalities have been observed extensively in the brain, revealed by DKI-derived metrics. Though the volumetric and voxel-wise analysis revealed no significant changes in the volume of cortical GM, decreased FA and kurtoses with increased diffusivities in MS group were sensitive to disclose the subtle alterations in global and regional cortical GM tissues. Significant correlations have been found between FA in the global, frontal and temporal cortical GM in relapsing-remitting MS patients and their disability scores, suggesting FA as an important biomarker to monitor the disease progress in cortical GM. Moreover, elevated kurtosis indices in MS patients did not correlate with diffusivities in caudate nucleus, putamen and thalamus, suggesting these metrics may be vulnerable to different pathologic aspects of the disease.&#13;\n In conclusion, DKI is sensitive to neural alterations during normal aging and in MS pathologies, and can provide complementary information to conventional MRI and DTI.

To retrospectively determine whether fractional anisotropy (FA) or mean diffusivity (MD) value at 3-T diffusion-tensor imaging is different between low- and high-grade gliomas and may be useful for glioma grading. Review board approval was obtained, and informed consent was waived. Diffusion-tensor imaging was performed in 27 patients with surgically proved gliomas (19 high-grade and 8 low-grade gliomas). Fractional anisotropy and MD values were measured in 3 regions; peritumoral edema, and enhancing and nonenhancing tumor regions. We compared mean FA and MD values of nonenhancing tumor regions between low- and high-grade gliomas and compared the FA and MD values among the 3 mentioned regions in high-grade gliomas. The relationship between FA and MD values of tumors was also investigated. Statistical analysis was performed using the Student t test and Pearson correlation coefficients. In the nonenhancing regions of tumors, FA ratios were not significantly different between low- and high-grade gliomas (0.472 and 0.701, P = 0.075), but MD ratios were significantly lower in high-grade gliomas (1.899 and 1.23, P < 0.001). In high-grade gliomas, enhancing tumors showed a tendency toward a lower FA ratio than nonenhancing tumors (P = 0.034), but FA values or ratios of peritumoral edema were not significantly different from those of enhancing or nonenhancing tumor. No strong relationship was found between FA and MD values. Fractional anisotropy values of low- and high-grade gliomas were not significantly different. However, MD values of nonenhancing low-grade gliomas were significantly higher than those of nonenhancing high-grade gliomas, which will be useful for the grading of nonenhancing infiltrative gliomas.

Intervertebral disc (IVD) degeneration is the main cause of neck pain. Although conventional magnetic resonance imaging can detect morphological changes in intervertebral disc degeneration, it cannot provide accurate and objective evaluations. Magnetic resonance diffusion tensor imaging (DTI) reflects the microstructural changes in tissues by describing the diffusion of water molecules. It was initially applied to the evaluation of lumbar disc degeneration; however, no study has used DTI to evaluate cervical disc degeneration. To conduct a prospective study to evaluate the efficacy and feasibility of DTI in quantifying cervical disc degeneration by correlating the main parameters of axial DTI of intervertebral discs, namely fractional anisotropy (FA) and mean diffusivity (MD) values, using the Pfirrmann grade. The cervical discs of 30 symptomatic volunteers with neck pain and 20 asymptomatic volunteers were assessed using a 3.0 T magnetic resonance scanner. We evaluated intervertebral discs from C3/4 to C6/7 in each volunteer. The Pfirrmann grades, FA value, and MD value on the conventional magnetic resonance imaging were evaluated. The Kruskal-Wallis test and Wilcoxon rank-sum test were used to compare the FA and MD values of subjects with different degeneration levels. Statistical analysis showed that the FA value of the nucleus pulposus in patients group was significantly higher than that in the asymptomatic volunteers, and the MD value of the nucleus pulposus was significantly lower than that in the asymptomatic volunteers, and the difference was significant (P < 0.05). In the study group, with an increase in cervical intervertebral disc grade, the FA value of the nucleus pulposus also showed a gradual upward trend, and this difference was significant (P < 0.05). The MD value of the nucleus pulposus showed a gradual downward trend, except between grades I and II, which indicates that the axial FA value can better show the early pathological changes of the cervical intervertebral disc. The FA and MD values of the cervical intervertebral disc can quantitatively evaluate the degree of degeneration of the cervical intervertebral disc; axial DTI imaging technology can provide a good theoretical basis for the imaging diagnosis of cervical intervertebral disc degeneration and has important clinical application value.