Echo-planar Imaging Diffusion Research Articles

"Pscore": A Novel Percentile-Based Metric to Accurately Assess Individual Deviations in Non-Gaussian Distributions of Quantitative MRI Metrics.

Quantitative magnetic resonance imaging (MRI) metrics could be used in personalized medicine to assess individuals against normative distributions. Conventional Zscore analysis is inadequate in the presence of non-Gaussian distributions. Therefore, if quantitative MRI metrics deviate from normality, an alternative is needed. To confirm non-Gaussianity of diffusion MRI (dMRI) metrics on a publicly available dataset, and to propose a novel percentile-based method, "Pscore" to address this issue. Retrospective cohort. Nine hundred and sixty-one healthy young adults (age: 22-35 years, females: 53%) from the Human Connectome Project. 3-T, spin-echo diffusion echo-planar imaging, T1-weighted: MPRAGE. The dMRI data were preprocessed using the TORTOISE pipeline. Forty-eight regions of interest (ROIs) from the JHU atlas were redrawn on a study-specific diffusion tensor (DT) template and average values were computed from various DT and mean apparent propagator (MAP) metrics. For each ROI, percentile ranks across participants were computed to generate "Pscores"-which normalized the difference between the median and a participant's value with the corresponding difference between the median and the 5th/95th percentile values. ROI-wise distributions were assessed using log transformations, Zscore, and the "Pscore" methods. The percentages of extreme values above-95th and below-5th percentile boundaries (PEV>95 (%), PEV<5 (%)) were also assessed in the overall white matter. Bootstrapping was performed to test the reliability of Pscores in small samples (N = 100) using 100 iterations. The dMRI metric distributions were systematically non-Gaussian, including positively skewed (eg, mean and radial diffusivity) and negatively skewed (eg, fractional and propagator anisotropy) metrics. This resulted in unbalanced tails in Zscore distributions (PEV>95 ≠ 5%, PEV<5 ≠ 5%) whereas "Pscore" distributions were symmetric and balanced (PEV>95 = PEV<5 = 5%); even for small bootstrapped samples (average [SD]). The inherent skewness observed for dMRI metrics may preclude the use of conventional Zscore analysis. The proposed "Pscore" method may help estimating individual deviations more accurately in skewed normative data, even from small datasets. 1 TECHNICAL EFFICACY: Stage 1.

Immediate effect of upright position on lumbar disc using multiposture MRI: Preliminary results.

Gravity loading on lumbar intervertebral discs (IVDs) is affected by body position. Although the long-term effects of gravity on IVDs have been reported, the immediate effects of gravity on IVDs remain unclear. We considered that changes in IVD structure in the upright and supine positions provided new diagnostic information. Therefore, we compared the apparent diffusion coefficient (ADC), transverse relaxation time (T2), and morphology of the lumbar spine between the quickly changing upright and supine positions using an original magnetic resonance imaging (MRI) system that can obtain images in any position (multiposture MRI). On a 0.4-T multiposture MRI, diffusion-weighted images of the lumbar spine in seven healthy volunteers were obtained using single-shot diffusion echo-planar imaging (b = 0 and 600 s/mm2) in quickly changing upright and supine positions. Moreover, spin-echo images with multiple echo times (echo time = 30, 60, 90, and 120 ms) were obtained in each position. We calculated the ADC and T2 of each IVD (L1 and S1) without any disc degeneration. In addition, the lumbar lordosis angle and length of the lumbar spine were measured to evaluate the morphology of the lumbar spine. The T2 of the IVD between L4 and L5 in the upright position was significantly lower than that in the supine position (P < 0.05). No significant differences were observed in the ADC. The morphology of the lumbar spine did not differ significantly between the two positions. The T2 of the IVD between L4 and L5 was likely decreased by the effect of gravity due to the postural change from supine to upright.

ADEPT: Accurate Diffusion Echo-Planar imaging with multi-contrast shoTs.

To introduce a novel imaging and parameter estimation framework for accurate multi-shot diffusion MRI. We propose a new framework called ADEPT (Accurate Diffusion Echo-Planar imaging with multi-contrast shoTs) that enables fast diffusion MRI by allowing diffusion contrast settings to change between shots in a multi-shot EPI acquisition (i.e., intra-scan modulation). The framework estimates diffusion parameter maps directly from the acquired intra-scan modulated k-space data, while simultaneously accounting for shot-to-shot phase inconsistencies. The performance of the estimation framework is evaluated using Monte Carlo simulation studies and in-vivo experiments and compared to that of reference methods that rely on parallel imaging for shot-to-shot phase correction. Simulation and real-data experiments show that ADEPT yields more accurate and more precise estimates of the diffusion metrics in multi-shot EPI data in comparison with the reference methods. ADEPT allows fast multi-shot EPI diffusion MRI without significantly degrading the accuracy and precision of the estimated diffusion maps.

Assessment of intraoperative diffusion EPI distortion and its impact on estimation of supratentorial white matter tract positions in pediatric epilepsy surgery

The effectiveness of correcting diffusion Echo Planar Imaging (EPI) distortion and its impact on tractography reconstruction have not been adequately investigated in the intraoperative MRI setting, particularly for High Angular Resolution Diffusion Imaging (HARDI) acquisition. In this study, we evaluated the effectiveness of EPI distortion correction using 27 legacy intraoperative HARDI datasets over two consecutive surgical time points, acquired without reverse phase-encoded data, from 17 children who underwent epilepsy surgery at our institution. The data was processed with EPI distortion correction using the Synb0-Disco technique (Schilling et al., 2019) and without distortion correction. The corrected and uncorrected b0 diffusion-weighted images (DWI) were first compared visually. The mutual information indices between the original T1-weighted images and the fractional anisotropy images derived from corrected and uncorrected DWI were used to quantify the effect of distortion correction. Sixty-four white matter tracts were segmented from each dataset, using a deep-learning based automated tractography algorithm for the purpose of a standardized and unbiased evaluation. Displacement was calculated between tracts generated before and after distortion correction. The tracts were grouped based on their principal morphological orientations to investigate whether the effects of EPI distortion vary with tract orientation. Group differences in tract distortion were investigated both globally, and regionally with respect to proximity to the resecting lesion in the operative hemisphere. Qualitatively, we observed notable improvement in the corrected diffusion images, over the typically affected brain regions near skull-base air sinuses, and correction of additional distortion unique to intraoperative open cranium images, particularly over the resection site. This improvement was supported quantitatively, as mutual information indices between the FA and T1-weighted images were significantly greater after the correction, compared to before the correction. Maximum tract displacement between the corrected and uncorrected data, was in the range of 7.5 to 10.0 mm, a magnitude that would challenge the safety resection margin typically tolerated for tractography-informed surgical guidance. This was particularly relevant for tracts oriented partially or fully in-line with the acquired diffusion phase-encoded direction. Portions of these tracts passing close to the resection site demonstrated significantly greater magnitude of displacement, compared to portions of tracts remote from the resection site in the operative hemisphere. Our findings have direct clinical implication on the accuracy of intraoperative tractography-informed image guidance and emphasize the need to develop a distortion correction technique with feasible intraoperative processing time.

Non-Echoplanar Diffusion Weighted Imaging and 3D Fiesta Magnetic Resonance Imaging Sequences with High Resolution Computed Tomography Temporal Bone in Assessment and Predicting the Outcome of Chronic Suppurative Otitis Media with Cholesteatoma

Introduction: Cholesteatomas are lesions that develop in pneumatized areas of the temporal bone, such as the middle ear and mastoid, or both, and are extremely rarely detected in the external auditory canal. Because it has benefits over CT, diffusion weighted imaging MRI (DWI-MRI) can be a useful technique in the identification of cholesteatoma. Image distortion and artefacts are less visible with non-echo planar imaging DWI techniques than with other DWI techniques. Aims and Objectives: 1) To assess the usefulness of HRCT scan in Chronic suppurative otitis media (CSOM) with cholesteatoma in depicting the status of the middle ear structures. 2) To correlate HRCT findings of temporal bone with surgical findings in Chronic suppurative otitis media (CSOM) with cholesteatoma with respect to the following parameters: Presence or absence of cholesteatoma, Extent of cholesteatoma, Status of ossicular chain, Integrity of the facial canal, Detection of erosions or dehisence in the bony labyrinth, and Detection of erosions or dehisence in the dural or sinus plates. 3) Comparison with Non Echo planar imaging diffusion weighted for presence or absence of cholesteatoma. 4) 3D FIESTA Magnetic resonance imaging with 3D reconstruction of membranous vestibule and cochlea for better delineating associated complications. Materials and Methods: Total 40 patients of clinically suspected CSOM with cholestaetoma were enrolled for this study. All patients were scanned using a non-contrast High-resolution computed tomography technique and MRI. HRCT findings were noted according to the proforma. MRI DWI was recorded as either positive or negative for cholesteatoma &amp; directly correlated with post-surgical presence or absence of cholesteatoma.3D FIESTA for detection of membranous labyrinthine erosion/defect was correlated with surgical findings of bony labyrinthine erosions. Results: Cholesteatoma was shown to be common in the third decade of life in our study. The most often implicated middle ear structures in our investigation were the epitympanum, aditus, and antrum. The most often eroded ossicle is the stapes, followed by the incus. The tympanic section of the facial canal is the most often affected segment, while the posterior semicircular canal is the most commonly degraded of the bony labyrinth structures. Conclusion: HRCT temporal bone, in combination with non-echoplanar DWI MRI and 3D Fiesta, can help with accurate diagnosis and pre-operative assessment of cholesteatoma.

Magnetic resonance imaging applied to the assessment of intact yellowtail ( Seriola quinqueradiata ): Preliminary results

High-quality food fish, such as yellowtail often pass through a distribution channels in an intact state. Thus, the quality and composition of the fish meat can only ascertained after processing. We investigated whether magnetic resonance imaging (MRI) could be feasibly used for quality and composition assessments of intact yellowtail. Selected factors at the ventral, lateral-line, dorsal and blood-colour regions of a pectoral-fin slice and an anal slice from natural and cultured yellowtail (Seriola quinqueradiata) individuals were measured for comparison. Specifically, the fat fraction and T2* were measured using spoiled multi-echo gradient echo with T2* correction on a 3T MRI scanner. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were measured using single-shot diffusion echo-planar imaging. T2 and fascial density were measured using T2-weighted multi-echo turbo spin-echo. Fat fraction values at most regions were significantly higher in cultured yellowtail compared with natural fish. The highest fat fraction was observed at the ventral region of the pectoral-fin slice. FA and T2 values were larger, while those for ADC and T2* were smaller in cultured yellowtail than in natural fish. Fascial densities did not differ significantly between the natural and cultured yellowtail except in the ventral region of the pectoral-fin slice. MRI makes it possible to assess regional quality and composition of intact yellowtail.

Quantification of Regional Cerebral Blood Flow Using Diffusion Imaging With Phase Contrast.

The perfusion-related diffusion coefficient obtained from triexponential diffusion analysis is closely correlated with regional cerebral blood flow (rCBF), as assessed by arterial spin labeling (ASL) methods. However, this provides only a semiquantitative measure of rCBF, thereby making absolute rCBF quantification challenging. To obtain rCBF in a noninvasive manner using a novel diffusion imaging method with phase contrast (DPC), in which the total CBF from phase-contrast (PC) MRI was utilized to convert perfusion-related diffusion coefficients to rCBF values. Prospective. Eleven healthy volunteers (nine men and two women; mean age, 23.9 years) participated in this study. A 3.0 T, single-shot diffusion echo-planar imaging with multiple b-values (0-3000 s/mm2 ), PC-MRI, pulsed continuous ASL, and 3D T1 -weighted fast field echo. rCBF and its correlations in the gray matter (GM) and white matter (WM) were compared between DPC and ASL methods. rCBF in the GM and WM and the GM/WM ratio were compared with the literature values obtained using [15 O]-water positron emission tomography (15 O-H2 O PET). Spearman's correlation coefficient and Wilcoxon signed-rank test were used. Significance was set at P < 0.05. A significant positive correlation between DPC and ASL in terms of rCBF was observed in GM (R=0.9), whereas the correlation between the two methods was poor in WM (R=0.09). The rCBF in GM and WM and the GM/WM ratio obtained using DPC were consistent with the literature values assessed using 15 O-H2 O PET. The rCBF value obtained using DPC was significantly higher in the GM and WM than that using ASL. DPC enabled noninvasive quantification of rCBF. 2 TECHNICAL EFFICACY: Stage 1.

Triexponential Diffusion Analysis of Diffusion-weighted Imaging for Breast Ductal Carcinoma &lt;i&gt;in Situ&lt;/i&gt; and Invasive Ductal Carcinoma

PurposeTo obtain detailed information in breast ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) using triexponential diffusion analysis.MethodsDiffusion-weighted images (DWI) of the breast were obtained using single-shot diffusion echo-planar imaging with 15 b-values. Mean signal intensities at each b-value were measured in the DCIS and IDC lesions and fitted with the triexponential function based on a two-step approach: slow-restricted diffusion coefficient (Ds) was initially determined using a monoexponential function with b-values > 800 s/mm2. The diffusion coefficient of free water at 37°C was assigned to the fast-free diffusion coefficient (Df). Finally, the perfusion-related diffusion coefficient (Dp) was derived using all the b-values. Furthermore, biexponential analysis was performed to obtain the perfusion-related diffusion coefficient (D*) and the perfusion-independent diffusion coefficient (D). Monoexponential analysis was performed to obtain the apparent diffusion coefficient (ADC). The sensitivity and specificity of the aforementioned diffusion coefficients for distinguishing between DCIS and IDC were evaluated using the pathological results.ResultsThe Ds, D, and ADC of DCIS were significantly higher than those of IDC (P < 0.01 for all). There was no significant correlation between Dp and Ds, but there was a weak correlation between D* and D. The combination of Dp and Ds showed higher sensitivity and specificity (85.9% and 71.4%, respectively), compared to the combination of D* and D (81.5% and 33.3%, respectively).ConclusionTriexponential analysis can provide detailed diffusion information for breast tumors that can be used to differentiate between DCIS and IDC.

Changes in Apparent Diffusion Coefficient (ADC) during Cardiac Cycle of the Brain in Idiopathic Normal Pressure Hydrocephalus Before and After Cerebrospinal Fluid Drainage.

The causative mechanisms of idiopathic normal-pressure hydrocephalus (iNPH) symptoms are currently unknown. To assess the dynamic changes in the apparent diffusion coefficient (ADC) during the cardiac cycle (ΔADC) of the brain before and after the lumbar tap and shunt surgery for the purpose of determining changes in hydrodynamic and biomechanical properties in the brain after cerebrospinal fluid (CSF) drainage for iNPH. Retrospective. Overall, 22 patients suspected to have iNPH were examined before and after the lumbar tap and were divided into patients who showed symptomatic improvements (positive group, n = 17) and those without improvement (negative group, n = 5) after the lumbar tap. Seven patients in the positive group were examined after the shunt surgery. 1.5T, electrocardiographically synchronized single-shot diffusion echo-planar imaging. The frontal white matter ΔADC and mean ADC (ADCmean ) were compared between before and 24 hours after lumbar tap and from 1 week to 1 month after the shunt surgery. Wilcoxon signed-rank test was used. P < 0.05 was considered statistically significant. The ΔADC after the lumbar tap in the positive group was significantly lower than that before (P < 0.05), whereas no significant difference was found in the negative group (P = 0.23). After the lumbar tap, ΔADC decreased in 16 of 17 patients in the positive group, whereas ADCmean did not significantly change (P = 0.96). After the shunt surgery, ΔADC decreased in all seven patients (P < 0.05), whereas ADCmean did not significantly change (P = 0.87). The frontal white matter ΔADC in iNPH decreased after the lumbar tap and shunt surgery. ΔADC analysis may provide detailed information regarding changes in the hydrodynamic and biomechanical properties through CSF drainage. 4. 4.

The role of diffusion weighted imaging in magnetic resonance to evaluate breast masses

Aim: To investigate the role of diffusion weighted magnetic resonance imaging (MRI) in differentiation of benign and malignant breast lesions using apparent diffusion coefficient (ADC) values preoperatively. Methods: A total of 30 women between the ages of 14-75 years (mean, 47, 6 years) with 30 histopathologically verified breast lesions were investigated in this study. The patients were examined by a 1, 5 T MRI device using bilateral phased array breast coil. Spin echo planar diffusion imaging was used to scan patients. Images were obtained by b values 0 and 500 seconds/mm². Mean ADC values of the benign and malignant lesions were measured and calculated. The comparison between the histopathological diagnoses and the mean ADCs were performed by Mann Whitney U test. Results: The diagnosis of 30 patients with 30 breast lesions were as follows; malign lesions (n=13), benign lesions (n=17). The ADC values were as follows (in units of 10-3mm² /sec): benign breast lesions (range: 1, 09-1, 98, mean: 1, 45) and malignant breast lesions (range: 0, 59-1, 08, mean: 0, 76). The mean ADC obtained from malignant breast lesions was statistically different from that observed in benign solid lesions (p<0, 01). Conclusion: Diffusion imaging can be used in differentiation of malign and benign breast lesions.

Reduced field of view echo-planar imaging diffusion tensor MRI for pediatric spinal tumors.

Spine MRI is a diagnostic modality for evaluating pediatric CNS tumors. Applying diffusion-weighted MRI (DWI) or diffusion tensor imaging (DTI) to the spine poses challenges due to intrinsic spinal anatomy that exacerbates various image-related artifacts, such as signal dropouts or pileups, geometrical distortions, and incomplete fat suppression. The zonal oblique multislice (ZOOM)-echo-planar imaging (EPI) technique reduces geometric distortion and image blurring by reducing the field of view (FOV) without signal aliasing into the FOV. The authors hypothesized that the ZOOM-EPI method for spine DTI in concert with conventional spinal MRI is an efficient method for augmenting the evaluation of pediatric spinal tumors. Thirty-eight consecutive patients (mean age 8 years) who underwent ZOOM-EPI spine DTI for CNS tumor workup were retrospectively identified. Patients underwent conventional spine MRI and ZOOM-EPI DTI spine MRI. Two blinded radiologists independently reviewed two sets of randomized images: conventional spine MRI without ZOOM-EPI DTI, and conventional spine MRI with ZOOM-EPI DTI. For both image sets, the reviewers scored the findings based on lesion conspicuity and diagnostic confidence using a 5-point Likert scale. The reviewers also recorded presence of tumors. Quantitative apparent diffusion coefficient (ADC) measurements of various spinal tumors were extracted. Tractography was performed in a subset of patients undergoing presurgical evaluation. Sixteen patients demonstrated spinal tumor lesions. The readers were in moderate agreement (kappa = 0.61, 95% CI 0.30-0.91). The mean scores for conventional MRI and combined conventional MRI and DTI were as follows, respectively: 3.0 and 4.0 for lesion conspicuity (p = 0.0039), and 2.8 and 3.9 for diagnostic confidence (p < 0.001). ZOOM-EPI DTI identified new lesions in 3 patients. In 3 patients, tractography used for neurosurgical planning showed characteristic fiber tract projections. The mean weighted ADCs of low- and high-grade tumors were 1201 × 10-6 and 865 × 10-6 mm2/sec (p = 0.002), respectively; the mean minimum weighted ADCs were 823 × 10-6 and 474 × 10-6 mm2/sec (p = 0.0003), respectively. Diffusion MRI with ZOOM-EPI can improve the detection of spinal lesions while providing quantitative diffusion information that helps distinguish low- from high-grade tumors. By adding a 2-minute DTI scan, quantitative diffusion information and tract profiles can reliably be obtained and serve as a useful adjunct to presurgical planning for pediatric spinal tumors.

Phase-matched virtual coil reconstruction for highly accelerated diffusion echo-planar imaging

PurposeTo propose a virtual coil (VC) acquisition/reconstruction framework to improve highly accelerated single-shot EPI (SS-EPI) and generalized slice dithered enhanced resolution (gSlider) acquisition in high-resolution diffusion imaging (DI). MethodsFor robust VC-GRAPPA reconstruction, a background phase correction scheme was developed to match the image phase of the reference data with the corrupted phase of the accelerated diffusion-weighted data, where the corrupted phase of the diffusion data varies from shot to shot. A Gy prewinding-blip was also added to the EPI acquisition, to create a shifted-ky sampling strategy that allows for better exploitation of VC concept in the reconstruction. To evaluate the performance of the proposed methods, 1.5 mm isotropic whole-brain SS-EPI and 860 μm isotropic whole-brain gSlider-EPI diffusion data were acquired at an acceleration of 8–9 fold. Conventional and VC-GRAPPA reconstructions were performed and compared, and corresponding g-factors were calculated. ResultsThe proposed VC reconstruction substantially improves the image quality of both SS-EPI and gSlider-EPI, with reduced g-factor noise and reconstruction artifacts when compared to the conventional method. This has enabled high-quality low-noise diffusion imaging to be performed at 8–9 fold acceleration. ConclusionsThe proposed VC acquisition/reconstruction framework improves the reconstruction of DI at high accelerations. The ability to now employ such high accelerations will allow DI with EPI at reduced distortion and faster scan time, which should be beneficial for many clinical and neuroscience applications.

Disrupted functional connectivity and activity in the white matter of the sensorimotor system in patients with pontine strokes.

White matter (WM) blood oxygenation level-dependent (BOLD) signals are reported to be related to neural activity. However, sensitivity of WM BOLD signals to disease remains unclear. To investigate WM BOLD signal changes, directional variations of resting-state correlations in sensorimotor system in patients with pontine strokes, and to determine the relationship between WM BOLD signals and motor deficits. Prospective. Ethical approval was obtained from the local Ethics Committee and each participant gave written informed consent. Sixteen patients with focal pontine lesions and 16 age-matched control subjects were included. 3.0T T1 -weighted anatomic images using a 3D magnetization-prepared rapid gradient-echo sequence. Resting-state fMRI images using gradient-echo echo-planar imaging sequence. Diffusion-weighted images using single-shot spin-echo diffusion echo-planar imaging. Relevant WM tracts in the sensorimotor system by region of interest-wise analysis were identified. Power spectra of BOLD signals and anisotropy of resting-state correlations were measured in sensorimotor system and compared between two groups. Their relationships with clinical scores were analyzed. Two-sample t-test; partial correlation analysis. Power spectra of BOLD signals in nerve tracts on the ipsilesional side were significantly decreased (P < 0.05). Compared with that in healthy subjects, the anisotropy of resting-state correlations along identified WM tracts was decreased in the thalamus-dorsolateral prefrontal cortex bundle on the contralesional side, and all nerve tracts on the ipsilesional side. Partial least squares regression analysis showed the predicted outcome scores correlated significantly with actual Fugl-Meyer scores (R2 = 0.944, P = 0.013). Our findings suggest that disrupted activity and functional connectivity in WM areas of the sensorimotor system can be detected in pontine strokes, and may serve as a biomarker for motor function prediction. 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:478-486.

Read-out segmented echo planar diffusion imaging of the female pelvis-utility in endometrial carcinoma-a preliminary experience.

Susceptibility artefacts from bones and bowel, geometric distortion makes diffusion imaging of the pelvis difficult. We discuss the difficulties of single-shot-echo-planar(ss-ep)DWI and evaluate a new diffusion-weighted imaging (DWI)technique-readout segmented echo planar(rs-ep)DWI in endometrial carcinoma and discuss the imaging physics. Institute review board approval was obtained and five consecutive patients underwent both rs-ep and ss-ep-DWI of the female pelvis and two radiologists compared the images. ROIs were drawn on the endometrium on the b400 images-signal to noise was calculated and compared using Ftest. The rs-ep-DWI had less imaging artefacts, less bowel-related susceptibility and geometric distortion compared to ss-ep-DWI. There was statistically significant greater SNR in ss-ep-DWI compared to rs-ep-DWI. This resulted in increased graininess of the readout segmented diffusion images. Artefacts in SS-EPI-DTI may make fibre tracking fallacious and rs-ep DTI may have fewer artefacts. rs-ep-DWI is a new imaging arsenal in imaging of the female pelvis in general; however further reduction in imaging time and improvement in signal to noise may be desirable. rs-ep-DWI affords lesser imaging artefacts from susceptibility and geometric distortion; at a higher time dividend and may find a place in oncological imaging.

Oesophageal squamous cell carcinoma: histogram-derived ADC parameters are not predictive of tumour response to chemoradiotherapy

ObjectivesTo evaluate correlations between tumour response to definitive chemoradiotherapy (CRT) in oesophageal squamous cell carcinoma (SCC) and histogram-derived apparent diffusion coefficient (ADC) parameters on diffusion-weighted MR images.MethodsForty patients with clinical T3–4 oesophageal SCC underwent concurrent CRT. MR examination at 3 T was performed 1–3 days prior to CRT. Readout-segmented echo-planar diffusion imaging was used to acquire ADC maps. Pre- and post-treatment CT examinations were performed. Histogram parameters (mean, 10th, 25th, 50th, 75th, 90th percentiles, skewness and kurtosis) of the ADC values were compared with post-treatment disease status based on RECIST and the tumour regression ratio.ResultsNone of the ADC parameters showed significant correlation with post-treatment status (range of Spearman’s ρ values − 0.19 to 0.14, range of p values 0.22–0.47) or tumour regression ratio (range of Spearman’s ρ values − 0.045 to 0.18, range of p values 0.26–0.96). Neither progression-free survival (PFS) (p = 0.17) nor overall survival (OS) (p = 0.15) was significantly different between the two groups corresponding to the lower (< median) and upper arms (≥ median) of the mean ADC values.ConclusionsHistogram-derived pretreatment ADC parameters were not predictive imaging biomarkers for tumour response to CRT in patients with oesophageal SCC.Key Points• Apparent diffusion coefficient (ADC) values are derived from diffusion-weighted MR imaging.• High-resolution diffusion-weighted images are generated by readout-segmented echo-planar diffusion imaging.• Readout-segmented echo-planar diffusion-weighted imaging enabled evaluation of ADC parameters.• Pretreatment ADC parameters do not predict chemoradiotherapy response in patients with oesophageal carcinoma.

Hybrid quantitative MRI using chemical shift displacement and recovery-based simultaneous water and lipid imaging: A preliminary study

PurposeTo suppress olefinic signals and enable simultaneous and quantitative estimation of multiple functional parameters associated with water and lipid, we investigated a modified method using chemical shift displacement and recovery-based separation of lipid tissue (SPLIT) involving acquisitions with different inversion times (TIs), echo times (TEs), and b-values. Materials and methodsSingle-shot diffusion echo-planar imaging (SSD-EPI) with multiple b-values (0–3000 s/mm2) was performed without fat suppression to separate water and lipid images using the chemical shift displacement of lipid signals in the phase-encoding direction. An inversion pulse (TI = 292 ms) was applied to SSD-EPI to remove olefinic signals. Consecutively, SSD-EPI (b = 0 s/mm2) was performed with TI = 0 ms and TE = 31.8 ms for T1 and T2 measurements, respectively. Under these conditions, transverse water and lipid images at the maximum diameter of the right calf were obtained in six healthy subjects. T1, T2, and the apparent diffusion coefficients (ADC) were then calculated for the tibialis anterior (TA), gastrocnemius (GM), and soleus (SL) muscles, tibialis bone marrow (TB), and subcutaneous fat (SF). Perfusion-related (D*) and restricted diffusion coefficients (D) were calculated for the muscles. Lastly, the lipid fractions (LF) of the muscles were determined after T1 and T2 corrections. ResultsThe modified SPLIT method facilitated sufficient separation of water and lipid images of the calf, and the inversion pulse with TI of 292 ms effectively suppressed olefinic signals. All quantitative parameters obtained with the modified SPLIT method were found to be in general agreement with those previously reported in the literature. ConclusionThe modified SPLIT technique enabled sufficient suppression of olefinic signals and simultaneous acquisition of quantitative parameters including diffusion, perfusion, T1 and T2 relaxation times, and LF.

Evaluation of the impact of strain correction on the orientation of cardiac diffusion tensors with in vivo and ex vivo porcine hearts.

To evaluate the importance of strain-correcting stimulated echo acquisition mode echo-planar imaging cardiac diffusion tensor imaging. Healthy pigs (n = 11) were successfully scanned with a 3D cine displacement-encoded imaging with stimulated echoes and a monopolar-stimulated echo-planar imaging diffusion tensor imaging sequence at 3 T during diastasis, peak systole, and strain sweet spots in a midventricular short-axis slice. The same diffusion tensor imaging sequence was repeated ex vivo after arresting the hearts in either a relaxed (KCl-induced) or contracted (BaCl2 -induced) state. The displacement-encoded imaging with stimulated echoes data were used to strain-correct the in vivo cardiac diffusion tensor imaging in diastole and systole. The orientation of the primary (helix angles) and secondary (E2A) diffusion eigenvectors was compared with and without strain correction and to the strain-free ex vivo data. Strain correction reduces systolic E2A significantly when compared without strain correction and ex vivo (median absolute E2A = 34.3° versus E2A = 57.1° (P = 0.01), E2A = 60.5° (P = 0.006), respectively). The systolic distribution of E2A without strain correction is closer to the contracted ex vivo distribution than with strain correction, root mean square deviation of 0.027 versus 0.038. The current strain-correction model amplifies the contribution of microscopic strain to diffusion resulting in an overcorrection of E2A. Results show that a new model that considers cellular rearrangement is required. Magn Reson Med 79:2205-2215, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

* A 3D Tissue-Printing Approach for Validation of Diffusion Tensor Imaging in Skeletal Muscle.

The ability to noninvasively assess skeletal muscle microstructure, which predicts function and disease, would be of significant clinical value. One method that holds this promise is diffusion tensor magnetic resonance imaging (DT-MRI), which is sensitive to the microscopic diffusion of water within tissues and has become ubiquitous in neuroimaging as a way of assessing neuronal structure and damage. However, its application to the assessment of changes in muscle microstructure associated with injury, pathology, or age remains poorly defined, because it is difficult to precisely control muscle microstructural features in vivo. However, recent advances in additive manufacturing technologies allow precision-engineered diffusion phantoms with histology informed skeletal muscle geometry to be manufactured. Therefore, the goal of this study was to develop skeletal muscle phantoms at relevant size scales to relate microstructural features to MRI-based diffusion measurements. A digital light projection based rapid 3D printing method was used to fabricate polyethylene glycol diacrylate based diffusion phantoms with (1) idealized muscle geometry (no geometry; fiber sizes of 30, 50, or 70 μm or fiber size of 50 μm with 40% of walls randomly deleted) or (2) histology-based geometry (normal and after 30-days of denervation) containing 20% or 50% phosphate-buffered saline (PBS). Mean absolute percent error (8%) of the printed phantoms indicated high conformity to templates when "fibers" were >50 μm. A multiple spin-echo echo planar imaging diffusion sequence, capable of acquiring diffusion weighted data at several echo times, was used in an attempt to combine relaxometry and diffusion techniques with the goal of separating intracellular and extracellular diffusion signals. When fiber size increased (30-70 μm) in the 20% PBS phantom, fractional anisotropy (FA) decreased (0.32-0.26) and mean diffusivity (MD) increased (0.44 × 10-3 mm2/s-0.70 × 10-3 mm2/s). Similarly, when fiber size increased from 30 to 70 μm in the 50% PBS diffusion phantoms, a small change in FA was observed (0.18-0.22), but MD increased from 0.86 × 10-3 mm2/s to 1.79 × 10-3 mm2/s. This study demonstrates a novel application of tissue engineering to understand complex diffusion signals in skeletal muscle. Through this work, we have also demonstrated the feasibility of 3D printing for skeletal muscle with relevant matrix geometries and physiologically relevant tissue characteristics.

Value of readout-segmented echo-planar diffusion imaging on 3.0 T MRI for predicting the early efficacy of concurrent radiochemotherapy of advanced stage nasopharyngeal carcinoma patients

Objective: To discuss the value of RESOLVE for predicting early therapeutic effect of concourrent radiochemotherapy in advanced stage nasopharngeal carcinoma patients. Methods: Sixty-eight patients with nasopharyngeal carcinoma were confirmed by pathology in Henan Cancer Hospital from June 2014 to January 2016.All patients underwent RESLOVE(b value=800 s/mm(2)) with a 3.0 T MRI scanner.The ADC value and the area of the tumor was measured before treatment and 2 weeks after treatment independently performed by two radiologists with 5 years experiences and the agreement evaluation was performed using ANOVA analysis.The correlation among pretreatment ADC value, pathology type, gender, tumor area and the tumor regression rate were analyzed using Spearman rank correlation test.The difference between pretreatment ADC value was compared in CR group and non-CR group by independent sample t test.ROC curve was drawn and the maximum Youden index value was the cutoff calculating the ADC value and predicting the sensitivity, specificity and area under the curve. Results: (1)The agreement between 2 radiologist was excellent. The ICC values of the ADC and the area of the tumor before treatment and the area of the tumor after treatment were 0.89, 0.92 and 0.95, respectively. (2)The pretreatment ADC values of the CR group and the non-CR group were (0.877±0.103)×10(-3) mm(2)/s and (0.779±0.078)×10(-3) mm(2)/s, respectively. There was statistical difference t value=2.874, P value=0.005.(3)ROC curve showed that the sensitivity and specificity of the pretreatment ADC value in predicting CR was 85.2% and 71.0%, with the cut-off value of 0.792×10(-3) mm(2)/s, and the area under curve was 0.778.(4)There was apparently correlation beween the pretreatment ADC value and the tumor regression rate(r=0.333, P=0.006). There was no correlation among pretreatment ADC value, pathology type, gender and tumor area (P>0.05). Conclusion: There is important value using the pretreatment ADC value measured by RESOLVE for predicting the early effect of concurrent radiochemotherapy in advanced stage nasopharngeal carcinoma patients.

Water and lipid diffusion MRI using chemical shift displacement-based separation of lipid tissue (SPLIT)

PurposeTo obtain water and lipid diffusion-weighted images (DWIs) simultaneously, we devised a novel method utilizing chemical shift displacement-based separation of lipid tissue (SPLIT) imaging. Materials and methodsSingle-shot diffusion echo-planar imaging without fat suppression was used and the imaging parameters were optimized to separate water and lipid DWIs by chemical shift displacement of the lipid signals along the phase-encoding direction. Using the optimized conditions, transverse DWIs at the maximum diameter of the right calf were scanned with multiple b-values in five healthy subjects. Then, apparent diffusion coefficients (ADCs) were calculated in the tibialis anterior muscle (TA), tibialis bone marrow (TB), and subcutaneous fat (SF), as well as restricted and perfusion-related diffusion coefficients (D and D*, respectively) and the fraction of the perfusion-related diffusion component (F) for TA. ResultsWater and lipid DWIs were separated adequately. The mean ADCs of the TA, TB, and SF were 1.56±0.03mm2/s, 0.01±0.01mm2/s, and 0.06±0.02mm2/s, respectively. The mean D*, D, and F of the TA were 13.7±4.3mm2/s, 1.48±0.05mm2/s, and 4.3±1.6%, respectively. ConclusionSPLIT imaging makes it possible to simply and simultaneously obtain water and lipid DWIs without special pulse sequence and increases the amount of diffusion information of water and lipid tissue.