Motion-sensitized Driven-equilibrium Research Articles

Carotid and aortic plaque imaging using 3D gradient-echo imaging and the three-point Dixon method with improved motion-sensitized driven-equilibrium (iMSDE)

BackgroundWe devised a method that combines the 3D-Dixon-gradientecho (GRE) method with an improved motion-sensitized driven-equilibrium (iMSDE) to suppress blood flow signals. PurposeThe purpose of this study was to evaluate the effectiveness of the new method we developed plaque imaging method (3D-Dixon-GRE with the iMSDE method). Study typeRetrospective cohort. PopulationThirty-nine patients who underwent cervical plaque imaging.FIELD STRENGTH/SEQUENCE:3.0 T/3D-GRE. AssessmentSignal intensities of the common carotid artery, aorta, plaque, muscle, and subcutaneous fat were measured through the VISTA and the 3D-Dixon-GRE with iMSDE methods, and each contrast was calculated. Statistical testUsed the Mann Whitney U test. P-values below 0.05 were considered statistically significant. ResultsPlaque and muscle contrast estimated through the VISTA method and 3D-Dixon-GRE with iMSDE method was 1.60 ± 0.96 and 2.04 ± 1.06, respectively, (P < 0.05). The contrast between the flow (common carotid artery and Aorta) and muscle according to the VISTA method and 3D-Dixon-GRE with iMSDE method was 0.24 ± 0.11 and 0.40 ± 0.12, respectively (P < 0.001). Finally, the mean contrast for subcutaneous fat and muscle at six locations was 3.05 ± 1.25 and 0.81 ± 0.23 for the VISTA method and 3D-Dixon-GRE with the iMSDE method, respectively (P < 0.001). Data conclusionCompared to the conventional method (VISTA), the 3D-Dixon-GRE with iMSDE method is preferable in relation to the fat suppression effect, but it is disadvantageous regarding blood flow signal suppression. Therefore, the 3D-Dixon-GRE with the iMSDE method could be considered useful for plaque imaging.

High-resolution magnetic resonance imaging-based radiomic features aid in selecting endovascular candidates among patients with cerebral venous sinus thrombosis

ObjectivesCerebral venous sinus thrombosis (CVST) can cause sinus obstruction and stenosis, with potentially fatal consequences. High-resolution magnetic resonance imaging (HRMRI) can diagnose CVST qualitatively, although quantitative screening methods are lacking for patients refractory to anticoagulation therapy and who may benefit from endovascular treatment (EVT). Thus, in this study, we used radiomic features (RFs) extracted from HRMRI to build machine learning models to predict response to drug therapy and determine the appropriateness of EVT.Materials and methodsRFs were extracted from three-dimensional T1-weighted motion-sensitized driven equilibrium (MSDE), T2-weighted MSDE, T1-contrast, and T1-contrast MSDE sequences to build radiomic signatures and support vector machine (SVM) models for predicting the efficacy of standard drug therapy and the necessity of EVT.ResultsWe retrospectively included 53 patients with CVST in a prospective cohort study, among whom 14 underwent EVT after standard drug therapy failed. Thirteen RFs were selected to construct the RF signature and CVST-SVM models. In the validation dataset, the sensitivity, specificity, and area under the curve performance for the RF signature model were 0.833, 0.937, and 0.977, respectively. The radiomic score was correlated with days from symptom onset, history of dyslipidemia, smoking, fibrin degradation product, and D-dimer levels. The sensitivity, specificity, and area under the curve for the CVST-SVM model in the validation set were 0.917, 0.969, and 0.992, respectively.ConclusionsThe CVST-SVM model trained with RFs extracted from HRMRI outperformed the RF signature model and could aid physicians in predicting patient responses to drug treatment and identifying those who may require EVT.

The Role of Improved Motion-Sensitized Driven Equilibrium Blood Suppression and Fat Saturation on T2 Relaxation Time, Using GraSE Sequence in Cardiac Magnetic Resonance Imaging.

T2 mapping is a valuable technique in cardiac MR imaging that offers insights into the microstructural characteristics of myocardial tissue. However, it was shown that myocardial T2 relaxation times (T2 ) measured vary significantly depending on sequence, sequence parameters, and field strength. To assess T2 variability and image quality in cardiac T2 maps using four variants of the gradient-spin echo (GraSE) sequence, having different methods of blood signal suppression (double inversion recovery (DIR) and improved motion-sensitized driven equilibrium (iMSDE) and with and without the addition of fat saturation (FS). Prospective. 48 healthy volunteers (46.7 +/- 21.5 years, 24 male) with no cardiac history. GraSE sequence with DIR (GraSEDIR ), with iMSDE (GraSEiMSDE ) and FS (GraSEDIR -FS) and with both iMSDE and FS (GraSEiMSDE -FS) at 1.5T. Global T2 from three short axis myocardial slices. and image quality assessments using a 5-point Lickert scale (1, (non-diagnostic) to 5, (excellent)) were conducted to evaluate the impact of DB and FS techniques on myocardial T2 measurements and image quality. Paired t-tests or non-parametric equivalents for comparisons between sequences. The Bland-Altmann plots and Pearson rank correlation analyses, as appropriate. A P value <0.05 was considered statistically significant. The mean global T2 values for GraSEDIR , GraSEDIR -FS, GraSEiMSDE , and GraSEiMSDE -FS, were 52.84 ± 5.72 msec, 54.98 ± 3.59 msec, 53.9 ± 4.05 msec, and 55.14 ± 4.28 msec, respectively, with no significant differences (P = 0.092). High image quality scores (>4 out of 5) were obtained for all sequence variants with no significant differences between them (P = 0.11). All GraSE sequence variants exhibited approximately the same results and variations in the DB technique and addition of FS did not have significant impact on myocardial T2 values. 2 TECHNICAL EFFICACY: Stage 1.

Molecular Magnetic Resonance Imaging of Aneurysmal Inflammation Using a Redox Active Iron Complex.

Inflammation plays a key role in driving brain aneurysmal instability and rupture, but clinical tools to noninvasively differentiate between inflamed and stable aneurysms are lacking. We hypothesize that imaging oxidative changes in the aneurysmal microenvironment driven by myeloid inflammatory cells may represent a noninvasive biomarker to evaluate rupture risk. In this study, we performed initial evaluation of the oxidatively activated probe Fe-PyC3A as a tool for magnetic resonance imaging (MRI) of inflammation in a rabbit model of saccular aneurysm. The difference in longitudinal relaxivity ( r1 ) in reduced and oxidized states of Fe-PyC3A was measured in water and blood plasma phantoms at 3 T. A rabbit saccular aneurysm model was created by endovascular intervention/elastinolysis with subsequent decellularization in situ. Rabbits were imaged at 4 weeks (n = 4) or 12 weeks (n = 4) after aneurysmal induction, when luminal levels of inflammation reflected by the presence of myeloperoxidase positive cells are relatively high and low, respectively, using a 3 T clinical scanner. Both groups were imaged dynamically using a 2-dimensional T1-weighted fast field echo pulse MRI sequence before and up to 4 minutes postinjection of Fe-PyC3A. Dynamic imaging was then repeated after an injection of gadobutrol (0.1 mmol/kg) as negative control probe. Rabbits from the 12-week aneurysm group were also imaged before and 20 minutes and 3 hours after injection of Fe-PyC3A using an axial respiratory gated turbo-spin echo (TSE) pulse sequence with motion-sensitized driven equilibrium (MSDE) preparation. The MSDE/TSE imaging was repeated before, immediately after dynamic acquisition (20 minutes postinjection), and 3 hours after injection of gadobutrol. Aneurysmal enhancement ratios (ERs) were calculated by dividing the postinjection aneurysm versus skeletal muscle contrast ratio by the preinjection contrast ratio. After imaging, the aneurysms were excised and inflammatory infiltrate was characterized by fluorometric detection of myeloperoxidase activity and calprotectin immunostaining, respectively. In vitro relaxometry showed that oxidation of Fe-PyC3A by hydrogen peroxide resulted in a 15-fold increase of r1 at 3 T. Relaxometry in the presence of blood plasma showed no more than a 10% increase of r1 , indicating the absence of strong interaction of Fe-PyC3A with plasma proteins. Dynamic imaging with Fe-PyC3A generated little signal enhancement within the blood pool or adjacent muscle but did generate a transient increase in aneurysmal ER that was significantly greater 4 weeks versus 12 weeks after aneurysm induction (1.6 ± 0.30 vs 1.2 ± 0.03, P < 0.05). Dynamic imaging with gadobutrol generated strong aneurysmal enhancement, but also strong enhancement of the blood and muscle resulting in smaller relative ER change. In the 12-week group of rabbits, MSDE/TSE imaging showed that ER values measured immediately after dynamic MRI (20 minutes postinjection) were significantly higher ( P < 0.05) in the case of Fe-PyC3A (1.25 ± 0.06) than for gadobutrol injection (1.03 ± 0.03). Immunohistochemical corroboration using anticalprotectin antibody showed that leukocyte infiltration into the vessel walls and luminal thrombi was significantly higher in the 4-week group versus 12-week aneurysms (123 ± 37 vs 18 ± 7 cells/mm 2 , P < 0.05). Magnetic resonance imaging using Fe-PyC3A injection in dynamic or delayed acquisition modes was shown to generate a higher magnetic resonance signal enhancement in aneurysms that exhibit higher degree of inflammation. The results of our pilot experiments support further evaluation of MRI using Fe-PyC3A as a noninvasive marker of aneurysmal inflammation.

Evaluation of Intra-Aneurysmal Residual Blood Flow with the iMSDE T1-Black Blood Imaging after Flow Diverter Treatment.

We aimed to evaluate the efficacy of the "improved motion-sensitized driven-equilibrium (iMSDE)"-prepared T1-weighted black blood (T1-BB) MRI for monitoring treatment effect with a flow diverter (FD) for cerebral aneurysms. Following the exclusion of concomitant coiling and retreatment cases from 60 consecutive cases of cerebral aneurysms treated with FDs at our institution, 32 with imaging data were included in the analysis. Detectability of residual blood flow within the aneurysms was validated as follows: 1) comparison of MRI sequences (iMSDE-prepared T1-BB images, T1-weighted images [ T1WI], and time-of-flight [ TOF]-MRA) in cases of incompletely occluded aneurysms and 2) comparison of angiography and MRI sequences in the same period. 1) The probability of diagnosing intra-aneurysmal blood flow was significantly higher with iMSDE-prepared T1-BB (iMSDE-prepared T1-BB vs. T1WI, p <0.001; iMSDE-prepared T1-BB vs. TOF-MRA, p <0.001). 2) The diagnostic accuracy of residual aneurysmal blood flow was significantly higher with iMSDE-prepared T1-BB than that with T1WI (p = 0.032). Furthermore, in cases of incomplete occlusion, the probability of detecting intra-aneurysmal blood flow was significantly higher with iMSDE-prepared T1-BB (iMSDE-prepared T1-BB vs. T1WI, p <0.001; iMSDE-prepared T1-BB vs. TOF-MRA, p = 0.023). Our results demonstrated that iMSDE-prepared T1-BB could help distinguish between blood flow and thrombus within the aneurysms after FD treatment, especially in the early stages of FD treatment.

Improved Blood Suppression of Motion-Sensitized Driven Equilibrium in High-Resolution Whole-Brain Vessel Wall Imaging: Comparison of Contrast-Enhanced 3D T1-Weighted FSE with Motion-Sensitized Driven Equilibrium and Delay Alternating with Nutation for Tailored Excitation.

High-resolution vessel wall MR imaging is prone to slow-flow artifacts, particularly when gadolinium shortens the T1 relaxation time of blood. This study aimed to determine the optimal preparation pulses for contrast-enhanced high-resolution vessel wall MR imaging. Fifty patients who underwent both motion-sensitized driven equilibrium and delay alternating with nutation for tailored excitation (DANTE) preparation pulses with contrast-enhanced 3D-T1-FSE were retrospectively included. Qualitative analysis was performed using a 4-grade visual scoring system for black-blood performance in the small-sized intracranial vessels, overall image quality, severity of artifacts, and the degree of blood suppression in all cortical veins as well as transverse sinuses. Quantitative analysis of the M1 segment of the MCA was also performed. The qualitative analysis revealed that motion-sensitized driven equilibrium demonstrated a significantly higher black-blood score than DANTE in contrast-enhanced 3D-T1-FSE of the A3 segment (3.90 versus 3.58, P < .001); M3 (3.72 versus 3.26, P = .004); P2 to P3 (3.86 versus 3.64, P = .017); the internal cerebral vein (3.72 versus 2.32, P < .001); and overall cortical veins (3.30 versus 2.74, P < .001); and transverse sinuses (2.82 versus 2.38, P < .001). SNRlumen, contrast-to noise ratiowall-lumen, and SNRwall in the M1 vessel were not significantly different between the 2 preparation pulses (all, P > .05). Motion-sensitized driven equilibrium demonstrated improved blood suppression on contrast-enhanced 3D-T1-FSE in the small intracranial arteries and veins compared with DANTE. Motion-sensitized driven equilibrium is a useful preparation pulse for high-resolution vessel wall MR imaging to decrease venous contamination and suppress slow-flow artifacts when using contrast enhancement.

Application of motion-sensitized driven equilibrium based black blood 3D TSE sequence in the detection of brain metastases

PurposeTo investigate the value of contrast-enhanced motion-sensitized driven equilibrium (MSDE) based black blood three-dimensional (3D) turbo spin echo (TSE) sequence in the detection of brain metastases compared with 3D Turbo Field Echo (TFE) sequence. Material and methods53 patients with suspected brain metastases were included in this study between November 2021 and February 2022. Contrast-enhanced cranial 3D TFE and MSDE-based 3D black blood TSE MR imaging were performed for each patient. Two senior neuroradiologists independently evaluated all contrast-enhanced 3D TFE and 3D black blood TSE images to detect brain metastases. The images were divided into two groups: the TFE group and the black blood TSE group. Agreement between the two reviewers for detection of the brain metastases in each group was performed using the kappa test. The two reviewers determined the final result for brain metastasis in the two groups by consensus. A paired t-test was performed for the final detection of brain metastases between the black blood TSE group and the TFE group. ResultsThere was a very good agreement between the two reviewers for the TSE group (kappa = 0.823) and a good agreement for the TFE group (kappa = 0.663). There was a statistical difference in the detection of small cortical and subcortical metastases between the TFE and the black blood TSE groups (t = 5.039, P = 0.000 < 0.05). There was no statistical difference in the detection of small supratentorial deep lesions and subtentorial lesions between the two groups. ConclusionCompared with conventional 3D TFE sequence, MSDE-based black blood 3D TSE sequence was superior for visualizing small brain metastases, especially small cortical and subcortical metastases.

Free‐breathing three‐dimensional isotropic‐resolution MR sequence for simultaneous vessel wall imaging of bilateral renal arteries and abdominal aorta: Feasibility and reproducibility

Many diseases can simultaneously involve renal arteries and the adjacent abdominal aorta. This study proposed a free-breathing three-dimensional (3D) isotropic-resolution magnetic resonance sequence for simultaneous vessel wall imaging (VWI) of bilateral renal arteries and adjacent abdominal aorta. A respiratory-triggered isotropic-resolution sequence that combined the improved motion-sensitized driven-equilibrium (iMSDE) preparation with the spoiled gradient recalled (SPGR) readout (iMSDE-SPGR) was proposed for simultaneous VWI of renal arteries and abdominal aorta. The proposed iMSDE-SPGR sequence was optimized by positioning spatial saturation pulses (i.e., REST slabs) elaborately to further alleviate respiratory and gastrointestinal motion artifacts and selecting appropriate first-order gradient moment (m1 ) of the iMSDE preparation. Thirteen healthy subjects and 13 patients with renal artery stenosis underwent simultaneous VWI with the optimized iMSDE-SPGR sequence at 3.0 T. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and morphology of renal arterial wall and aortic wall were measured. Reproducibility of intra-observer, inter-observer, and scan-rescan (n=13 healthy subjects) in measuring SNR, CNR, and morphology was evaluated. For the reproducibility test, the agreement was determined using intraclass correlation coefficients (ICC), and the differences were compared using paired t-test or nonparametric Wilcoxon test when appropriate. Bland-Altman plots were used to calculate the bias between observers and between scans. The proposed iMSDE-SPGR sequence was feasible for simultaneous VWI both in the healthy subjects and the patients. The sequence showed good to excellent inter-observer (ICC: 0.615-0.999), excellent intra-observer (ICC: 0.801-0.998), and scan-rescan (ICC: 0.768-0.998) reproducibility in measuring morphology, SNR, and CNR. There were no significant differences in SNR, CNR, and morphology measurements between observers and between scans (all p>0.05). Bland-Altman plots showed small bias in assessing SNR, CNR, and morphology. The proposed free-breathing 3D isotropic-resolution iMSDE-SPGR technique is feasible and reproducible for simultaneous VWI of bilateral renal arteries and adjacent abdominal aorta.

Detection of Advanced Lesions of Atherosclerosis in Carotid Arteries Using 3-Dimensional Motion-Sensitized Driven-Equilibrium Prepared Rapid Gradient Echo (3D-MERGE) Magnetic Resonance Imaging as a Screening Tool.

Two-dimensional high-resolution multicontrast magnetic resonance imaging (2D-MC MRI) is currently the most reliable and reproducible noninvasive carotid vessel wall imaging technique. However, the long scan time required for 2D-MC MRI restricts its practical clinical application. Alternatively, 3-dimensional motion-sensitized driven-equilibrium prepared rapid gradient echo (3D-MERGE) vessel wall MRI can provide high isotropic resolution with extensive coverage in two minutes. In this study, we sought to prove that 3D-MERGE alone can serve as a screening tool to identify advanced carotid lesions. Two hundred twenty-seven subjects suspected of recent ischemic stroke or transient ischemic attack were imaged using 2D-MC MRI with an imaging time of 30 minutes, then with 3D-MERGE with an imaging time of 2 minutes, on 3T-MRI scanners. Two experienced reviewers interpreted plaque components using 2D-MC MRI as the reference standard and categorized plaques using a modified American Heart Association lesion classification for MRI. Plaques of American Heart Association type IV and above were classified as advanced. Arteries of American Heart Association types I to II and III were categorized as normal or with early lesions, respectively. One radiologist independently reviewed only 3D-MERGE and labeled the plaques as advanced if they had a wall thickness of >2 mm with high or low signal intensity compared with the adjacent sternocleidomastoid muscle. Sensitivity, specificity, and accuracy for 3D-MERGE were calculated. Four hundred forty-nine arteries from 227 participants (mean age 61.2 years old, 64% male) were included in the analysis. Sensitivity, specificity, and accuracy for identification of advanced lesions on 3D-MERGE were 95.0% (95% CI, 91.8-97.2), 86.9% (95% CI, 81.4-92.0), 93.8% (95% CI, 91.1-95.8), respectively. 3D-MERGE can accurately identify advanced carotid atherosclerotic plaques in patients suspected of stroke or transient ischemic attack. It has a more extensive coverage and higher sensitivity and specificity for advanced plaque detection with a much shorter acquisition time than 2D-MC MRI. URL: https://www.clinicaltrials.gov; Unique identifier: NCT02017756.

Pseudo-Enhancement in Intracranial Aneurysms on Black-Blood MRI: Effects of Flow Rate, Spatial Resolution, and Additional Flow Suppression.

Vessel-wall enhancement (VWE) on black-blood MRI (BB MRI) has been proposed as an imaging marker for a higher risk of rupture and associated with wall inflammation. Whether VWE is causally linked to inflammation or rather induced by flow phenomena has been a subject of debate. To study the effects of slow flow, spatial resolution, and motion-sensitized driven equilibrium (MSDE) preparation on signal intensities in BB MRI of patient-specific aneurysm flow models. Prospective. Aneurysm flow models based on 3D rotational angiography datasets of three patients with intracranial aneurysms were 3D printed and perfused at two different flow rates, with and without Gd-containing contrast agent. Variable refocusing flip angle 3D fast-spin echo sequence at 3 T with and without MSDE with three voxel sizes ((0.5 mm)3 , (0.7 mm)3 , and (0.9 mm)3 ); time-resolved with phase-contrast velocity-encoding 3D spoiled gradient echo sequence (4D flow MRI). Three independent observers performed a qualitative visual assessment of flow patterns and signal enhancement. Quantitative analysis included voxel-wise evaluation of signal intensities and magnitude velocity distributions in the aneurysm. Kruskal-Wallis test, potential regressions. A hyperintense signal in the lumen and adjacent to the aneurysm walls on BB MRI was colocalized with slow flow. Signal intensities increased by a factor of 2.56 ± 0.68 (P < 0.01) after administering Gd contrast. After Gd contrast administration, the signal was suppressed most in conjunction with high flows and with MSDE (2.41 ± 2.07 for slow flow without MSDE, and 0.87 ± 0.99 for high flow with MSDE). A clear result was not achieved by modifying the spatial resolution . Slow-flow phenomena contribute substantially to aneurysm enhancement and vary with MRI parameters. This should be considered in the clinical setting when assessing VWE in patients with an unruptured aneurysm. 2 TECHNICAL EFFICACY: Stage 2.

A Supplemental Technique for Preoperative Evaluation of Giant Intracranial Aneurysm.

Preoperative planning mainly relies on digital subtraction angiography (DSA) and computed tomography angiography. However, neither technique can reveal thrombi in giant intracranial aneurysms (GIAs). In this study, we aimed to reconstruct the circulating and noncirculating parts of GIAs with the time-of-flight (TOF) and motion-sensitized driven-equilibrium (MSDE) sequences with 3D Slicer to reveal an integrated presentation of GIAs, compare its accuracy, and validate the usefulness for preoperative planning. Patients with GIAs who were treated with microsurgery in our department were included in this study. Both the TOF and MSDE sequence data for each patient were loaded into 3D Slicer for reconstruction and segmentation. The parameters measured by 3D Slicer were compared with those measured by DSA. The mean diameter for all GIAs was 28.7 ± 1.5 mm (range, 25.9-31.9 mm). The mean diameter for all GIAs measured by DSA and 3D Slicer was 24.46 ± 5.25 and 28.66 ± 1.48 mm, respectively (t = 4.948, p < 0.01). When only the nonthrombotic GIAs were included, the mean diameter measured by DSA and 3D Slicer was 28.69 ± 2.03 and 28.97 ± 1.79 mm, respectively (t = 1.023, p = 0.323). The mean aneurysmal volume was 8,292.6 ± 1,175.1 mm3 and the mean thrombotic volume was 3,590.0 ± 1,003.7 mm3. The MSDE sequence brings diagnostic benefits as a comparison to other MRI sequences. Reconstruction of GIAs with 3D Slicer is a low-cost, dependable, and useful supplemental technique for surgical planning.

3D Cranial Nerve Imaging, a Novel MR Neurography Technique Using Black-Blood STIR TSE with a Pseudo Steady-State Sweep and Motion-Sensitized Driven Equilibrium Pulse for the Visualization of the Extraforaminal Cranial Nerve Branches.

This study investigated the feasibility of a 3D black-blood STIR TSE sequence with a pseudo steady-state sweep and motion-sensitized driven equilibrium pulse for extraforaminal cranial nerve imaging on a 3T system. Assessments of healthy volunteers showed near-perfect agreement in nerve visualization with excellent to good visualization of the extraforaminal trigeminal, greater occipital, and facial nerves. Suppression of surrounding tissues was excellent to good. 3D cranial nerve imaging can produce nerve selective imaging of extraforaminal cranial and spinal nerve branches.

Visualization of Cerebrospinal Fluid Motion in the Whole Brain Using Three-dimensional Dynamic Improved Motion-sensitized Driven-equilibrium Steady-state Free Precession.

The feasibility of the 3D dynamic improved motion-sensitized driven-equilibrium steady-state free precession (3D dynamic iMSDE SSFP) was evaluated for visualizing CSF motion and the appropriate parameters were determined. Both flow phantom and volunteer studies revealed that linear ordering and the shortest acquisition duration time were optimal. 3D dynamic iMSDE SSFP provides good quality imaging of CSF motion in the whole brain and enables visualization of flow in arbitrary planes from a single 3D volume scan.

The value of 3D-iMSDE MR neurography in the determination of the anatomical relationship between intraparotid facial nerve and parotid ducts and parotid tumors

Objective To investigate the spatial relationship between intraparotid facial nerve and parotid ducts in different types of parotid neoplasms with 3D improved motion-sensitized driven-equilibrium pulse (3D-iMSDE) MR neurography, and to guide the operation plan. Methods By means of prospective research methods, the sequences of 3D-iMSDE and 3D-T2-fast field echo (3D-T2-FFE) were obtained in 30 healthy volunteers and 40 patients with parotid gland tumors, respectively. All patients with parotid mass were found by physical examination, by maxillofacial surgeons or by ultrasonography or other imaging examinations. Facial nerve trunk with its first branches and parotid ducts were evaluated independently on images of iMSDE and T2-FFE sequence for volunteers. The signal intensity ratio (SIR) of both facial nerve and parotid ducts were compared respectively in two sequences The relationship between intraparotid facial nerve and parotid ducts with the lesion were analyzed on images of iMSDE and T2-FFE sequences for 40 patients. The results were compared with intra-operative anatomy and post-operative pathological findings.Wilcoxon symbolic rank test, t test and chi-square test were used Results The image scores of intra-parotid facial nerve and parotid ducts in iMSDE sequence were higher than that of T2-FFE sequence in all 30 healthy volunteers. The difference was statistically significant (Z=-6.197,P<0.05). Both the facial nerve and parotid duct on images of iMSDE sequence had higher SIR than that of T2-FFE. The differences were statistically significant (t=10.772,11.586, respectively;P<0.05). Forty patients with parotid gland tumors had a total of 41 lesions. Compared with the intraoperative anatomy, the accuracy of iMSDE and T2-FFE sequences in showing the relationship between the facial nerve and its primary branches with the mass were 36/41 (87.8%), and 22/41 (53.7%) respectively, and the accuracy of the two sequences in showing the relationship between the dominant duct of the parotid gland and the mass were 38/41 (92.7%) and 30/41 (73.2%), respectively.The accuracy rate in showing the relationship between facial nerve and its primary branch and the mass on images of iMSDE sequence were higher than that of T2-FFE sequence, and also in showing the relationship of parotid duct and the mass. The statistical differences were significant (χ2=9.725, 5.513;P<0.05,respectively). In the iMSDE sequence, the relationship between the facial nerve and its first branches (temporofacial and cervicofacial division) with the tumor was correctly demonstrated in 36 cases. 38 cases of parotid ducts were satisfactorily displayed on image of iMSDE sequence. Conclusions The 3D-iMSDE MRN sequence can correctly show the relationship between intraparotid facial nerve and parotid duct and the parotid gland neoplasms. Key words: Parotid neoplasms; Facial nerve; Magnetic resonance imaging; Parotid duct

Insufficient slow-flow suppression mimicking aneurysm wall enhancement in magnetic resonance vessel wall imaging: a phantom study.

MR vessel wall imaging (VWI) is increasingly performed in clinical settings to support treatment decision-making regarding intracranial aneurysms. Aneurysm wall enhancement after contrast agent injection is expected to be related to aneurysm instability and rupture status. However, the authors hypothesize that slow-flow artifacts mimic aneurysm wall enhancement. Therefore, in this phantom study they assess the effect of slow flow on wall-like enhancement by using different MR VWI techniques. The authors developed an MR-compatible aneurysm phantom model, which was connected to a pump to enable pulsatile inflow conditions. For VWI, 3D turbo spin echo sequences-both with and without motion-sensitized driven equilibrium (MSDE) and delay alternating with nutation for tailored excitation (DANTE) preparation pulses-were performed using a 3-T MR scanner. VWI was acquired both before and after Gd contrast agent administration by using two different pulsatile inflow conditions (2.5 ml/sec peak flow at 77 and 48 beats per minute). The intraluminal signal intensity along the aneurysm wall was analyzed to assess the performance of slow-flow suppression. The authors observed wall-like enhancement after contrast agent injection, especially in low pump rate settings. Preparation pulses, in particular the DANTE technique, improved the performance of slow-flow suppression. Near-wall slow flow mimics wall enhancement in VWI protocols. Therefore, VWI should be carefully interpreted. Preparation pulses improve slow-flow suppression, and therefore the authors encourage further development and clinical implementation of these techniques.

Vessel wall enhancement of intracranial aneurysms: fact or artifact?

For patients with subarachnoid hemorrhage (SAH) and multiple intracranial aneurysms, it is often challenging to identify the ruptured aneurysm. Some investigators have asserted that vessel wall imaging (VWI) can be used to identify the ruptured aneurysm since wall enhancement after contrast agent injection is presumably related to inflammation in unstable and ruptured aneurysms. The aim of this study was to determine whether additional factors contribute to aneurysm wall enhancement by assessing imaging data in a series of patients. Patients with symptoms of SAH who subsequently underwent VWI in the period between January 2017 and September 2018 were eligible for study inclusion. Three-dimensional turbo spin-echo sequences with motion-sensitized driven-equilibrium preparation pulses were acquired using a 3-T MRI scanner to visualize the aneurysm wall. Identification of the ruptured aneurysm was based on aneurysm characteristics and hemorrhage distributions on MRI. Complementary imaging data (CT, DSA, MRI) were used to assess potential underlying enhancement mechanisms. Additionally, aneurysm luminal diameter measurements on MRA were compared with those on contrast-enhanced VWI to assess the intraluminal contribution to aneurysm enhancement. Six patients with 14 aneurysms were included in this series. The mean aneurysm size was 5.8 mm (range 1.1-16.9 mm). A total of 10 aneurysms showed enhancement on VWI; 5 ruptured aneurysms showed enhancement, and 1 unruptured but symptomatic aneurysm showed enhancement on VWI and ruptured 1 day later. Four unruptured aneurysms showed enhancement. In 6 (60%) of the 10 enhanced aneurysms, intraluminal diameters appeared notably smaller (≥ 0.8 mm smaller) on contrast-enhanced VWI compared to their appearance on multiple overlapping thin slab acquisition time of flight (MOTSA-TOF) MRA and/or precontrast VWI, suggesting that enhancement was at least partially in the aneurysm lumen itself. Several factors other than the hypothesized inflammatory response contribute to aneurysm wall enhancement. In 60% of the cases in this study, enhancement was at least partially caused by slow intraaneurysmal flow, leading to pseudo-enhancement of the aneurysm wall. Notwithstanding, there seems to be clinical value in differentiating ruptured from unruptured aneurysms using VWI, but the hypothesis that we image the inflammatory cell infiltration in the aneurysm wall is not yet confirmed.

A Comparison of Black-blood T2 Mapping Sequences for Carotid Vessel Wall Imaging at 3T: An Assessment of Accuracy and Repeatability.

Purpose:This study is to compare the accuracy of four different black-blood T2 mapping sequences in carotid vessel wall.Methods:Four different black-blood T2 mapping sequences were developed and tested through phantom experiments and 17 healthy volunteers. The four sequences were: 1) double inversion-recovery (DIR) prepared 2D multi-echo spin-echo (MESE); 2) DIR-prepared 2D multi-echo fast spin-echo (MEFSE); 3) improved motion-sensitized driven-equilibrium (iMSDE) prepared 3D FSE and 4) iMSDE prepared 3D fast spoiled gradient echo (FSPGR). The concordance correlation coefficient and Bland–Altman statistics were used to compare the sequences with a gold-standard 2D MESE, without blood suppression in phantom studies. The volunteers were scanned twice to test the repeatability. Mean and standard deviation of vessel wall T2, signal-to-noise (SNR), the coefficient of variance and interclass coefficient (ICC) of the two scans were compared.Results:The phantom study demonstrated that T2 measurements had high concordance with respect to the gold-standard (all r values >0.9). In the volunteer study, the DIR 2D MEFSE had significantly higher T2 values than the other three sequences (P < 0.01). There was no difference in T2 measurements obtained using the other three sequences (P > 0.05). iMSDE 3D FSE had the highest SNR (P < 0.05) compared with the other three sequences. The 2D DIR MESE has the highest repeatability (ICC: 0.96, [95% CI: 0.88–0.99]).Conclusion:Although accurate T2 measurements can be achieved in phantom by the four sequences, in vivo vessel wall T2 quantification shows significant differences. The in vivo images can be influenced by multiple factors including black-blood preparation and acquisition method. Therefore, a careful choice of acquisition methods and analysis of the confounding factors are required for accurate in vivo carotid vessel wall T2 measurements. From the settings in this study, the iMSDE prepared 3D FSE is preferred for the future volunteer/patient scans.

Three-dimensional arterial spin labeling imaging with a DANTE preparation pulse

On arterial spin-labeled (ASL) images, areas of bright intravascular signal will appear when the post labeling delay time is shorter than arterial transit time. Vascular suppression (VS) schemes reduce artefactual bright signal by dephasing intravascular labeled spins. However, existing VS methods, such as Motion-Sensitized Driven-Equilibrium (MSDE), decrease the uniformity of the signal intensity distribution and extend the echo time. The purpose of this study is to compare VS using a Delays Alternating with Nutation for Tailored Excitation (DANTE) preparation pulse, with MSDE for ASL imaging on a flow phantom and volunteer data. In the phantom study, the signal decay pattern of moving water was similar for both methods. In the volunteer study, the bright intravascular signal artifact was decreased by both methods. However right–left differences in signal intensity were smaller using DANTE-prepared ASL. The proposed DANTE-prepared ASL sequence has a vessel suppression effect while maintaining a uniform signal intensity distribution. This study indicates that DANTE is a potentially useful method for vessel suppression in ASL imaging.

Assessment of longitudinal distribution of subclinical atherosclerosis in femoral arteries by three-dimensional cardiovascular magnetic resonance vessel wall imaging

BackgroundLower extremity peripheral artery disease has become a significant health burden worldwide. Since the treatment strategies can be different if atherosclerotic disease involves different femoral artery segments, it is important to assess plaque distribution among different segments of femoral arteries. We sought to investigate the longitudinal distribution of subclinical femoral artery atherosclerosis in asymptomatic elderly adults using cardiovascular magnetic resonance (CMR) vessel wall imaging.MethodsAsymptomatic elderly subjects underwent three-dimensional (3D) CMR vessel wall imaging for femoral arteries. The 3D motion sensitized-driven equilibrium prepared rapid gradient-echo (3D-MERGE) sequence was acquired from the common femoral artery to the popliteal artery. The femoral artery was divided into 4 segments: common femoral artery (CFA), proximal superficial femoral artery (pSFA), adductor canal (AC) segment of femoral artery, and popliteal artery (PA). The morphological characteristics including lumen area, wall area, maximum and minimum wall thickness, normalized wall index (NWI = wall area / [lumen area + wall area] × 100%), and eccentricity index ([maximum wall thickness - minimum wall thickness] / maximum wall thickness), luminal stenosis, and presence of atherosclerotic plaque were evaluated and compared between bilateral sides and among different femoral artery segments in each side of femoral artery. The associations between ankle-brachial index (ABI) and cardiovascular risk factors and femoral artery plaque characteristics were also determined.ResultsOf 107 recruited subjects (71.9 ± 5.6 years; 48 males), 70 (65.4%) were found to have femoral artery plaques. The atherosclerotic plaques were most frequently found in PA (41.1%) and CFA (40.2%) segments, followed by pSFA (31.8%) and AC (23.4%) segments (p = 0.002). Similarly, PA and CFA segments showed significantly greater maximum wall thickness and eccentricity index compared with pSFA and AC segments (all p < 0.001). Significant differences can be found in NWI among four segments of femoral arteries (p < 0.001) and PA showed the highest NWI (54.8%), followed by AC (54.3%), pSFA (52.4%) and CFA (45.9%) segments. Compared with right femoral artery, left femoral artery had significant smaller lumen area and greater NWI in most of segments (p < 0.002). There were no significant differences in ABI between subjects with and without atherosclerotic plaques (p = 0.161). The presence of subclinical atherosclerotic plaque in femoral arteries was significantly associated with cardiovascular risk factors including age (odds ratio [OR], 1.133; 95% confidence interval [CI], 1.048–1.224, p = 0.002), male gender (OR, 3.914; 95% CI, 1.612–9.501, p = 0.003), and hypertension (OR, 4.000; 95% CI, 1.700–9.411, p = 0.001), respectively.ConclusionsSubclinical femoral artery atherosclerosis is prevalent in the elderly population, particularly in the left femoral artery and segments of CFA and PA, and is associated with age, male gender and hypertension. Our findings suggest that, for screening subclinical atherosclerosis, more attention needs to be paid to the specific side and segments of femoral arteries, particularly older individuals and those with these cardiovascular disease risk factors.

The Usefulness of the Contrast-enhanced Motion-sensitized Driven-equilibrium Three-dimensional Turbo Spin Echo (MSDE-3D-TSE) Sequence Method in Cases with Multiple Ruptured Cerebral Arterial Aneurysms

The Usefulness of the Contrast-enhanced Motion-sensitized Driven-equilibrium Three-dimensional Turbo Spin Echo (MSDE-3D-TSE) Sequence Method in Cases with Multiple Ruptured Cerebral Arterial Aneurysms