Aneurysmal wall enhancement and hemodynamics: pixel-level correlation between spatial distribution

Transition of intracranial aneurysmal wall enhancement from high to low wall shear stress mediation with size increase: A hemodynamic study based on 7T magnetic resonance imaging

Background

Wall shear stress (WSS) has been proved to be related to the formation, development and rupture of intracranial aneurysms. Aneurysm wall enhancement (AWE) on magnetic resonance imaging (MRI) can be caused by inflammation and have confirmed its relationship with low WSS. High WSS can also result in inflammation but the research of its correlation with AWE is lack because of the focus on large aneurysms limited by 3T MRI in most previous studies.This study aimed to assess the potential association between high or low WSS and AWE in different aneuryms. Especially the relationship between high WSS and AWE in small aneurysm.

Methods

Forty-three unruptured intracranial aneurysms in 42 patients were prospectively included for analysis. 7.0 T MRI was used for imaging. Aneurysm size was measured on three-dimensional time-of-flight (TOF) images. Aneurysm-to-pituitary stalk contrast ratio (CRstalk) was calculated on post-contrast black-blood T1-weighted fast spin echo sequence images. Hemodynamics were assessed by four-dimensional flow MRI.

Results

The small aneurysms group had more positive WSS-CRstalk correlation coefficient distribution (dome: 78.6 %, p = 0.009; body: 50.0 %, p = 0.025), and large group had more negative coefficient distribution (dome: 44.8 %, p = 0.001; body: 69.0 %, p = 0.002). Aneurysm size was positively correlated with the significant OSI-CRstalk correlation coefficient at the dome (p = 0.012) and body (p = 0.010) but negatively correlated with the significant WSS-CRstalk correlation coefficient at the dome (p < 0.001) and body (p = 0.017).

Conclusion

AWE can be mediated by both high and low WSS, and translate from high WSS- to low WSS-mediated pathways as size increase. Additionally, AWE may serve as an indicator of the stage of aneurysm development via different correlations with hemodynamic factors.

Modified no-touch technique for radio-cephalic arteriovenous fistula increases primary patency and decreases juxta-anastomotic stenosis

OBJECTIVE

Low primary patency rate is a major problem of radio-cephalic arteriovenous fistula (RC-AVF) creation. Radial artery deviation and reimplantation (RADAR) is associated with low juxta-anastomotic stenosis rate. However, inflow artery stenosis is prominent with RADAR. To further reduce injury to veins and arteries during operation, a modified no-touch technique (MNTT) was used to create RC-AVF.

METHODS

We retrospectively reviewed our prospectively maintained database of patients with end-stage renal disease (ESRD)s undergoing RC-AVF creation for hemodialysis using either the MNTT between January 2021 and January 2022 (MNTT group) or conventional surgical procedure ( end-to-side vein-to-artery anastomosis) between October 2016 and October 2017 (Control group). Patients who chose to undergo RC-AVF surgery underwent standardized preoperative mapping and postoperative fistula evaluations using duplex ultrasound. Additionally, 4D flow MRI data were used to visualize and quantify the hemodynamics of one RC-AVF by MNTT. Outcomes included primary patency, juxta-anastomotic stenosis, and maturation rates.

RESULTS

Forty patients underwent RC-AVFs by MNTT, compared to 60 patients in the control group. The MNTT group had a higher primary unassisted patency rate than the control group (p = 0.038). Juxta-anastomotic stenosis (all on the cephalic vein) occurred in 4 (10%) patients who underwent MNTT. RC-AVF maturation rates after 3 months were not different between both groups (maturation rate: 90% and 81.7% in the MNTT and control groups, respectively, p = 0.253). COX regression showed that both conventional AVF surgery (p = 0.031) and smaller cephalic vein diameter (p = 0.034) were associated with higher odds of RC-AVF failure. The AVF flow within the proximal vein remained helical during cardiac cycle. The distribution of wall shear stress (WSS) and oscillatory shear index (OSI) differed from that of conventional surgical AVF.

CONCLUSION

RC-AVF by MNTT increases primary patency rate and decreases juxta-anastomotic stenosis rate. The improvement in hemodynamics may be one of the important reasons for the better patency rate of in the RC-AVF by MNTT group.

Hemodynamic assessments of unilateral pulsatile tinnitus with jugular bulb wall dehiscence using 4D flow magnetic resonance imaging

Background

Pulsatile tinnitus (PT) is a type of tinnitus characterized by a rhythmic sound that is synchronous with the heartbeat. One of the possible causes of PT is the jugular bulb wall dehiscence (JBWD). However, the hemodynamics of this condition are not well understood. To elucidate this issue, the present study aimed to compare the blood flow of PT patients with JBWD, PT patients with sigmoid sinus wall dehiscence (SSWD), and volunteers.

Methods

A retrospective case-control study was conducted, which enrolled patients with unilateral PT who had undergone both computed tomography angiography (CTA) and four-dimensional (4D) flow magnetic resonance imaging (MRI) examinations at the Department of Otolaryngology-Head and Neck Surgery of Beijing Friendship Hospital affiliated to Capital Medical University between January 2019 and July 2023. After excluding the possible causes of PT, the patients were divided into the JBWD group and SSWD group according to the presence or absence of JBWD and/or SSWD. Finally, 11 female unilateral PT patients with JBWD (JBWD group, 11sides), 22 age- and side-matched female patients with SSWD (SSWD group, 22 sides), and 22 age-matched female volunteers (volunteer group, 36 sides) were enrolled. The area, maximum voxel velocity (Vv-max), maximum velocity (Vmax), average velocity (Vavg), and average blood flow rate (Q) were measured in the transverse sinuses (TSs), sigmoid sinuses (SSs), and jugular bulb (JB). The vortex flow pattern was also assessed. Fisher's exact test and Bonferroni correction were used for count data, with P<0.017 was considered statistically significant. Shapiro-Wilk test, one-way analysis of variance (ANOVA), Kruskal-Wallis H test, paired-samples t-test, and Wilcoxon matched-pairs signed-rank test were used for continuous variables depending on the distribution and variance of the data. The P<0.05 and corrected P<0.05 was considered statistically significant.

Results

The area and Q of TSs and JB on the symptomatic side were higher than those on the contralateral side in the JBWD group (TSs: Parea=0.004, Pflow=0.002; JB: Parea=0.034, Pflow=0.018). The area was larger and velocities were lower in the JBWD group at the TSs than the SSWD group (Parea=0.004, PVv-max=0.009, PVmax=0.021, PVavg=0.026), and velocities were higher at the distal TSs and SSs than the volunteer group (TSs: PVv-max=0.042, PVmax=0.046, PVavg=0.040; SSs: PVv-max=0.007, PVmax=0.001, PVavg=0.001). At the JB, the JBWD group also had higher Vv-max than the volunteer group (P=0.012). The occurrence rate of vortex at JB in the JBWD group was higher than both the JBWD and the volunteer groups (P=0.002<0.017 and P=0.009<0.017, respectively).

Conclusions

The blood flow of the intracranial venous sinus was different between the JBWD group and the SSWD group. The indicators that can differentiate include Vv-max, Vmax, Vavg, vortex, and TSs cross-sectional area.

Association Between Serum Homocysteine Concentration, Aneurysm Wall Inflammation, and Aneurysm Symptoms in Intracranial Fusiform Aneurysm

RATIONALE AND OBJECTIVES

The pathophysiology of fusiform intracranial aneurysm (FIA) involves inflammatory processes, and homocysteine plays a role in the inflammatory processes in the vessel wall. Moreover, aneurysm wall enhancement (AWE) has emerged as a new imaging biomarker of aneurysm wall inflammatory pathologies. To investigate the pathophysiological mechanisms of aneurysm wall inflammation and FIA instability, we aimed to determine the associations between the homocysteine concentration, AWE, and FIAs' related symptoms.

MATERIALS AND METHODS

We retrospectively reviewed the data of 53 patients with FIA who underwent both high-resolution magnetic resonance imaging and serum homocysteine concentration measurement. FIAs' related symptoms were defined as ischemic stroke or transient ischemic attack, cranial nerve compression, brainstem compression, and acute headache. The contrast ratio of the signal intensity of the aneurysm wall to the pituitary stalk (CRstalk) was used to indicate AWE. Multivariate logistic regression and receiver operating characteristic (ROC) curve analyses were performed to determine how well the independent factors could predict FIAs' related symptoms. Predictors of CRstalk were also investigated. Spearman's correlation coefficient was used to identify the potential associations between these predictors.

RESULTS

Fifty-three patients were included, of whom 23 (43.4%) presented with FIAs' related symptoms. After adjusting for baseline differences in the multivariate logistic regression analysis, the CRstalk (odds ratio [OR]=3.207, P = .023) and homocysteine concentration (OR=1.344, P = .015) independently predicted FIAs' related symptoms. The CRstalk was able to differentiate between FIAs with and without symptoms (area under the ROC curve [AUC]=0.805), with an optimal cutoff value of 0.76. The homocysteine concentration could also differentiate between FIAs with and without symptoms (AUC=0.788), with an optimal cutoff value of 13.13. The combination of the CRstalk and homocysteine concentration had a better ability to identify symptomatic FIAs (AUC=0.857). Male sex (OR=0.536, P = .018), FIAs' related symptoms (OR=1.292, P = .038), and homocysteine concentration (OR=1.254, P = .045) independently predicted the CRstalk.

CONCLUSION

A higher serum homocysteine concentration and greater AWE indicate FIA instability. Serum homocysteine concentration may be a useful biomarker of FIA instability; however, this needs to be verified in future studies.

Three-dimensional aneurysm wall enhancement in fusiform intracranial aneurysms is associated with aneurysmal symptoms

Background and purpose

Aneurysm wall enhancement (AWE) in high-resolution magnetic resonance imaging (HR-MRI) is a potential biomarker for evaluating unstable aneurysms. Fusiform intracranial aneurysms (FIAs) frequently have a complex and curved structure. We aimed to develop a new three-dimensional (3D) aneurysmal wall enhancement (AWE) characterization method to enable comprehensive FIA evaluation and to investigate the ability of 3D-AWE to predict symptomatic FIA.

Methods

We prospectively recruited patients with unruptured FIAs and received 3 T HR-MRI imaging from September 2017 to January 2019. 3D models of aneurysms and parent arteries were generated. Boundaries of the FIA were determined using 3D vessel diameter measurements. D_max was the greatest diameter in the cross-section, while L_max was the length of the centerline of the aneurysm. Signal intensity of the FIA was normalized to the pituitary stalk and then mapped onto the 3D model, then the average enhancement (3D-AWE_avg), maximum enhancement (3D-AWE_max), enhancement area (AWE_area), and enhancement ratio (AWE_ratio) were calculated as AWE indicators, and the surface area of the entire aneurysm (A_area) was also calculated. Areas with high AWE were defined as those with a value >0.9 times the signal intensity of the pituitary stalk. Multivariable logistic regression analyses were performed to determine independent predictors of aneurysm-related symptoms. FIA subtypes were defined as fusiform, dolichoectasia, and transitional. Differences between the three FIA subtypes were also examined.

Results

Forty-seven patients with 47 FIAs were included. Mean patient age was 55 ± 12.62 years and 74.5% were male. Twenty-nine patients (38.3%) were symptomatic. After adjusting for baseline differences in age, hypertension, L_max, and FIA subtype, the multivariate logistics regression models showed that 3D-AWE_avg (odds ratio [OR], 4.029; p = 0.019), 3D-AWE_max (OR, 3.437; p = 0.022), AWE_area (OR, 1.019; p = 0.008), and AWE_ratio (OR, 2.490; p = 0.045) were independent predictors of aneurysm-related symptoms. D_max and A_area were larger and 3D-AWE_avg, 3D-AWE_max, AWE_area, and AWE_ratio were higher with the transitional subtype than the other two subtypes.

Conclusion

The new 3D AWE method, which enables the use of numerous new metrics, can predict symptomatic FIAs. Different 3D-AWE between the three FIA subtypes may be helpful in understanding the pathophysiology of FIAs.

Aneurysm wall enhancement, hemodynamics, and morphology of intracranial fusiform aneurysms

Background and objective

Intracranial fusiform aneurysms (IFAs) are considered to have a complex pathophysiology process and poor natural history. The purpose of this study was to investigate the pathophysiological mechanisms of IFAs based on the characteristics of aneurysm wall enhancement (AWE), hemodynamics, and morphology.

Methods

A total of 21 patients with 21 IFAs (seven fusiform types, seven dolichoectatic types, and seven transitional types) were included in this study. Morphological parameters of IFAs were measured from the vascular model, including the maximum diameter (Dmax), maximum length (Lmax), and centerline curvature and torsion of fusiform aneurysms. The three-dimensional (3D) distribution of AWE in IFAs was obtained based on high-resolution magnetic resonance imaging (HR-MRI). Hemodynamic parameters including time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), gradient oscillatory number (GON), and relative residence time (RRT) were extracted by computational fluid dynamics (CFD) analysis of the vascular model, and the relationship between these parameters and AWE was investigated.

Results

The results showed that Dmax (p = 0.007), Lmax (p = 0.022), enhancement area (p = 0.002), and proportion of enhancement area (p = 0.006) were significantly different among three IFA types, and the transitional type had the largest Dmax, Lmax, and enhancement area. Compared with the non-enhanced regions of IFAs, the enhanced regions had lower TAWSS but higher OSI, GON, and RRT (p &lt; 0.001). Furthermore, Spearman’s correlation analysis showed that AWE was negatively correlated with TAWSS, but positively correlated with OSI, GON, and RRT.

Conclusion

There were significant differences in AWE distributions and morphological features among the three IFA types. Additionally, AWE was positively associated with the aneurysm size, OSI, GON, and RRT, while negatively correlated with TAWSS. However, the underlying pathological mechanism of the three fusiform aneurysm types needs to be further studied.

Systemic immune-inflammation index is associated with aneurysmal wall enhancement in unruptured intracranial fusiform aneurysms

Introduction

Inflammation plays a key role in the progression of intracranial aneurysms. Aneurysmal wall enhancement (AWE) correlates well with inflammatory processes in the aneurysmal wall. Understanding the potential associations between blood inflammatory indices and AWE may aid in the further understanding of intracranial aneurysm pathophysiology.

Methods

We retrospectively reviewed 122 patients with intracranial fusiform aneurysms (IFAs) who underwent both high-resolution magnetic resonance imaging and blood laboratory tests. AWE was defined as a contrast ratio of the signal intensity of the aneurysmal wall to that of the pituitary stalk ≥ 0.90. The systemic immune-inflammation (SII) index (neutrophils × platelets/lymphocytes) was calculated from laboratory data and dichotomized based on whether or not the IFA had AWE. Aneurysmal symptoms were defined as sentinel headache or oculomotor nerve palsy. Multivariable logistic regression and receiver operating characteristic curve analyses were performed to determine how well the SII index was able to predict AWE and aneurysmal symptoms. Spearman's correlation coefficients were used to explore the potential associations between variables.

Results

This study included 95 patients, of whom 24 (25.3%) presented with AWE. After adjusting for baseline differences in neutrophil to lymphocyte ratios, leukocytes, and neutrophils in the multivariable logistic regression analysis, smoking history (P = 0.002), aneurysmal symptoms (P = 0.047), maximum diameter (P = 0.048), and SII index (P = 0.022) all predicted AWE. The SII index (P = 0.038) was the only independent predictor of aneurysmal symptoms. The receiver operating characteristic curve analysis revealed that the SII index was able to accurately distinguish IFAs with AWE (area under the curve = 0.746) and aneurysmal symptoms (area under the curve = 0.739).

Discussion

An early elevation in the SII index can independently predict AWE in IFAs and is a potential new biomarker for predicting IFA instability.