Concentration of Lp(a) (Lipoprotein[a]) in Aneurysm Sac Is Associated With Wall Enhancement of Unruptured Intracranial Aneurysm.

BACKGROUND AND PURPOSE: Atherosclerotic remodeling of the aneurysm wall, which could be detected as aneurysm wall enhancement (AWE) by magnetic resonance-vessel wall imaging, is a part of degenerative change of unruptured intracranial aneurysms (UIAs). The purpose of this study was to determine whether the luminal concentrations of atherosclerotic proteins in the aneurysm sac were associated with increased wall enhancement of UIAs in vessel wall imaging. METHODS: We performed a prospective study of subjects undergoing endovascular treatments for UIAs. All subjects underwent evaluation using 3T-magnetic resonance imaging, including pre/postcontrast vessel wall imaging of the UIAs. Blood samples were collected from the aneurysm sac and the parent artery during endovascular procedures. Presence/absence of AWE was correlated with the delta difference in concentration for each atherosclerotic protein between the lumen of UIA and in the parent artery. RESULTS: A total of consecutive 17 patients with 19 UIAs were enrolled. The delta difference of lipoprotein(a) was significantly higher in UIAs with AWE compared with those without AWE (-6.9±16.0 versus -45.4±44.9 µg/mL, P=0.03). CONCLUSIONS: Higher luminal concentrations of lipoprotein(a) in the aneurysm sac were significantly associated with increased wall enhancement of UIAs. A larger study is needed to confirm these findings.

Gadolinium as a contrast agent for infusion sialograms in patients with iodine allergy.

Objectives: To assess the adequacy of gadolinium in sialography as an alternative contrast agent for patients with iodine allergies. To directly compare images taken with gadolinium versus iodine-based contrast agents using the Iowa Sialography Classification System. Methods: Retrospective chart review was performed on patients undergoing sialography between February 2008 and July 2022. Patients with sialograms obtained with gadolinium were identified and matched to similar sialograms obtained with iodine-based contrast agent. Patients were matched based on duct location, duct side, and initial radiology findings. Blinded reevaluation of sialograms was performed first independently and then by consensus by two head and neck radiologists to evaluate overall image adequacy and grade using the Iowa Sialography Classification System. Results: Four patients with six sialograms (one bilateral parotid and one parotid + submandibular) obtained with gadolinium were identified and reevaluated. Five patients with six sialograms (one bilateral parotid) obtained with iodine-based were matched to the gadolinium sialograms. The overall adequacy of images for gadolinium sialograms was graded at an average of 4.25 (4 = good and 5 = excellent); whereas, the overall adequacy of iodine-based sialograms was graded at an average of 5. Inter-observer variability was observed in three sialograms obtained with gadolinium (50%), while no interobserver variability was observed in sialograms obtained with iodine-based contrast agent. Conclusion: Gadolinium is an adequate alternative to use in sialography for patients with iodine allergies undergoing contemporary digital infusion sialography. Adverse reactions to iodine contrast agents are rare in sialography; however, the precautionary use of gadolinium is acceptable for the diagnostic and therapeutic benefits in sialography.Level of Evidence: IV.

Volumetric surveillance of brain aneurysms: Pitfalls of MRA.

INTRODUCTION: Untreated brain aneurysms are usually surveilled with serial MR imaging and evaluated with 2D multiplanar measurements. The assessment of aneurysm growth may be more accurate with volumetric analysis. We evaluated the accuracy of a magnetic resonance angiography (MRA) segmentation pipeline for aneurysm volume measurement and surveillance. METHODS: A pipeline to determine aneurysm volume was developed and tested on two aneurysm phantoms imaged with time-of flight (TOF) MRA and 3D rotational angiography (3DRA). The accuracy of the pipeline was then evaluated by reconstructing 10 aneurysms imaged with contrast enhanced-MRA (CE-MRA) and 3DRA. This calibrated and refined post-processing pipeline was subsequently used to analyse aneurysms from our prospectively acquired database. Volume changes above the threshold of error were considered true volume changes. The accuracy of these measurements was analysed. RESULTS: TOF-MRA reconstructions were not as accurate as CE-MRA reconstructions. When compared to 3DRA, CE-MRA underestimated aneurysm volume by 7.8% and did not accurately register the presence of blebs. Eighteen aneurysms (13 saccular and 5 fusiform) were analysed with the optimized 3D volume reconstruction pipeline, with a mean follow-up time of 11 months. Artifact accounted for 10.2% error in volume measurements using serial CE-MRA. When this margin of error was used to assess aneurysms volume in serial imaging with CE-MRA, only two fusiform aneurysms changed in volume. The variations in volume of these two fusiform aneurysms were caused by intra-mural and intrasaccular thrombosis. CONCLUSIONS: CE-MRA and TOF-MRA 3D volume reconstructions may not register minor morphological changes such as the appearance of blebs. CE-MRA underestimates volume by 7.8% compared to 3DRA. Serial CE-MRA volume measurements had a larger margin of error of approximately 10.2%. MRA-based volumetric measurements may not be appropriate for aneurysm surveillance.

Conventional and MR-sialography of accessory submandibular glands: A case report.

Our review of the literature shows anatomical variation of the submandibular gland is a rare entity, unlike the variation that can be seen in parotid glands. Specifically, bilateral submandibular abnormality has only been reported on one occasion with limited imaging in our review. We report a 78-year-old female with a history of sialadenitis and sialolithiasis who presents with swelling and pain in the right submandibular gland. Sialography of the right submandibular gland disclosed a second primary duct branching off the main duct to a second submandibular gland. Cannulation of the left submandibular duct was unsuccessful due to scarring of the duct orifice; however, subsequent MR sialography identified marked submandibular duct dilation and the incidental finding of a second anteriorly located left submandibular gland. The anatomic detail provided by conventional digital sialography is contrasted to the useful but less-defined imaging provided by MR sialography. To our knowledge, this is the first reported case of bilateral accessory submandibular glands that has been evaluated using both conventional and MR sialography.

Performance of Aneurysm Wall Enhancement Compared with Clinical Predictive Scales: PHASES, ELAPSS, and UIATS.

OBJECTIVE: To correlate the presence of objectively measured wall enhancement on high-resolution vessel wall imaging (HR-VWI) with the clinical predictive scales PHASES, ELAPSS, and UIATS. METHODS: Patients with unruptured intracranial aneurysm (UIAs) prospectively underwent HR-VWI on a 3-T magnetic resonance imaging scanner at diagnosis. Aneurysmal wall enhancement was objectively quantified on T1 postcontrast magnetic resonance imaging using signal intensity values adjusted for the pituitary stalk to calculate a contrast ratio (CRstalk). UIAs with CRstalk ≥0.60 were considered "enhancing." Patients' demographics, comorbidities, and aneurysm morphology were reviewed to calculate PHASES, ELAPSS, and UIATS scores. Pearson coefficients were applied for statistical correlation. Univariable and multivariable logistic regressions were performed to assess for confounders. RESULTS: One-hundred and twenty-three patients harboring 178 UIAs underwent HR-VWI. A total of 101 patients with 135 UIAs were analyzed. Enhancing UIAs were larger (8.4 ± 5.5 mm vs. 5.5 ± 2.3 mm; P < 0.001), had higher aspect ratio (2.3 ± 1.5 vs. 1.8 ± 0.7; P = 0.008), higher size ratio (3.0 ± 1.8 vs. 2.4 ± 1.1; P = 0.016), scored higher on PHASES (5.6 ± 3.9 vs. 4.4 ± 2.6; P = 0.04) and ELAPSS (19.4 ± 8.9 vs. 15.4 ± 7.3; P = 0.006) compared with nonenhancing UIAs. Treatment allocation as defined by UIATS was measured independently to enhancement status. No significant differences were found for UIATS between enhancing and nonenhancing UIAs (P = 0.63). Multivariable regression showed that size was the only independent factor significantly associated with UIA enhancement (odds ratio, 1.76; P = 0.005). CONCLUSIONS: Enhancing UIAs score higher in PHASES and ELAPSS scales. This association is largely explained by aneurysm size, aspect, and size ratios. Morphologic UIA features should be accounted for in clinical predictive scales of aneurysm instability.

High-resolution vessel wall imaging after mechanical thrombectomy.

OBJECTIVES: High-resolution magnetic resonance imaging has the potential of characterising arterial wall changes after endovascular mechanical thrombectomy. The purpose of this study is to evaluate high-resolution magnetic resonance imaging features of large intracranial arteries following mechanical thrombectomy. METHODS: Patients who presented with acute ischaemic stroke due to large vessel occlusion and underwent mechanical thrombectomy were prospectively recruited. Subjects underwent high-resolution magnetic resonance imaging within 24 hours of the procedure. Magnetic resonance imaging sequences included whole brain T1 pre and post-contrast black-blood imaging, three-dimensional T2, contrast-enhanced magnetic resonance angiography and susceptibility-weighted imaging. Arterial wall enhancement was objectively assessed after normalisation with the pituitary stalk. The contrast ratio of target vessels was compared with non-affected reference vessels. RESULTS: Twenty patients with 22 target vessels and 20 reference vessels were included in the study. Sixteen patients were treated with stentriever with or without aspiration, and four with contact aspiration only. Significantly higher arterial wall enhancement was identified on the target vessel when compared to the reference vessel (U = 22.5, P < 0.01). The stentriever group had an 82% increase in the contrast ratio of the target vessel (x̄ = 0.75 ± 0.21) when compared to the reference vessel (x̄ = 0.41 ± 0.13), whereas the contact aspiration group had a 64% increase of the contrast ratio difference between target (x̄ = 0.62 ± 0.07) and reference vessels (x̄ = 0.38 ± 0.12). Approximately 65% of patients in the stentriever group had a positive parenchymal susceptibility-weighted imaging versus 25% in the contact aspiration group. There was no statistically significant correlation between susceptibility-weighted imaging volume and the percentage increase in the contrast ratio (rs = 0.098, P = 0.748). CONCLUSIONS: This prospective pilot study used the objective quantification of arterial wall enhancement in determining arterial changes after mechanical thrombectomy. Preliminary data suggest that the use of stentrievers is associated with a higher enhancement as compared to reperfusion catheters.

Insights into the pathogenesis of cerebral fusiform aneurysms: high-resolution MRI and computational analysis.

BACKGROUND: Intracranial fusiform aneurysms are complex and poorly characterized vascular lesions. High-resolution magnetic resonance imaging (HR-MRI) and computational morphological analysis may be used to characterize cerebral fusiform aneurysms. OBJECTIVE: To use advanced imaging and computational analysis to understand the unique pathophysiology, and determine possible underlying mechanisms of instability of cerebral fusiform aneurysms. METHODS: Patients with unruptured intracranial aneurysms prospectively underwent imaging with 3T HR-MRI at diagnosis. Aneurysmal wall enhancement was objectively quantified using signal intensity after normalization of the contrast ratio (CR) with the pituitary stalk. Enhancement between saccular and fusiform aneurysms was compared, as well as enhancement characteristics of fusiform aneurysms. The presence of microhemorrhages in fusiform aneurysms was determined with quantitative susceptibility mapping (QSM). Three distinct types of fusiform aneurysms were analyzed with computational fluid dynamics (CFD) and finite element analysis (FEA). RESULTS: A total of 130 patients with 160 aneurysms underwent HR-MRI. 136 aneurysms were saccular and 24 were fusiform. Fusiform aneurysms had a significantly higher CR and diameter than saccular aneurysms. Enhancing fusiform aneurysms exhibited more enhancement of reference vessels than non-enhancing fusiform aneurysms. Ten fusiform aneurysms underwent QSM analysis, and five aneurysms showed microhemorrhages. Microhemorrhage-positive aneurysms had a larger volume, diameter, and greater enhancement than aneurysms without microhemorrhage. Three types of fusiform aneurysms exhibited different CFD and FEA patterns. CONCLUSION: Fusiform aneurysms exhibited more contrast enhancement than saccular aneurysms. Enhancing fusiform aneurysms had larger volume and diameter, more enhancement of reference vessels, and more often exhibited microhemorrhage than non-enhancing aneurysms. CFD and FEA suggest that various pathophysiological processes determine the formation and growth of fusiform aneurysms.

Analysis of Cerebral Aneurysm Wall Tension and Enhancement Using Finite Element Analysis and High-Resolution Vessel Wall Imaging.

Biomechanical computational simulation of intracranial aneurysms has become a promising method for predicting features of instability leading to aneurysm growth and rupture. Hemodynamic analysis of aneurysm behavior has helped investigate the complex relationship between features of aneurysm shape, morphology, flow patterns, and the proliferation or degradation of the aneurysm wall. Finite element analysis paired with high-resolution vessel wall imaging can provide more insight into how exactly aneurysm morphology relates to wall behavior, and whether wall enhancement can describe this phenomenon. In a retrospective analysis of 23 unruptured aneurysms, finite element analysis was conducted using an isotropic, homogenous third order polynomial material model. Aneurysm wall enhancement was quantified on 2D multiplanar views, with 14 aneurysms classified as enhancing (CRstalk≥0.6) and nine classified as non-enhancing. Enhancing aneurysms had a significantly higher 95th percentile wall tension (µ = 0.77 N/cm) compared to non-enhancing aneurysms (µ = 0.42 N/cm, p < 0.001). Wall enhancement remained a significant predictor of wall tension while accounting for the effects of aneurysm size (p = 0.046). In a qualitative comparison, low wall tension areas concentrated around aneurysm blebs. Aneurysms with irregular morphologies may show increased areas of low wall tension. The biological implications of finite element analysis in intracranial aneurysms are still unclear but may provide further insights into the complex process of bleb formation and aneurysm rupture.