RPS 2611 - Vascular: other than acute stroke

Author Block: S. Yang; Changsha/CN
Purpose or Learning Objective: To assess the alterations in the topological properties of the white matter brain network in carotid vulnerable plaque group and carotid hard plaque group based on magnetic resonance diffusion tensor imaging(DTI).
Methods or Background: One hundred and nineteen volunteers were included and performed DTI examination, among who, 58 volunteers had carotid vulnerable plaques, 23 volunteers had carotid hard plaques. The differences in the topological properties among the three groups were explored at both the global and local levels using one-way ANOVA and Bonferroni t-test (p<0.05). Then network-based statistic (NBS) method was employed to assess the alterations of the interregional connections among three groups (NBS corrected, p<0.001 at voxel level, p<0.05 at cluster level, permutated for 5000 times).
Results or Findings: Compared with the control group and vulnerable plaque group, the hard plaque group demonstrated significantly increased betweenness centrality in the left supramarginal gyrus region. Compared with the control group and hard plaque group, the vulnerable plaque group demonstrated significantly decreased nodal clustering coefficiency in the left putamen region. The vulnerable-plaque group presented a significantly decreased subnetwork component and two significantly increased subnetwork components in the NBS analysis results.
Conclusion: The topological organisation of white matter networks in carotid hard plaque group is different from vulnerable plaque group, which tends to increase the local efficiency of network communication to compensate. Furthermore, the carotid vulnerable plaque group showed more disorder of topological properties.
Limitations: First, we were limited by the cross-sectional design and small sample size of this study. Second, we only analysed the anatomical connectivity of white matter. The combination of structural and functional network analysis might provide a more comprehensive perspective for the disorder of topological properties in patients with carotid vulnerable plaques.
Ethics committee approval: Approved by the institutional review boards of Xiangya Hospital.
Funding for this study: No funding was received for this study.

Author Block: Q. Song; Dalian/CN
Purpose or Learning Objective: Explore the impact of acceleration factors of CS on the image quality of 3D-TOF-MRA for cervical vessels.
Methods or Background: 22 healthy volunteers were recruited and underwent the 3D-TOF MRA scan of neck vessels on a 3.0 T MR scanner. Four groups with different acceleration schemes were set up in our study, group A with a routine clinical setup of SENSE acceleration factor 3, and groups B, C, and D with CS factors of 4, 6, and 8. Regions of interest were placed manually at both sides of the carotid artery and nearby sternocleidomastoid muscle by experienced radiologists for the measurement of SNR and CNR. The two observers used a four-point scoring method to evaluate the quality of the four groups of images. The Kappa statistics were calculated for determining the interobserver agreement. The assessment of intermethod agreement was based on the evaluation of the senior physicians. Kruskal-Wallis test was employed to assess the difference of SNR, CNR and image scores between the 4 groups. Mann-Whitney U test was used to make a pairwise comparison.
Results or Findings: There were no statistically significant differences in SNR, CNR between the four groups. However, if CS acceleration factor of 8 was used, the subjective scores decreased obviously (p < 0.05, Table. 3). And no significant differences in image quality were detected between conventional SENSE acceleration with a factor of 3 and CS acceleration with factors of 4 and 6.
Conclusion: CS acceleration factor of 6 is recommended for clinical 3D-TOF carotid MRA to achieve an optimal balance between imaging time and image quality.
Limitations: This study was limited by the few amount of volunteers.
Ethics committee approval: This study has been approved by the local IRB.
Funding for this study: Not applicable.

Author Block: M. Correia de Verdier, J. Wikström; Uppsala/SE
Purpose or Learning Objective: To assess the effects of spatial resolution, number of excitations (NEX) and velocity encoding (VENC) on accuracy and precision of phase-contrast (PC) MRI measurements in a vessel phantom with a small lumen diameter.
Methods or Background: A 3 T scanner and a 32-channel head coil were used for all the PC-MRI measurements. An in vitro flow model consisting of a plastic tube (2.3 mm inner diameter) passing through an agar gel was constructed to provide a continuous flow. The flow rate was controlled using a reservoir with a scale and timer and used as the standard reference. A PC-MRI sequence was performed with varying voxel size (0.6 x 0.8 x 5 mm, 1 x 1 x 5 mm, 1.2 x 1.2 x 5 mm), NEX (1, 2, 3) and VENC (200, 300, 400 cm/s). Measurements were repeated 9 times for each setting. Mean flow and peak velocity were calculated for each combination of settings and the least detectable difference (LDD) was computed.
Results or Findings: All PC-MRI mean flow measurements were higher than our standard reference (mean values ranging from 7.3 to 9.5 ml/s compared with 6.5 ml/s). Decreasing voxel size improved the accuracy of mean flow measurements, with measured values changing from 9.5 to 7.3 ml/s. LDD for mean flow decreased with increasing voxel size and NEX (p<0.05). LDD for peak velocity decreased with increasing voxel size (p<0.05). No change in LDD was observed with different VENC settings.
Conclusion: Accuracy in PC-MRI flow measurements in a small vessel phantom is low, with higher measured values than control. Improved accuracy is obtained with increased spatial resolution. Improved precision is obtained with decreased spatial resolution and increased NEX.
Limitations: Not applicable.
Ethics committee approval: Not applicable.
Funding for this study: Not applicable.

Author Block: X. Fan, T. Lin, Z. Lai, H. You, J. Qu, F. Feng; Beijing/CN
Purpose or Learning Objective: To explore and compare the predictive ability of collateral score systems assessed with single-delay ASL and conventional CT/MRI protocols for cerebral hyperperfusion after carotid endarterectomy (CEA).
Methods or Background: Eighty-five patients who underwent CEA between May 2015 and July 2021 were included (mean age 65.3±7.1 years, 76.5% male). Cerebral hyperperfusion was defined as an increase in cerebral blood flow >100% compared with preoperative values. Preoperative ASL images were scored based on the presence of arterial transit artefacts (ATAs) in 10 regions of interest corresponding to ASPECTS methodology as follows: 0, no or minimal ASL signal; 1, low/moderate ASL signal with ATA; 2, high ASL signal with ATA; and 3, normal perfusion without ATA. The degree of stenosis, primary and secondary collaterals were evaluated on conventional CTA, MRA and T2 FLAIR images.
Results or Findings: Cerebral hyperperfusion was presented in 16 (18.8%) patients. Preoperative ASL score was an independent predictor of cerebral hyperperfusion (OR=0.47, 95% CI [0.32-0.71], p<0.001). ROC curve analysis revealed that the predictive ability for cerebral hyperperfusion was statistically higher for ASL score (AUC=0.98, 95% CI [0.923-0.998]) than for degree of stenosis (AUC=0.786, 95% CI [0.684-0.868], p=0.002), type of circle of Willis (AUC=0.771, 95% CI [0.667-0.855], p=0.002) or leptomeningeal collaterals (AUC=0.798, 95% CI [0.697-0.877],p=0.004). The ASL score performed as well as the combination of degree of stenosis, type of circle of Willis and leptomeningeal collaterals (AUC=0.947, 95% CI [0.876, 0.984],p=0.258).
Conclusion: Single-delay ASL can non-invasively predict cerebral hyperperfusion after CEA in patients with carotid stenosis.
Limitations: The sample size was relatively small.
Ethics committee approval: This study was approved by the Medical Ethics Committee of the Peking Union Medical College Hospital.
Funding for this study: This work was supported by the Beijing Natural Science Foundation grant (L182067) and National Nature Science Foundation of China grant (82071899).

Author Block: O. Giyab, B. L. Balogh, P. P. Bogner, G. Orsi, A. Tóth; Pécs/HU
Purpose or Learning Objective: Our aim was to prove our hypothesis according to which cerebral fat embolism commonly presents with a characteristic microbleed pattern on MRI.
Methods or Background: We searched the literature and the database of our home institution for cases of cerebral fat embolism (CFE). The hypothesized CFE characteristic microbleed pattern (diffuse presence of round microbleeds of monotonous size in the subcortical white matter involving but not limited to the U-fibers, internal capsule and the corpus callosum, mostly sparing the corona radiata and the non-subcortical centrum semiovale on T2* GRE or SWI images), the starfield pattern as described by Parizel et al (scattered bright spots on a dark background in DWI with diffusion restriction), and confluent diffusion restriction in the corpus callosum were statistically compared. Temporal characteristics of the imaging features were also analysed.
Results or Findings: 141 patients with cerebral fat embolism were included. The characteristic ""walnut kernel microbleed pattern"" was found in 89.74%. Diffusion abnormality in general was seen in 97.64%. A definitive starfield pattern was ascertained in 68.5%. Confluent restricted diffusion was seen in the corpus callosum in 77.27%. The walnut kernel microbleed pattern had a more consistent presence among time periods compared to the starfield pattern.
Conclusion: Microbleeds in CFE are very common and mainly occur in a characteristic pattern in SWI or T2*, which along with the starfield pattern and corpus callosum diffusion restriction in DWI/ADC appear to be the most important imaging markers of CFE and may aid the differential diagnosis in clinically equivocal cases.
Limitations: More articles investigated diffusion abnormalities than microbleeds.
Ethics committee approval: The Institutional Review Board approved the institutional medical database search that was performed related to this study.
Funding for this study: Funding was received from the Bolyai Scholarship Hungarian Academy of Science.