Calcification as a Risk Factor for Rupture of Abdominal Aortic Aneurysm
Ruben V.C. BuijsTineke P. WillemsRené A. TioHendrikus H. BoersmaI.F.J. TielliuRiemer H. J. A. SlartClark J. Zeebregts
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Background:
Increased biomechanical stresses within the abdominal aortic aneurysm (AAA) wall contribute to its rupture. Calcification and intraluminal thrombus can be commonly found in AAAs, but the relationship between calcification/intraluminal thrombus and AAA wall stress is not completely described.
Methods:
Patient-specific three-dimensional AAA geometries were reconstructed from computed tomographic images of 20 patients. Structural analysis was performed to calculate the wall stresses of the 20 AAA models and their altered models when calcification or intraluminal thrombus was not considered. A nonlinear large-strain finite element method was used to compute the wall stress distribution. The relationships between wall stresses and volumes of calcification and intraluminal thrombus were sought.
Results:
Maximum stress was not correlated with the percentage of calcification, and was negatively correlated with the percentage of intraluminal thrombus (r = -0.56; P = .011). Exclusion of calcification from analysis led to a significant decrease in maximum stress by a median of 14% (range, 2%-27%; P < .01). When intraluminal thrombus was eliminated, maximum stress increased significantly by a median of 24% (range, 5%-43%; P < .01).
Conclusion:
The presence of calcification increases AAA peak wall stress, suggesting that calcification decrease the biomechanical stability of AAA. In contrast, intraluminal thrombus reduces the maximum stress in AAA. Calcification and intraluminal thrombus should both be considered in the evaluation of wall stress for risk assessment of AAA rupture.
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Objective To compare the capability of contrast-enhanced ultrasonography (CEUS) and CT angiography(CTA)in evaluating abdominal aortic aneurysm. Methods Both CEUS and CTA examinations were performed in 18 patients (diagnosis before surgery in 10 patients, surveillance after surgery in 8 patients). The CEUS contrast agent was Sonovue. The diagnosis and the appearance about abdominal aortic aneurysm, dissecting aortic aneurysm, aortic pseudoaneurysm and the image after operation were compared. Results There were abdominal aortic aneurysm in 5 patients, dissecting aortic aneurysm in 4 patients and aortic pseudoaneurysm without operation in 1 patient. The 8 patients under surveillance after operation including endovascular abdominal aortic aneurysm repair in 4 patients and open repair with artificial vascular in 4 patients. Both CEUS and CTA had the same results. Conclusion The CEUS is comparable to CTA in diagnosing abdominal aortic aneurysm. The CEUS is worthy of application in abdominal aortic aneurysm.
Pseudoaneurysm
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Introduction
About 85% of the non-traumatic SAH are caused by ruptured aneurysms1. Identifying those aneurysms as the bleeding cause is essential for further therapy.Aim of study
The study evaluates the detection of cerebral aneurysm in unenhanced CT images of patients with subarachnoid hemorrhage by a relative hypodense structure in the hyperdense bleeding, the sparing aneurysm sign (SAS).Methods
Three neuroradiologic experienced radiologists rated the aneurysm location and size by applying the SAS in 50 CT-examinations of patients with aneurysmal SAH who underwent an initial CT scan followed by a DSA. The results were analyzed for correlations between aneurysm location, aneurysm size, Fisher-score and the detectability of a SAS. Further a quantitative analysis of the average HU of the aneurysm and the SAH was performed.Results
In 75% of the cases the aneurysm was identified correctly just using the SAS, influenced significant by aneurysm location (p=0.019), Fisher-Score (p=0.008) and aneurysm size (p=0.017). The highest rate of aneurysm detection was given for MCA- (90%) and BA-aneurysms (90%), followed by ACOM- (80%) and ACA-aneurysm (80%). The measured aneurysm size in the correctly identified aneurysm significantly corelates to the size measured in the DSA (p<0.001) and a cut point of 51 HU discriminates aneurysm from SAH with a specificity of 92% and a sensitivity of 86% (Youden´s index 0.78).Conclusions
The aneurysm location and size can be determined in unenhanced CT images in many cases using the new SAS (sparing aneurysm sign). Whereas quantitative measurements of HU can support the aneurysm detection.References
Connolly ES, Rabinstein AA, Carhuapoma JR, et al. Guidelines for the Management of Aneurysmal Subarachnoid Hemorrhage. Stroke. 2012;43. Do you have any conflict of interest to declare?: NoCite
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Microsurgical clipping is a widely used surgical technique in intracranial aneurysm treatment. It can be difficult in large sized aneurysms, and those with wide necks, thick walls and calcification located in the vicinity of the neck. This study reviewed calcification of the intracranial aneurysm wall and its relation to patient age, gender, location and size of the aneurysm. A possible cut-off value after which the aneurysm calcification rate increases was also investigated to classify patients' risk factors for microclipping.A retrospective review of all unruptured intracranial aneurysms that underwent digital subtraction angiography at a single centre was performed. Flat-detector computed tomography images of the aneurysm were reviewed for aneurysm location, size and calcification. The independent samples t test and χ(2) test were used to show the relation between aneurysm wall calcification and patient age, gender, aneurysm localisation and size.None of the reviewed factors were statistically significantly related to aneurysm calcification except aneurysm size (P < 0.01). Receiver operating characteristic curves showed aneurysms greater than 10.5 mm could be predicted to be calcified with a sensitivity of 80% and specificity of 63%.In this study, the presence of calcification was related to aneurysm size. Larger aneurysms were more likely to be calcified. Aneurysms greater than 10.5 mm should be further investigated with a modality such as flat-detector computed tomography to show the calcification in detail, especially if microclipping is considered.
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OBJECTIVE: To objectively compare computed tomographic angiography (CTA) with selective digital subtraction angiography (DSA) in the detection and anatomic definition of intracranial aneurysms, particularly in the setting of acute subarachnoid hemorrhage (SAH). METHODS: In a blinded prospective study, 40 patients with known or suspected intracranial saccular aneurysms underwent both CTA and DSA, including 32 consecutive patients with SAH in whom CTA was performed after CT images were obtained diagnostic for SAH. The CT angiograms were interpreted for the presence, location, and size of the aneurysms, and anatomic features, such as the number of aneurysm lobes, aneurysm neck size (≤ 4 mm), and the number of adjacent arterial branches were assessed. The images obtained with CTA were then compared with the images obtained with DSA, with the latter images serving as controls. RESULTS: DSA revealed 43 aneurysms in 30 patients and ruled out intracranial aneurysms in the remaining 10 patients. For aneurysm presence alone, the sensitivity and specificity for CTA was 86 and 90%, respectively. For the presence of an aneurysm, six CT angiograms showed false negative results and one CT angiogram showed a false positive result. False negative results were usually caused by technical problems with the image, tiny aneurysm domes(<3 mm), and unusual aneurysm locations (i.e., intracavernous carotid or posterior inferior cerebellar artery aneurysms). The results obtained with CTA were, compared with the results obtained with DSA, more than 95% accurate in determining dome and neck size of aneurysm, aneurysm lobularity, and the presence and number of adjacent arterial branches. In addition, CTA provided a three-dimensional representation of the aneurysmal lesion, which was considered useful for surgical planning. CONCLUSION: CTA is useful for rapid and relatively noninvasive detection of aneurysms in common locations, and the anatomic information provided in images showing positive results is at least equivalent to that provided by DSA. In cases of SAH in which the nonaugmented CT and CTA results indicate a clear source of bleeding and provide adequate anatomic detail, we think it is possible to forego DSA before urgent early aneurysm surgery. In all other cases, DSA is indicated.
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OBJECTIVE: To objectively compare computed tomographic angiography (CTA) with selective digital subtraction angiography (DSA) in the detection and anatomic definition of intracranial aneurysms, particularly in the setting of acute subarachnoid hemorrhage (SAH). METHODS: In a blinded prospective study, 40 patients with known or suspected intracranial saccular aneurysms underwent both CTA and DSA, including 32 consecutive patients with SAH in whom CTA was performed after CT images were obtained diagnostic for SAH. The CT angiograms were interpreted for the presence, location, and size of the aneurysms, and anatomic features, such as the number of aneurysm lobes, aneurysm neck size (≤ 4 mm), and the number of adjacent arterial branches were assessed. The images obtained with CTA were then compared with the images obtained with DSA, with the latter images serving as controls. RESULTS: DSA revealed 43 aneurysms in 30 patients and ruled out intracranial aneurysms in the remaining 10 patients. For aneurysm presence alone, the sensitivity and specificity for CTA was 86 and 90%, respectively. For the presence of an aneurysm, six CT angiograms showed false negative results and one CT angiogram showed a false positive result. False negative results were usually caused by technical problems with the image, tiny aneurysm domes(<3 mm), and unusual aneurysm locations (i.e., intracavernous carotid or posterior inferior cerebellar artery aneurysms). The results obtained with CTA were, compared with the results obtained with DSA, more than 95% accurate in determining dome and neck size of aneurysm, aneurysm lobularity, and the presence and number of adjacent arterial branches. In addition, CTA provided a three-dimensional representation of the aneurysmal lesion, which was considered useful for surgical planning. CONCLUSION: CTA is useful for rapid and relatively noninvasive detection of aneurysms in common locations, and the anatomic information provided in images showing positive results is at least equivalent to that provided by DSA. In cases of SAH in which the nonaugmented CT and CTA results indicate a clear source of bleeding and provide adequate anatomic detail, we think it is possible to forego DSA before urgent early aneurysm surgery. In all other cases, DSA is indicated.
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Identification of the source of subarachnoid haemorrhage (SAH) can be a challenge in the presence of multiple aneurysms. This study was carried out to assess whether radioanatomical features on noncontrast enhanced computerised tomography (CT) scans may be of value in localizing ruptured intracranial aneurysms. The diagnostic CT scans of 56 consecutive patients, investigated for SAH with cerebral angiography, over a period of six months were available for review. Various radioanatomical features were assessed: (1) pattern of subarachnoid blood (e.g. predominant site and location near major vessel bifurcation), (2) presence of intraparenchymal haematoma, (3) presence of aneurysm contour and (4) hydrocephalus. On the basis of the findings an estimation of the anatomical location of the source of bleeding was made and then compared with the angiogram findings to which the reviewer was blinded. The location of the aneurysm was correctly identified in 89.5% of cases. Careful analysis of the pattern of bleeding was essential for the successful localization of the aneurysm in all these cases. The presence of an aneurysm contour was also associated with correct identification of the source of bleeding (chi(2) = 6.067, P = 0.02). Our findings suggest that radioanatomical features on CT scans in SAH can be a valuable aid in the correct identification of the location of the ruptured aneurysm. This would be of particular significance in the presence of multiple intracranial aneurysms.
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Although the clinical and biological importance of calcification is well recognized for the extracerebral vasculature, its role in cerebral vascular disease, particularly, intracranial aneurysms (IAs), remains poorly understood. Extracerebrally, 2 distinct mechanisms drive calcification, a nonatherosclerotic, rapid mineralization in the media and a slower, inflammation driven, atherosclerotic mechanism in the intima. This study aims to determine the prevalence, distribution, and type (atherosclerotic, nonatherosclerotic) of calcification in IAs and assess differences in occurrence between ruptured and unruptured IAs. Approach and Results: Sixty-five 65 IA specimens (48 unruptured, 17 ruptured) were resected perioperatively. Calcification and lipid pools were analyzed nondestructively in intact samples using high resolution (0.35 μm) microcomputed tomography. Calcification is highly prevalent (78%) appearing as micro (<500 µm), meso (500 µm-1 mm), and macro (>1 mm) calcifications. Calcification manifests in IAs as both nonatherosclerotic (calcification distinct from lipid pools) and atherosclerotic (calcification in the presence of lipid pools) with 3 wall types: Type I-only calcification, no lipid pools (20/51, 39%), Type II-calcification and lipid pools, not colocalized (19/51, 37%), Type III-calcification colocalized with lipid pools (12/51, 24%). Ruptured IAs either had no calcifications or had nonatherosclerotic micro- or meso-calcifications (Type I or II), without macro-calcifications.
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