RESUMO
OBJECTIVES: Atherosclerotic plaque features, such as fibrous cap erosion, ulceration and rupture and presence of haemorrhage in carotid plaque are two important characteristics associated with subsequent cerebrovascular events and juxtaluminal haemorrhage/thrombus (JLH/T) indicates these two high-risk characteristics. This study aims to investigate the association between JLH/T and subsequent events in patients suffering from transient ischaemic attack (TIA). Three-dimensional mechanical analysis was employed to represent the critical mechanical stress (P-CStress) and stretch (P-CStretch) within the plaque. METHODS: Fifty TIA patients with mild-to-moderate carotid stenosis (30-69%) underwent high-resolution magnetic resonance imaging (MRI) within 72 h of the acute event and eight were excluded from the analysis due to various reasons. A total of 21 patients were found to have JLH/T in the carotid plaque and 21 did not (N-JLH/T). During a 2-year follow-up period, 11 (52.4%) patients in the JLH/T group experienced recurrent events and none in the N-JLH/T group. Three-dimensional plaque structure was reconstructed based on the in vivo MRI for the mechanical analysis. RESULTS: P-CStress of both groups was comparable (N-JLH/T: 174.45 ± 63.96 kPa vs. JLH/T: 212.60 ± 89.54 kPa; p = 0.120), but P-CStretch of JLH/T was significantly bigger than that of N-JLH/T (N-JLH/T: 1.21 ± 0.08 vs. JLH/T: 2.10 ± 0.53; p < 0.0001). Moreover, there were much bigger variations in stress and stretch of the JLH/T group during one cardiac cycle than in those of N-JLH/T group. CONCLUSIONS: In vivo MRI-depicted JLH/T might be a high risk factor initiating recurrent events, as big deformation appearing around the rupture site might prevent healing and tear the haemorrhage/thrombus away from the host structure and prompt further thrombo-embolic events.
Assuntos
Estenose das Carótidas/fisiopatologia , Hemorragia/fisiopatologia , Imageamento Tridimensional , Ataque Isquêmico Transitório/diagnóstico , Imageamento por Ressonância Magnética , Placa Aterosclerótica/fisiopatologia , Idoso , Pressão Sanguínea , Artéria Carótida Interna/patologia , Artéria Carótida Interna/fisiopatologia , Estenose das Carótidas/complicações , Feminino , Análise de Elementos Finitos , Hemorragia/complicações , Humanos , Ataque Isquêmico Transitório/fisiopatologia , Masculino , Placa Aterosclerótica/diagnóstico , Recidiva , Estresse MecânicoRESUMO
BACKGROUND: Vulnerable carotid plaques are associated with cerebrovascular ischaemic events. High-resolution magnetic resonance (MR) imaging not only allows the morphological assessment of such plaques, but also provides geometrical data, which can be used for biomechanical stress analysis. We assess its utility to assess the plaque stress profiles of symptomatic (transient ischaemic attack (TIA) and non-disabling stroke) and asymptomatic patients. METHODS: A total of 70 consecutive patients with confirmed underlying carotid artery disease underwent carotid MR imaging of their carotid artery in a 1.5-T MR system using a standard carotid atheroma imaging protocol. MR images were manually segmented for different plaque components and used for biomechanical stress analysis. The maximum critical stress (M-CStress) for various clinical groups was determined and compared. RESULTS: M-CStress of symptomatic plaques (n = 45) was significantly higher than for asymptomatic plaques (n = 25) (median (interquartile range (IQR): 275 kPa (190-390) vs. 165 kPa (120-200), p = 0.0001)). Within the symptomatic group, no M-CStress differences were present between the TIA (n = 30) and stroke (n = 15) patients (260 kPa (190-370) vs. 295 kPa (200-510), p = 0.31). Within the TIA patient cohort, those who had presented with recurrent TIAs (n = 6) had significantly higher stresses than patients who had suffered a single episode (n = 24) (425 kPa (285-580) vs. 250 kPa (180-310), p = 0.001). CONCLUSIONS: Symptomatic carotid plaques, particularly those associated with recurrent TIAs, have high biomechanical stresses. As there is pre-existing evidence to suggest that high biomechanical stresses are associated with plaque vulnerability, MR-imaging-based stress analysis has the potential to identify high-risk patients with vulnerable plaques.
Assuntos
Artéria Carótida Interna/patologia , Artéria Carótida Interna/fisiopatologia , Ataque Isquêmico Transitório/fisiopatologia , Placa Aterosclerótica/fisiopatologia , Estresse Mecânico , Acidente Vascular Cerebral/fisiopatologia , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Estenose das Carótidas/patologia , Estenose das Carótidas/fisiopatologia , Humanos , Ataque Isquêmico Transitório/patologia , Imageamento por Ressonância Magnética/métodos , Pessoa de Meia-Idade , Modelos Biológicos , Placa Aterosclerótica/patologia , Recidiva , Acidente Vascular Cerebral/patologiaRESUMO
OBJECTIVES: Abdominal aortic aneurysms (AAAs), being predominantly atherosclerotic in nature, have underlying inflammatory activity. As it is well established that ultrasmall superparamagnetic iron oxide (USPIO) particles accumulate in the macrophages within atheromatous lesions, USPIO-enhanced magnetic resonance (MR) imaging can be potentially effective in the quantification of the associated inflammatory processes. METHODS: A total of 14 patients underwent USPIO-enhanced MR imaging using a 1.5T-MR system. Quantitative T(2)* and T(2) relaxation time data were acquired before and 36 h after UPSIO infusion at identical AAA locations. The pre- and post-USPIO-infusion relaxation times (T(2)(∗) and T(2)) were quantified and the correlation between pre- and post-USPIO infusion T(2)* and T(2) values was investigated. RESULTS: There was a significant difference between pre- and post-infusion T(2)* and T(2) values (both respective p-values = 0.005). A significant correlation between T(2)* and T(2) values post-USPIO infusion was observed (r = 0.90, p < 0.001), which indicates USPIO uptake by the aortic wall. CONCLUSIONS: Aortic wall inflammation using USPIO-enhanced MR imaging is feasible. Use of quantitative T(2) and T(2)* pulse sequences provides a quantitative method for assessing USPIO uptake by the aortic wall.
Assuntos
Aneurisma da Aorta Abdominal/diagnóstico , Ruptura Aórtica/diagnóstico , Aortite/diagnóstico , Meios de Contraste , Dextranos , Angiografia por Ressonância Magnética , Nanopartículas de Magnetita , Idoso , Idoso de 80 Anos ou mais , Aneurisma da Aorta Abdominal/complicações , Ruptura Aórtica/etiologia , Aortite/complicações , Inglaterra , Estudos de Viabilidade , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Masculino , Valor Preditivo dos Testes , Prognóstico , Medição de RiscoRESUMO
BACKGROUND: High-resolution magnetic resonance (MR) imaging has been used for MR imaging-based structural stress analysis of atherosclerotic plaques. The biomechanical stress profile of stable plaques has been observed to differ from that of unstable plaques; however, the role that structural stresses play in determining plaque vulnerability remains speculative. METHODS: A total of 61 patients with previous history of symptomatic carotid artery disease underwent carotid plaque MR imaging. Plaque components of the index artery such as fibrous tissue, lipid content and plaque haemorrhage (PH) were delineated and used for finite element analysis-based maximum structural stress (M-C Stress) quantification. These patients were followed up for 2 years. The clinical end point was occurrence of an ischaemic cerebrovascular event. The association of the time to the clinical end point with plaque morphology and M-C Stress was analysed. RESULTS: During a median follow-up duration of 514 days, 20% of patients (n = 12) experienced an ischaemic event in the territory of the index carotid artery. Cox regression analysis indicated that M-C Stress (hazard ratio (HR): 12.98 (95% confidence interval (CI): 1.32-26.67, p = 0.02), fibrous cap (FC) disruption (HR: 7.39 (95% CI: 1.61-33.82), p = 0.009) and PH (HR: 5.85 (95% CI: 1.27-26.77), p = 0.02) are associated with the development of subsequent cerebrovascular events. Plaques associated with future events had higher M-C Stress than those which had remained asymptomatic (median (interquartile range, IQR): 330 kPa (229-494) vs. 254 kPa (166-290), p = 0.04). CONCLUSIONS: High biomechanical structural stresses, in addition to FC rupture and PH, are associated with subsequent cerebrovascular events.
Assuntos
Aterosclerose/fisiopatologia , Isquemia Encefálica/fisiopatologia , Estenose das Carótidas/fisiopatologia , Imageamento por Ressonância Magnética , Idoso , Idoso de 80 Anos ou mais , Aterosclerose/complicações , Fenômenos Biomecânicos , Isquemia Encefálica/etiologia , Estenose das Carótidas/complicações , Eletrocardiografia , Feminino , Análise de Elementos Finitos , Humanos , Interpretação de Imagem Assistida por Computador , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Modelos de Riscos Proporcionais , Estatísticas não Paramétricas , Estresse MecânicoRESUMO
INTRODUCTION: Ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI has been shown to be a useful modality to image activated macrophages in vivo, which are principally responsible for plaque inflammation. This study determined the optimum imaging time-window to detect maximal signal change post-USPIO infusion using T1-weighted (T1w), T2*-weighted (T2*w) and quantitative T2* (qT2*) imaging. METHODS: Six patients with an asymptomatic carotid stenosis underwent high resolution T1w, T2*w and qT2* MR imaging of their carotid arteries at 1.5 T. Imaging was performed before and at 24, 36, 48, 72 and 96 h after USPIO (Sinerem, Guerbet, France) infusion. Each slice showing atherosclerotic plaque was manually segmented into quadrants and signal changes in each quadrant were fitted to an exponential power function to model the optimum time for post-infusion imaging. RESULTS: The power function determining the mean time to convergence for all patients was 46, 41 and 39 h for the T1w, T2*w and qT2* sequences, respectively. When modelling each patient individually, 90% of the maximum signal intensity change was observed at 36 h for three, four and six patients on T1w, T2*w and qT2*, respectively. The rates of signal change decrease after this period but signal change was still evident up to 96 h. CONCLUSION: This study showed that a suitable imaging window for T1w, T2*w and qT2* signal changes post-USPIO infusion was between 36 and 48 h. Logistically, this would be convenient in bringing patients back for one post-contrast MRI, but validation is required in a larger cohort of patients.
Assuntos
Estenose das Carótidas/patologia , Ferro , Angiografia por Ressonância Magnética/métodos , Óxidos , Idoso , Artérias Carótidas/patologia , Simulação por Computador , Dextranos , Feminino , Óxido Ferroso-Férrico , Humanos , Nanopartículas de Magnetita , Masculino , Pessoa de Meia-Idade , Dinâmica não Linear , Fatores de TempoRESUMO
Despite recent therapeutic advances, acute ischemic complications of atherosclerosis remain the primary cause of morbidity and mortality in Western countries, with carotid atherosclerotic disease one of the major preventable causes of stroke. As the impact of this disease challenges our healthcare systems, we are becoming aware that factors influencing this disease are more complex than previously realized. In current clinical practice, risk stratification relies primarily on evaluation of the degree of luminal stenosis and patient symptomatology. Adequate investigation and optimal imaging are important factors that affect the quality of a carotid endarterectomy (CEA) service and are fundamental to patient selection. Digital subtraction angiography is still perceived as the most accurate imaging modality for carotid stenosis and historically has been the cornerstone of most of the major CEA trials but concerns regarding potential neurological complications have generated substantial interest in non-invasive modalities, such as contrast-enhanced magnetic resonance angiography. The purpose of this review is to give an overview to the vascular specialist of the current imaging modalities in clinical practice to identify patients with carotid stenosis. Advantages and disadvantages of each technique are outlined. Finally, limitations of assessing luminal stenosis in general are discussed. This article will not cover imaging of carotid atheroma morphology, function and other emerging imaging modalities of assessing plaque risk, which look beyond simple luminal measurements.
Assuntos
Angioscopia/métodos , Estenose das Carótidas/diagnóstico , Diagnóstico por Imagem/métodos , Humanos , Reprodutibilidade dos Testes , Fatores de RiscoRESUMO
Subdural haematomas can present with a wide variety of symptoms. An atypical presentation can be movement disorders. The key feature is that the history of onset is more rapid than with neurological conditions such as Parkinson's disease. The symptoms can also be an acute worsening of pre-existing disorder. The case discussed involved an 80 year old woman with bilateral choreathetoid movements attributed to a unilateral chronic subdural haematoma. The haematoma was surgically drained and the symptoms resolved. Sporadic reports of similar cases of movement disorders associated with subdural haematomas exist in the literature, but rarely do unilateral haematomas present with bilateral symptoms. Pressure effects, neurotransmitter abnormality and ischaemia have been postulated as reasons for this type of presentation. Unexplained and sudden movement disorders might warrant imaging to rule out a subdural haematoma as the cause.
Assuntos
Atetose/etiologia , Coreia/etiologia , Hematoma Subdural Crônico/complicações , Idoso de 80 Anos ou mais , Drenagem , Feminino , Hematoma Subdural Crônico/diagnóstico por imagem , Hematoma Subdural Crônico/cirurgia , Humanos , Tomografia Computadorizada por Raios X , Resultado do TratamentoRESUMO
Central nervous system (CNS) stimulation is becoming increasingly prevalent. Deep brain stimulation (DBS) has been proven to be an invaluable treatment for movement disorders and is also useful in many other neurological conditions refractory to medical treatment, such as chronic pain and epilepsy. Neuroimaging plays an important role in operative planning, target localization and post-operative follow-up. The use of imaging in determining the underlying mechanisms of DBS is increasing, and the dependence on imaging is likely to expand as deep brain targeting becomes more refined. This article will address the expanding role of radiology and highlight issues, including MRI safety concerns, that radiologists may encounter when confronted with a patient with CNS stimulation equipment in situ.
Assuntos
Doenças do Sistema Nervoso Central/diagnóstico , Doenças do Sistema Nervoso Central/terapia , Neuroimagem , Estimulação Encefálica Profunda , HumanosRESUMO
Previous studies have used [35S]-sulfate as a specific marker to autoradiographically localize sulfated glycosaminoglycans, proteoglycans, and glycoproteins. Embryonic chicks were labeled with [35S]-sulfate, followed by previously reported routine fixation and processing techniques. Subsequent processing revealed loss of radiolabeled macromolecules and retention of unincorporated label in the tissue, using these procedures. Biochemical analysis after various fixation and processing procedures demonstrated that an additional agent, such as cetylpyridinium chloride, was necessary in the fixative to retain the highly aqueous soluble sulfated macromolecular components. Molecular sieve chromatography was used to monitor digestate solutions for the identity of glycosaminoglycans and proteoglycans as indicated by selective enzymatic removal. Retained unincorporated [35S]-sulfate could be completely removed by rinsing the tissue in dehydration solutions containing exogenous sodium sulfate. This new procedure ensures the quantitative retention of sulfate labeled macromolecules in fixed tissue with the complete removal of unincorporated radiotracer, both of which are necessary for meaningful autoradiography.
Assuntos
Autorradiografia/métodos , Fixadores , Glicoconjugados/metabolismo , Animais , Embrião de Galinha , Sulfatos/metabolismoRESUMO
Neottialges (Pelecanectes) ibisicola sp. n. is described from the subcutaneous tissues of the White-faced Ibis, Plegadis chihi, from west Texas. The new species is similar to N. (P.) plegadicola Fain, but differs from this and other species of the subgenus by idiosomal chaetotaxy, presence of a bifurcate apical extension on Tarsus III, solenidion phi on Tibia I less than 1/2 as long in the new species, lateroventral seta of Tibia I whiplike, structure of the genital sclerite and suckers, and presence of punctations on the dorsal idiosoma. The morphology and host-parasite relationships of the new species are compared with those of related species of hypopi from the host family Threskiornithidae.
Assuntos
Aves/parasitologia , Ácaros/classificação , Animais , Ácaros/anatomia & histologiaRESUMO
Rallinyssus sorae sp. n. is described from the nasal turbinates of the sora, Porzana carolina, collected in Maryland and Ohio. The new species is most similar to Rallinyssus verheyeni Fain but differs in number of setae on the female ventral opisthosoma, structure of the fixed and movable digits of the male and female chelicerae, chaetotaxy of legs I to IV, and presence of a sternal plate in the male. The taxonomy and host-parasite relationships of the various species of Rallinyssus are discussed.
Assuntos
Aves/parasitologia , Ácaros/anatomia & histologia , Animais , Feminino , Interações Hospedeiro-Parasita , Masculino , Ácaros/classificação , Cavidade Nasal/parasitologiaRESUMO
OBJECTIVES: This study reports quantitative comparisons of signal-to-noise ratio (SNR) at 1.5 and 3 T from images of carotid atheroma obtained using a multicontrast, cardiac-gated, blood-suppressed fast spin echo protocol. METHODS: 18 subjects, with carotid atherosclerosis (>30% stenosis) confirmed on ultrasound, were imaged on both 1.5 and 3 T systems using phased-array coils with matched hardware specifications. T(1) weighted (T(1)W), T(2) weighted (T(2)W) and proton density-weighted (PDW) images were acquired with identical scan times. Multiple slices were prescribed to encompass both the carotid bifurcation and the plaque. Image quality was quantified using the SNR and contrast-to-noise ratio (CNR). A phantom experiment was also performed to validate the SNR method and confirm the size of the improvement in SNR. Comparisons of the SNR values from the vessel wall with muscle and plaque/lumen CNR measurements were performed at a patient level. To account for the multiple comparisons a Bonferroni correction was applied. RESULTS: One subject was excluded from the protocol owing to image quality and protocol failure. The mean improvement in SNR in plaque was 1.9, 2.1 and 2.1 in T(1)W, T(2)W and PDW images, respectively. All plaque SNR improvements were statistically significant at the p<0.05 level. The phantom experiment reported an improvement in SNR of 2.4 for PDW images. CONCLUSIONS: Significant gains in SNR can be obtained for carotid atheroma imaging at 3 T compared with 1.5 T. There was also a trend towards increased CNR. However, this was not significant after the application of the Bonferroni correction.
Assuntos
Estenose das Carótidas/diagnóstico , Imageamento por Ressonância Magnética/métodos , Placa Aterosclerótica/diagnóstico , Intensificação de Imagem Radiográfica , Razão Sinal-Ruído , Idoso , Estenose das Carótidas/diagnóstico por imagem , Estudos de Coortes , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Posicionamento do Paciente , Imagens de Fantasmas , Placa Aterosclerótica/diagnóstico por imagem , Estudos Prospectivos , Controle de Qualidade , Índice de Gravidade de Doença , Estatísticas não Paramétricas , Ultrassonografia DopplerRESUMO
Currently carotid imaging has 2 main focuses: assessment of luminal stenosis and classification of atherosclerotic plaque characteristics. Measurement of the degree of stenosis is the main assessment used for current treatment decision making, but an evolving idea that is now driving imaging is the concept of vulnerable plaque, which is where plaque components are identified and used to define which plaques are at high risk of causing symptoms compared with those at low risk. This review article covers the methods used for noninvasive assessment of carotid luminal stenosis and the options available for plaque imaging.