A hidrocefalia ainda é um desafio no que diz respeito ao diagnóstico, tratamento e acompanhamento na população pediátrica. O tratamento, por meio das derivações ventriculares ou ventriculostomias endoscópicas, está bem estabelecido. Contudo, o diagnóstico de mau funcionamento das derivações, associado à hipertensão intracraniana, permanece um problema, especialmente em crianças menores e com fontanelas não patentes. Os exames radiológicos, tais como: ultrassonografia, tomografia computadorizada e ressonância magnética, possibilitam apenas o acesso indireto à pressão intracraniana, enquanto os métodos para sua avaliação direta podem apresentar riscos e raramente são utilizados em crianças. O objetivo deste estudo foi avaliar um dispositivo não invasivo para acessar alguns parâmetros da curva de pressão intracraniana em crianças portadoras de hidrocefalia. Para tanto, foi realizado um estudo descritivo-analítico, não experimental, prospectivo. A amostra foi composta por indivíduos menores de 18 anos, incluindo 28 pacientes portadores de hidrocefalia e 28 crianças em seguimento rotina de puericultura (grupo controle). Os participantes foram divididos em quatro grupos: grupo A: hidrocefalia compensada clinicamente; grupo B: pacientes com hidrocefalia, sem sinais clínicos sugestivos de hipertensão intracraniana e já submetidos à cirurgia para tratamento da hidrocefalia; grupo C: pacientes com hidrocefalia aguda e hipertensão intracraniana; grupo D: crianças sem qualquer doença neurológica (controle). Os dados foram coletados entre 2014 e 2016, por meio da instalação de um sensor extracraniano de deformação, acoplado sobre o couro cabeludo, com registro da curva de pressão intracraniana não invasiva. A análise dos dados foi realizada com software Freemat® 4, Origin Pro® 8 e R® 3.1.3. Foram analisados parâmetros obtidos na curva de pressão intracraniana como \"relação P2/P1\", \"classificação de P1 e P2\" (P1>P2 ou P2>P1) e \"inclinação de P1\". Os resultados apontaram, que na amostra estudada, o índice P2>P1 apresentou sensibilidade de 80% e especificidade de 100%, a \"classificação de P1 e P2\" sensibilidade de 100% e especificidade de 80% para predição de hipertensão intracraniana em hidrocefalia, sendo que a \"inclinação de P1\" não apresentou relação estatística. Conclui-se que, apesar de limitações operacionais, o método de monitorização não invasiva da pressão intracraniana se mostrou útil na detecção de hipertensão intracraniana e apresenta perspectivas de aplicação clínica futura. / Hydrocephalus is still a challenge regarding diagnosis, treatment and monitoring in the pediatric population. Currently, treatments by ventricular or endoscopic ventriculostomies are well established. However, to date, the diagnosis of malfunctioning shunts associated with intracranial hypertension remains a problem, especially in young children and without patent fontanelles. Radiological examinations, such as ultrasonography, computerized tomography and magnetic resonance, allow only an indirect access to the intracranial pressure, whilst methods for direct assessment may present risks and therefore are rarely used in children. The aim of this study was to evaluate a noninvasive device to assess some parameters of the intracranial pressure curve in children with hydrocephalus. For this, we performed a prospective and non-experimental descriptive-analytic study. The sample consisted of children (under 18 years), including 28 patients with hydrocephalus and 28 children following routine child care (control group). Participants were divided into four groups; Group A: children with clinically compensated hydrocephalus; B: patients with hydrocephalus, but with no clinical signs of intracranial hypertension and no history of medical surgery for the treatment of hydrocephalus; C: patients with acute intracranial hypertension due to hydrocephalus, and D: children without neurological disease (control). Data were collected between 2014 and 2016, through the installation of an extracranial deformation sensor, coupled to the children\'s scalp, which allowed registration of non-invasive intracranial pressure curves. Data analysis was performed using Freemat® 4, Origin Pro® 8 and R® 3.1.3 software. Parameters obtained from the intracranial pressure curves were analyzed, such as \"ratio P2 / P1\", \"classification P1 and P2\" (P1> P2 or P2> P1) and \"P1 slope.\" The results showed that P2>P1 index had a sensitivity of 80% and specificity of 100%, while the \"classification of P1 and P2\" had 100% of sensitivity and 80% of specificity for predicting intracranial hypertension. \"P1 slope\" presented no statistical difference. In summary, despite some operational limitations, this study showed an useful and non-invasive method for monitoring intracranial pressure, which was able to indicate the intracranial hypertension in children with hydrocephalus and, thus, should be further investigated for clinical applications.

As últimas estimativas da Organização Mundial da Saúde mostram a ocorrência de 14,1 milhões de novos casos de câncer em 2012. Sendo que desses casos, 8,2 milhões virão a óbito. Os tumores paravertebrais e intracraniais, também chamados de cânceres do Sistema Nervoso Central, tem origem no cérebro, nervos cranianos e meninges. Uma nova modalidade de braquiterapia começou a ser usada nesta última década. Neste procedimento, placas poliméricas flexíveis, carregando fósforo-32, são colocadas próximas ou em contato ao tumor para o tratamento. Este tratamento apresenta vantagens em relação aos demais porque aplica uma alta taxa de dose no tumor poupando tecidos sadios. A produção destas placas ainda é pouco estudada, embora já existam resultados satisfatórios no seu uso para o tratamento dos cânceres do sistema nervoso central. Neste trabalho foram realizados estudos iniciais para a produção deste tipo de placas poliméricas para braquiterapia. Foram avaliadas as propriedades mecânicas e a capacidade de imobilização de material radioativo de duas resinas comercias, uma poliuretânica e outra epoxídica, com e sem presença de substrato de policarbonato. Os testes iniciais apontaram o uso da resina epoxídica como melhor alternativa e com o uso dela foram feitos os primeiros protótipos e testes. O uso do policarbonato como substrato não foi necessário em uma das metodologias, facilitando o procedimento, mas oferecendo uma barreira menor de segurança. Os ensaios de tração mostraram que a adição de solução ácida à resina epóxi alterou suas características mecânicas, mas houve uma pequena melhora em sua flexibilidade. Os testes de adesão evidenciaram uma melhor adesão da resina à face texturizada do policarbonato. A termogravimetria mostrou que a solução ácida adicionada a resina fica presa à estrutura mesmo com elevações de temperatura acima de 100°C. A resina epoxídica utilizada teve a capacidade de incorporar o material radioativo em forma de solução ácida e manter-se estanque após testes de esfregaço e imersão em líquido quente. De acordo com os resultados obtidos, a produção destas placas com resina epoxídica é possível e atende às normas internacionais de segurança contra vazamento de material radioativo para fontes utilizadas em braquiterapia. / The latest estimates of the World Health Organization show the occurrence of 14.1 million new cases of cancer in 2012. From these cases, 8.2 million will come to death. The paraspinal and intracranial tumors, also called central nervous system cancers, are originated in the brain, cranial nerves and meninges. A new brachytherapy modality began to be used in the last decade. In this procedure, flexible, polymeric plaques carrying phosphorus-32 are placed in contact or close to the tumor for treatment. This treatment has advantages over others because it applies a high dose rate in the tumor sparing healthy tissues. The production of these plaques is not well known, although there are satisfactory results in its use for the treatment of central nervous system cancers. This work carried out initial studies for the production of this type of polymer plaques for brachytherapy. The mechanical properties and immobilization capacity of radioactive material, from two commercial resins, epoxy and polyurethane, with or without the presence of polycarbonate as substrate were evaluated. Initial tests showed the use epoxy resin as the best alternative and the first prototypes and tests with use of it were made. The use of polycarbonate as a substrate was not required on one of the methodologies, facilitating the procedure but offering a lower security barrier. The tensile tests showed that addition of acid to the epoxy resin solution changed its mechanical properties, but there was a small improvement in flexibility. Adhesion tests showed better adhesion of the resin to the textured surface of the polycarbonate. The thermogravimetric analysis showed that the acid solution added to the resin structure is sealed even with temperature rises above 100°C. The epoxy resin used has the ability to incorporate the radioactive material in the form of acid solution and remain tight after wiping and immersion in hot liquid tests. According to the results, the production of these plaques with epoxy resin is possible and meets international safety standards for leakage of radioactive material in radioactive sources used in brachytherapy.

Thesis (Ph. D.)--University of Florida, 2003. / Title from title page of source document. Includes vita. Includes bibliographical references.

abstract: Intracranial pressure is an important parameter to monitor, and elevated intracranial pressure can be life threatening. Elevated intracranial pressure is indicative of distress in the brain attributed by conditions such as aneurysm, traumatic brain injury, brain tumor, hydrocephalus, stroke, or meningitis. Electrocorticography (ECoG) recordings are invaluable in understanding epilepsy and detecting seizure zones. However, ECoG electrodes cause a foreign body mass effect, swelling, and pneumocephaly, which results in elevation of intracranial pressure (ICP). Thus, the aim of this work is to design an intracranial pressure monitoring system that could augment ECoG electrodes. A minimally invasive, low-cost epidural intracranial pressure monitoring system is developed for this purpose, using a commercial pressure transducer available for biomedical applications. The system is composed of a pressure transducer, sensing cup, electronics, and data acquisition system. The pressure transducer is a microelectromechanical system (MEMS)-based die that works on piezoresistive phenomenon with dielectric isolation for direct contact with fluids. The developed system was bench tested and verified in an animal model to confirm the efficacy of the system for intracranial pressure monitoring. The system has a 0.1 mmHg accuracy and a 2% error for the 0-10 mmHg range, with resolution of 0.01 mmHg. This system serves as a minimally invasive (2 mm burr hole) epidural ICP monitor, which could augment existing ECoG electrode arrays, to simultaneously measure intracranial pressure along with the neural signals. This device could also be employed with brain implants that causes elevation in ICP due to tissue - implant interaction often leading to edema. This research explores the concept and feasibility for integrating the sensing component directly on to the ECoG electrode arrays. / Dissertation/Thesis / Masters Thesis Bioengineering 2015

Non-invasive techniques to explore intracranial compliance and pressure have been extensively explored in recent years. Previous techniques have used expensive technologies to make these measurements, often with difficulty. We present a novel, inexpensive provocative test to observe trends in intracranial compliance measurement targeted towards the treatment and management of hydrocephalus. Two techniques are proposed which derive data from the digital and supraorbital arteries as well as tympanic membrane displacement. This requires the use of two photo-plethysmographic sensors and a TMD sensor. A common tilt table apparatus is used to methodically and artificially increase intracranial pressure to stress the cranial system during the test. The results from this test are computed using a digital signal processing algorithm to determine phase difference between the waveforms. Further research is also proposed.

No description available.

Introdução: A evolução clínica da trombose venosa cerebral (TVC) pode variar desde a recuperação completa ao óbito. Séries européias e um estudo multicêntrico identificaram alguns fatores indicativos de prognóstico da TVC, dado importante na decisão da melhor terapêutica para os pacientes. Este estudo busca identificar, a partir do seguimento prospectivo de cento e onze pacientes com TVC, os fatores prognósticos envolvidos na evolução clínica durante o período de 2 anos. Pacientes Métodos: Foram acompanhados prospectivamente 111 pacientes com diagnóstico de TVC desde a fase aguda do diagnóstico, confirmado por meio de RM de encéfalo e/ou angiografia cerebral (ARM, ATC ou angiografia digital). Obtidos dados do quadro clínico e seguimento por um protocolo clínico. 96% dos pacientes foram anticoagulados na fase aguda com heparina e seguida de anticoagulação com warfarina. Submetidos a investigação para os fatores predisponentes para TVC. A evolução clínica foi quantificada por meio da escala modificada de Rankin (EMR) após 3, 6, 12 e 24 meses, definindo os pacientes de bom prognóstico EMR 1, e mau prognóstico EMR 2. Comparamos dados clínicos da fase aguda e resultados encontrados nos exames de imagem e laboratoriais como possíveis fatores prognósticos, através da análise univariada pelo teste 2 e os fatores de significância estatística (p<0,1), foram analisados com regressão logística ajustada e cálculo da razão de chances (RC), (intervalo de confiança IC=95%). Resultados: A média da idade dos pacientes foi de 35 anos, 72% mulheres, 40% afro-brasileiros. As principais manifestações clínicas foram: cefaléia 97%, déficit focal 47%, crise epiléptica 40%, alteração da consciência 28%, síndrome de HIC (SHIC) isolada 40%. Quanto aos fatores predisponentes; 75% das mulheres usavam anticoncepcional, 31% dos pacientes apresentavam trombofilia hereditária, 13% SAAF, 6% eram portadores de vasculites, 25% outros estados pro trombóticos, 7 % apresentavam fatores locais (infecciosos ou MAV); e 5% das mulheres estavam no puerpério ou gestação. Os dados de neuroimagem revelaram que 42% apresentaram trombose em mais de um sistema venoso, 33% tiveram infartos hemorrágicos e 18% infartos venosos isquêmicos, e 20% dos pacientes apresentaram trombose de veias e seios profundos. Após 24 meses 18 pacientes (17%) apresentaram EMR 2 e os fatores determinantes de pior prognóstico foram: a etnia afro-brasileira p=0,001; RC= 11,37 (95% IC 2.81- 46,08), alteração do nível de consciência p=0,007; RC=4.56 (95% IC 1.61-19.45), sexo masculino p=0,049 RC=3.55 (95% IC 1.00-12.55) e idade acima de 32 anos p=0,05 RC = 3.95 (95% IC 0,97-15.20). A presença isolada de ACO como fator predisponente está associado ao melhor prognóstico p = 0,016; RC=5,17(95% IC 1.37-19.57) e após 24 meses a mortalidade foi de 4,5%. Conclusão: A análise deste trabalho evidencia que a maioria dos pacientes portadores de TVC (83%) apresenta uma evolução benigna com o tratamento, estando após 24 meses assintomáticos ou com sintomas mínimos, e a presença de ACO como fator predisponente isolado a TVC está relacionado ao melhor prognóstico. Os pacientes com pior evolução clínica têm a raça afro-brasileira, a alteração do nível de consciência, sexo masculino e idade acima de 32 anos como fatores determinantes de pior prognóstico em vinte e quatro meses. A identificação destes fatores é importante por direcionar um melhor tratamento na fase aguda da TVC para casos selecionados / Introduction: The cerebral venous thrombosis (CVT) clinical evolution is quite variable from complete recovery to death. Some European series and a multicenter study had identified prognostic factors related to CVT prognosis. The identification of these factors is important for the best therapeutic decision to patients. This study aims to identify the prognostic factors enrolled in clinical evolution of 111 patients with CVT in a prospective outcome clinical trial during two years. Subjects and Methods: One hundred and eleven patients were prospective followed with the diagnosis of CVT since acute phase diagnosis, confirmed by brain MRI and/or brain angiography (MRA , CTA or digital angiography). Information about clinical features and follow-up were filled on a clinical form. 96% of the patients were anticoagulated on heparin followed by warfarin treatment. The patients were investigated to predisposing factors to CVT. The clinical evaluation was accessed by the modified Rakin scale (mRs) after 3, 6, 12 and 24 months, considering patients with good outcome when mRs 2. The acute phase clinical features, laboratory and imaging data were compared as possible prognosis factors beyond univariate 2 test and the factors with statistical significance (p<0,1) and then analyzed by logistic regression adjusted and Odds Ratio values (confidence interval CI=95%). Results: The mean age of the patients was 35 years, 72% were women, and 40% were African Brazilian. The main clinical features observed were: headache 97%, focal sign 47%, epileptic seizure 40%, isolated ICH syndrome 40% and altered mental status 28%. All the patients were investigated to predisposing factors; 75% of the women were on oral contraceptive, 31% of the patients presented hereditary thrombophilia, 13 % antiphospholipid syndrome, 6% presented vasculitis, 25% other protrhrombotic state, 7% presented some local feature (arterialvenous malformation or infection) and 5% of women were pregnant or on puerperium. The neuroimaging data showed that 42% of the patients presented thrombosis in more than one venous system, 33% had hemorrhage infarcts, 18% ischemic venous infarcts and 20% of the patients had thrombosis of the deep venous system. After two years 17% had a mRs > 2 and the features enrolled on poor prognosis were: African Brazilian patients p=0,001; OR= 11,37 (95% IC 2.81- 46,08), altered mental status p=0,007; OR=4.56 (95% IC 1.61-19.45), male gender p=0,049 OR=3.55 (95% IC 1.00-12.55) and age over 32 years p=0,05 OR = 3.95 (95% IC 0,97- 15.20). The presence of oral contraceptives as isolated predisposing factor was related to good outcome CVT p=0,016; OR=5,17(95% IC 1.37-19.57) and after two years the mortality rate was 4,5%. Conclusion: This study data show that most patients with the diagnosis of CVT (83%) has a good outcome with the treatment, after two years follow up they have no symptoms or minimal deficits, and the presence of oral contraceptives as isolated predisposing factor was related to better outcome CVT. The patients with poor prognosis have the African Brazilian ethnic group, altered mental status, male gender and age over 32 years as the factors enrolled on bad clinical evolution in two years. The identification of these factors can have future value on treatment better choice on acute phase to selected CVT patients

Intracranial pressure (ICP) is an important monitoring modality in the clinical management of several neurological diseases carrying the risk of fatal intracranial hypertension. However, this parameter is not always considered due to its invasive assessment. In this scenario, a non-invasive estimation of ICP (nICP) may be essential, and indeed it has become a Holy Grail in Clinical Neurosciences: extensively searched, albeit never found. This thesis is devoted to the assessment, applications and development of transcranial Doppler (TCD)-based non-invasive methods for ICP and cerebral perfusion pressure (CPP) monitoring. The thesis is divided into three sections: I) The accuracy of existing TCD-based nICP estimators in various scenarios of varying ICP (traumatic brain injury, rise of ICP during plateau waves, and rise in ICP induced by infusion of cerebrospinal fluid during infusion test). The estimators of nICP consisted of a mathematical black box model, methods based on non-invasive CPP, and a method based on TCD pulsatility index. II) The feasibility of the best performing nICP estimator in clinical practice, including patients with closed TBI and brain midline shift, patients with acute liver failure during liver transplant surgery, and patients during non-neurosurgical surgery in the beach chair position. III) The description and assessment of a novel methodology for non-invasive assessment of cerebral perfusion pressure (nCPP) based on spectral arterial blood volume accounting. As main results, TCD-based non-invasive methods could replicate changes in direct ICP across time confidently, and could provide reasonable accuracy in comparison to the standard invasive techniques. Furthermore, in feasibility studies, nICP in association with other TCD physiological parameters provided a comprehensive interpretation of cerebral haemodynamics in conditions presenting impairment of cerebral blood flow circulation. The new method of nCPP estimation could identify changes in CPP across time reliably in conditions of decreasing and increasing CPP. These findings support the use of TCD-based nICP methods in a variety of clinical conditions requiring management of ICP and brain perfusion. More importantly, the low costs associated with nICP methods, since TCD is a widely available medical device, could contribute to its widespread use as a reliable alternative for ICP monitoring in everyday clinical practice.

在亞洲人群包括中國人群中，顱內動脈粥樣硬化（ICAS）發病率很高，是缺血性卒中和短暫性腦缺血發作（TIA）的首要病因。然而，目前ICAS 並未被深入研究。因此我們在一系列研究中通過運用傳統及創新的神經影像學方法，來研究ICAS 的臨床及血流動力學特徵，以期促進其全面評價及危險分層。 / 既往研究發現亞洲人群和西方人群在頭頸部動脈粥樣硬化的發生和發展上存在種族差異。爲了進一步驗證這些種族差異，我們開展了一項社區研究，以探索無癥狀性顱內外動脈粥樣硬化在中國社區成年居民中的發病情況，以及二者之間的相互關係。在該研究中，我們分別採用經顱多普勒（TCD）和頸部血管超聲（CD）來評價顱內和顱外動脈的粥樣硬化。在研究納入的537 例研究對象中，我們發現顱內動脈粥樣硬化的發展優先於頸動脈粥樣硬化，而且不同階段的頸動脈粥樣硬化與顱內動脈粥樣硬化並無獨立相關關係。該結果提示，在中國人群的全身系統性粥樣硬化的過程中，顱內動脈粥樣硬化可能是一個比較早期而且相對獨立的過程，這與西方人群的情況不同。本研究結果進一步支持東西方人群在顱內外動脈粥樣硬化進程上存在的種族差異。 / 根據既往研究結果，病因為癥狀性ICAS的缺血性卒中或TIA患者卒中復發的風險很高。目前，癥狀性ICAS患者的危險分層大多基於其動脈管腔的狹窄程度。然而，管腔的解剖學狹窄程度並不一定與其血流動力學的嚴重程度成比例，而後者也可能影響相關患者的卒中復發風險。因此，我們進行了以下的一系列研究， 以評價癥狀性ICAS的血流動力學特徵，同時初步探索其在相關患者危險分層中的應用價值。 / 我們首先進行了三項研究，採用一種基於磁共振血管成像（MRA）的創新方法來評價癥狀性ICAS的血流動力學嚴重程度。基於時間飛躍法（TOF）MRA的信號對比機制，我們提出了一項名為信號強度比值（SIR）的參數來定量地評價癥狀性ICAS 的血流動力學效應；該參數代表TOF MRA 影像上經過背景信號強度校正后的ICAS 病變后和病變前的信號強度比值。在一項初步研究中，我們確定了該參數的評價和計算方法。在26例癥狀性ICAS病變中，我們發現該參數的計算操作簡便，在臨床上可行，且在同一評價者的兩次評價中具有很高的可重複性。在隨後的一項研究中，我們在102例癥狀性ICAS病變中發現該參數在兩位評價者之間具有顯著的可重複性。在第三項研究中，我們在36例具有癥狀性ICAS的缺血性卒中患者中發現SIR與患者的急性梗死灶體積顯著相關，但我們並未發現該參數與患者1年的卒中復發風險相關，可能由於該研究的樣本量過小。以上三項研究證實，SIR作為一種基於TOF MRA的評價癥狀性ICAS血流動力學嚴重程度的方法，具有可重複性及臨床可行性；而其對於相關患者危險分層的價值需要在前瞻性的較大型研究中進一步驗證。 / 在如下的另外兩項研究中，我們採用計算機流體動力學（CFD）技術對癥狀性ICAS患者的計算機斷層掃描血管成像（CTA）影像進行重建，從而評價其ICAS 病變的血流動力學特徵。首先，在一項初步研究中，我們探索了採用臨床常規CTA影像進行CFD模型重建的可行性。在10例癥狀性ICAS病變中，9例病變的CTA原始圖像成功重建為CFD模型。重建的CFD模型可以定量地反映ICAS病變的各種血流動力學特徵。該初步研究證實了基於臨床常規CTA進行CFD建模從而評價ICAS血流動力學特徵的可行性。在隨後的一項研究中，我們探索了CFD 模型反映的癥狀性ICAS 的血流動力學特徵對於相關患者卒中復發的預測價值。在32例具有70-99%管腔狹窄的癥狀性ICAS病例中，我們發現病變前後血流動力學參數的變化（包括壓力，剪切應變率及血流速度）可能預測患者的卒中復發風險。以上兩項研究證實，基於臨床常規CTA進行CFD模型重建從而定量評價癥狀性ICAS的血流動力學特徵具可行性，同時，這些血流動力學特徵可能對相關患者的卒中復發風險具有預測價值。 / 綜上所述，通過以上研究，我們進一步證實了亞洲人群和西方人群在顱內外動脈粥樣硬化的進程上存在的種族差異。更重要的是，我們的研究證實評價癥狀性ICAS病變的血流動力學特徵具有臨床意義。對於相關患者，採用以上研究中的兩種方法評價癥狀性ICAS的血流動力學特徵，可能對患者的危險分層具有潛在的指導意義。在未來的前瞻性大樣本研究中，上述方法對癥狀性ICAS患者卒中復發風險的預測價值需要進一步證實，以期促進相關的臨床決策，從而在長遠目標上降低相關患者的卒中復發風險。 / Intracranial atherosclerosis (ICAS) is of high prevalence in Asia, which is the leading cause for ischemic stroke and transient ischemic attack (TIA) in Asians, including the Chinese. However, it has not been fully appreciated or adequately investigated in relevant studies. In this thesis, we tried to delineate the hemodynamics and clinical implications of ICAS, by using several traditional and novel neuroimaging methods. / Previous studies had suggested differences in atherogenesis of intra- and extracranial arteries between Asians and Caucasians. To find further evidence, we performed a study to investigate asymptomatic ICAS and carotid atherosclerosis and their correlations in community-dwelling Chinese adults, by using transcranial Doppler and carotid duplex ultrasonography, respectively. For the 537 subjects studied, we found more advanced asymptomatic ICAS than carotid atherosclerosis, and there were no independent correlations between different stages of carotid atherosclerosis and presence of ICAS. The results suggested that atherogenesis of intracranial arteries might be a relatively independent course in systemic atherosclerosis in the Chinese population, which is unlike the case in Caucasians. By combing with previous findings, results of this study further supported the existence of racial differences in cervicocerebral atherogenesis between Asians and Caucasians. / According to previous studies, stroke patients with symptomatic ICAS are at high risk of recurrence. Currently, risk stratification of symptomatic ICAS are usually based on the percentage of luminal stenosis. However, the anatomic severity does not always proportionate to its hemodynamic significance, which may also impact on the risk of stroke recurrence in symptomatic ICAS. Therefore, we performed a series of studies as follows to evaluate the hemodynamics of symptomatic ICAS, and to assess its value in risk stratification of those with such lesions. / We first performed three studies based on time-of-flight (TOF) magnetic resonance angiography (MRA), to gauge the hemodynamic significance of symptomatic ICAS. Based on the signal contrast mechanism of TOF MRA, we developed a novel index, signal intensity ratio (SIR), representing changes of signal intensities (SI) across an ICAS on maximum intensity projections of TOF MRA, to quantify its hemodynamic significance: SIR = (mean post-stenotic SI - mean background SI) / (mean pre-stenotic SI - mean background SI). In a pilot study to establish the methodology of this index, we found it easy to perform, and highly reproducible between repetitive measurements by a same observer in 26 symptomatic ICASs. In a subsequent study, we also found this index to be substantially reproducible between measurements from two observers in 102 symptomatic ICAS lesions. In a third study, we tried to investigate the relationships between SIR of ICAS, other imaging features, and 1 year outcomes of patients with symptomatic ICAS. In the 36 patients enrolled, SIR was found to be significantly, linearly and negatively correlated to acute infarct volume on diffusion-weighted MR images. However, we did not establish a definite correlation between SIR and recurrent ischemic stroke, probably due to the small sample size. These studies suggested that SIR as evaluated on MRA was a feasible and reproducible method to gauge the hemodynamic and functional significance of ICAS. The role of this index in predicting further recurrent risks in those with symptomatic ICAS needs to be verified in future studies. / In another two studies, we applied the computational fluid dynamics (CFD) modeling technique in processing computed tomography angiography (CTA) images, to evaluate the hemodynamic characteristics of ICAS. In a pilot study, we tested the feasibility of CFD modeling of ICAS based on CTA images. Among 10 cases of symptomatic ICAS identified on CTA, the CTA source images of 9 were successfully processed to CFD models, which were able to quantitatively delineate the hemodynamic environment across the lesions. This pilot study demonstrated the feasibility of constructing CFD models of ICAS out of routinely obtained CTA source images. Then in a second study, we preliminarily explored the values of hemodynamics of ICAS revealed by such CFD models, in predicting recurrent risks in patients with symptomatic ICAS of 70-99% luminal stenosis. In the 32 cases evaluated, we found that changes of hemodynamic features across an ICAS lesion, including the changes of pressure, shear strain rate, and blood flow velocity, may be able to predict the recurrent risk in this patient subset. Therefore, it was feasible to model hemodynamics of symptomatic ICAS based on CTA images, and future prospective studies with larger sample sizes are warranted to further validate the role of CFD modeling in risk stratification of affected patients. / In conclusion, in this thesis we found further evidence to support the existence of racial differences in atherogenesis of cervicocerebral arteries between Caucasians and Asians. More importantly, we demonstrated that hemodynamics of symptomatic ICAS could be of clinical significance in characterization of such lesions. In patients with symptomatic ICAS, the two methods to evaluate hemodynamic features of ICAS as used in this thesis, may yield potential values in predicting the recurrent risk of these patients. In the near future, prospective studies enrolling more patients are warranted to further validate findings in this thesis, to embrace more reasonable and comprehensive evaluation of symptomatic ICAS, so as to facilitate decision making in clinical scenarios and patient selection in clinical studies, which in the long run may help reduce the risk of stroke recurrence in affected patients. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Leng, Xinyi. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 131-146). / Abstracts also in Chinese.

Spontaneous intracerebral hemorrhage, the non-traumatic rupture of cerebral blood vessels, is the most devastating form of stroke. The disease is dynamic, unpredictable, and patients can worsen acutely within the first 24 hours secondary to hematoma expansion: re-bleeding of a baseline hemorrhage. Hematoma expansion is a major predictor of mortality and poor long-term outcome. This secondary analysis thesis proposes to advance the current understanding of this phenomenon through three separate research endeavors: 1) a scoping review of hematoma expansion prediction scores, 2) an independent validation of a non-contrast prediction score, and 3) an assessment and revision of the dichotomous definition of hematoma expansion used in clinical trials. These three projects will offer different contributions that will advance the science of intracerebral hemorrhage, a field where treatment options, outcome measures, and basic definitions, are all under active debate.