Assessment of aortic stiffness in computed tomography : methodology of radiological examination from 2000 to 2020

Introduction: Vascular elasticity may be a predictive factor of various diseases. Although stiffening is thought to be a natural consequence of ageing, it can be accelerated by a number of pathological conditions such as hypertension, diabetes, or renal diseases. Aim of the study was to discuss the methodology used to assess aortic stiffness, with particular emphasis on radiological examination. Material and methods: The PubMed and Google Scholar databases were screened from inception to the year 2000 by 2 independent analysts initially working separately and then comparing their results. Results: Assessment of stiffness can be divided into methods not requiring computed tomography scan, such as tonometry of carotid femoral pulse wave velocity, bioelectrical impedance analysis, and cardio ankle vascular index, and methods requiring it, such as multidetector row computed tomography - ECG gated, in which indexes such as aortic distensibility, aortic stiffness, and aortic compliance can be obtained with simultaneous calcification evaluation based on the Agatston score. Discussion: Aortic stiffness was corelated with left ventricular afterload, prehypertension, coronary artery plaques, predic tion of coronary artery diseases, bone demineralization, chronic obstructive pulmonary diseases, and diabetes mellitus. Conclusions: Being a factor of various severe diseases, aortic stiffness may play an important role in the early detection of patients requiring additional medical care

hospital factory for manufacturing customised patient specific 3d anatomo functional models and prostheses

The fabrication of personalised prostheses tailored on each patient is one of the major needs and key issues for the future of several surgical specialties. Moreover, the production of patient-specific anatomo-functional models for preoperative planning is an important requirement in the presence of tailored prostheses, as also the surgical treatment must be optimised for each patient. The presence of a prototyping service inside the hospital would be a benefit for the clinical activity, as its location would allow a closer interaction with clinicians, leading to significant time and cost reductions. However, at present, these services are extremely rare worldwide. Based on these considerations, we investigate enhanced methods and technologies for implementing such a service. Moreover, we analyse the sustainability of the service and, thanks to the development of two prototypes, we show the feasibility of the production inside the hospital

Comparison of existing aneurysm models and their path forward

The two most important aneurysm types are cerebral aneurysms (CA) and abdominal aortic aneurysms (AAA), accounting together for over 80\% of all fatal aneurysm incidences. To minimise aneurysm related deaths, clinicians require various tools to accurately estimate its rupture risk. For both aneurysm types, the current state-of-the-art tools to evaluate rupture risk are identified and evaluated in terms of clinical applicability. We perform a comprehensive literature review, using the Web of Science database. Identified records (3127) are clustered by modelling approach and aneurysm location in a meta-analysis to quantify scientific relevance and to extract modelling patterns and further assessed according to PRISMA guidelines (179 full text screens). Beside general differences and similarities of CA and AAA, we identify and systematically evaluate four major modelling approaches on aneurysm rupture risk: finite element analysis and computational fluid dynamics as deterministic approaches and machine learning and assessment-tools and dimensionless parameters as stochastic approaches. The latter score highest in the evaluation for their potential as clinical applications for rupture prediction, due to readiness level and user friendliness. Deterministic approaches are less likely to be applied in a clinical environment because of their high model complexity. Because deterministic approaches consider underlying mechanism for aneurysm rupture, they have improved capability to account for unusual patient-specific characteristics, compared to stochastic approaches. We show that an increased interdisciplinary exchange between specialists can boost comprehension of this disease to design tools for a clinical environment. By combining deterministic and stochastic models, advantages of both approaches can improve accessibility for clinicians and prediction quality for rupture risk.Comment: 46 pages, 5 figure

Extracellular volume quantification in Cardiac CT: a new marker of cardiovascular risk in HIV positive individuals?

Inflammation in response to infection and injury is a critical survival mechanism used by all higher vertebrates. Chronic inflammatory conditions are associated with the prolongerelease of inflammatory mediators and the activation of harmful signal transduction pathways, all of which contribute disease development and phenotypes. Extracellular Volume Fraction (ECV) may be able to detect subtle abnormalities such as diffuse inflammation acute or chronic due to infection and/or fibrosis. The validity of this technique was preliminarily evaluated in a study with 20 patients suspected to have diffuse inflammation in the myocardial tissue. Using HU (Hounsfield Unit) values before and after administration of an Extracellular Contrast Agent (ECA) allows the additional calculation of the ECV, well established in CT. In fact, the ratio of the change in blood and tissue attenuation (HU) represents the contrast agent partition coefficient. People living with HIV (PLWH) have an increase vulnerability to sub-clinical and clinical cardiovascular (CV) diseases. Purpose: PLWH are prone to develop sub-clinical Cardiovascular (sCV) disease, despite the effectiveness of combined AntiRetroviral Therapy (cART). Algorithms developed to predict CV risk in the general population could be inaccurate when applied to PLWH. Myocardial Extra-Cellular Matrix (ECM) expansion, measured by computed tomography, has been associated with an increased CV vulnerability in HIV-negative population. Measurement of Myocardial ECV by computed tomography or magnetic resonance, is considered a useful surrogate for clinical evaluation of ECM expansion. In the present study, we aimed to determine the extent of cardiovascular involvement in asymptomatic HIV-infected patients with the use of a comprehensive cardiac computed tomography (CCT) approach. In this study, ECV in low atherosclerotic CV risk PLWH was compared with ECV of age and gender matched HIV- individuals. 53 asymptomatic HIV+ individuals (45 males, median age 48 (IQR:42.5-48) years) on effective cART (CD4+ cell count: 450 cells/μL (IQR: 328-750); plasma HIV RNA: <37 copies/ml in all subjects) and 18 age and gender matched controls (14 males, median age 55 (IQR:44.5-56) years) were retrospectively enrolled. All participants underwent CCT protocol to obtain native and postcontrast Hounsfield unit values of blood and myocardium, ECM was calculated accordingly. The ECV was significantly higher in HIV+ patients than in the control group (ECV: 31% (IQR: 28%-31%) vs 27.4% (IQR: 25%-28%), p<0.001). The duration of cART (standardized=0.56 (0.33-0.95), p=0.014) and the years of exposure to HIV infection [standardized=0.53 (0.4-0.92), p<0.001], were positively and strongly associated with ECV values. Differences in ECV (p<0.001) were also observed regarding the duration of exposure to cART (<5 years, 5-10 years and >10 years). Moreover, ECV was independently associated with age of participants [standardized = 0.42 (0.33-0.89), p=0.084]. We hypothesized that quantitative assessment of tissue ECV would be clinically useful for detecting both focal and diffuse tissue abnormalities in a variety of acute and chronic infectious conditions. ECV imaging can quantitatively characterize tissue inflammation, atypical diffuse fibrosis, and subtle tissue abnormalities not clinically apparent on different method images. Therefore, ECV not only can detect tissue inflammation and/or fibrosis but also might quantify response to treatment during follow-up. HIV infection and exposure to antiretrovirals play a detrimental role on ECV expansion. An increase in ECV indicates ECM expansion, which has been associated to a higher CV risk in the general population. The non-invasive evaluation of ECM trough ECV could represent an important tool to further understand the relationship between HIV infection, cardiac pathophysiology and the increased CV risk observed in PLWH

Ultrasonic Pulse Wave Imaging for in vivo Assessment of Vascular Wall Dynamics and Characterization of Arterial Pathologies

Arterial diseases such as hypertension, carotid stenosis, and abdominal aortic aneurysm (AAA) may progress silently without symptoms and contribute to acute cardiovascular events such as heart attack, stroke, and aneurysm rupture, which are consistently among the leading causes of death worldwide. The arterial pulse wave, regarded as one of the fundamental vital signs of clinical medicine, originates from the heart and propagates throughout the arterial tree as a pressure, flow velocity, and wall displacement wave, giving rise to the natural pulsation of the arteries. The dynamic properties of the pulse wave are intimately related to the physical state of the cardiovascular system. Thus, the assessment of the arterial wall dynamics driven by the pulse wave may provide valuable insights into vascular mechanical properties for the early detection and characterization of arterial pathologies. The focus of this dissertation was to develop and clinically implement Pulse Wave Imaging (PWI), an ultrasound elasticity imaging-based method for the visualization and spatio-temporal mapping of the pulse wave propagation at any accessible arterial location. Motion estimation algorithms based on cross-correlation of the ultrasound radio-frequency (RF) signals were used to track the arterial walls and capture the pulse wave-induced displacements over the cardiac cycle. PWI facilitates the image-guided measurement of clinically relevant pulse wave features such as propagation speed (pulse wave velocity, or PWV), uniformity, and morphology as well as derivation of the pulse pressure waveform. A parametric study investigating the performance of PWI in two canine aortas ex vivo and 10 normal, healthy human arteries in vivo established the optimal image acquisition and signal processing parameters for reliable measurement of the PWV and wave propagation uniformity. Using this framework, three separate clinical feasibility studies were conducted in patients diagnosed with hypertension, AAA, and carotid stenosis. In a pilot study comparing hypertensive and aneurysmal abdominal aortas with normal controls, the AAA group exhibited significantly higher PWV and lower wave propagation uniformity. A “teetering” motion upon pulse wave arrival was detected in the smaller aneurysms ( 5.5 cm in diameter). While no significant difference in PWV or propagation uniformity was observed between normal and hypertensive aortas, qualitative differences in the pulse wave morphology along the imaged aortic segment may be an indicator of increased wave reflection caused by elevated blood pressure and/or arterial stiffness. Pulse Wave Ultrasound Manometry (PWUM) was introduced as an extension of the PWI method for the derivation of the pulse pressure (PP) waveform in large central arteries. A feasibility study in 5 normotensive, 9 pre-hypertensive, and 5 hypertensive subjects indicated that a significantly higher PP in the hypertensive group was detected in the abdominal aorta by PWUM but not in the peripheral arteries by alternative devices (i.e. a radial applanation tonometer and the brachial sphygmomanometer cuff). A relatively strong positive correlation between aortic PP and both radial and brachial PP was observed in the hypertensive group but not in the normal and pre-hypertensive groups, confirming the notion that PP variation throughout the arterial tree may not be uniform in relatively compliant arteries. The application of PWI in 10 stenotic carotid arteries identified phenomenon such as wave convergence, elevated PWV, and decreased cumulative displacement around and/or within regions of atherosclerotic plaque. Intra-plaque mapping of the PWV and cumulative strain demonstrated the potential to quantitatively differentiate stable (i.e. calcified) and vulnerable (i.e. lipid) plaque components. The lack of correlation between quantitative measurements (PWV, modulus, displacement, and strain) and expected plaque stiffness illuminates to need to consider several physiological and imaging-related factors such as turbulent flow, wave reflection, imaging location, and the applicability of established theoretical models in vivo. PWI presents a highly translational method for visualization of the arterial pulse wave and the image-guided measurement of several clinically relevant pulse wave features. The aforementioned findings collectively demonstrated the potential of PWI to detect, diagnose, and characterize vascular disease based on qualitative and quantitative information about arterial wall dynamics under pathological conditions

Application of Patient-Specific Computational Fluid Dynamics in Coronary and Intra-Cardiac Flow Simulations: Challenges and Opportunities

The emergence of new cardiac diagnostics and therapeutics of the heart has given rise to the challenging field of virtual design and testing of technologies in a patient-specific environment. Given the recent advances in medical imaging, computational power and mathematical algorithms, patient-specific cardiac models can be produced from cardiac images faster, and more efficiently than ever before. The emergence of patient-specific computational fluid dynamics (CFD) has paved the way for the new field of computer-aided diagnostics. This article provides a review of CFD methods, challenges and opportunities in coronary and intra-cardiac flow simulations. It includes a review of market products and clinical trials. Key components of patient-specific CFD are covered briefly which include image segmentation, geometry reconstruction, mesh generation, fluid-structure interaction, and solver techniques