Perfusion Magnetic Resonance Imaging: A Comprehensive Update on Principles and Techniques

Perfusion is a fundamental biological function that refers to the delivery of oxygen and nutrients to tissue by means of blood flow. Perfusion MRI is sensitive to microvasculature and has been applied in a wide variety of clinical applications, including the classification of tumors, identification of stroke regions, and characterization of other diseases. Perfusion MRI techniques are classified with or without using an exogenous contrast agent. Bolus methods, with injections of a contrast agent, provide better sensitivity with higher spatial resolution, and are therefore more widely used in clinical applications. However, arterial spin-labeling methods provide a unique opportunity to measure cerebral blood flow without requiring an exogenous contrast agent and have better accuracy for quantification. Importantly, MRI-based perfusion measurements are minimally invasive overall, and do not use any radiation and radioisotopes. In this review, we describe the principles and techniques of perfusion MRI. This review summarizes comprehensive updated knowledge on the physical principles and techniques of perfusion MRI.

Asociación patomorfológica y morfométrica de la lesión aterosclerótica en siete diferentes sectores arteriales / Pathomorphological and morphometric association of the atherosclerotic lesion in seven different arterial sectors

Se investigaron 460 necropsias de pacientes procedentes del Hospital Docente Dr Carlos J Finlay, realizadas entre 1999 y 2003. Se analizaron 18 arterias procedentes de los siete sectores vasculares siguientes: el polígono de Willis, considerado como una sola arteria, las tres coronarias epicárdicas (derecha, descendente anterior y circunfleja izquierda), la aorta (torácica y abdominal), las renales, las ilíacas y las femorales. Para el estudio patomorfológico y morfométrico se utilizó el sistema aterométrico. Las arterias se disecaron, se fijaron, se colorearon y se les realizaron los análisis cualitativo y cuantitativo para el estudio estadístico mediante la correlación canónica. Entre los resultados más relevantes se observaron muy fuertes correlaciones entre la estría adiposa, la placa fibrosa y la placa grave en los análisis entre todas las arterias investigadas, con algunas excepciones. El conjunto de estos resultados sugiere que la aterosclerosis es un proceso de distribución sistémica.

Four hundred and sixty necropsies of patients from Carlos J Finlay Hospital performed between 1999 and 2003 were investigated. Eighteen arteries from the following seven vascular arteries were analyzed: Willis circle, considered as only one artery, the three epicardial coronaries (right, anterior descending and left circumflex), the aorta (thoracic and abdominal); the two renal, the iliac and the phemoral. An atherometric system was used for the pathomorphological and morphometric study. The arteries were dissected, fixed and coloured. A qualitative and quantitative analysis was made for the statistical study by canonical correlation. Among the most important results there were observed very strong correlations between the adipose stria, the fibrous plaque and the severe plaque in the analyses of all among all the investigated arteries, with a few exceptions. All these results strongly suggest that atherosclerosis is a process of systemic distribution.

Efecto de la vitamina C, sobre la actividad de glutation peroxidasa y la formación de ateromas, en conejos expuestos a dieta hiperlipidémica / Effects vitamin C, on glutathione peroxidase activity and atheroma formation, in rabbits exposed to a hyperlipidaemic diet

El estrés oxidativo juega un papel muy importante en la aterosclerosis; de hecho existe evidencias que indican que los antioxidantes son moléculas capaces de retardar y/o revertir el proceso aterosclerótico. El objetivo del presente estudio fue comparar el efecto de la vitamina C (Vit C), sobre la actividad de la Glutation peroxidasa (GPx) y la formación de ateromas en conejos. Se estudiaron 36 conejos divididos en 3 grupos: Grupo 1 (Control): conejarina, Grupo 2: huevo y conejarina, Grupo 3: huevo, conejarina y Vit C (100mg/diarios). el período experimental duró 12 semanas. Se determinó perfil lipídico por métodos enzimáticos y la actividad de GPx por cinética en 0 y 12va semana. Los conejos fueron sacrificados y se les realizó estudio histológico de su aorta. Los resultados revelaron un incremento en la actividad de la GPx en los grupos 2 y 3 con respecto al control en la 12va semana de experimentación (p<0,05). Hubo inhibición de lesiones ateroscleróticas en los conejos del grupo 3. En conclusión en condiciones de hiperlipidemia con o sin suplementación de Vit C, existe incremento en la actividad de GPx. Por otra parte, la Vit C disminuye y evita la progresión de ateromas.

Oxidative stress plays an important role in artherosclerosis; so antioxidants are molecules have been used to slow down or inihibit atherosclerosis. The objetive of the presents study was to compare the effect of Vitamin C (Vit C), on serum Glutathione peroxidase activity (GPx) and on the formation of aortic lesions in rabbits. 36 rabbits were studied: Group 1: "conejarina" (commercial rrabit food); Group 2: egg and conejarina, Group 3: egg, conejarina and Vit C (100mg/day). The experimental lasted 12 weeks. Lipid profile was done by enzymatic methods and GPx by kinetic method in weeks 0 and 12. Histological study of rabbit's aorta was done. GPx activity in groups 2 and 3, increased compared with controls, from weeks 12 of experimentation (o<0,05). There was inihition of aortic lesions in groups 3. In conclusion, under hyperlipidemic conditions, with or without Vit C supplementation, activity of GPx there is increase. Vit C reduces and prevents the progression of atheromas.

Distribuição comparativa dos glicosaminoglicanos em artérias e veias de diferentes mamíferos / Comparative distribution of glycosaminoglycans in arteries and veins of different mammals

Foi realizada análise comparativa sobre a distribuição dos glicosaminoglicanos de artérias e veias em ratos, cachorros e humanos. Os nossos resultados demonstraram que dermatam sulfato foi o principal glicosaminoglicano encontrado tanto para as artérias quanto para as veias estudadas. Entretanto, a proporção de dermatam sulfato foi maior nas veias do que nas artérias nas três espécies analisadas. Este aumento pode estar associado às diferenças estruturais e funcionais encontradas na parede destes dois tipos de vasos sangüíneos (nas veias a pressão sangüínea é significativamente mais baixa). Além disso, a quantidade total dos glicosaminoglicanos foi maior nas artérias do que nas veias, sendo as maiores concentrações encontradas nas aortas independentemente da espécie animal estudada. Estes achados abrem perspectiva para o melhor conhecimento das alterações das macromoléculas que possam estar relacionadas ao processo degenerativo vascular, especialmente nas transformações estruturais que as veias safenas sofrem, quando empregadas como enxertos na revascularização do miocárdio

Gaz du sang arteriel: [aspects techniqueset interpretetation]

This study concerns the technical aspects and the interpretation methods of arterial blood gases. In the technical part, the PO2, PCO2 and pH electrodes o will be treated as well as the directs and indirects evaluation methods of arterial blood gases. In the interpretation part, the information will be dealt with analysis of partial pressure of oxygen [PaO2], the partial pressure of carbon dioxide [PaCO2], the pH and the bicarbonate concentration in arterial blood. The information concerns the level of hypoxemia, the state of ventilation that are evaluated by the analysis of PaO2 and PaCO2 respectively, and the disorders of acid-base balance that is evaluated by the analysis of pH, PaCO2 and bicarbonate