Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 73
Filtrar
Más filtros

Bases de datos
País/Región como asunto
Tipo del documento
Intervalo de año de publicación
1.
Am J Transplant ; 18(1): 53-62, 2018 01.
Artículo en Inglés | MEDLINE | ID: mdl-28637093

RESUMEN

Robot-assisted kidney transplantation is feasible; however, concerns have been raised about possible increases in warm ischemia times. We describe a novel intra-abdominal cooling system to continuously cool the kidney during the procedure. Porcine kidneys were procured by standard open technique. Groups were as follows: Robotic renal transplantation with (n = 11) and without (n = 6) continuous intra-abdominal cooling and conventional open technique with intermittent 4°C saline cooling (n = 6). Renal cortex temperature, magnetic resonance imaging, and histology were analyzed. Robotic renal transplantation required a longer anastomosis time, either with or without the cooling system, compared to the open approach (70.4 ± 17.7 min and 74.0 ± 21.5 min vs. 48.7 ± 11.2 min, p-values < 0.05). The temperature was lower in the robotic group with cooling system compared to the open approach group (6.5 ± 3.1°C vs. 22.5 ± 6.5°C; p = 0.001) or compared to the robotic group without the cooling system (28.7 ± 3.3°C; p < 0.001). Magnetic resonance imaging parenchymal heterogeneities and histologic ischemia-reperfusion lesions were more severe in the robotic group without cooling than in the cooled (open and robotic) groups. Robot-assisted kidney transplantation prolongs the warm ischemia time of the donor kidney. We developed a novel intra-abdominal cooling system that suppresses the noncontrolled rewarming of donor kidneys during the transplant procedure and prevents ischemia-reperfusion injuries.


Asunto(s)
Cavidad Abdominal , Hipotermia Inducida/instrumentación , Trasplante de Riñón , Laparoscopía , Nefrectomía , Daño por Reperfusión/prevención & control , Robótica/métodos , Animales , Frío , Masculino , Daño por Reperfusión/cirugía , Porcinos , Supervivencia Tisular
2.
Br J Surg ; 103(4): 417-26, 2016 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-26891212

RESUMEN

BACKGROUND: Livers with parenchymal abnormalities tolerate ischaemia-reperfusion (IR) injury poorly. IR injury is a risk factor for hepatocellular carcinoma (HCC) recurrence. This study assessed the link between liver parenchymal abnormalities and HCC recurrence, and evaluated the protective effect of ischaemic preconditioning. METHODS: C57BL/6 mice were fed a choline-deficient diet for 6 and 12 weeks, or standard chow. Hepatic IR and ischaemic preconditioning were achieved by clamping liver blood inflow. Hepa 1-6 HCC cells were inoculated through the spleen. Thereafter, tumour burden, serum α-fetoprotein and cancer cell aggressiveness were compared among groups. RESULTS: Hepatocellular damage and expression of inflammatory genes (encoding interleukin 6, tumour necrosis factor α, hypoxia inducible factor 1α and E-selectin) were exacerbated after IR injury in mice with severe steatosis. Compared with control livers or those with minimal steatosis, livers exposed to a prolonged choline-deficient diet developed larger tumour nodules and had higher serum α-fetoprotein levels. Non-ischaemic liver lobes from mice with steatosis were not protected from accelerated tumour growth mediated by IR injury. This remote effect was linked to promotion of the aggressiveness of HCC cells. Ischaemic preconditioning before IR injury reduced the tumour burden to the level of that in non-ischaemic steatotic controls. This protective effect was associated with decreased cancer cell motility. CONCLUSION: Livers with steatosis tolerated IR poorly, contributing to more severe HCC recurrence patterns in mice with increasingly severe steatosis. IR injury also had a remote effect on cancer cell aggressiveness. Ischaemic preconditioning before IR injury reduced tumour load and serum α-fetoprotein levels. SURGICAL RELEVANCE: Liver ischaemia-reperfusion (IR) injury is associated with organ dysfunction and surgical morbidity. Livers with steatosis tolerate IR injury poorly in the setting of both liver resection and liver transplantation. Ischaemic preconditioning is a simple method to mitigate IR injury. This study shows that ischaemic preconditioning of mouse livers with steatosis reduces ischaemia-mediated tumour growth acceleration. Liver parenchymal abnormalities such as warm IR injury and liver steatosis should be taken into account to predict accurately the risk of liver cancer recurrence after surgical management. Ischaemic preconditioning strategies may hold therapeutic potential not only to mitigate surgical morbidity but also to reduce postoperative recurrence of liver cancer.


Asunto(s)
Carcinoma Hepatocelular/terapia , Hígado Graso/etiología , Precondicionamiento Isquémico/métodos , Neoplasias Hepáticas/terapia , Neoplasias Experimentales , Animales , Biomarcadores de Tumor/biosíntesis , Biomarcadores de Tumor/genética , Western Blotting , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/patología , Línea Celular Tumoral , Movimiento Celular , Proliferación Celular , ADN de Neoplasias/genética , Hígado Graso/genética , Hígado Graso/terapia , Regulación de la Expresión Génica , Inmunohistoquímica , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Reacción en Cadena en Tiempo Real de la Polimerasa
3.
Osteoporos Int ; 27(3): 1169-1179, 2016 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-26576541

RESUMEN

SUMMARY: Ex vivo analyses of humeri and radii from an anthropological collection and in vivo analyses of the distal radius of retired men indicate that occupation-dependent loading positively influences bone strength by an increase of bone size when young followed by a slowdown of the age-related endocortical and trabecular bone alteration. INTRODUCTION: Skeleton responds to mechanical stimuli, but it is not established whether chronic loading in the context of occupational activities (OA) influences bone properties. We assessed the impact of occupation-dependent loading on upper limb bone strength. METHODS: Individuals were classified according to the intensity of physical loading associated with their OA in two models. Ex vivo, computed tomography scans of the humeri and radii of 219 male skeletons (age of death, 20-93 years) from an anthropological collection of the 20th century (Simon collection) were used to determine estimates of bone strength and cross-sectional geometry. In vivo, distal radius were analysed in 180 men enrolled in the Geneva Retirees Cohort study using high-resolution peripheral quantitative computed tomography and finite element analysis. RESULTS: Heavy-loading OA was associated with higher bone strength in both models. This benefit was associated with higher total area (Tt.Ar), medullary area (Me.Ar) and cortical area (Ct.Ar) in young adult skeletons, but the difference decreased in older age. In older men, the humerus supporting heavy loading had a lower Me.Ar. This effect resulted in greater asymmetries of the Me.Ar and the Ct.Ar/Tt.Ar ratio between the humeri of men with unilateral versus bilateral heavy-loading OA. In vivo, an additional benefit of heavy-loading OA was observed on the distal radius trabecular density and microstructure. CONCLUSION: Repeated occupation-dependent loading positively influences bone strength by an increase of bone size when young followed by a slowdown of the age-related endocortical and trabecular bone alteration. These data supports the necessity to promote bone health in the context of sedentary occupation.


Asunto(s)
Densidad Ósea/fisiología , Salud Laboral , Soporte de Peso/fisiología , Adulto , Anciano , Anciano de 80 o más Años , Envejecimiento/patología , Envejecimiento/fisiología , Restos Mortales/anatomía & histología , Restos Mortales/diagnóstico por imagen , Restos Mortales/fisiología , Lateralidad Funcional/fisiología , Humanos , Húmero/anatomía & histología , Húmero/diagnóstico por imagen , Húmero/fisiología , Masculino , Persona de Mediana Edad , Radio (Anatomía)/anatomía & histología , Radio (Anatomía)/diagnóstico por imagen , Radio (Anatomía)/fisiología , Tomografía Computarizada por Rayos X , Adulto Joven
4.
Int J Legal Med ; 129(3): 559-67, 2015 May.
Artículo en Inglés | MEDLINE | ID: mdl-25108450

RESUMEN

Postmortem MRI (PMMR) examinations are seldom performed in legal medicine due to long examination times, unfamiliarity with the technique, and high costs. Furthermore, it is difficult to obtain access to an MRI device used for patients in clinical settings to image an entire human body. An alternative is available: ex situ organ examination. To our knowledge, there is no standardized protocol that includes ex situ organ preparation and scanning parameters for postmortem MRI. Thus, our objective was to develop a standard procedure for ex situ heart PMMR examinations. We also tested the oily contrast agent Angiofil® commonly used for PMCT angiography, for its applicability in MRI. We worked with a 3 Tesla MRI device and 32-channel head coils. Twelve porcine hearts were used to test different materials to find the best way to prepare and place organs in the device and to test scanning parameters. For coronary MR angiography, we tested different mixtures of Angiofil® and different injection materials. In a second step, 17 human hearts were examined to test the procedure and its applicability to human organs. We established two standardized protocols: one for preparation of the heart and another for scanning parameters based on experience in clinical practice. The established protocols enabled a standardized technical procedure with comparable radiological images, allowing for easy radiological reading. The performance of coronary MR angiography enabled detailed coronary assessment and revealed the utility of Angiofil® as a contrast agent for PMMR. Our simple, reproducible method for performing heart examinations ex situ yields high quality images and visualization of the coronary arteries.


Asunto(s)
Autopsia/métodos , Vasos Coronarios/patología , Corazón , Imagen por Resonancia Magnética/métodos , Miocardio/patología , Animales , Medios de Contraste , Angiografía Coronaria/métodos , Técnicas In Vitro , Angiografía por Resonancia Magnética/métodos , Porcinos
5.
Magn Reson Med ; 68(5): 1544-52, 2012 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-22294467

RESUMEN

The emerging importance of nanoparticle technology, including iron oxide nanoparticles for monitoring development, progression, and treatment of inflammatory diseases such as arthritis, drives development of imaging techniques. Studies require an imaging protocol that is sensitive and quantifiable for the detection of iron oxide over a wide range of concentrations. Conventional signal loss measurements of iron oxide nanoparticle containing tissues saturate at medium concentrations and show a nonlinear/nonproportional intensity to concentration profile due to the competing effects of T1 and T2 relaxation. A concentration calibration phantom and an in vivo study of intra-articular injection in a rat knee of known concentrations of iron oxide were assessed using the difference-ultrashort echo time sequence giving a positive, quantifiable, unambiguous iron signal and monotonic, increasing concentration response over a wide concentration range in the phantom with limited susceptibility artifacts and high contrast in vivo to all other tissues. This improved dynamic response to concentration opens possibilities for quantification due to its linear nature at physiologically relevant concentrations.


Asunto(s)
Algoritmos , Dextranos/administración & dosificación , Aumento de la Imagen/métodos , Interpretación de Imagen Asistida por Computador/métodos , Articulaciones/anatomía & histología , Imagen por Resonancia Magnética/métodos , Nanopartículas de Magnetita/administración & dosificación , Animales , Medios de Contraste/administración & dosificación , Femenino , Inyecciones Intraarteriales , Ratas , Ratas Endogámicas Lew , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
6.
Am J Transplant ; 11(6): 1158-68, 2011 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-21564535

RESUMEN

The Automatic Quantitative Ultrashort Echo Time imaging (AQUTE) protocol for serial MRI allows quantitative in vivo monitoring of iron labeled pancreatic islets of Langerhans transplanted into the liver, quantifying graft implantation and persistence in a rodent model. Rats (n = 14), transplanted with iron oxide loaded cells (0-4000 islet equivalents, IEQ), were imaged using a 3D radial ultrashort echo time difference technique (dUTE) on a Siemens MAGNETOM 3T clinical scanner up to 5 months postsurgery. In vivo 3D dUTE images gave positive contrast from labeled cells, suppressing liver signal and small vessels, allowing automatic quantification. Position of labeled islet clusters was consistent over time and quantification of hyperintense pixels correlated with the number of injected IEQs (R² = 0.898, p < 0.0001), and showed persistence over time (5 months posttransplantation). Automatic quantification was superior to standard imaging and manual counting methods, due to the uniform suppressed background and high contrast, resulting in significant timesavings, reproducibility and ease of quantification. Three-dimensional coverage of the whole liver in the absence of cardiac/respiratory artifact provided further improvement over conventional imaging. This imaging protocol reliably quantifies transplanted islet mass and has high translational potential to clinical studies of transplanted pancreatic islets.


Asunto(s)
Medios de Contraste , Trasplante de Islotes Pancreáticos , Islotes Pancreáticos/patología , Imagen por Resonancia Magnética/métodos , Animales , Ratas , Ratas Sprague-Dawley , Reproducibilidad de los Resultados
7.
Int J Obes (Lond) ; 34 Suppl 2: S67-81, 2010 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-21151150

RESUMEN

Despite intense effort, obesity is still rising throughout the world. Links between obesity and cardiovascular diseases are now well established. Most of the cardiovascular changes related to obesity can be followed by magnetic resonance imaging (MRI) or by magnetic resonance spectroscopy (MRS). In particular, we will see in this review that MRI/MRS is extremely well suited to depict (1) changes in cardiac mass and function, (2) changes in stroke volume, (3) accumulation of fat inside the mediastinum or even inside the cardiomyocytes, (4) cell viability and (5) molecular changes during early cardiovascular diseases.


Asunto(s)
Enfermedades Cardiovasculares/diagnóstico , Síndrome Metabólico/diagnóstico , Obesidad/complicaciones , Enfermedades Cardiovasculares/fisiopatología , Diagnóstico Precoz , Femenino , Humanos , Imagen por Resonancia Magnética , Espectroscopía de Resonancia Magnética , Masculino , Síndrome Metabólico/fisiopatología , Obesidad/fisiopatología
8.
Phys Rev Lett ; 105(1): 018104, 2010 Jul 02.
Artículo en Inglés | MEDLINE | ID: mdl-20867484

RESUMEN

A high throughput method was designed to produce hyperpolarized gases by combining low-temperature dynamic nuclear polarization with a sublimation procedure. It is illustrated by applications to 129Xe nuclear magnetic resonance in xenon gas, leading to a signal enhancement of 3 to 4 orders of magnitude compared to the room-temperature thermal equilibrium signal at 7.05 T.


Asunto(s)
Espectroscopía de Resonancia Magnética/métodos , Transición de Fase , Xenón/química , Temperatura
9.
Br J Cancer ; 100(8): 1230-5, 2009 Apr 21.
Artículo en Inglés | MEDLINE | ID: mdl-19337253

RESUMEN

We investigated variations in sensitivity of an immunochemical (I-FOBT) and a guaiac (G-FOBT) faecal occult blood test according to type and location of lesions in an average-risk 50- to 74-year-old population. Screening for colorectal cancer by both non-rehydrated Haemoccult II G-FOBT and Magstream I-FOBT was proposed to a sample of 20 322 subjects. Of the 1615 subjects with at least one positive test, colonoscopy results were available for 1277. A total of 43 invasive cancers and 270 high-risk adenomas were detected. The gain in sensitivity associated with the I-FOBT was calculated using the ratio of sensitivities (RSN) according to type and location of lesions, and amount of bleeding. The gain in sensitivity by using I-FOBT increased from invasive cancers (RSN=1.48 (1.16-4.59)) to high-risk adenomas (RSN=3.32 (2.70-4.07)), and was inversely related to the amount of bleeding. Among cancers, the gain in sensitivity was confined to rectal cancer (RSN=2.09 (1.36-3.20)) and concerned good prognosis cancers, because they involve less bleeding. Among high-risk adenomas, the gain in sensitivity was similar whatever the location. This study suggests that the gain in sensitivity by using an I-FOBT instead of a G-FOBT greatly depends on the location of lesions and the amount of bleeding. Concerning cancer, the gain seems to be confined to rectal cancer.


Asunto(s)
Enfermedades del Colon/diagnóstico , Neoplasias Colorrectales/diagnóstico , Heces/química , Guayaco , Hemoglobinas/análisis , Sangre Oculta , Adenoma/diagnóstico , Adenoma/epidemiología , Adenoma/patología , Anciano , Enfermedades del Colon/clasificación , Neoplasias del Colon/diagnóstico , Neoplasias del Colon/epidemiología , Neoplasias Colorrectales/epidemiología , Neoplasias Colorrectales/patología , Femenino , Francia/epidemiología , Humanos , Inmunohistoquímica/métodos , Masculino , Tamizaje Masivo/métodos , Persona de Mediana Edad , Invasividad Neoplásica , Estadificación de Neoplasias , Neoplasias del Recto/diagnóstico , Neoplasias del Recto/epidemiología , Sensibilidad y Especificidad
10.
Prog Urol ; 19(5): 307-12, 2009 May.
Artículo en Francés | MEDLINE | ID: mdl-19393535

RESUMEN

INTRODUCTION: Marginal kidneys must be reanimated before their transplantation. Reanimation is conducted with hypothermic pulsatile perfusion. The tests used generally to demonstrate the viability is the vascular resistance which is not convenient for everybody. We have developed a magnetic resonance compatible perfusional technology allowing us to test the organs during the perfusion by Gd-perfusion MRI. METHODS AND RESULTS: We have used pigs' kidneys with no warm ischemic time to establish the basis in a normal kidney. After an eight-hour hypothermic pulsatile perfusion, kidneys are submitted to a Gd perfusion. First, we measure the anatomy of the vessels, then the distribution of Gd in the kidney. We obtain simultaneously a dynamic study of the organs where T0 represents the Gd bolus arrival in the cortex and TP the maximum saturation time of Gd. CONCLUSION: We have observed that a normal T0 is inferior to 30s and TP is inferior to one minute. We have compared these values with ATP resynthesis in these organs and found that they correlate. We hope for the future through that predictive use of Gd-MRI to avoid the clinical use of "too" marginal kidneys or the discard of good kidneys but not corresponding with the vascular resistance theory.


Asunto(s)
Medios de Contraste , Trasplante de Riñón , Riñón/diagnóstico por imagen , Imagen por Resonancia Magnética , Meglumina , Compuestos Organometálicos , Supervivencia Tisular , Animales , Cintigrafía , Porcinos
11.
Int J Pharm ; 568: 118496, 2019 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-31279053

RESUMEN

Magnetic resonance angiography (MRA) requires the use of contrast agents (CAs) to enable accurate diagnosis. There are currently no CAs on the market with appropriate pharmacokinetic (PK) parameters, namely long persistence in the blood, that can be easily used for MRA. We have recently synthesized amphiphilic building blocks loaded with gadolinium (Gd), which self-assemble into Gd-micelles in aqueous media, and have evaluated their potential as a blood-pool contrast agent (BPCA) in vivo. To assess the short and long term PK of Gd-micelles, the blood and organs of the mice were analyzed at t = 30 min, 1, 2, 3 h, 7, 14 and 21 days. Gd-DOTA was used as a control because it is the gold-standard CA for MRA despite its rapid clearance from the blood compartment. Gd-micelles circulated in the blood for more than 3 h postinjection whereas Gd-DOTA was eliminated less than half an hour postinjection. No side effects were observed in the mice up to the end of the study at 21 days and no accumulation of Gd was observed in the brain or bones. The Magnetic Resonance Imaging (MRI) parameters and the results of this in vivo study indicate the true BCPA properties of Gd-micelles and warrant further development.


Asunto(s)
Medios de Contraste/farmacocinética , Gadolinio/farmacocinética , Compuestos Heterocíclicos/farmacocinética , Micelas , Compuestos Organometálicos/farmacocinética , Animales , Supervivencia Celular/efectos de los fármacos , Medios de Contraste/administración & dosificación , Gadolinio/administración & dosificación , Compuestos Heterocíclicos/administración & dosificación , Humanos , Células MCF-7 , Imagen por Resonancia Magnética , Masculino , Ratones Endogámicos BALB C , Compuestos Organometálicos/administración & dosificación , Distribución Tisular
12.
Am J Transplant ; 8(3): 701-6, 2008 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-18294167

RESUMEN

There is a crucial need for noninvasive assessment tools after cell transplantation. This study investigates whether a magnetic resonance imaging (MRI) strategy could be clinically applied to islet transplantation. The purest fractions of seven human islet preparations were labeled with superparamagnetic iron oxide particles (SPIO, 280 microg/mL) and transplanted into four patients with type 1 diabetes. MRI studies (T2*) were performed prior to and at various time points after transplantation. Viability and in vitro and in vivo functions of labeled islets were similar to those of control islets. All patients could stop insulin after transplantation. The first patient had diffuse hypointense images on her baseline liver MRI, typical for spontaneous high iron content, and transplant-related modifications could not be observed. The other three patients had normal intensity on pretransplant images, and iron-loaded islets could be identified after transplantation as hypointense spots within the liver. In one of them, i.v. iron therapy prevented subsequent visualization of the spots because of diffuse hypointense liver background. Altogether, this study demonstrates the feasibility and safety of MRI-based islet graft monitoring in clinical practice. Iron overload (spontaneous or induced) represents the major obstacle to the technique.


Asunto(s)
Medios de Contraste , Rechazo de Injerto/diagnóstico , Trasplante de Islotes Pancreáticos , Islotes Pancreáticos , Imagen por Resonancia Magnética/métodos , Nanopartículas del Metal , Adulto , Femenino , Compuestos Férricos/química , Humanos , Masculino , Nanopartículas del Metal/química , Persona de Mediana Edad , Coloración y Etiquetado
13.
Rev Med Suisse ; 4(147): 576-8, 580, 2008 Mar 05.
Artículo en Francés | MEDLINE | ID: mdl-18402015

RESUMEN

Nephrogenic systemic fibrosis, another problem for patients with chronic renal failure Nephrogenic systemic fibrosis is a rare but severe disease described in patients with kidney failure. High morbidity ant mortality are associated with this new condition. Epidemiological studies strongly suggest a link between nephrogenic systemic fibrosis and gadolinium administration for magnetic resonance imaging enhancement. The disease is primarily cutaneous, with oedema affecting the limbs, later evolving to fibrosis that leads to joints contractures. The lesions can spread to the trunk and involve systemic organs like the heart, lungs and muscles. Given the lack of proved efficient therapy, careful evaluation of the risks and benefits of gadolinium administration should be done in patients with kidney disease. If really needed, a highly stable contrast media should be used.


Asunto(s)
Fibrosis/inducido químicamente , Fallo Renal Crónico/complicaciones , Medios de Contraste/efectos adversos , Fibrosis/diagnóstico , Fibrosis/terapia , Gadolinio DTPA/efectos adversos , Humanos , Imagen por Resonancia Magnética
14.
Sci Rep ; 6: 30088, 2016 07 21.
Artículo en Inglés | MEDLINE | ID: mdl-27439482

RESUMEN

A need exists to noninvasively assess renal interstitial fibrosis, a common process to all kidney diseases and predictive of renal prognosis. In this translational study, Magnetic Resonance Imaging (MRI) T1 mapping and a new segmented Diffusion-Weighted Imaging (DWI) technique, for Apparent Diffusion Coefficient (ADC), were first compared to renal fibrosis in two well-controlled animal models to assess detection limits. Validation against biopsy was then performed in 33 kidney allograft recipients (KARs). Predictive MRI indices, ΔT1 and ΔADC (defined as the cortico-medullary differences), were compared to histology. In rats, both T1 and ADC correlated well with fibrosis and inflammation showing a difference between normal and diseased kidneys. In KARs, MRI indices were not sensitive to interstitial inflammation. By contrast, ΔADC outperformed ΔT1 with a stronger negative correlation to fibrosis (R(2) = 0.64 against R(2) = 0.29 p < 0.001). ΔADC tends to negative values in KARs harboring cortical fibrosis of more than 40%. Using a discriminant analysis method, the ΔADC, as a marker to detect such level of fibrosis or higher, led to a specificity and sensitivity of 100% and 71%, respectively. This new index has potential for noninvasive assessment of fibrosis in the clinical setting.


Asunto(s)
Fibrosis/diagnóstico , Fibrosis/patología , Procesamiento de Imagen Asistido por Computador/métodos , Enfermedades Renales/diagnóstico , Enfermedades Renales/patología , Imagen por Resonancia Magnética/métodos , Adulto , Anciano , Animales , Femenino , Histocitoquímica , Humanos , Masculino , Persona de Mediana Edad , Ratas , Sensibilidad y Especificidad
15.
Eur J Radiol ; 54(1): 124-35, 2005 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-15797302

RESUMEN

The aim of this study was to refine the description of the renal function based on MR images and through transit-time curve analysis on a normal population and on a population with renal failure, using the quantitative model of the up-slope. Thirty patients referred for a kidney MR exam were divided in a first population with well-functioning kidneys and in a second population with renal failure from ischaemic kidney disease. The perfusion sequence consisted of an intravenous injection of Gd-DTPA and of a fast GRE sequence T1-TFE with 90 degrees magnetisation preparation (Intera 1.5 T MR System, Philips Medical System). To convert the signal intensity into 1/T1, which is proportional to the contrast media concentration, a flow-corrected calibration procedure was used. Following segmentation of regions of interest in the cortex and medulla of the kidney and in the abdominal aorta, outflow curves were obtained and filtered to remove the high frequency fluctuations. The model of the up-slope method was then applied. Significant reduction of the cortical perfusion (Qc = 0.057+/-0.030 ml/(s 100 g) to Qc = 0.030 +/- 0.017 ml/(s 100 g), P < 0.013) of the medullary perfusion (Qm = 0.023 +/- 0.018 ml/(s 100 g) to Qm = 0.011 +/- 0.006 ml/(s 100 g), P < 0.046) and of the accumulation of contrast media in the medulla (Qa = 0.005 +/- 0.003 ml/(s 100 g) to Qa = 0.0009 +/- 0.0008 ml/(s 100 g), P < 0.001) were found in presence of renal failure. High correlations were found between the creatinine level and the accumulation Qa in the medulla (r2 = 0.72, P < 0.05), and between the perfusion ratio Qc/Qm and the accumulation Qa in the medulla (r2 = 0.81, P < 0.05). No significant difference was found in times to peak between both populations despite a trend showing Ta the time to the end of the increasing contrast accumulation period in the medulla, arriving later for renal failure. Advances in MR signal calibration with the building of quantitative model such as the up-slope allow to assess kinetic and haemodynamic and functional parameters of the diseased kidney.


Asunto(s)
Imagen por Resonancia Magnética/métodos , Insuficiencia Renal/fisiopatología , Medios de Contraste/farmacocinética , Femenino , Gadolinio DTPA/farmacocinética , Humanos , Pruebas de Función Renal , Masculino , Persona de Mediana Edad , Circulación Renal , Estadísticas no Paramétricas
16.
Invest Radiol ; 36(1): 15-21, 2001 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-11176257

RESUMEN

RATIONALE AND OBJECTIVES: To evaluate the potential of an iron oxide-based MR contrast agent for the detection and delineation of experimental liver tumors during the early vascular phase of the compound. METHODS: Superparamagnetic blood pool agent (SBPA) was administered intravenously to rabbits bearing VX2 tumors. Images were acquired before the injection, immediately after, and 1 or 3 weeks later. The variations of signal intensity were measured in the tumors and in several tissues for various T1-weighted spin-echo, T2-weighted fast spin-echo, and T2-weighted gradient-recalled-echo sequences. RESULTS: Fourteen and 12 of the 16 tumors were detected immediately after SBPA injection using, respectively, the T2-weighted fast spin-echo and T2-weighted gradient-recalled-echo sequences. A significant decrease in signal intensity was observed in well-perfused organs, and blood signal was abolished even at the lowest injected dose and using a T1-weighted sequence. In the late phase, the loss in signal intensity of the liver was even more pronounced. CONCLUSION: The dominant T2 effect of SBPA induces an increase in the tumor-to-liver and tumor-to-blood contrast during the vascular phase, improving the detection of the tumors and allowing the distinction between small lesions and vessels through plane. This effect on the liver signal persists for several days because of the incorporation of SBPA in the reticuloendothelial system.


Asunto(s)
Medios de Contraste , Compuestos Férricos , Neoplasias Hepáticas/patología , Neoplasias Experimentales/patología , Animales , Óxido Ferrosoférrico , Imagen por Resonancia Magnética , Conejos
17.
Urology ; 53(4): 812-5, 1999 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-10197863

RESUMEN

OBJECTIVES: The association among vesicoureteral reflux (VUR), renal scarring, and reflux nephropathy is well established. Screening programs for children who present with urinary tract infection (UTI) and their siblings, along with medical and surgical management, have been promoted by pediatric medical and urologic specialists in Buffalo and the surrounding community for more than two decades. Has this comprehensive and costly effort resulted in a decrease in VUR-related morbidity and should it be continued? METHODS: The records of all active patients who presented from 1982 through 1997 to this region's single pediatric nephrology referral center were reviewed. One hundred twenty-two children and adolescents (73 boys, 49 girls) were identified with hypertension (HTN), renal insufficiency (RI), and end-stage renal disease (ESRD) requiring dialysis or transplantation. RESULTS: There were 70 patients (57%) with HTN, 19 (16%) with RI, and 33 (27%) with ESRD. Reflux nephropathy was the underlying cause in 6 patients (5%)-3 with HTN and 3 with ESRD. The etiologies of morbidity in the remaining patients were medical renal disease, 61 (50%); idiopathic, 17 (14%); obstructive uropathy, 14 (11%); primary congenital renal hypoplasia, 12 (10%); and vascular, 12 (10%). Of the 6 patients with VUR-related morbidity, 4 were boys (3 with ESRD, 1 with HTN) and 2 were girls (with HTN). Five children presented in the 1980s and 1 in the 1990s. Only 1 patient had a history of UTI, and she presented early in the series in 1982 at 5 years of age. Ages of presentation were infancy (2 boys), early childhood (1 boy, 1 girl), and adolescence (1 boy, 1 girl). Reasons for presentation were failure to thrive (n = 2), voiding dysfunction without UTI (n = 1), muscle cramps (n = 1), UTI (n = 1), and HTN (n = 1). Reflux grade ranged from I to V, but 4 patients had grade III or less. CONCLUSIONS: Awareness of VUR-related morbidity has led to more widespread diagnosis and treatment, which appears to have resulted in a dramatic decrease in the numbers of affected patients in this community. The diagnosis and treatment of VUR has altered the epidemiology of HTN and renal failure in children and young adults.


Asunto(s)
Enfermedades Renales/epidemiología , Enfermedades Renales/etiología , Reflujo Vesicoureteral/complicaciones , Adolescente , Niño , Preescolar , Femenino , Humanos , Incidencia , Lactante , Masculino
18.
Magn Reson Imaging ; 11(8): 1139-45, 1993.
Artículo en Inglés | MEDLINE | ID: mdl-8271900

RESUMEN

Superparamagnetic iron oxide particles (SPIOs) are usually referred to as T2 MR contrast agents, reducing signal intensity (SI) on T2-weighted MR images (negative enhancement). This study reports the original use of SPIOs as T1-enhancing contrast agents, primarily assessed in vitro, and then applied to an in vivo investigation of a myocardial perfusion defect. Using a strongly T1-weighted subsecond MR sequence with SPIOs intravenous (IV) bolus injection, MR imaging of myocardial vascularization after reperfusion was performed, on a dog model of coronary occlusion followed by reperfusion. Immediately after the intravenous bolus injection of 20 mumol/kg of SPIOs, a positive signal intensity enhancement was observed respectively, in the right and left ventricular cavity and in the nonischemic left myocardium. Moreover, compared to normal myocardium, the remaining ischemic myocardial region (anterior wall of the left ventricle) appeared as a lower and delayed SI enhancing area (cold spot). Mean peak SIE in the nonischemic myocardium (posterior wall) was significantly higher than in the ischemic myocardium (anterior wall) (110 +/- 23% vs. 74 +/- 22%, Mann-Whitney test alpha < 1%, n1 = 6, n2-n1 = 0, U > 2). In conclusion, the T1 effect of SPIOs at low dose, during their first intravascular distribution, suggests their potential use as positive markers to investigate the regional myocardial blood flow and some perfusion defects such as the "no-reflow phenomenon."


Asunto(s)
Medios de Contraste , Hierro , Imagen por Resonancia Magnética/métodos , Isquemia Miocárdica/diagnóstico , Miocardio/patología , Óxidos , Animales , Dextranos , Perros , Óxido Ferrosoférrico , Procesamiento de Imagen Asistido por Computador , Nanopartículas de Magnetita
19.
Acad Radiol ; 3(12): 1030-7, 1996 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-9017019

RESUMEN

RATIONALE AND OBJECTIVES: To evaluate whether decoupling improves signal-to-noise ratio and frequency resolution of in vivo kidney spectra, and to compare native and well-functioning transplant kidneys. METHODS: Proton decoupling in conjunction with three-dimensional chemical shift imaging (3D-CSI) in phosphorus-31 magnetic resonance (MR) spectroscopy was used with a spatial resolution of 64 cm3 and 17-minute acquisition time to compare native (n = 10) and well-functioning transplant (n = 9) kidneys. RESULTS: Proton decoupling improved peak amplitudes by almost 30%, as well as chemical shift resolution of in vivo kidney spectra. No statistically significant differences in phosphometabolite ratios and renal spectra were observed between healthy volunteers and patients with nonrejecting transplants. The phosphodiester-phosphomonoester ratio was 3.02 +/- 0.88, phosphomonoester-inorganic phosphate ratio was 1.07 +/- 0.44, and inorganic phosphate-adenosine triphosphate ratio was 0.58 +/- 0.22 after correction for saturation effects. CONCLUSION: Improved spectra of native and transplant kidneys can be obtained in vivo with MR spectroscopy by using a short acquisition time.


Asunto(s)
Trasplante de Riñón/fisiología , Riñón/metabolismo , Espectroscopía de Resonancia Magnética , Adenosina Trifosfato/análisis , Adulto , Glicerilfosforilcolina/análisis , Humanos , Aumento de la Imagen/métodos , Espectroscopía de Resonancia Magnética/instrumentación , Espectroscopía de Resonancia Magnética/métodos , Masculino , Persona de Mediana Edad , Organofosfatos/análisis , Fosfatos/análisis , Fosfatidiletanolaminas/análisis , Fosfocreatina/análisis , Fósforo/análisis , Protones , Procesamiento de Señales Asistido por Computador
20.
Acad Radiol ; 4(1): 26-34, 1997 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-9040867

RESUMEN

RATIONALE AND OBJECTIVES: The authors investigated the usefulness of dynamic phosphorus-31 magnetic resonance (MR) spectroscopy in the assessment of hepatic function by studying the effect of a fructose load on a rat model of liver cirrhosis. METHODS: In vivo P-31 MR liver spectra of eight rats with bile duct ligature and 10 control rats were obtained every 4.6 minutes before and after intraperitoneal fructose load (10 mmol per kilogram of body weight). RESULTS: In the basal spectra of the experimental group, the phosphomonoester peak was higher than in the control group (P = .026). After the fructose load, the phosphomonoester peak increase and the inorganic phosphate peak decrease were significantly less marked in the experimental group (P = .003). There was a linear correlation between the serum level of bilirubin and the phosphomonoester increase (r = .61, P < .001). CONCLUSION: Dynamic P-31 MR spectroscopy may be useful in the assessment of hepatic function in chronic liver disease.


Asunto(s)
Cirrosis Hepática Experimental/fisiopatología , Hígado/fisiopatología , Espectroscopía de Resonancia Magnética , Análisis de Varianza , Animales , Fructosa , Hígado/metabolismo , Cirrosis Hepática Experimental/metabolismo , Masculino , Fósforo , Ratas , Ratas Wistar
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA