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1.
Sci Rep ; 14(1): 3567, 2024 02 12.
Artículo en Inglés | MEDLINE | ID: mdl-38347085

RESUMEN

Excessive loads at lower limb joints can lead to pain and degenerative diseases. Altering joint loads with muscle coordination retraining might help to treat or prevent clinical symptoms in a non-invasive way. Knowing how much muscle coordination retraining can reduce joint loads and which muscles have the biggest impact on joint loads is crucial for personalized gait retraining. We introduced a simulation framework to quantify the potential of muscle coordination retraining to reduce joint loads for an individuum. Furthermore, the proposed framework enables to pinpoint muscles, which alterations have the highest likelihood to reduce joint loads. Simulations were performed based on three-dimensional motion capture data of five healthy adolescents (femoral torsion 10°-29°, tibial torsion 19°-38°) and five patients with idiopathic torsional deformities at the femur and/or tibia (femoral torsion 18°-52°, tibial torsion 3°-50°). For each participant, a musculoskeletal model was modified to match the femoral and tibial geometry obtained from magnetic resonance images. Each participant's model and the corresponding motion capture data were used as input for a Monte Carlo analysis to investigate how different muscle coordination strategies influence joint loads. OpenSim was used to run 10,000 simulations for each participant. Root-mean-square of muscle forces and peak joint contact forces were compared between simulations. Depending on the participant, altering muscle coordination led to a maximum reduction in hip, knee, patellofemoral and ankle joint loads between 5 and 18%, 4% and 45%, 16% and 36%, and 2% and 6%, respectively. In some but not all participants reducing joint loads at one joint increased joint loads at other joints. The required alteration in muscle forces to achieve a reduction in joint loads showed a large variability between participants. The potential of muscle coordination retraining to reduce joint loads depends on the person's musculoskeletal geometry and gait pattern and therefore showed a large variability between participants, which highlights the usefulness and importance of the proposed framework to personalize gait retraining.


Asunto(s)
Marcha , Músculos , Adolescente , Humanos , Método de Montecarlo , Marcha/fisiología , Fémur/fisiología , Tibia/fisiología , Articulación de la Rodilla/fisiología , Fenómenos Biomecánicos , Músculo Esquelético/fisiología
2.
Eur J Radiol ; 68(3): 465-70, 2008 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-17913428

RESUMEN

PURPOSE: To compare the performance of 64-slice with 16-slice CT scanners for the in vitro evaluation of coronary artery stents. METHODS AND MATERIALS: Twelve different coronary artery stents were placed in the drillings of a combined heart and chest phantom, which was scanned with a 16- and 64-slice CT scanner. Coronal reformations were evaluated for artificial lumen narrowing, intraluminal attenuation values, and false widening of the outer stent diameter as an indicator of artifacts outside the stent. RESULTS: Mean artificial lumen narrowing was not significantly different between the 16- and 64-slice CT scanner (44% versus 39%; p=0.408). The differences between the Hounsfield Units (HU) measurements inside and outside the stents were significantly lower (p=0.001) with 64- compared to 16-slice CT. The standard deviation of the HU measurements inside the stents was significantly (p=0.002) lower with 64- than with 16-slice CT. Artifacts outside the stents were not significantly different between the scanners (p=0.866). CONCLUSION: Visualization of the in-stent lumen is improved with 64-slice CT when compared with 16-slice CT as quantified by significantly lesser intraluminal image noise and less artificial rise in intraluminal HU measurement, which is the most important parameter for the evaluation of stent patency in vivo.


Asunto(s)
Prótesis Vascular , Angiografía Coronaria/instrumentación , Angiografía Coronaria/métodos , Vasos Coronarios/cirugía , Stents , Tomografía Computarizada por Rayos X/instrumentación , Tomografía Computarizada por Rayos X/métodos , Diseño de Equipo , Análisis de Falla de Equipo , Humanos , Fantasmas de Imagen , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
3.
AJR Am J Roentgenol ; 184(2): 505-10, 2005 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-15671371

RESUMEN

OBJECTIVE: Our aim was to measure the arterial, portal venous, and total perfusion of the liver parenchyma with dynamic, single-section CT in patients with liver cirrhosis before and after transjugular intrahepatic portosystemic shunt (TIPS) placement and to compare the results with normal values. SUBJECTS AND METHODS: Perfusion of the liver parenchyma was measured in 24 healthy volunteers and 41 patients with liver cirrhosis using dynamic single-section CT. Seventeen patients underwent TIPS placement, and CT measurements were repeated within 7 days. CT scans were obtained at a single level comprising the liver, spleen, aorta, and portal vein. Scans were obtained over a period of 88 sec (one baseline scan followed by 16 scans every 2 sec and eight scans every 7 sec) beginning with the injection of a contrast agent bolus (40 mL at 10 mL/sec). Parenchymal and vascular contrast enhancement was measured with regions of interest, and time-density curves were obtained. These data were processed with a pharmaco-dynamic fitting program (TopFit), and the arterial and portal venous component and the total perfusion of the hepatic parenchyma were calculated (milliliters of perfusion per minute per 100 mL of tissue). RESULTS: Mean normal values for hepatic arterial, portal venous, and total perfusion were 20, 102, and 122 mL/min per 100 mL, respectively. In patients with cirrhosis before TIPS, mean hepatic arterial, portal venous, and total perfusion was 28, 63, and 91 mL/min per 100 mL, respectively, which was statistically significant for all values (p <0.05). After TIPS, hepatic perfusion increased to a mean value of 48, 65, 113 mL/min per 100 mL for arterial (p <0.01), portal venous, and total (p=0.011) perfusion, respectively. CONCLUSION: In patients with cirrhosis, the hepatic arterial perfusion increased, whereas portal venous and total perfusion decreased compared with that of healthy volunteers. TIPS placement caused a statistically significant increase of the hepatic arterial and total hepatic perfusion. The portal venous parenchymal perfusion remained unchanged.


Asunto(s)
Circulación Hepática/fisiología , Cirrosis Hepática/cirugía , Derivación Portosistémica Intrahepática Transyugular , Tomografía Computarizada por Rayos X , Adulto , Anciano , Anciano de 80 o más Años , Medios de Contraste , Femenino , Humanos , Modelos Lineales , Cirrosis Hepática/diagnóstico por imagen , Masculino , Persona de Mediana Edad , Radiografía Intervencional , Valores de Referencia
4.
Radiology ; 226(3): 675-85, 2003 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-12616016

RESUMEN

PURPOSE: To evaluate the spectrum of magnetic resonance (MR) imaging appearances of the liver in primary sclerosing cholangitis (PSC) and to examine their correlation with clinical stage of disease. MATERIALS AND METHODS: Fifty-two patients (25 female, 27 male; mean age, 43 years; age range, 11-87 years) with PSC underwent nonenhanced and gadolinium-enhanced MR imaging. Two abdominal radiologists retrospectively reviewed all images (independently and then in consensus) for the imaging pattern of the liver parenchyma, presence and grade of intrahepatic biliary ductal dilatation, and presence of areas of parenchymal atrophy or abnormal signal intensity and/or gadolinium enhancement. Imaging findings were correlated with Child class, Child-Turcotte-Pugh score, and Mayo end-stage liver disease (MELD) score. Statistical analyses (kappa scoring for interobserver agreement, McNemar test, Mann-Whitney U test, multiple regression analysis, Spearman correlation) were performed. RESULTS: Of 52 patients, seven (13%) had no imaging findings of cirrhosis, 17 (33%) had a diffuse pattern of cirrhosis, and 28 (54%) had a large macronodular pattern (with nodules >or=3 cm) (kappa = 0.84). Intrahepatic biliary ductal dilatation was observed in 44 (85%) patients and was general in 18 (35%) and segmental in 26 (50%). Peripheral wedge-shaped areas of parenchyma were observed with atrophy in 23 (44%) and 25 (48%) patients by the two readers (kappa = 0.76) and without atrophy in 18 (35%) patients by both readers (kappa = 1.00). No correlation was found between imaging findings and clinical scores (P >.05, multiple regression analysis; P =.25-.75, Mann-Whitney U test; Spearman correlation coefficients between -0.33 and 0.33). CONCLUSION: The spectrum of MR imaging appearances of PSC is diverse and comprises distinct patterns that do not appear to correlate with severity of disease. Large regenerative nodules are a frequent finding and may help to establish the diagnosis.


Asunto(s)
Colangitis Esclerosante/patología , Cirrosis Hepática/patología , Imagen por Resonancia Magnética/métodos , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Distribución de Chi-Cuadrado , Niño , Medios de Contraste/administración & dosificación , Femenino , Gadolinio DTPA/administración & dosificación , Humanos , Masculino , Persona de Mediana Edad , Análisis de Regresión , Estudios Retrospectivos , Índice de Severidad de la Enfermedad , Estadísticas no Paramétricas
5.
Radiol Clin North Am ; 41(1): 89-96, 2003 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-12630687

RESUMEN

Although MRCP is still an evolving technique, it has established itself as clinically useful and comparable with ERCP for the evaluation of various biliary or pancreatic ductal diseases. MRCP is not only comparable with ERCP in its diagnostic ability, but it has the tremendous advantage of being noninvasive. Furthermore, MR imaging is useful in patients with incomplete or failed ERCP, and in patients with certain biliary or gastrointestinal surgical procedures it is the imaging modality of choice. ERCP will remain an extremely important modality because of the great clinical importance for interventional biliary procedures with this technique. Nonetheless, MRCP may in the near future replace most of the diagnostic imaging of the biliary tree, with diagnostic results even more improved with further developments of hardware and technique.


Asunto(s)
Enfermedades de las Vías Biliares/diagnóstico , Imagen por Resonancia Magnética/métodos , Enfermedades Pancreáticas/diagnóstico , Medios de Contraste , Humanos
6.
J Magn Reson Imaging ; 15(1): 31-8, 2002 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-11793454

RESUMEN

PURPOSE: To determine the potential of a modified breath-hold 3D gradient-echo technique for visualizing pulmonary parenchymal diseases. MATERIALS AND METHODS: Twenty-one magnetic resonance imaging (MRI) studies of the lungs were performed in 20 patients (15 male and 5 female; age range, 7.7-86.1 years) with pulmonary diseases comprising non-small-cell, small-cell, and bronchioalveolar carcinomas, endobronchial mucoepidermoid carcinoma, metastases, pneumonia, Wegener's granulomatosis, chronic obstructive pulmonary disease, arterio-venous malformation, and bronchogenic cyst. Confirmation of diagnoses was obtained via histopathology (14 patients) and follow-up (6 patients). MRI studies were performed at 1.5 T before and after administration of gadolinium using a modified volumetric interpolated breath-hold examination (VIBE) sequence. All images were evaluated prospectively regarding lesion detection and characterization. MR findings were correlated with final diagnoses. Retrospective grading (scores, 1-4) was performed for general image quality (rated "poor" to "excellent"); presence of artifacts ("negligible" to "severe"); and imaging quality of pulmonary lesions (conspicuity and contrast on pre- and postgadolinium images). RESULTS: Twenty-three solid pulmonary lesions, 25 infiltrates and segmental atelectases, and 1 cyst were detected and prospectively correctly diagnosed. Sizes ranged from 0.3-10 cm. The mean scores for image quality and presence of artifacts were 3.3 (SD, 0.7) and 1.8 (SD, 0.7), respectively. Conspicuity and contrast of pulmonary lesions received mean scores between 3.0 and 3.8 (SD, 0.4-0.7). CONCLUSION: This MRI technique allows imaging of a wide spectrum of solid and nonsolid pulmonary parenchymal diseases with reproducible high image quality, effective suppression of artifacts, high resolution, and visualization of gadolinium enhancement.


Asunto(s)
Enfermedades Pulmonares/diagnóstico , Imagen por Resonancia Magnética/métodos , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Niño , Medios de Contraste , Diagnóstico Diferencial , Femenino , Gadolinio DTPA , Humanos , Procesamiento de Imagen Asistido por Computador , Imagenología Tridimensional , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Reproducibilidad de los Resultados , Estadísticas no Paramétricas
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