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1.
Magn Reson Med ; 62(6): 1646-51, 2009 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-19785020

RESUMEN

Gliomas are the most common primary brain tumors and the majority are highly malignant, with one of the worst prognoses for patients. Gliomas are characterized by invasive growth into normal brain tissue that makes complete surgical resection and accurate radiotherapy planning extremely difficult. We have performed independent component analysis of magnetic resonance spectroscopy imaging data from human gliomas to segment brain tissue into tumor core, tumor infiltration, and normal brain, with confirmation by diffusion tensor imaging analysis. Our data are consistent with previous studies that compared anomalies in isotropic and anisotropic diffusion images to determine regions of potential glioma infiltration. We show that coefficients of independent components can be used to create colored images for easy visual identification of regions of infiltrative tumor growth.


Asunto(s)
Biomarcadores de Tumor/análisis , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/metabolismo , Imagen de Difusión por Resonancia Magnética/métodos , Glioma/diagnóstico , Glioma/metabolismo , Espectroscopía de Resonancia Magnética/métodos , Algoritmos , Humanos , Aumento de la Imagen/métodos , Interpretación de Imagen Asistida por Computador/métodos , Proteínas de Neoplasias/análisis , Reconocimiento de Normas Patrones Automatizadas/métodos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
2.
Brain Res ; 1164: 108-16, 2007 Aug 20.
Artículo en Inglés | MEDLINE | ID: mdl-17632090

RESUMEN

Magnetic resonance spectroscopy (MRS) has demonstrated age-related changes in brain metabolites that may underlie micro-structural brain changes, but few studies have examined their relationship with cognitive decline. We performed a cross-sectional study of brain metabolism and cognitive function in 82 healthy adults (aged 50-90) participating in the GENIE (St GEorge's Neuropsychology and Imaging in the Elderly) study. Absolute metabolite concentrations were measured by proton chemical shift imaging within voxels placed in the centrum semiovale white matter. Cognitive abilities assessed were executive function, working memory, information processing speed, long-term memory and fluid intelligence. Correlations showed that all cognitive domains declined with age. Total creatine (tCr) concentration increased with age (r=0.495, p<0.001). Regression analyses were performed for each cognitive variable, including estimated intelligence and the metabolites, with age then added as a final step. A significant relationship was observed between tCr and executive function, long-term memory, and fluid intelligence, although these relationships did not remain significant after age was added as a final step in the regression. The regression analysis also demonstrated a significant relationship between N-acetylaspartate (NAA) and executive function. As there was no age-related decline in NAA, this argues against axonal loss with age; however the relationship between NAA and executive function independent of age and estimated intelligence is consistent with white matter axonal integrity having an important role in executive function in normal individuals.


Asunto(s)
Envejecimiento/fisiología , Encéfalo/metabolismo , Cognición/fisiología , Fibras Nerviosas Mielínicas/metabolismo , Anciano , Anciano de 80 o más Años , Ácido Aspártico/análogos & derivados , Ácido Aspártico/análisis , Ácido Aspártico/metabolismo , Encéfalo/anatomía & histología , Trastornos del Conocimiento/etiología , Trastornos del Conocimiento/metabolismo , Trastornos del Conocimiento/fisiopatología , Estudios Transversales , Femenino , Humanos , Inteligencia/fisiología , Imagen por Resonancia Magnética , Espectroscopía de Resonancia Magnética , Masculino , Trastornos de la Memoria/metabolismo , Trastornos de la Memoria/fisiopatología , Persona de Mediana Edad , Pruebas Neuropsicológicas , Valor Predictivo de las Pruebas , Degeneración Walleriana/diagnóstico , Degeneración Walleriana/metabolismo , Degeneración Walleriana/fisiopatología
3.
J Hypertens ; 19(9): 1595-600, 2001 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-11564979

RESUMEN

BACKGROUND: Several studies in isolated cells have reported that intracellular pH (pHi) in individuals with essential hypertension may be relatively alkaline compared to normotensive individuals. Such an abnormality of pHi in hypertension would be consistent with enhanced sodium-hydrogen exchanger activity and may provide potential mechanisms by which hypertension and its complications could develop. OBJECTIVES: To determine in-vivo intracellular pH of skeletal muscle at rest and during recovery from exercise-induced acidosis in hypertensive and normotensive subjects. METHODS: Using 31-phosphorus magnetic resonance spectroscopy, pHi of the dominant flexor digitorum superficialis was measured in 20 Caucasian subjects (14 male) with essential hypertension and 20 normotensive controls matched for gender, age, race and body mass index. Measurements were made at rest and during the exercise and recovery periods of a stepped incremental maximal exercise protocol. The rate of pHi recovery from exercise-induced acidosis was calculated by linear regression over the first 210 s of recovery from the pHi time plots of respective subjects. RESULTS: Mean resting pHi in the hypertensive (7.05 +/- 0.04) and normotensive groups (7.06 +/- 0.04) were not significantly different. There was a significant effect of gender on pHi: mean pHi was 7.07 +/- 0.03 in males and 7.02 +/- 0.03 in females, respectively (P < 0.0005). The mean intracellular pH achieved by exercise was 6.74 +/- 0.31 in hypertensive individuals and not significantly different in normotensive individuals (6.68 +/- 0.19; P = 0.4). The mean rate of pHi recovery in the hypertensives was 0.08 +/- 0.03 pH units/min and not significantly different in normotensives (0.08 +/- 0.02; P = 0.4). CONCLUSIONS: These results contrast with previously documented abnormalities in the control of pHi in hypertension and demonstrate the absence of major in-vivo disturbances of pHi in skeletal muscle, both at rest and during recovery from exercise-induced acidosis, in essential hypertension. Therefore, it is possible that previously documented abnormalities of pHi and activity of the exchanger may be either specific to cell type or not present under in-vivo conditions.


Asunto(s)
Ejercicio Físico/fisiología , Hidrógeno/metabolismo , Hipertensión/metabolismo , Membranas Intracelulares/metabolismo , Músculo Esquelético/metabolismo , Femenino , Humanos , Concentración de Iones de Hidrógeno , Espectroscopía de Resonancia Magnética , Masculino , Persona de Mediana Edad , Fósforo , Valores de Referencia , Descanso , Caracteres Sexuales
4.
Novartis Found Symp ; 240: 46-62; discussion 62-7, 152-3, 2001.
Artículo en Inglés | MEDLINE | ID: mdl-11727936

RESUMEN

31P MRS studies have shown that the intracellular compartment ot tumours is kept near neutrality, whereas the interstitial fluid is acidic (pH 6.5-6.8). Why is this compartment acidic? Balance studies confirm that tumours produce excessive lactic acid, although less than usually supposed, but this cannot be the whole story, since Tannock and co-workers have shown interstitial acidity in glycolysis-deficient tumours. Another major acid load is caused by hydration of CO2 molecules to carbonic acid, catalysed by carbonic anhydrase. The distance that H+ must diffuse from cancer cells to capillaries is further than in normal tissue and this will increase acidification near the cells. We show that previous quantitative models based on simple H+ diffusion are unsatisfactory. This is because most H+ ions cross the interstitial space bound to buffers such as inorganic phosphate. Although these protonated buffers (i.e. conjugate acids) diffuse much more slowly than H+ ions they carry most of the protons, so the pH predicted by this model is closer to neutrality for a given proton production rate than that predicted by the dissolved H+ model. We have developed a mathematical model of this carrier-mediated system that predicts pHe values as low as those observed in some tumours.


Asunto(s)
Espacio Extracelular/fisiología , Concentración de Iones de Hidrógeno , Neoplasias/fisiopatología , Difusión , Humanos , Modelos Biológicos
5.
J Magn Reson ; 130(1): 58-62, 1998 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-9469897

RESUMEN

An imaging sequence based on a spin-echo train has been developed which is free from geometric distortions in the imaging plane due to main field inhomogeneity. Such inhomogeneities, and chemical shifts, cause only a displacement in the selected slice, which is minimized by the use of high gradient strengths and short radiofrequency pulses. Additionally, variations in the radiofrequency field strength cause variations in the image amplitude but cause no other artifacts. This allows the use of low-flip-angle refocusing pulses, reducing the power deposition to levels which are safe in vivo at high field strengths. The sequence was implemented on a Bruker whole-body 3T system. Example images from a perfluorocarbon phantom and a human head are presented.


Asunto(s)
Encéfalo/anatomía & histología , Fluorocarburos , Imagen por Resonancia Magnética/métodos , Fantasmas de Imagen , Magnetismo , Modelos Teóricos , Temperatura
6.
J Cataract Refract Surg ; 12(3): 292-7, 1986 May.
Artículo en Inglés | MEDLINE | ID: mdl-3712271

RESUMEN

We present a clinicopathological analysis of an explanted STAAR model B silicone intraocular lens (IOL) that was sent to the Center for Intraocular Lens Research for evaluation. Extracapsular cataract extraction (ECCE), using phacoemulsification and insertion of the silicone IOL, had been accomplished through a 3-mm scleral tunnel incision. The IOL was folded and inserted into the ciliary sulcus. Complications, including blurred vision, movement of the IOL within the eye, and glaucoma, eventually led to IOL exchange at three months post-ECCE. After removal of the silicone IOL, a modified J-loop IOL was placed in the intact capsular bag, with subsequent resolution of the increased intraocular pressure and a 20/20 + 3 visual acuity. Pathologic examination of the explanted silicone lens revealed grooves indented into the optic, extensive molding flash, and opalescence of the optic.


Asunto(s)
Glaucoma/patología , Lentes Intraoculares , Complicaciones Posoperatorias/patología , Siliconas , Trastornos de la Visión/patología , Anciano , Humanos , Masculino , Microscopía Electrónica de Rastreo , Diseño de Prótesis , Falla de Prótesis , Agudeza Visual
9.
Neurology ; 66(2): 217-22, 2006 Jan 24.
Artículo en Inglés | MEDLINE | ID: mdl-16434657

RESUMEN

BACKGROUND: Damage to white matter tracts, resulting in "cerebral disconnection," may underlie age-related cognitive decline. METHODS: Using diffusion tensor MRI (DTI) to investigate white matter damage, and magnetic resonance spectroscopy (MRS) to look at its underlying pathologic basis, the authors investigated the relationship between white matter structure and cognition in 106 healthy middle-aged and elderly adults. Fractional anisotropy (FA) and mean diffusivity (MD) values, whole brain white matter histograms, and regions of interest placed in the white matter of the centrum semiovale were analyzed. Correlations with executive function, working memory, and information-processing speed were performed. RESULTS: There was a progressive reduction in FA and increase in diffusivity with age in both region of interest (r = 0.551, p < 0.001), and whole brain histograms (r = 0.625, p < 0.001). DTI values correlated with performance in all three cognitive domains. After controlling for age, DTI parameters correlated with working memory but not with the other two cognitive domains. MRS studies found a correlation of N-acetyl aspartate, a neuronal marker, with DTI parameters (r = 0.253, p < 0.05). CONCLUSION: The results are consistent with white matter damage due to axonal loss, causing age- related cognitive decline. Working memory may be particularly dependent on complex networks dependent on white matter connections.


Asunto(s)
Envejecimiento/psicología , Encéfalo/patología , Trastornos del Conocimiento/diagnóstico , Trastornos del Conocimiento/etiología , Imagen por Resonancia Magnética , Anciano , Anciano de 80 o más Años , Cognición , Trastornos del Conocimiento/psicología , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Espectroscopía de Resonancia Magnética , Masculino , Persona de Mediana Edad , Pruebas Neuropsicológicas
10.
J Am Intraocul Implant Soc ; 4(1): 51-3, 1978 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-701147

RESUMEN

The health of the corneal endothelium is a critical factor in the final outcome of intraocular surgery . With the advent of intraocular lens implantation, the hazard of inadvertent endothelial trauma is greatly increased. A rigorous technique has been presented which will minimize the risk of such trauma in extracapsular cataract surgery with implantation of Binkhorst type intraocular lenses.


Asunto(s)
Córnea/patología , Lentes Intraoculares/métodos , Endotelio/patología , Humanos , Lentes Intraoculares/instrumentación , Complicaciones Posoperatorias/prevención & control , Riesgo
11.
J Am Intraocul Implant Soc ; 5(2): 151-3, 1979 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-383669

RESUMEN

The bimanual technique utilizing the iris manipulator and a full air bubble allows excellent control of anterior chamber depth and IOL position. It also minimizes the risk of trauma to the underlying lens, posterior capsule or vitreous during placement of iris sutures; and its use may prevent the tragedy of severe endothelial damage during insertion of the McCannel suture.


Asunto(s)
Lentes Intraoculares , Procedimientos Quirúrgicos Oftalmológicos , Técnicas de Sutura , Humanos
12.
Ophthalmic Surg ; 10(11): 47-51, 1979 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-523059

RESUMEN

A series of small instruments to assist with insertion of intraocular lenses and placement of lens fixation sutures has been described. Added to the main function of each, is the capability for infusion of fluid or injection of air and medication.


Asunto(s)
Lentes Intraoculares , Irrigación Terapéutica/instrumentación , Cámara Anterior , Cateterismo/instrumentación , Humanos , Iris
13.
J Am Intraocul Implant Soc ; 6(3): 282-4, 1980 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-7410186

RESUMEN

The bicurved fish hook needle allows placement of consistently short bites to close cataract, keratoplasty or traumatic corneal wounds with minimal tissue compression and astigmatism. The technique of handling is different than that for traditional single-radius needles, however it is easily learned. This bicurved needle should find wide application in other microsurgical procedures, such as vascular anastomosis, tuboplasty and vasovasostomy.


Asunto(s)
Agujas , Oftalmología/instrumentación , Instrumentos Quirúrgicos , Humanos
14.
J Am Intraocul Implant Soc ; 5(4): 346-8, 1979 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-528351

RESUMEN

Calibrating comparative endothelial biomicroscopy with a corneal endothelial microscope (Heyer-Schulte Medical Optics), we have obtained clinically useful estimates of endothelial cell density. This simple and inexpensive technique allows rapid examination and evaluation of a large number of endothelial cells across various corneal diameters. It is, however, a clinical rather than investigative procedure and is not intended to replace the quantitative features of endothelial specular photomicrography for scientific studies.


Asunto(s)
Córnea/citología , Oftalmología/métodos , Fotomicrografía/métodos , Calibración , Recuento de Células , Endotelio/citología , Humanos , Fotomicrografía/instrumentación
15.
Ophthalmology ; 92(3): 364-5, 1985 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-3991125

RESUMEN

In conjunction with ultraviolet filtration and to further minimize the risk of phototoxic retinal damage during anterior segment surgery, the operation microscope has been modified to eliminate on demand all light entering the eye by eclipsing the pupil when the red reflex is not required. Retinal light exposure may be reduced as much as 75%.


Asunto(s)
Cámara Anterior/cirugía , Filtración/instrumentación , Luz/efectos adversos , Microcirugia/instrumentación , Traumatismos por Radiación/prevención & control , Retina/efectos de la radiación , Humanos
16.
Magn Reson Med ; 17(1): 33-40, 1991 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-2067405

RESUMEN

Recently, we introduced a new numerical approach to the design and optimization of NMR selective pulses, which we have christened "SPINCALC" (J. T. Ngo and P. G. Morris, Biochem. Soc. Trans. 14, 1271 (1986); J. T. Ngo and P. G. Morris, Magn. Reson. Med. 5, 217 (1987]. The first practical application of pulses generated by SPINCALC is demonstrated on a standard 0.5-T clinical MRI system. Results are shown for single phase pi pulses suitable both for selective inversion and for selective refocusing. The extension of SPINCALC to multidimensional pulses is illustrated by the design of a two-dimensional pi pulse.


Asunto(s)
Algoritmos , Imagen por Resonancia Magnética , Espectroscopía de Resonancia Magnética , Análisis de Fourier , Humanos , Modelos Estructurales , Modelos Teóricos
17.
NMR Biomed ; 2(5-6): 257-66, 1989 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-2641898

RESUMEN

The need for NMR selective pulses in magnetic resonance imaging and spectroscopy is reviewed. The shortcomings of the current generation of pulses are discussed and the need for new categories of pulse identified. Strategies for selective pulse design are outlined and two numerical optimization methods, simulated annealing and SPINCALC (a method recently introduced by us: J. T. Ngo and P. G. Morris, Magn. Reson. Med. 5, 217 (1987], are discussed in detail. Their use is illustrated and compared for the design of pi/2 phase-compensated pulses. Both methods require substantial amounts of CPU time, with simulated annealing the more demanding. Unconstrained, simulated annealing also tends to produce pulses with discontinuous waveforms. A crude two-dimensional pulse derived from a low flip angle approximation is illustrated.


Asunto(s)
Imagen por Resonancia Magnética/métodos , Espectroscopía de Resonancia Magnética/métodos , Diseño de Software
18.
NMR Biomed ; 14(7-8): 497-506, 2001.
Artículo en Inglés | MEDLINE | ID: mdl-11746943

RESUMEN

The sensitivity of blood oxygenation level dependent (BOLD) contrast techniques to changes to tumour deoxyhaemoglobin concentration is of relevance to many strategies in cancer treatments. In the context of tumour studies, which frequently involve the use of agents to modify blood flow, there are underlying physiological changes different to those of BOLD in the brain. Hence we use the term, flow and oxygenation dependent (FLOOD) contrast, to emphasize this difference and the importance of flow effects. We have measured the R(2)* changes in a prolactinoma tumour model for a variety of vasoactive challenges [carbogen, 100% oxygen and 100% nitrogen as different breathing gases, and administration of tumour blood flow modifiers such as calcitonin gene related peptide (CGRP), hydralazine and nicotinamide]. In addition we have measured other relevant physiological parameters, such as bioenergetic status from (31)P MRS, and blood pH and glucose, that may change during a vasoactive challenge. Here we discuss how they relate to our understanding of FLOOD contrast in tumours. We frequently observe R(2)* changes that match the expected action of the vascular stimulus: R(2)* decreases with agents expected to improve tumour oxygenation and blood flow, and increases with agents designed to increase tumour hypoxia. Unlike most normal tissues, tumours have a chaotic and poorly regulated blood supply, and a mix of glycolytic and oxidative metabolism; thus the response to a vasoactive challenge is not predictable. Changes in blood volume can counteract the effect of blood oxygenation changes, and changes in blood pH and glucose levels can alter oxygen extraction. This can lead to R(2)* changes that are smaller or the reverse of those expected. To properly interpret FLOOD contrast changes these effects must be accounted for.


Asunto(s)
Imagen por Resonancia Magnética , Neoplasias Experimentales/diagnóstico , Oxígeno/sangre , Animales , Presión Sanguínea , Humanos , Concentración de Iones de Hidrógeno , Neoplasias Experimentales/irrigación sanguínea , Neoplasias Experimentales/metabolismo , Neoplasias Hipofisarias/diagnóstico , Prolactinoma/diagnóstico , Ratas
19.
Br J Cancer Suppl ; 27: S226-31, 1996 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-8763886

RESUMEN

It is well known that low levels of tissue oxygen (pO2) protect tumour cells from ionising radiation and some chemotherapeutic agents. Thus, numerous studies have been aimed at developing methods to measure tissue oxygenation. An initial discussion of some of the traditional methods for measuring oxygenation is included, followed by a discussion of magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) methods for measuring tumour and normal tissue oxygenation. The latter methods are of interest because of the non-invasive nature of magnetic resonance (MR). Some of the MR methods described herein include: 31P MRS, 1H MRS and MRI, and 19F MRS and MRI. Each method is detailed, including a brief assessment of its ability to measure tumour oxygenation and its potential for clinical application.


Asunto(s)
Neoplasias/metabolismo , Oxígeno/metabolismo , Espectroscopía de Resonancia por Spin del Electrón , Humanos , Ácido Láctico/metabolismo , Imagen por Resonancia Magnética , Espectroscopía de Resonancia Magnética , Mioglobina/metabolismo
20.
Magn Reson Med ; 46(3): 586-91, 2001 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-11550253

RESUMEN

The first in vivo hyperpolarized 129Xe NMR study in experimental tumors is presented. Hyperpolarized 129Xe was dissolved in solutions, and was injected intratumorally in GH-3 prolactinomas in rats and RIF-1 fibrosarcomas in mice. The 129Xe NMR spectra and apparent spin-lattice relaxation times in the two tumor types present characteristic differences. These differences are discussed in terms of xenon exchange between the carrier medium and the tissue compartments.


Asunto(s)
Medios de Contraste/farmacocinética , Fibrosarcoma/diagnóstico , Aumento de la Imagen , Procesamiento de Imagen Asistido por Computador , Espectroscopía de Resonancia Magnética , Prolactinoma/diagnóstico , Isótopos de Xenón/farmacocinética , Animales , Femenino , Fibrosarcoma/patología , Humanos , Ratones , Ratones Endogámicos C3H , Trasplante de Neoplasias , Prolactinoma/patología , Ratas , Ratas Endogámicas WF , Células Tumorales Cultivadas/patología
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