Persona:
Santa Marta Pastrana, Cristina María

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0000-0001-8664-5990
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Santa Marta Pastrana
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Cristina María
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2004 - 20052
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Fecha de finalización: 2009 × Tiene archivos: true ×

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Mostrando 1 - 2 de 2
  • Miniatura
    Publicación
    Resolution recovery in Turbo Spin Echo using segmented Half Fourier acquisition.
    (Elsevier, 2004-04) Lafuente, Javier; Vaquero, Juan José; Garcia Barreno, Pedro; Desco, Manuel; Santa Marta Pastrana, Cristina María
    Turbo Spin Echo (TSE) is a sequence of choice for obtaining T2-weighted images. TSE reduces acquisition time by acquiring several echoes within each TR, at the cost of introducing an exponential weighting in the k-space that leads to a certain image blurring. This is particularly important for short-T2 structures, which can even disappear if their size in the phase encoding direction is comparable to the degree of blurring. This article suggests the use of a combination of Half Fourier (HF) and segmented (multishot) TSE (sHF-TSE) to recover the original resolution of the SE images. The improved symmetry of the dataset achieved by HF reconstruction is used to increase the resolution of the TSE images. The proposed combination, available in most clinical scanners, reduces the blurring artifact inherent to the TSE sequence without increasing the scan time or the number of acquisitions, but at the cost of a slight reduction of the signal-to-noise ratios (SNR). Qualitative and quantitative results are presented using both numerical simulation and imaging. Significant edge enhancement has been achieved for structures with short T2, (narrowing of the full width at half maximum [FWHM] up to 45%). The proposed sequence is more sensitive to movement artifacts but has proven to be superior to the conventional TSE for imaging static structures.
  • Miniatura
    Publicación
    N-acetyl-aspartate levels in the dorsolateral prefrontal cortex in the early years of schizophrenia are inversely related to disease duration.
    (Elsevier, 2005-03-01) Molina, Vicente; Reig Redondo, Santiago; Benito, Carlos; Pascau González-Garzón, Javier; Sarramea, Fernando; Gispert, Juan Domingo; Misiego, José M.; Palomo, Tomás; Desco, Manuel; Domínguez Sánchez, Francisco Javier; Sanz Pérez, Javier; Santa Marta Pastrana, Cristina María
    Magnetic resonance spectroscopy studies in schizophrenia have revealed consistently reduced N-acetyl aspartate (NAA) levels in chronic patients, but not in recent-onset patients. Studies on the relationship between this marker and disease duration have commonly been negative, although it is also true that they have been conducted in patients with long-standing disease. We compared NAA levels in the dorsolateral prefrontal cortex in 16 recent-onset patients (duration: 1.8±0.6 years), 19 chronic patients (duration: 9.7±6.1 years), and 20 healthy controls. We studied the NAA/creatine and choline/creatine ratios in the dorsolateral prefrontal cortex in both hemispheres, controlling for the effect of age. Chronic patients had significantly lower NAA/Cr ratios in the left hemisphere compared to recent-onset patients and healthy controls, with no difference in Cho/Cr ratio. There were no differences between controls and recent-onset patients. There was a significant inverse relationship between left-side NAA/Cr and disease duration, suggesting that prefrontal NAA levels may progressively decrease in schizophrenia. Taken within the context of the existing literature, these results indicate that this process may be limited to the early years following the onset of the disease. Therefore, reduced prefrontal levels of NAA may be limited to chronic schizophrenia patients.