PubMed · 14188547
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M H CHARLTON. 1964. READING DIFFICULTY AND LANGUAGE TYPE.. https://doi.org/10.1159/000263015
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Currently, images acquired via magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI) technology are reconstructed using the discrete inverse Fourier transform. While computationally convenient, this approach is not able to filter out noise. This is a serious limitation because the amount of noise in MRI and fMRI can be substantial. In this paper, we propose an alternative approach to reconstruction, based on penalized likelihood methodology. In particular, we focus on non-linear shrinkage estimators and show that this approach achieves a great reduction in integrated mean squared error (IMSE) of the estimated image with respect to the currently used estimator. This approach is extremely fast and easy to implement computationally. In addition, it can be combined with various alternative approaches to MR image reconstruction and can be easily adapted to other, non-MRI contexts, in which the observed data and the quantities of interest are related via a linear transform.
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OBJECTIVE: To evaluate the progression in utero of mild isolated fetal ventriculomegaly (defined as a transverse diameter of the atrium of the lateral ventricle measuring between 10 and 15 mm), and to estimate the proportion of fetuses that normalize (diameter decreasing to less than 10mm), stabilize (remaining between 10 and 15 mm), or progress to more severe ventriculomegaly (becoming greater than 15 mm). METHODS: The obstetric databases of 3 institutions were queried for any studies mentioning ventriculomegaly or hydrocephalus. Reports and original images were reviewed to verify cases of isolated mild ventriculomegaly, with no other anomalies on comprehensive ultrasonographic examination. Fetuses that had 2 or more evaluations more than 3 weeks apart were included. RESULTS: A total of 63 fetuses met the criteria for isolated mild ventriculomegaly. The mean gestational age and ventricular measurements were 24.7+/-3.7 weeks and 11.8+/-1.1mm, respectively, at the initial scan and 34+/-2.9 weeks and 12.1 +/-3.8mm, respectively, at the final scan. The mean number of scans was 3.75 per fetus (range, 2-6). Amniocentesis revealed the deletion of 5p, which causes the cri du chat, in 1 of 21 fetuses; 26 fetuses (41%) showed normalization of the lateral ventricles; 10 fetuses (16%) showed progression; and 27 (43%) appeared stable. shows the statistics of the individual groups. Three of the fetuses that "stabilized" improved from 15 mm to 11, 11.5, and 11.7 mm, respectively. Two worsened from 10.2 to 14 mm and from 11.4 to 13 mm. CONCLUSIONS: More than 40% of the cases of mild isolated fetal ventriculomegaly resolved in utero. The significant overlap in measurements for the different groups precludes prediction in individual cases. However, of the 13 cases where the transverse diameter measured 13 mm or more, only 1 normalized, while 9 of the remaining 12 cases stabilized and 3 progressed.