Automatic algorithm for correcting motion artifacts in time-resolved two-dimensional magnetic resonance angiography using convex projections.

Time-resolved contrast enhanced magnetic resonance angiography (MRA) may suffer from involuntary patient motion. It is noted that while MR signal change associated with motion is large in magnitude and has smooth phase variation in k-phase, signal change associated with vascular enhancement is small in magnitude and has rapid phase variation in k-space. Based upon this observation, a novel projection onto convex sets (POCS) algorithm is developed as an automatic iterative method to remove motion artifacts. The presented POCS algorithm consists of high-pass phase filtering and convex projections in both k-space and image space. Without input of detailed motion knowledge, motion effects are filtered out, while vasculature information is preserved. The proposed method can be effective for a large class of nonrigid motions, including through-plane motion. The algorithm is stable and converges quickly, usually within five iterations. A double-blind evaluation on a set of clinical MRA cases shows that a completely unsupervised version of the algorithm produces significantly better rank scores (P=0.038) when compared to angiograms produced manually by an experienced radiologist.     

Simultaneous Quantification of an Enantiomer and the Racemic Compound of Ibuprofen by X-ray Powder Diffractometry

Purpose. An X-ray powder diffractometric method was developed for the simultaneous quantification of the relative amounts of the racemic compound (±) of ibuprofen (I) and S(+)-ibuprofen (II), when they occur as a mixture. Methods. The X-ray powder diffraction patterns of I and II show pronounced differences. This formed the basis for the determination of the relative amounts of I and II when they occur as a mixture. X-ray lines with d-spacings of 14.41 and 4.37 Å were unique to I and II, respectively. Mixtures containing different proportions of I and II were prepared which also contained lithium fluoride (III) as an internal standard. Results. A linear relationship was obtained when the intensity ratio (intensity of the 4.37 Å line of II/intensity of the 2.01 Å line of III) was plotted as a function of the weight fraction of II in the mixture. Similar results were obtained in the case of I. Using these standard curves, the weight fractions of I and II in 'unknown' mixtures were determined. The experimentally determined analyte concentration ranged between 98 and 104% of the true value. The relative error in the analyses of individual samples was < 10%. The minimum detectable weight fraction of I in II and II in I were 0.032 (3.2% w/w) and 0.034 (3.4% w/w), respectively. The minimum quantifiable weight fractions were 0.136 for I and 0.112 for II. Since the X-ray diffraction patterns of S(+)-ibuprofen and R(–)-ibuprofen are identical, the conclusions drawn regarding mixtures of I and II will also hold true in the quantitative analyses of mixtures of I and R(–)-ibuprofen.     

Virtual histology intravascular ultrasound in carotid interventions.

PURPOSE: To report early clinical experience with virtual histology intravascular ultrasound (VH IVUS) in carotid endoluminal repair. TECHNIQUE: A 2.9-F, 20-MHz catheter that utilizes computer software to demonstrate the histological components of arteriosclerotic plaque was evaluated during carotid angioplasty and stenting. VH IVUS images were created following a pullback through the carotid stenosis and produced a color-coded map of the different histological constituents of the disease (dark green: fibrous, yellow/green: fibrofatty, white: calcified, and red: necrotic lipid core plaque). CONCLUSION: VH IVUS produces a color-coded map of the different histological components of artery plaque. It has the potential to predict how the plaque is likely to behave at the moment of endoluminal treatment.     

Neurilemmoma of tongue

Neurilemmoma is usually soimry, benign tumour derived from schwan cells of the Sheaths of peripheral cranial or autonomie nerves. In thehead and neck region it occurs most commonly in association with acoustic nerve within the skuil and is rely fottnd in the oral cavity (1,2). We report here two cases of the iongue diagnosed on histopathohgy.     

Molecular breakpoint analysis and relevance of variable mosaicism in a woman with short stature,primary amenorrhea,unilateral gonadoblastoma,and a 46,X,del(Y)(q11)/45,X karyotype

Congenital hydrocephalus associated with aqueductal stenosis and/or agenesis of the corpus callosum has been described in newborn males with mutations in L1CAM, a gene that encodes a neural cell adhesion molecule. These males usually have severe mental retardation and may have spastic paraplegia and adducted thumbs. In contrast, Hirschsprung disease, or absence of ganglion cells in the distal gut, has rarely been described in such individuals. We report a male infant who had severe hydrocephalus identified in the prenatal period with evidence of aqueductal stenosis and adducted thumbs at birth. He developed chronic constipation, and rectal biopsy confirmed the diagnosis of Hirschsprung disease. Molecular testing of the L1CAM gene revealed a G2254A mutation, resulting in a V752M amino acid substitution. A common polymorphism in RET, but no mutation, was identified. Our patient represents the third example of coincident hydrocephalus and Hirschsprung disease in an individual with an identified L1CAM mutation. We hypothesize that L1CAM‐mediated cell adhesion may be important for the ability of ganglion cell precursors to populate the gut, and that L1CAM may modify the effects of a Hirschsprung disease–associated gene to cause intestinal aganglionosis. © 2002 Wiley‐Liss, Inc.