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Fewer Artifacts (fewer + artifact)
Selected AbstractsGranular cell tumor of the neurohypophysis: Report of a case with intraoperative cytologic diagnosisDIAGNOSTIC CYTOPATHOLOGY, Issue 1 2008Maria Luisa C. Policarpio-Nicolas M.D. Abstract Cytological techniques including touch and smear preparations are very useful diagnostic modality in the evaluation of central nervous system (CNS) lesions and, in many instances, may be effectively used as the sole modality of tissue preparation for intraoperative consultation. Cytologic preparations offer many advantages over frozen sections for CNS specimens. These include selective examination of multiple areas from small biopsy specimens, superior preservation and details of cellular morphology, fewer artifacts, faster results, and improved cost-effectiveness. We describe the cytologic diagnosis of a granular cell tumor (GCT) of the neurohypophysis in a 33-year-old male who presented with headache and blurred vision. CT scan revealed an enlarged sella with a 2.15 × 2.0 cm pituitary lesion. Transsphenoidal resection of the mass was performed and submitted for intraoperative consultation. Smears and touch preparations were made on a portion of the mass that showed uniform polygonal cells with round to ovoid nuclei and abundant eosinophilic granular cytoplasm. An intraoperative cytological diagnosis of "favor GCT" was rendered. The histologic sections of the remaining material confirmed the diagnosis. Although GCT of the neurohypophysis is very rare, a specific intraoperative cytological diagnosis is possible. We report the clinical, cytological, and pathological findings of a GCT affecting the neurohypophysis. Diagn. Cytopathol. 2008;36:58,63. © 2007 Wiley,Liss, Inc. [source] Dimensionality estimate of the manifold in chemical composition space for a turbulent premixed H2 + air flame,INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 6 2004Shaheen R. Tonse The dimensionality () of manifolds of active chemical composition space has been measured using three different approaches: the Hausdorff geometrical binning method, Principal Component Analysis, and the Grassberger-Procaccia cumulative distribution method. A series of artificial manifolds is also generated using a Monte Carlo approach to discern the advantages and limitations of the three methods. Dimensionality is quantified for different levels of turbulent intensity in a simulation of the interactions of a 2D premixed hydrogen flame with a localized region of turbulence superimposed over the cold region upstream of the flame front. The simulations are conducted using an adaptive mesh refinement code for low Mach number reacting flows. By treating the Ns species and temperature of the local thermo-chemical state as a point in multidimensional chemical composition space, a snapshot of a flame region is mapped into chemical composition space to generate the manifold associated with the 2-D flame system. An increase in was observed with increasing turbulent intensity for all three methods. Although each method provides useful information, the Grassberger-Procaccia method is subject to fewer artifacts than the other two thereby providing the most reliable quantification of . © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 326,336, 2004 [source] High-resolution renal MRA: Comparison of image quality and vessel depiction with different parallel imaging acceleration factorsJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2006Henrik J. Michaely MD Abstract Purpose To investigate the image quality and vessel depiction of renal MRA with integrated parallel imaging techniques (iPAT) using acceleration factors of 2 and 3. Materials and Methods In this prospective study renal MRA was performed on 14 and 12 patients with acceleration factors of 3 and 2, respectively. For the MRA a 3D-GRE sequence with an acquired spatial resolution of 0.9 × 0.8 × 1.0 mm3 was applied (TR/TE = 3.79 msec/1.39 msec, FOV = 400 mm × 320 mm, acquired matrix = 512 × 384, flip angle = 25°) on a 32-channel 1.5T MR scanner. The acquisition time was 26 seconds with iPAT 2, and 19 seconds with iPAT3. All parameters other than acquisition time and acceleration factor were kept constant. To assess the signal-to-noise ratio (SNR) we performed repetitive phantom measurements using iPAT 2 and 3. The images were rated by two radiologists in terms of noise, artifacts, and the quality of vessel depiction for the proximal, segmental, and subsegmental renal artery. A Mann-Whitney U-test and kappa-test were used for statistical analysis. Results SNR decreased significantly with iPAT 3 in the phantom measurements. The two readers found no difference in noise, but significantly fewer artifacts with iPAT 3. The depiction of segmental vessels was significantly better for both readers with iPAT 3, and the subsegmental vessels were rated significantly better by one reader. iPAT 3 also resulted in a better interreader agreement. Conclusion The use of iPAT 3 for renal MRA enables a better depiction of the distal parts of the renal artery. The decrease in SNR is not diagnostically impairing. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] MR coronary vessel wall imaging: Comparison between radial and spiral k-space samplingJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 5 2006Marcus Katoh MD Abstract Purpose To compare radial and spiral k-space sampling in navigator-gated ECG-triggered three-dimensional (3D) coronary vessel wall imaging. Materials and Methods The right coronary artery (RCA) vessel walls of eight healthy subjects were imaged using a modified double-inversion prepulse in concert with radial and spiral data acquisition. For data analysis, two investigators blinded to the sequence parameters subjectively assessed image quality in terms of artifacts and vessel wall visualization. Objective measures of the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and vessel wall definition were also determined. Results Radial k-space sampling demonstrated fewer artifacts and led to improved visualization of the coronary vessel wall compared to spiral imaging (P < 0.05). This finding was also reflected in a better vessel wall definition using radial data acquisition (P < 0.05). SNR and CNR were found to be higher when spiral k-space sampling was used (n.s.). Conclusion Radial k-space sampling in concert with free-breathing navigator-gated cardiac-triggered MRI of the coronary vessel wall resulted in fewer motion artifacts and improved vessel wall definition compared to spiral k-space sampling. The proposed approach therefore appears to be preferable. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] Small bowel hydro-MR imaging for optimized ileocecal distension in Crohn's disease: Should an additional rectal enema filling be performed?JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2005Waleed Ajaj MD Abstract Purpose To assess the impact of an additional rectal enema filling in small bowel hydro-MRI in patients with Crohn's disease. Materials and Methods A total of 40 patients with known Crohn's disease were analyzed retrospectively: 20 patients only ingested an oral contrast agent (group A), the other 20 subjects obtained an additional rectal water enema (group B). For small bowel distension, a solution containing 0.2% locust bean gum (LBG) and 2.5% mannitol was used. In all patients, a breathhold contrast-enhanced T1w three-dimensional volumetric interpolated breathhold examination (VIBE) sequence was acquired. Comparative analysis was based on image quality and bowel distension as well as signal-to-noise ratio (SNR) measurements. MR findings were compared with those of conventional colonoscopy, as available (N = 25). Results The terminal ileum and rectum showed a significantly higher distension following the rectal administration of water. Furthermore, fewer artifacts were seen within group B. This resulted in a higher reader confidence for the diagnosis of bowel disease, not only in the colon, but also in the ileocecal region. Diagnostic accuracy in diagnosing inflammation of the terminal ileum was 100% in group B; in the nonenema group there were three false-negative diagnoses of terminal ileitis. Conclusion Our data show that the additional administration of a rectal enema is useful in small bowel MRI for the visualization of the terminal ileum. The additional time needed for the enema administration was minimal, and small and large bowel pathologies could be diagnosed with high accuracy. Thus, we suggest that a rectal enema in small bowel MR imaging be considered. J. Magn. Reson. Imaging 2005;22:92,100. © 2005 Wiley-Liss, Inc. [source] | ||||||||||