Search PubMed⌕ Search
Home/Archive/PubMed

PubMed · 9416658

Orbital imaging techniques.

C J Belden·S J Zinreich
View original source ↗Export metadata ↓

Abstract

In the past 20 years, CT and MR imaging have emerged as the primary modalities for the evaluation of orbital disease. One can safely say that plain films have no role in the detailed evaluation of disorders of this morphological area. Given the bony enclosure, small size, soft tissue and fat content of this region, as well as globe movement, obtaining high-quality images of the orbit can be technically challenging. Our aim in this article, is to provide specific parameters for properly evaluating the orbit with CT and MRI.

Explore related subjects

ArtifactsDiagnostic Techniques, OphthalmologicalHumansImage Processing, Computer-AssistedMagnetic Resonance ImagingOrbitOrbital DiseasesReproducibility of ResultsSensitivity and SpecificityTomography, X-Ray ComputedJournal ArticleReview

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

C J Belden, S J Zinreich. 1997. Orbital imaging techniques.. https://doi.org/10.1016/s0887-2171(97)90003-2

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2026

Striping artifact removal in VisiumHD data through nuclear counts modeling.

MOTIVATION: 10x Genomics VisiumHD enables spatial transcriptomics at 2 µm × 2 µm resolution but exhibits slide-specific, non-periodic striping artifacts due to lane-width variability. These multiplicative row/column effects distort bin total counts and can bias downstream analyses. The state-of-the-art destriping approach is the normalization procedure used as a preprocessing step in bin2cell; it applies sequential high-quantile row- then column-wise normalization, which is asymmetric and can introduce edge effects/macro-stripes and distortions of large-scale total-count structure. RESULTS: We propose a statistical destriping approach that leverages nuclei segmentation from the co-registered H&E image. Assuming transcript abundance is constant within each nucleus, we model bin counts with a negative binomial distribution whose mean is a product of a nucleus-specific concentration and row- and column-specific stripe-factors reflecting lane-width variation. We fit all parameters in a generalized linear modeling framework with cross-validated regularization on stripe-factors and iterative dispersion estimation, and use the fitted parameters to correct the observed counts into a destriped image. On synthetic data with known ground truth, our method improves stripe-factor estimation accuracy and reduces error in corrected counts relative to bin2cell and bin2cell-derived baselines. Across four public VisiumHD slides, it consistently lowers striping intensity while substantially better preserving biological signal present in the large-scale global count structure and avoiding the artifacts introduced by other methods. AVAILABILITY AND IMPLEMENTATION: All source code and links to publicly available data used for this study are available at https://github.com/paolamalsot/destriping-GLM.

Artifacts↗
PubMed2001

The cell in absence of aggregation artifacts.

Eduard Kellenberger understood that the conventional resin-embedding, he helped to develop (Ryter, A., Kellenberger, E., 1958. L'inclusion au polyester pour l'ultramicrotomie. J. Ultrastruct. Res. , 2, 200-214), was prone to aggregation artifacts (Kellenberger, E., 1987. The response to biological macromolecules and supramolecular structures to the physics of specimen cryo-preparation. In: Steinbrecht, R.A., Zierold, K. (Eds.), Cryo-techniques in Biological Electron Microscopy, Springer, Berlin, pp. 35-63). He was instrumental in developing various methods to overcome this limitation, for instance, by using low temperature-embedding and partially hydrophilic resins (Carlemalm, E., Garavito, R.M., Villiger, W., 1982. Resin development for electron microscopy and an analysis of embedding at low temperature. J. Microstruct., 126, 123-143; Villiger,W., 1993. Low temperature-embedding with Lowicryl resins. In: Robards, A.W., Wilson, A.J. (Eds.), Procedures in electron microscopy, Wiley, Chichester, UK, pp. 16:7.3-16:7.6). In principle, cryo-electron microscopy of vitreous sections is free of any aggregation artifact since the material remains fully hydrated and is free of chemical fixation or staining. The method is technically difficult still, but recent progress has made it amenable to routine practical applications. We compare here electron microscopical aspects of Zea mays meristem cells prepared by: (1) conventional resin-embedding and sectioning; (2) low temperature-embedding and sectioning of freeze substituted samples; and (3) cryo-sections of vitrified samples. The appearance of the extra-cellular space, the cytoplasm and the nucleoplasm are very different in conditions (1) and (3). They appear as compact, irregular and well delineated structures in conventional resin sections, whereas they are more diffuse and homogeneous in the vitreous sections. In the resin sections, the material seems to form a complex matrix, whereas it looks more like a thick soup in the vitreous sample. Low temperature-embedding (condition 2) shows an intermediate appearance. We suggest that regardless of the difference due to staining and different sectioning conditions, the other image differences are the consequence of aggregation artifacts in the resin-embedded specimens.

Artifacts↗
PubMed2000

The PCR plateau phase - towards an understanding of its limitations.

The DNA polymerases from Thermus aquaticus and Thermus flavus were recently found to bind to short double-stranded DNA fragments without sequence specificity [Kainz et al. (2000) Biotechniques 28, 278-82]. In the present study, it is shown that the accumulation of amplification products during later PCR cycles also exerts an inhibitory effect on several enzymes tested. To simulate later cycle conditions, a 1.7 kb sequence from phage lambda DNA was amplified in the presence of various amounts of a 1 kb double-stranded DNA fragment. A 30-fold molar excess of fragments to polymerase molecules was found to be required for a complete inhibition of Taq, Tfl and Pwo DNA polymerase. This stoichiometric relation remained constant when PCR amplifications were performed using polymerase concentrations of 0.5, 1 or 1.5 U/50 microl reaction volume. The amount of 1 kb DNA fragments required for a complete inhibition was similar to the product yield of the controls (no fragment added), that were run to plateau phase levels. Additionally, PCR mixtures, that were subjected to different numbers of cycles, were compared in their ability to extend 3'-recessed ends by using a hairpin extension assay. The presence of endogenous amplicon DNA accumulated in later PCR cycles was found to inhibit completely the activity of DNA polymerase. PCR mixtures still in quasi-linear phase partially extended the hairpins. In both cases, a further addition of polymerase significantly improved their function. These results indicate that the main factor contributing to the plateau phase in PCR consists of binding of DNA polymerase to its amplification products.

Artifacts↗