Determination of size distributions of non-spherical pores or particles from single x-ray phase contrast images.

Although x-ray tomography is commonly used to characterize the three-dimensional structure of materials, sometimes this is impractical due either to limited time for data collection (such as in rapidly-evolving systems) or the need to limit the radiation exposure of the sample. In such situations, it is desirable to extract as much information as possible from a more limited data set. In this paper, we describe how to extract the size distribution of non-spherical pores (or, equivalently, particles) from single x-ray phase contrast imaging (XPCI). Because the pores overlap in projection, interpreting the images and extracting quantitative information about the size distribution is non-trivial. In this paper we extend a previously-developed Fourier-based framework for interpreting the speckle pattern of XPCI images from materials with spherical pores to the more challenging case of non-spherical pores. We develop an analytical expression for the XPCI image from a distribution of randomly-oriented ellipsoidal pores, and show that we can use this expression to extract quantitative information about the size distribution from single images. We discuss three approaches to evaluating this expression, corresponding to different assumptions about the nature of the size distribution, and validate our results with simulated XPCI images and experimental data from Berea sandstone.

X-ray reflectivity measurement of interdiffusion in metallic multilayers during rapid heating.

A technique for measuring interdiffusion in multilayer materials during rapid heating using X-ray reflectivity is described. In this technique the sample is bent to achieve a range of incident angles simultaneously, and the scattered intensity is recorded on a fast high-dynamic-range mixed-mode pixel array detector. Heating of the multilayer is achieved by electrical resistive heating of the silicon substrate, monitored by an infrared pyrometer. As an example, reflectivity data from Al/Ni heated at rates up to 200 K s-1 are presented. At short times the interdiffusion coefficient can be determined from the rate of decay of the reflectivity peaks, and it is shown that the activation energy for interdiffusion is consistent with a grain boundary diffusion mechanism. At longer times the simple analysis no longer applies because the evolution of the reflectivity pattern is complicated by other processes, such as nucleation and growth of intermetallic phases.

Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading.

We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ~10(3)-10(4) s(-1) in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10-20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (~40 µs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation.

Using fluctuation microscopy to characterize structural order in metallic glasses.

We have used fluctuation microscopy to reveal the presence of structural order on length scales of 1-2 nm in metallic glasses. We compare results of fluctuation microscopy measurements with high resolution transmission electron microscopy and electron diffraction observations on a series of metallic glass samples with differing degrees of structural order. The agreement between the fluctuation microscopy results and those of the other techniques is good. In particular, we show that the technique used to make thin specimens for electron microscopy affects the structure of the metallic glass, with ion thinning inducing more structural order than electro-polishing. We also show that relatively minor changes in the composition of the alloy can have a significant effect on the medium-range order; this increased order is correlated with changes in mechanical behavior.

Painful ophthalmoplegia caused by neurotropic malignant melanoma.

Progressive cranial nerve palsies and painful ophthalmoplegia developed in a 76-year-old man with lentigo maligna of the forehead 18 months after the excision of a spindle cell tumour of the forehead that proved on immunohistochemical study to be a malignant melanoma. The signs and symptoms were caused by neurotropic spread of the malignant melanoma into the cavernous sinus and subsequent neurosarcomatous transformation of the orbital metastasis.

Ghost-cell tumor of the optic chiasm. Primary CNS lymphoma.

A case of steroid-responsive malignant lymphoma of the optic chiasm is reported in a 58-year-old woman presenting with subacute vision loss, headaches, and decreased hearing. The exquisite sensitivity of magnetic resonance imaging (MRI) of the parasellar area and the usefulness of MR-directed stereotactic biopsy in identifying a chiasmatic lesion are shown. Primary CNS lymphomas are briefly reviewed. Ophthalmologists will be asked to evaluate patients with malignant lymphoma of the optic chiasm with increased frequency in the future, as CNS lymphomas are expected to be the most common neurological neoplasm by 1991.

"Empty sella" with invasive microprolactinoma.

We describe the unique association of an aggressive prolactin secreting pituitary microadenoma invading through the sphenoid sinus with an empty sella, in which the pituitary tumor remained clinically undiagnosed. The postmortem anatomy of this empty sella syndrome is presented. It is concluded that the phrase "empty sella", although universally accepted, correlates poorly with the underlying disease, and that terms such as "intrasellar arachnoidocele" or "intrasellar subarachnoid herniation" would be more properly descriptive.

Immunohistochemistry of capillary hemangioblastoma. Immunoperoxidase-labeled antibody staining resolves the differential diagnosis with metastatic renal cell carcinoma, but does not explain the histogenesis of the capillary hemangioblastoma.

We used a battery of antigens to determine whether immunohistochemistry can (a) contribute to resolving the histogenesis of the stromal component of the capillary hemangioblastoma, and (b) answer cases of difficult pathologic differential diagnosis with metastatic clear cell carcinoma. The stromal cells of the capillary hemangioblastoma are antigenically polymorphous and may express immunoreactive erythropoietin, renin, keratin, Leu M1, Leu 7, actin, neuron-specific enolase, S100 protein, and glial fibrillary acidic protein. However, the use of epithelial membrane antigen allows certain histopathologic distinction between capillary hemangioblastoma and metastatic clear cell carcinoma.

Malignant glioma of the optic chiasm eight years after radiotherapy for prolactinoma.

A 41-year-old man had rapidly progressive visual loss caused by a malignant glioma that developed in the optic chiasm eight years after radiation therapy for a recurrent prolactinoma. Radiation-induced glioma should be considered as a cause of progressive visual loss in patients who have received irradiation in the region of the sella turcica.

Hemangiopericytoma of the ciliary body.

A 60-year-old woman had a ciliary body tumor that resembled an amelanotic malignant melanoma by clinical examination. The magnetic resonance imaging scan correlated with the clinical diagnosis. Because of apparent rapid growth, her eye was enucleated. However, histopathologic examination revealed a highly vascularized, spindle-cell tumor harboring immunoreactive actin and vimentin. Electron microscopy further supported the diagnosis of hemangiopericytoma with smooth-muscle differentiation. To our knowledge, this is the first report of a hemangiopericytoma of the ciliary body.

[Microangioma and optochiasmatic apoplexy. Description of an anatomo-clinical entity associating spontaneous hemorrhages of the anterior optic pathways and rupture of cryptic vascular anomalies]. / Microangiomes et apoplexie opto-chiasmatique. Description d'une entité anatomo-clinique associant hémorragies spontanées des voies optiques antérieures et rupture d'anomalies vasculaires cryptiques.

A 39 year-old women presented for the third time in 9 years, with an acute chiasmal syndrome caused by hemorrhage within a ruptured intra-chiasmatic cryptic angioma. We have reviewed this entity described as "chiasmal apoplexy" and defined its clinicopathological characteristics. Sub-frontal microsurgical approach to the optic chiasm is recommended to confirm the diagnosis and to decompress the optic chiasm. However, surgery does not prevent the possibility of recurrences. We have precised the concept of cryptic vascular malformation.

Ciliary body neurilemoma recurring after 15 years.

A 57-year-old white female presented with a recurring neurilemoma (benign solitary schwannoma) of the ciliary body 15 years after the primary modified iridocyclectomy. As neurilemoma are encapsulated, successful "tumorectomy" was twice accomplished with total anatomical and functional preservation of the globe. The pathological diagnosis of spindle cell tumors of the uvea is discussed.

Desmoplastic fibroma of parietal bone simulating eosinophilic granuloma. Case report.

Desmoplastic fibroma is a distinctive and rare neoplasm of bone. Only one previous example has been reported in the calvaria. The diagnostic and surgical aspects of a case of desmoplastic fibroma of the skull that radiographically simulated eosinophilic granuloma are reported.

Corneal wound healing after excimer laser keratotomy in a human eye.

A pulsed excimer argon-fluorine laser was used to produce corneal incisions in vivo in a human cornea. Fourteen days after the laser surgery, the incisions were examined by light and transmission electron microscopy. There was good initial healing, with no inflammatory or immune reactions in the incisions.

Orbital angiosarcoma with subconjunctival presentation. Report of a case and literature review.

An otherwise healthy 37-year-old woman had, over the course of 2 years, a recurring subconjunctival lesion associated with blepharoptosis. Computed tomography (CT) demonstrated a large anterior and superior orbital mass. A diagnosis of angiosarcoma (AS) was made from biopsy material. The patient is alive and well 18 months after exenteration and radiation therapy. The clinical and histopathologic features of this tumor are discussed with emphasis on the differential diagnosis of malignant vascular tumors of the orbit.

Immunohistochemical and ultrastructural studies on the exenterated orbital tissues of a patient with Graves' disease.

The exenterated orbital contents obtained post mortem from a 47-year-old man who had an eight-month history of treated hyperthyroidism and a two-month history of visual complaints were examined histopathologically, immunohistochemically, and by electron microscopy. All of the extraocular muscles were massively enlarged, due to early diffuse endomysial fibrosis, mucopolysaccharide deposition, and a predominantly perivascular lymphocytic and plasmacytic infiltration. Histochemical stains revealed that the intramuscular mucopolysaccharides were weakly sulfated and polycarboxylated, establishing that they were products of fibroblastic activation rather than derived from mast cells. Subsarcolemmal deposits in the myofibers were shown by electron microscopy to be collections of glycogen rosettes with intermixed lipid deposits. These inclusions were interpreted as secondary phenomena due to abnormal muscle energetics from restrictions in contractility, and not as evidence of a primary degeneration of the extraocular muscle fibers themselves. The sarcomeric organization of the striated muscle cells was undisturbed, and therefore the pathologic changes occurred int he interstitial space of the endomysium. A monoclonal antibody specific for neurofilaments (antibody 4.3 F9) revealed, in comparison with normal controls, a preferential loss of large-type axons of the proximal segment of the orbital portion of the optic nerve as well as in the intracanalicular portion. The axonal loss was associated with a mildly increased number of astrocytes as demonstrated by an antibody against glial fibrillary acidic protein. The meninges of the optic nerve, the orbital fat, and the tendons of the extraocular muscles were uninflamed. The foregoing findings are compatible with a compressive optic neuropathy mediated by the massively swollen extraocular muscles impinging upon the optic nerve at the orbital apex.