Determining the ion temperature and energy distribution in a lithium-plasma interaction test stand with a retarding field energy analyzer.

The ThermoElectric-driven Liquid-metal plasma-facing Structures (TELS) experiment at the University of Illinois is a gas-puff driven, theta-pinch plasma source that is used as a test stand for off-normal plasma events incident on materials in the edge and divertor regions of a tokamak. The ion temperatures and resulting energy distributions are crucial for understanding how well a TELS pulse can simulate an extreme event in a larger, magnetic confinement device. A retarding field energy analyzer (RFEA) has been constructed for use with such a transient plasma due to its inexpensive and robust nature. The innovation surrounding the use of a control analyzer in conjunction with an actively sampling analyzer is presented and the conditions of RFEA operation are discussed, with results presented demonstrating successful performance under extreme conditions. Such extreme conditions are defined by heat fluxes on the order of 0.8 GW m-2 and on time scales of nearly 200 µs. Measurements from the RFEA indicate two primary features for a typical TELS discharge, following closely with the pre-ionizing coaxial gun discharge characteristics. For the case using the pre-ionization pulse (PiP) and the theta pinch, the measured ion signal showed an ion temperature of 23.3 ± 6.6 eV for the first peak and 17.6 ± 1.9 eV for the second peak. For the case using only the PiP, the measured signal showed an ion temperature of 7.9 ± 1.1 eV for the first peak and 6.6 ± 0.8 eV for the second peak. These differences illustrate the effectiveness of the theta pinch for imparting energy on the ions. This information also highlights the importance of TELS as being one of the few linear pulsed plasma sources whereby moderately energetic ions will strike targets without the need for sample biasing.

Nanostructuring of Palladium with Low-Temperature Helium Plasma.

Impingement of high fluxes of helium ions upon metals at elevated temperatures has given rise to the growth of nanostructured layers on the surface of several metals, such as tungsten and molybdenum. These nanostructured layers grow from the bulk material and have greatly increased surface area over that of a not nanostructured surface. They are also superior to deposited nanostructures due to a lack of worries over adhesion and differences in material properties. Several palladium samples of varying thickness were biased and exposed to a helium helicon plasma. The nanostructures were characterized as a function of the thickness of the palladium layer and of temperature. Bubbles of ~100 nm in diameter appear to be integral to the nanostructuring process. Nanostructured palladium is also shown to have better catalytic activity than not nanostructured palladium.

Evaluation of MMP substrate concentration and specificity for neovascularization of hydrogel scaffolds.

Controlled vascular response in scaffolds following implantation remains a significant clinical challenge. A critical biomaterial design criterion is the synchronization of the rates of scaffold degradation and vascularized tissue formation. Matrix metalloproteinases (MMPs) are key enzymes that regulate neovascularization and extracellular matrix remodelling. Synthetic protease-sensitive hydrogels offer controllable environments for investigating the role of matrix degradation on neovascularization. In this study, PEG hydrogels containing MMP-sensitive peptides with increased catalytic activity for MMPs expressed during neovascularization were investigated. Scaffolds were functionalized with MMP-2-, MMP-14- or general collagenase-sensitive peptides and with varying peptide concentration using crosslinkers containing one (SSite) or multiple (TSite) repeats of each protease-sensitive sequence. Increasing peptide concentration enhanced the degradation kinetics of scaffolds functionalized with MMP-specific sequences while 80% of the collagenase-sensitive scaffolds remained upon exposure to MMP-2 and MMP-14. In vitro neovascularization was consistent with in vivo tissue invasion with significantly increased invasion occurring within SSite MMP-specific as compared to collagenase-sensitive hydrogels and with further invasion in TSite as compared to SSite hydrogels regardless of peptide specificity. All scaffolds supported in vivo neovascularization; however, this was not dependent on peptide specificity. These findings demonstrate that peptide concentration and specificity regulate in vivo scaffold degradation, neovascularization and matrix remodelling.

Does sodium hyaluronate- and carboxymethylcellulose-based bioresorbable membrane (Seprafilm) decrease operative time for loop ileostomy closure?

BACKGROUND: Adhesions can result in serious clinical complications and make ileostomy closure, which is relatively simple procedure into a complicated and prolonged one. The use of sodium hyaluronate and carboxymethyl cellulose membrane (Seprafilm) was proven to significantly reduce the postoperative adhesions at the site of application. The aim of this study was to assess the incidence and severity of adhesions around a loop ileostomy and to analyze the length of time and morbidity for mobilization at the time of ileostomy closure with and without the use of Seprafilm. METHODS: Twenty-nine surgeons from 15 institutions participated in this multicenter prospective randomized study. 191 patients with loop ileostomy construction were randomly assigned to either receive Seprafilm under the midline incision and around the stoma (Group I), only under the midline incision (Group II), or not to receive Seprafilm (Group III). At ileostomy closure, adhesions were quantified and graded; operative morbidity was also measured. RESULTS: All 3 groups were comparable relative to gender, mean age and number of patients with prior operations (26, 25 and 19, respectively). Group II patients were significantly more likely to have pre-existing adhesions than Group III patients (30.6% vs. 14.1%, p = 0.025). At stoma mobilization, significantly more patients in Group III than in Group I had adhesions around the stoma (95.2% vs. 82.3%, p = 0.021). Mean operative times were 27, 25, and 28 minutes, respectively (p = 0.38), with significant differences among sites. There was no significant difference in the number of patients needing myotomy or enterotomy (29, 27 and 24 patients, respectively), nor in the number of postoperative complications (7, 9 and 7 patients, respectively). CONCLUSIONS: When consistently applied, Seprafilm significantly decreased adhesion formation around the stoma but not operative times without any increase in the need for myotomy or enterotomy. These findings were not seen in the overall study population possibly due to the large number of surgeons using a variety of application techniques.

Fat attenuation lesions of the mediastinum.

The identification of fat within a focal or diffuse mediastinal lesion significantly narrows the differential diagnosis. In many cases, a specific diagnosis can be suggested on the basis of CT findings. In this article, we illustrate and review the characteristic CT features of common and uncommon fat attenuation lesions of the mediastinum, including focal masses and diffuse abnormalities.

Fibrosing mediastinitis.

Fibrosing mediastinitis is a rare benign disorder caused by proliferation of acellular collagen and fibrous tissue within the mediastinum. Although many cases are idiopathic, many (and perhaps most) cases in the United States are thought to be caused by an abnormal immunologic response to Histoplasma capsulatum infection. Affected patients are typically young and present with signs and symptoms of obstruction or compression of the superior vena cava, pulmonary veins or arteries, central airways, or esophagus. There may be two types of fibrosing mediastinitis: focal and diffuse. The focal type usually manifests on computed tomographic (CT) or magnetic resonance (MR) images as a localized, calcified mass in the paratracheal or subcarinal regions of the mediastinum or in the pulmonary hila. The diffuse type manifests on CT or MR images as a diffusely infiltrating, often noncalcified mass that affects multiple mediastinal compartments. CT and MR imaging play a vital role in the diagnosis and management of fibrosing mediastinitis.

Bronchogenic cyst: imaging features with clinical and histopathologic correlation.

PURPOSE: To characterize the imaging features of bronchogenic cysts. MATERIALS AND METHODS: The computed tomographic (CT) and/or magnetic resonance (MR) or ultrasonographic images in 68 histopathologically proved cases of bronchogenic cyst in 38 male and 30 female patients, aged newborn to 72 years (mean, 22 years), were retrospectively reviewed. RESULTS: There were 58 mediastinal and 10 extramediastinal cysts. At CT (n = 62), 60 cysts were sharply marginated with smooth (n = 35) or lobulated (n = 25) borders. Twenty-five cysts were of water attenuation, 25 were of soft-tissue attenuation, two were air filled, two had an air-fluid level, and two had dependent milk of calcium. On T1-weighted MR images (n = 23), 18 cysts were hyperintense and five were isointense to cerebrospinal fluid. On T2-weighted MR images (n = 18), 17 cysts were isointense or hyperintense to cerebrospinal fluid. Of the 25 soft-tissue-attenuation lesions at CT, 11 appeared cystic because of internal homogeneity, lack of internal enhancement, mural enhancement, and characteristic location. Fourteen appeared solid based on morphology and attenuation. MR imaging of nine of the latter showed marked hyperintensity on T2-weighted images. CONCLUSION: CT of bronchogenic cysts typically shows sharply marginated mediastinal masses of soft-tissue or water attenuation. Most appear cystic. A minority appear solid and can be confused with other lesions; MR imaging can be useful for elucidating the cystic nature of these lesions.

Primary cardiac and pericardial neoplasms: radiologic-pathologic correlation.

Primary cardiac and pericardial neoplasms are rare lesions and include both benign and malignant histologic types. Myxoma is the most frequent primary cardiac neoplasm, but other benign tumors include papillary fibroelastoma, rhabdomyoma, fibroma, hemangioma, lipoma, and paraganglioma. Cardiac sarcoma represents the second most common primary cardiac neoplasm. Lymphoma can also affect the heart primarily. Pericardial tumors that affect the heart include benign teratomas and malignant mesotheliomas. Patients affected with cardiac or pericardial neoplasms often present with cardiovascular compromise or embolic phenomena and exhibit cardiomegaly at chest radiography. Benign cardiac tumors typically manifest as intracavitary, mural, or epicardial focal masses, whereas malignant tumors demonstrate invasive features and may involve the heart diffusely. Benign lesions can usually be successfully excised, but patients with malignant lesions have an extremely poor prognosis.

Pulmonary pathology of Erdheim-Chester disease.

Erdheim-Chester disease (ECD) is a rare non-Langerhans' cell histiocytosis that may present with pulmonary symptoms. The condition seems to be nonfamilial and typically affects middle-aged adults. Radiographic and pathologic changes in the long bones are diagnostic, but patients often present with extraskeletal manifestations. Advanced pulmonary lesions are associated with extensive fibrosis that may lead to cardiorespiratory failure. The clinical, radiologic, and pathologic features of six patients with ECD with lung involvement are presented. The patients were three men and three women (mean age, 57). Five presented with progressive dyspnea, and one presented with diabetes insipidus. Open-lung biopsies showed histiocytic infiltrates in a lymphangitic pattern with associated fibrosis and lymphoplasmacytic inflammatory infiltrates. The histiocytes did not stain with periodic acid-Schiff. Immunoperoxidase studies performed on specimens from five of six patients showed that the histiocytes were positive for CD68 and Factor XIIIa and negative for CD1a. Specimens from two patients exhibited immunoreactivity for S-100 protein. Electron microscopy studies performed on specimens from two patients showed phagocytic lysosomes but no Birbeck granules. Clinical follow-up of up to 16 years was available. At the end of that time, five patients were dead of complications related to their disease; one patient remains alive 4 years after diagnosis but with severe respiratory compromise. ECD is a rare non-Langerhans' cell histiocytosis that may present as interstitial lung disease and resemble other pulmonary conditions, particularly usual interstitial pneumonitis and pulmonary Langerhans' cell histiocytosis. Recognition of this entity will allow better assessment of its true incidence, therapeutic options, and prognosis.

From the archives of the AFIP: pulmonary vasculature: hypertension and infarction.

Pulmonary hypertension is the hemodynamic consequence of vascular changes within the precapillary (arterial) or postcapillary (venous) pulmonary circulation. These changes may be idiopathic, as in primary pulmonary hypertension or pulmonary veno-occlusive disease, but more commonly they represent a secondary response to alterations in pulmonary blood flow. The pulmonary and systemic bronchial circulations form broad anastomoses that largely prevent infarction except in settings of markedly elevated pulmonary venous pressure, underlying malignancy, or excessive embolic burden. Causes of precapillary pulmonary hypertension include long-standing cardiac left-to-right shunt, chronic thromboembolic disease, and widespread pulmonary embolism arising from intravascular malignant cells, parasites, or foreign materials. The classic radiologic features of precapillary pulmonary hypertension are central arterial enlargement, sharply pruned peripheral vascularity, and right-sided heart hypertrophy and chamber dilatation. Postcapillary pulmonary hypertension may develop secondary to focal venous constriction or to compromised pulmonary venous drainage due to left atrial neoplasia, mitral stenosis, or left ventricular failure. Radiologic manifestations of postcapillary pulmonary hypertension include prominent septal lines, small pleural effusions, and occasionally air-space opacities. In addition, radiologic evaluation of postcapillary pulmonary hypertension may demonstrate evidence of pulmonary arterial hypertension, secondary to the retrograde transmission of elevated pulmonary venous pressure across the capillary bed.

Tumors of the thymus.

Thymic neoplasms are a common cause of an anterior mediastinal mass and may be benign or malignant. Thymic cysts are congenital or acquired and may be associated with a thymic malignancy. True thymic hyperplasia and thymic lymphoid hyperplasia may enlarge the thymus and simulate a neoplasm. Thymoma and thymic carcinoma are epithelial malignancies with distinct clinicopathologic features. Thymic carcinoid is a rare aggressive neuroendocrine malignancy associated with multiple endocrine neoplasia 1. Thymolipoma is a benign neoplasm. Hodgkin and non-Hodgkin lymphoma may primarily or secondarily involve the thymus. Primary mediastinal germ cell tumors may arise primarily within the thymus and include mature teratoma, seminoma, and non-seminomatous malignant germ cell tumors.

Thoracic carcinoids: radiologic-pathologic correlation.

Carcinoids are neuroendocrine neoplasms. Bronchial carcinoids are unusual, malignant primary neoplasms that characteristically involve the central airways and typically exhibit well-defined margins and bronchial-related growth. Bronchial carcinoids include low-grade typical carcinoids and the more aggressive atypical carcinoids. These tumors usually affect patients in the 3rd through 7th decades of life who are often symptomatic with cough, hemoptysis, or obstructive pneumonia. Bronchial carcinoids radiologically manifest as hilar or perihilar masses, with or without associated atelectasis, pneumonia, bronchiectasis, or mucoid impaction. At computed tomography, an anatomic relationship of these tumors to a bronchus is usually seen, and they may show contrast material enhancement or calcification. In rare cases, carcinoids occur in the thymus; when they do, they are aggressive tumors that affect adults who usually present with chest pain, cough, and dyspnea. Thymic carcinoids manifest radiologically as anterior mediastinal masses and may mimic thymomas. Thoracic carcinoids are treated by surgical excision. The prognosis for patients with typical bronchial carcinoids is excellent; patients with atypical bronchial or thymic carcinoids have a worse prognosis.

Opportunistic fungal pneumonia.

Opportunistic fungal infection is a common cause of serious morbidity and mortality in immunocompromised patients. These infections occur primarily in patients with chemotherapy-induced neutropenia, acquired immunodeficiency syndrome. or immunosuppression after solid organ or bone marrow transplantation. The most important opportunistic fungal pathogens include Cryptococcus neoformans, Candida and Aspergillus species, and the fungi that cause mucormycosis. Opportunistic pneumonia caused by previously unrecognized pathogens, such as Fusarium, Penicillium, and the dematiaceous fungi, are increasingly reported. The clinical and radiologic features of opportunistic fungal pneumonia are highly variable and often nonspecific. Diagnosis requires knowledge of the various modes of presentation, radiologic manifestations, and epidemiology of these infections. Because many of these organisms can colonize the upper airway, sputum cultures are considered diagnostically unreliable. Instead, definitive diagnosis requires culture of the fungus from infected tissue or demonstration of the organism on microscopic examination.

Castleman disease of the thorax: radiologic features with clinical and histopathologic correlation.

PURPOSE: To correlate the radiologic manifestations of thoracic Castleman disease with the clinical and histopathologic features. MATERIALS AND METHODS: The clinical, surgical, and histopathologic records; chest radiographs; and computed tomographic (CT) and magnetic resonance (MR) images in 30 pathologically proved cases of thoracic Castleman disease were reviewed. RESULTS: Patients with localized Castleman disease (n = 24) typically had the hyaline-vascular type (n = 23), were asymptomatic (n = 14), and had solitary, well-circumscribed mediastinal masses (n = 24). All lesions at contrast material-enhanced CT (n = 13) enhanced. All lesions at MR imaging (n = 5) were heterogeneous and had increased signal intensity on T1- and T2-weighted images. Three patterns were observed on CT or MR images in 20 patients: a solitary, noninvasive mass (n = 10); a dominant infiltrative mass with associated lymphadenopathy (n = 8); or matted lymphadenopathy without a dominant mass (n = 2). Patients with disseminated Castleman disease (n = 6) typically had the plasma cell type (n = 4), were symptomatic at presentation (n = 5), and had bilateral mediastinal masses on chest radiographs (n = 4). At CT, all lesions manifested with diffuse mediastinal lymphadenopathy. All lesions at contrast-enhanced CT (n = 5) enhanced. CONCLUSION: Localized Castleman disease manifests as either a solitary, well-circumscribed mediastinal mass or an infiltrative mass with associated lymphadenopathy on CT or MR images. Disseminated Castleman disease manifests with diffuse mediastinal lymphadenopathy.

Pulmonary angiitis and granulomatosis: radiologic-pathologic correlation.

Five distinct clinical syndromes of pulmonary angiitis and granulomatosis are currently recognized: Wegener granulomatosis, lymphomatoid granulomatosis, necrotizing sarcoid granulomatosis, bronchocentric granulomatosis, and allergic angiitis and granulomatosis (Churg-Strauss syndrome). Patients typically present in middle age with fever, cough, hemoptysis, dyspnea, or chest discomfort. Upper airway involvement such as sinusitis suggests Wegener granulomatosis. Medical renal disease is associated with Wegener granulomatosis and Churg-Strauss syndrome. Asthma may be present in bronchocentric granulomatosis and Churg-Strauss syndrome. Pathologic examination of these entities demonstrates vasculitis, granulomatous inflammation, and parenchymal necrosis. The radiologic manifestations of pulmonary disease are varied, but the most typical appearance is that of multiple nodules or masses that may demonstrate cavitation. Diffuse multifocal air-space opacities with or without cavitation may also be seen. Pulmonary hemorrhage is a well-known presenting manifestation of Wegener granulomatosis and, less commonly, of Churg-Strauss syndrome. Because of the multifocal lung involvement in these diseases, pulmonary metastases and infectious causes are often considered in the differential diagnosis. Affected patients are treated with cytotoxic agents and corticosteroids. The prognosis is variable, depending on the specific syndrome, but may be favorable in the absence of significant complications.