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379 results on '"Tenhunen, M."'

6. Large Animal Model for Healthy Tissue Tolerance Study in BNCT

Author

Benczik, J., Seppälä, T., Hopewell, J., Snellman, M., Auterinen, I., Joensuu, R., Ramadan, U. Abo, Tanttu, J., Vähätalo, J., Kulvik, M., Joensuu, H., Tenhunen, M., Savolainen, S., Kallio, M., Färkkilä, M., Hawthorne, M. Frederick, editor, Shelly, Kenneth, editor, and Wiersema, Richard J., editor

Published
2001
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20. Radiation shielding study of Advanced Data and Power Management Systems (ADPMS) housing using Geant4

Author

Garcia, F., Kurvinen, K., Brander, T., Orava, R., Heino, J., Virtanen, A., Kettunen, H., and Tenhunen, M.

Subjects
Shielding (Radiation) -- Methods, Space ships -- Design and construction, Space ships -- Materials, Space vehicles -- Design and construction, Space vehicles -- Materials, Nuclear power plants -- Shielding (Radiation), Nuclear power plants -- Methods, Business, Electronics, Electronics and electrical industries
Abstract

A design goal for current space system is to reduce the mass used to enclose components of the spacecraft. One potential target is to reduce the mass of electronics and its housings. The use of composite materials, especially CFRP (Carbon Fiber Reinforced Plastic) is a well known and vastly used approach to mass reduction. A design goal, cost reduction, has increased the use of commercial (non-space qualified) electronics. These commercial circuits and other components cannot tolerate as high radiation levels as space qualified components. Therefore, the use of standard electronics components poses a challenge in terms of the radiation protection capability of the ADPMS housings. The main goal of this study is to provide insight on the radiation shielding protection produced by different configurations of CFRP tungsten laminates of epoxies and cyanate esters and then to compare them to the protection given by the commonly used aluminum. For a spacecraft operating in LEO and MEO orbits the main components of the space radiation environment are energetic electrons and protons, therefore in our study we will compare the experimental and simulation results of the radiation attenuation of different types of laminates for those particles. At the same time the experimental data has been used to validate the Geant4 model of the laminates, which can be used for future optimizations of the laminate structures. Index Terms--Advanced equipment design, carbon composite laminates, GEANT4, LEO and MEO orbits, low Z-high Z-low Z concept, radiation attenuation, shielding.

Published
2008

35. Human breast cancer in vitro: matching histo-pathology with small-angle x-ray scattering and diffraction enhanced x-ray imaging

Author

Fernandez, M, Keyrilainen, J, Serimaa, R, Torkkeli, M, Karjalainen-Lindsberg, M, Leidenius, M, von Smitten, K, Tenhunen, M, Fiedler, S, Bravin, A, Weiss, T, Suortti, P, Fernandez M, Keyrilainen J, Serimaa R, Torkkeli M, Karjalainen-Lindsberg ML, Leidenius M, von Smitten K, Tenhunen M, Fiedler S, Bravin A, Weiss TM, Suortti P, Fernandez, M, Keyrilainen, J, Serimaa, R, Torkkeli, M, Karjalainen-Lindsberg, M, Leidenius, M, von Smitten, K, Tenhunen, M, Fiedler, S, Bravin, A, Weiss, T, Suortti, P, Fernandez M, Keyrilainen J, Serimaa R, Torkkeli M, Karjalainen-Lindsberg ML, Leidenius M, von Smitten K, Tenhunen M, Fiedler S, Bravin A, Weiss TM, and Suortti P

Abstract

Twenty-eight human breast tumour specimens were studied with small-angle x-ray scattering (SAXS), and 10 of those were imaged by the diffraction enhanced x-ray imaging (DEI) technique. The sample diameter was 20 mm and the thickness 1 mm. Two examples of ductal carcinoma are illustrated by histology images, DEI, and maps of the collagen d-spacing and scattered intensity in the Porod regime, which characterize the SAXS patterns from collagen-rich regions of the samples. Histo-pathology reveals the cancer-invaded regions, and the maps of the SAXS parameters show that in these regions the scattering signal differs significantly from scattering by the surrounding tissue, indicating a degradation of the collagen structure in the invaded regions. The DEI images show the borders between collagen and adipose tissue and provide a co-ordinate system for tissue mapping by SAXS. In addition, degradation of the collagen structure in an invaded region is revealed by fading contrast of the DEI refraction image. The 28 samples include fresh, defrosted tissue and formalin-fixed tissue. The d-values with their standard deviations are given. In the fresh samples there is a systematic 0.76% increase of the d-value in the invaded regions, averaged over 11 samples. Only intra-sample comparisons are made for the formalin- fixed samples, and with a long fixation time, the difference in the d-value stabilizes at about 0.7%. The correspondence between the DEI images, the SAXS maps and the histo-pathology suggests that definitive information on tumour growth and malignancy is obtained by combining these x-ray methods.

Published
2005

36. Visualisation of calcifications and thin collagen strands in human breast tumour specimens by the diffraction-enhanced imaging technique: A comparison with conventional mammography and histology

Author

Keyrilainen, J, Fernandez, M, Fiedler, S, Bravin, A, Karjalainen-Lindsberg, M, Virkkunen, P, Elo, E, Tenhunen, M, Suortti, P, Thomlinson, W, Keyrilainen J, Fernandez M, Fiedler S, Bravin A, Karjalainen-Lindsberg ML, Virkkunen P, Elo EM, Tenhunen M, Suortti P, Thomlinson W, Keyrilainen, J, Fernandez, M, Fiedler, S, Bravin, A, Karjalainen-Lindsberg, M, Virkkunen, P, Elo, E, Tenhunen, M, Suortti, P, Thomlinson, W, Keyrilainen J, Fernandez M, Fiedler S, Bravin A, Karjalainen-Lindsberg ML, Virkkunen P, Elo EM, Tenhunen M, Suortti P, and Thomlinson W

Abstract

Six excised human breast tissue specimens carrying benign and malignant tumours were examined with the diffraction-enhanced imaging technique. Diffraction-enhanced images were compared with diagnostic screen-film mammograms and the correlation with histological information of the specimens was established. The enhanced visibility of calcifications, some of which were smaller than 0.15 mm in diameter, is reported in detail. Fine details of the structures such as strands of collagen and contours between glandular and adipose tissue, which are barely visible at the contrast detection limit in the conventional absorption-based mammograms, are clearly visible in the diffraction-enhanced images. Microscopic study of the stained histopathological sections unequivocally confirms the correlation of the radiographic findings with the morphologic changes in specimens. An increased soft tissue contrast and a combination of information obtained with disparate diffraction-enhanced images provide better visibility of mammographically indistinguishable features. This kind of additional structural information of the breast tissue is required to improve assessment accuracy and earlier detection of the breast lesions. These advances in image quality make the method a very promising candidate for mammography.

Published
2005

37. Imaging lobular breast carcinoma: comparison of synchrotron radiation DEI-CT technique with clinical CT, mammography and histology

Author

Fiedler, S, Bravin, A, Keyrilainen, J, Fernandez, M, Suortti, P, Thomlinson, W, Tenhunen, M, Virkkunen, P, Karjalainen-Lindsberg, M, Fiedler S, Bravin A, Keyrilainen J, Fernandez M, Suortti P, Thomlinson W, Tenhunen M, Virkkunen P, Karjalainen-Lindsberg ML, Fiedler, S, Bravin, A, Keyrilainen, J, Fernandez, M, Suortti, P, Thomlinson, W, Tenhunen, M, Virkkunen, P, Karjalainen-Lindsberg, M, Fiedler S, Bravin A, Keyrilainen J, Fernandez M, Suortti P, Thomlinson W, Tenhunen M, Virkkunen P, and Karjalainen-Lindsberg ML

Abstract

Different modalities for imaging cancer-bearing breast tissue samples are described and compared. The images include clinical mammograms and computed tomography (CT) images, CT images with partly coherent synchrotron radiation (SR), and CT and radiography images taken with SR using the diffraction enhanced imaging (DEI) method. The images are evaluated by a radiologist and compared with histopathological examination of the samples. Two cases of lobular carcinoma are studied in detail. The indications of cancer are very weak or invisible in the conventional images, but the morphological changes due to invasion of cancer become pronounced in the images taken by the DEI method. The strands penetrating adipose tissue are seen clearly in the DEI-CT images, and the histopathology confirms that some strands contain the so-called 'Indian file' formations of cancer cells. The radiation dose is carefully measured for each of the imaging modalities. The mean glandular dose (MGD) for 50% glandular breast tissue is about 1 mGy in conventional mammography and less than 0.25 mGy in projection DEI, while in the clinical CT imaging the MGD is very high, about 45 mGy. The entrance dose of 95 mGy in DEI-CT imaging gives rise to an MGD of 40 mGy, but the dose may be reduced by an order of magnitude, because the contrast is very large in most images.

Published
2004

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