| 1. |
- Cheddad, Abbas, 1975-, et al.
(author)
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Image processing assisted algorithms for optical projection tomography
- 2012
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In: IEEE Transactions on Medical Imaging. - 0278-0062 .- 1558-254X. ; 31:1, s. 1-15
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Journal article (peer-reviewed)abstract
- Since it was first presented in 2002, optical projection tomography (OPT) has emerged as a powerful tool for the study of biomedical specimen on the mm to cm scale. In this paper, we present computational tools to further improve OPT image acquisition and tomographic reconstruction. More specifically, these methods provide: semi-automatic and precise positioning of a sample at the axis of rotation and a fast and robust algorithm for determination of postalignment values throughout the specimen as compared to existing methods. These tools are easily integrated for use with current commercial OPT scanners and should also be possible to implement in "home made" or experimental setups for OPT imaging. They generally contribute to increase acquisition speed and quality of OPT data and thereby significantly simplify and improve a number of three-dimensional and quantitative OPT based assessments.
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| 2. |
- Cheddad, Abbas, et al.
(author)
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Improving signal detection in emission optical projection tomography via single source multi-exposure image fusion
- 2013
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In: Optics Express. - : Optical Society of America. - 1094-4087. ; 21:14, s. 16584-16604
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Journal article (peer-reviewed)abstract
- We demonstrate a technique to improve structural data obtained from Optical Projection Tomography (OPT) using Image Fusion (IF) and contrast normalization. This enables the visualization of molecular expression patterns in biological specimens with highly variable contrast values. In the approach, termed IF-OPT, different exposures are fused by assigning weighted contrasts to each. When applied to projection images from mouse organs and digital phantoms our results demonstrate the capability of IF-OPT to reveal high and low signal intensity details in challenging specimens. We further provide measurements to highlight the benefits of the new algorithm in comparison to other similar methods.
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| 3. |
- Eriksson, Anna U., et al.
(author)
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Near infrared optical projection tomography for assessments of beta-cell mass distribution in diabetes research
- 2013
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In: Journal of Visualized Experiments. - : MyJove Corporation. - 1940-087X. ; 71
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Journal article (peer-reviewed)abstract
- By adapting OPT to include the capability of imaging in the near infrared (NIR) spectrum, we here illustrate the possibility to image larger bodies of pancreatic tissue, such as the rat pancreas, and to increase the number of channels (cell types) that may be studied in a single specimen. We further describe the implementation of a number of computational tools that provide: 1/ accurate positioning of a specimen's (in our case the pancreas) centre of mass (COM) at the axis of rotation (AR)2; 2/ improved algorithms for post-alignment tuning which prevents geometric distortions during the tomographic reconstruction2 and 3/ a protocol for intensity equalization to increase signal to noise ratios in OPT-based BCM determinations3. In addition, we describe a sample holder that minimizes the risk for unintentional movements of the specimen during image acquisition. Together, these protocols enable assessments of BCM distribution and other features, to be performed throughout the volume of intact pancreata or other organs (e.g. in studies of islet transplantation), with a resolution down to the level of individual islets of Langerhans.
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| 4. |
- Hörnblad, Andreas, 1982-, et al.
(author)
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An improved protocol for optical projection tomography imaging reveals lobular heterogeneities in pancreatic islet and β-cell mass distribution
- 2011
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In: Islets. - Austin : Landes Bioscience. - 1938-2014 .- 1938-2022. ; 3:4, s. 204-208
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Journal article (peer-reviewed)abstract
- Optical projection tomography (OPT) imaging is a powerful tool for three-dimensional imaging of gene and protein distribution patterns in biomedical specimens. We have previously demonstrated the possibility, by this technique, to extract information of the spatial and quantitative distribution of the islets of Langerhans in the intact mouse pancreas. In order to further increase the sensitivity of OPT imaging for this type of assessment, we have developed a protocol implementing a computational statistical approach: contrast limited adaptive histogram equalization (CLAHE). We demonstrate that this protocol significantly increases the sensitivity of OPT imaging for islet detection, helps preserve islet morphology and diminish subjectivity in thresholding for tomographic reconstruction. When applied to studies of the pancreas from healthy C57BL/6 mice, our data reveal that, at least in this strain, the pancreas harbors substantially more islets than has previously been reported. Further, we provide evidence that the gastric, duodenal and splenic lobes of the pancreas display dramatic differences in total and relative islet and β-cell mass distribution. This includes a 75% higher islet density in the gastric lobe as compared to the splenic lobe and a higher relative volume of insulin producing cells in the duodenal lobe as compared to the other lobes. Altogether, our data show that CLAHE substantially improves OPT based assessments of the islets of Langerhans and that lobular origin must be taken into careful consideration in quantitative and spatial assessments of the pancreas.
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| 5. |
- Yogarajah, Pratheepan, et al.
(author)
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A dynamic threshold approach for skin tone detection in colour images
- 2012
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In: International Journal of Biometrics (IJBM). - : InderScience Publishers. - 1755-8301 .- 1755-831X. ; 4:1, s. 38-55
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Journal article (peer-reviewed)abstract
- This paper presents a novel dynamic threshold approach to discriminate skin pixels and non-skin pixels in colour images. Fixed decision boundaries (or fixed threshold) classification approaches are successfully applied to detect human skin tone in colour images. These fixed thresholds mostly failed in two situations as they only search for a certain skin colour range: • any non-skin object may be classified as skin if non-skin objects's colour values belong to fixed threshold range • any true skin may be mistakenly classified as non-skin if the skin colour values do not belong to fixed threshold range. Therefore in this paper, instead of predefined fixed thresholds, novel online learned dynamic thresholds are used to overcome the above drawbacks. The experimental results show that our method is robust in overcoming these drawbacks. © 2012 Inderscience Enterprises Ltd.
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| 6. |
- Yogarajah, Pratheepan, et al.
(author)
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An Improved Self-embedding Algorithm : Digital Content Protection against Compression Attacks in Digital Watermarking
- 2010
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In: Image Processing and Communications Challenges 2. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642162947 - 9783642162954 ; , s. 59-66
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Book chapter (other academic/artistic)abstract
- Lossy compression attacks in digital watermarking are one of the major issues in digital watermarking. Cheddad et al. proposed a robust secured self-embedding method which is resistant to a certain amount of JPEG compression. Our experimental results show that the self-embedding method is resistant to JPEG compression attacks and not resistant to other lossy compression attacks such as Block Truncation Coding (BTC) and Singular Value Decomposition (SVD). Therefore we improved Cheddad et al's. method to give better protection against BTC and SVD compression attacks.
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| 7. |
- Yogarajah, Pratheepan, et al.
(author)
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Embed, track and authenticate images online with SDW-WebCrawler
- 2011
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In: 2011 Irish Machine Vision and Image Processing Conference. - : IEEE. - 9780769546292 - 9781467302302 ; , s. 76-81
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Conference paper (peer-reviewed)abstract
- The Internet is a widely open source to everyone to access Web pages. Using a web browser anyone can access websites. Because of this facility people can easily download images from websites without the owner's knowledge and use them in their own documents. Also image content may be modified for illegal purposes. Therefore a system is needed to authenticate images over the Web. Web image authentication is a challenging task that requires web crawlers to track and download images for authentication. Most of the known web image tracking engines such as TinEye and PicScout retrieve images according to the image infringement of the original image. However, these systems do not have the facility to authenticate the retrieved image, i.e. whether the retrieved image is similar to the original image or any image content alteration has occurred in the retrieved image and who is the copyrighted owner of the retrieved image.In order to solve the above mentioned drawbacks this paper presents a framework to protect image content, track it over the internet and authenticate the content. The proposed framework is based on self-embedding (i.e. where secret data and a binary version of the image are encrypted and embedded into the image), tracking (i.e. where a web crawler traverses over the internet to download images) and self-authentication (i.e. where the binary version of the hidden data is extracted to authenticate the image). Also another advantage of the proposed system is that it does not need the original image for the authentication process.
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