| 1. |
- Y Banaem, Hossein, et al.
(författare)
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Brain tumor modeling : glioma growth and interaction with chemotherapy
- 2011
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Ingår i: International Conference on Graphic and Image Processing (ICGIP 2011). - : SPIE. ; 8285
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Konferensbidrag (refereegranskat)abstract
- In last decade increasingly mathematical models of tumor growths have been studied, particularly on solid tumors which growth mainly caused by cellular proliferation. In this paper we propose a modified model to simulate the growth of gliomas in different stages. Glioma growth is modeled by a reaction-advection-diffusion. We begin with a model of untreated gliomas and continue with models of polyclonal glioma following chemotherapy. From relatively simple assumptions involving homogeneous brain tissue bounded by a few gross anatomical landmarks (ventricles and skull) the models have been expanded to include heterogeneous brain tissue with different motilities of glioma cells in grey and white matter. Tumor growth is characterized by a dangerous change in the control mechanisms, which normally maintain a balance between the rate of proliferation and the rate of apoptosis (controlled cell death). Result shows that this model closes to clinical finding and can simulate brain tumor behavior properly.
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| 2. |
- Kothapalli, Veera Venkata Satya Naray, 1985-, et al.
(författare)
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Unique pumping-out fracturing mechanism of a polymer-shelled contrast agent : An acoustic characterization and optical visualization
- 2014
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 62:3, s. 451-462
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Tidskriftsartikel (refereegranskat)abstract
- This work describes the fracturing mechanism of air-filled microbubbles (MBs) encapsulated by a cross-linked poly(vinyl alcohol) (PVA) shell. The radial oscillation and fracturing events following the ultrasound exposure were visualized with an ultrahigh-speed camera, and backscattered timedomain signals were acquired with the acoustic setup specific for harmonic detection. No evidence of gas emerging from defects in the shell with the arrival of the first insonation burst was found. In optical recordings, more than one shell defect was noted, and the gas core was drained without any sign of air extrusion when several consecutive bursts of 1 MPa amplitude were applied. In acoustic tests, the backscattered peak-to-peak voltage gradually reached its maximum and exponentially decreased when the PVA-based MB suspension was exposed to approximately 20 consecutive bursts arriving at pulse repetition frequencies of 100 and 500 Hz. Taking into account that the PVA shell is porous and possibly contains large air pockets between the cross-linked PVA chains, the aforementioned acoustic behavior might be attributed to pumping gas from these pockets in combination with gas release from the core through shell defects. We refer to this fracturing mechanism as pumping-out behavior, and this behavior could have potential use for the local delivery of therapeutic gases, such as nitric oxide.
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| 3. |
- Grönlund, Christer, et al.
(författare)
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Imaging two-dimensional mechanical waves of skeletal muscle contraction
- 2013
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Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629 .- 1879-291X. ; 39:2, s. 360-369
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Tidskriftsartikel (refereegranskat)abstract
- Skeletal muscle contraction is related to rapid mechanical shortening and thickening. Recently, specialized ultrasound systems have been applied to demonstrate and quantify transient tissue velocities and one-dimensional (1-D) propagation of mechanical waves during muscle contraction. Such waves could potentially provide novel information on musculoskeletal characteristics, function and disorders. In this work, we demonstrate two-dimensional (2-D) mechanical wave imaging following the skeletal muscle contraction. B-mode image acquisition during multiple consecutive electrostimulations, speckle-tracking and a time-stamp sorting protocol were used to obtain 1.4 kHz frame rate 2-D tissue velocity imaging of the biceps brachii muscle contraction. The results present novel information on tissue velocity profiles and mechanical wave propagation. In particular, counter-propagating compressional and shear waves in the longitudinal direction were observed in the contracting tissue (speed 2.8-4.4 m/s) and a compressional wave in the transverse direction of the non-contracting muscle tissue (1.2-1.9 m/s). In conclusion, analysing transient 2-D tissue velocity allows simultaneous assessment of both active and passive muscle tissue properties. (E-mail: christer.gronlund@vll.se) (C) 2013 World Federation for Ultrasound in Medicine & Biology.
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| 4. |
- Yousefi, Hossein, et al.
(författare)
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An optimised linear mechanical model for estimating brain shift caused by meningioma tumours
- 2013
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Ingår i: International Journal of Biomedical Science and Engineering. - : Science Publishing Group. - 2376-7227 .- 2376-7235. ; 1:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Estimation of brain deformation plays an important role in computer-aided therapy and image-guided neurosurgery systems. Tumour growth can cause brain deformation and change stress distribution in the brain. Biomechanical models exist that use a finite element method to estimate brain shift caused by tumour growth. Such models can be categorised as linear and non-linear models, both of which assume finite deformation of the brain after tumour growth. Linear models are easy to implement and fast enough to for applications such as IGS where the time is a great of concern. However their accuracy highly dependent on the parameters of the models in this paper, we proposed an optimisation approach to improve a naive linear model to achieve more precise estimation of brain displacements caused by tumour growth. The optimisation process has improved the accuracy of the model by adapting the brain model parameters according to different tomour sizes.We used patient-based tetrahedron finite element mesh with proper material properties for brain tissue and appropriate boundary conditions in the tumour region. Anatomical landmarks were determined by an expert and were divided into two different sets for evaluation and optimisation. Tetrahedral finite element meshes were used and the model parameters were optimised by minimising the mean square distance between the predicted locations of the anatomical landmarks derived from Brain Atlas images and their actual locations on the tumour images. Our results demonstrate great improvement in the accuracy of an optimised linear mechanical model that achieved an accuracy rate of approximately 92%.
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| 5. |
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| 6. |
- Grönlund, Christer, 1975-, et al.
(författare)
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Significant beat-to-beat variability of E/e’ irrespective of respiration
- 2013
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Ingår i: International cardiovascular forum. - : Barcaray Publishing. - 2409-3424 .- 2410-2636. ; 1:2, s. 88-89
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Tidskriftsartikel (refereegranskat)abstract
- The E/e’ ratio is commonly used in Doppler echocardiographic examinations to estimate the pulmonary capillary wedge pressure. The rationale of using this ratio is to combine left ventricular (LV) filling (E) and relaxation (e’) velocities to indirectly assess left atrial pressure. However, the accuracy of this index has recently been questioned, particularly in patients with controlled heart failure. Likewise, the potential beat-to-beat variability of such measurements remains undetermined. The cardiovascular system is subject to several oscillations with the potential of influencing LV function and its intra-cavitary pressures, hence measurements of its filling and relaxation velocities. The aim of this pilot study was to assess the beat-to-beat variability of the E/e’ ratio in one minute long examination in healthy subjects, and patients with various severity of amyloid heart disease. The results show that despite critical application of the standard echocardiographic recording recommendations, E/e’ beat-to-beat variability was 36 % (22 to 50%) in healthy subjects and 17 % (11-26%) in patients, and where the most severe amyloid heart disease had the least variability. Thus, clinical use of a single or few cardiac beats might not necessarily reflect an accurate ratio between the two velocities, and hence casts doubt over their diagnostic value.
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| 7. |
- Molin, Jesper, 1987, et al.
(författare)
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Feature-enhancing zoom to facilitate Ki-67 hot spot detection
- 2014
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422. - 9780819498342 ; 9041
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Konferensbidrag (refereegranskat)abstract
- Image processing algorithms in pathology commonly include automated decision points such as classifications. While this enables efficient automation, there is also a risk that errors are induced. A different paradigm is to use image processing for enhancements without introducing explicit classifications. Such enhancements can help pathologists to increase efficiency without sacrificing accuracy. In our work, this paradigm has been applied to Ki-67 hot spot detection. Ki-67 scoring is a routine analysis to quantify the proliferation rate of tumor cells. Cell counting in the hot spot, the region of highest concentration of positive tumor cells, is a method increasingly used in clinical routine. An obstacle for this method is that while hot spot selection is a task suitable for low magnification, high magnification is needed to discern positive nuclei, thus the pathologist must perform many zooming operations. We propose to address this issue by an image processing method that increases the visibility of the positive nuclei at low magnification levels. This tool displays the modified version at low magnification, while gradually blending into the original image at high magnification. The tool was evaluated in a feasibility study with four pathologists targeting routine clinical use. In a task to compare hot spot concentrations, the average accuracy was 75±4.1% using the tool and 69±4.6% without it (n=4). Feedback on the system, gathered from an observer study, indicate that the pathologists found the tool useful and fitting in their existing diagnostic process. The pathologists judged the tool to be feasible for implementation in clinical routine.
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| 8. |
- Moshavegh, Ramin, et al.
(författare)
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Automated segmentation of free-lying cell nuclei in Pap smears for malignancy-associated change analysis
- 2012
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Ingår i: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS. - 1557-170X. - 9781424441198 ; , s. 5372-5375
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Konferensbidrag (refereegranskat)abstract
- This paper presents an automated algorithm for robustly detecting and segmenting free-lying cell nuclei in bright-field microscope images of Pap smears. This is an essential initial step in the development of an automated screening system for cervical cancer based on malignancy associated change (MAC) analysis. The proposed segmentation algorithm makes use of gray-scale annular closings to identify free-lying nuclei-like objects together with marker-based watershed segmentation to accurately delineate the nuclear boundaries. The algorithm also employs artifact rejection based on size, shape, and granularity to ensure only the nuclei of intermediate squamous epithelial cells are retained. An evaluation of the performance of the algorithm relative to expert manual segmentation of 33 fields-of-view from 11 Pap smear slides is also presented. The results show that the sensitivity and specificity of nucleus detection is 94.71% and 85.30% respectively, and that the accuracy of segmentation, measured using the Dice coefficient, of the detected nuclei is 97.30±1.3%.
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| 9. |
- Persson, Mikael, 1959, et al.
(författare)
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Microwave based diagnostics and treatment in practice
- 2013
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Ingår i: 2013 IEEE MTT-S International Microwave Workshop Series on RF and Wireless Technologies for Biomedical and Healthcare Applications, IMWS-BIO 2013 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- Globally, around 15 million people each year suffer a stroke. Only a small fraction of stroke patients who could benefit from thrombolytic treatment reach diagnosis and treatment in time. To increase this low figure we have developed microwave technology aiming to differentiate hemorrhagic from ischemic stroke patients. The standard method for breast cancer diagnosis today is X-ray mammography. Despite its recognized ability to detect tumors it suffers from some limitations. Neither the false positive nor the false negative detection rates are negligible. An interesting alternative being researched extensively today is microwave tomography. In our current strive to develop a clinical prototype we have found that the most suitable design consists of an antenna array placed in a full 3D pattern. During the last decade clinical studies have demonstrated the ability of microwave hyperthermia to dramatically enhance cancer patient survival. The fundamental challenge is to adequately heat deep-seated tumors while preventing surrounding healthy tissue from undesired heating and damage. We are specifically addressing the challenge to deliver power levels with spatial control, patient treatment planning, and noninvasive temperature measurements. © 2013 IEEE.
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| 10. |
- Qaiser, Mahmood, 1981
(författare)
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Automated Patient-Specific Multi-tissue Segmentation of MR Images of the Head
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The automated segmentation of magnetic resonance (MR) images of the human head is an active area of research in the field of neuroimaging. The resulting segmentation yields a patient-specific labeling of individual tissues and makes possible quantitative characterization of these tissues (e.g. in the study of Alzheimers disease and multiple sclerosis). The segmentation is also useful for assigning individual tissues conductivity or biomechanical properties for patient-specific electromagnetic and biomechanical simulations respectively. The former are of importance in applications such as EEG (electroencephalography) source localization in epilepsy patients and hyperthermia treatment planning for head and neck tumors. The latter are of interest in applications such as patient-specific motion correction and in surgical simulation.Automated and accurate segmentation of MR images is a challenging task in the field of neuroimaging because of noise, spatial intensity inhomogeneities, difficulty of MR intensity normalization and partial volume effects (a single voxel represents more than one tissue type). Consequently most of the techniques proposed to date require manual correction or intervention to achieve an accurate segmentation of the brain or whole-head. As a result they are time consuming,laborious and subjective. This thesis presents two automatic and unsupervised segmentation methods, for multi-tissue segmentation of the brain and whole-head respectively from multi-modal MR images, that are more accurate than the state-of-the-art algorithms. The brain segmentation method is based on the mean shift algorithm with a Bayesian-based adaptive bandwidth estimator. The method is called BAMS (Bayesian adaptive mean shift) and can be used to segment the brain into multiple tissue types; e.g. white matter (WM), gray matter (GM) and cerebrospinal fluid (CSF). The accuracy of BAMS was evaluated relative to that of several competing methods using both synthetic and real MRI data. The results show that it is robust to both noise and spatial intensity in- homogeneities compared to competing methods. The whole-head segmentation method is based on a hierarchical segmentation approach (HSA) incorporating the BAMS method. The segmentation performance of HSA-BAMS was evaluated relative to a reference method BET-FAST (based on the BET and FAST tools in the well-known FMRIB Software Library) and three other instantiations of the HSA, using synthetic MRI data with varying noise levels, and real MRI data. The segmentation results show the efficacy and accuracy of proposed method and that it consistently outperforms the BET-FAST reference method. HSA-BAMS was also evaluated indirectly in terms of its impact on the accuracy of EEG source localization using electromagnetic simulations based on a tissue conductivity labeling derived from the segmentation. The results demonstrate that HSA-BAMS outperforms the competing methods, and suggest that it has potential as a surrogate for manual segmentation for EEG source localization.
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