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1
Content available Application of ultrasound to noninvasive imaging of temperature distribution induced in tissue
Karwat P., Kujawska T., Secomski W., Gambin B., Litniewski J.
Hydroacoustics
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2016
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Vol. 19
219--228
EN
Therapeutic and surgical applications of High Intensity Focused Ultrasound (HIFU) require monitoring of local temperature rises induced inside tissues. It is needed to appropriately target the focal plane, and hence the whole focal volume inside the tumor tissue, prior to thermo-ablative treatment, and the beginning of tissue necrosis. In this study we present an ultrasound method, which calculates the variations of the speed of sound in the locally heated tissue. Changes in velocity correspond to temperature change. The method calculates a 2D distribution of changes in the sound velocity, by estimation of the local phase shifts of RF echo-signals backscattered from the heated tissue volume (the focal volume of the HIFU beam), and received by an ultrasound scanner (23). The technique enabled temperature imaging of the heated tissue volume from the very inception of heating. The results indicated that the contrast sensitivity for imaging of relative changes in the sound speed was on the order of 0.06%; corresponding to an increase in the tissue temperature by about 2 °C.
2
Content available Spatial and Frequency Compounding in Application to Attenuation Estimation in Tissue
Klimonda Z., Litniewski J., Karwat P., Nowicki A.
Archives of Acoustics
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2014
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Vol. 39, No. 4
519--527
EN
The soft tissue attenuation is an interesting parameter from medical point of view, because the value of attenuation coefficient is often related to the state of the tissue. Thus, the imaging of the attenuation coefficient distribution within the tissue could be a useful tool for ultrasonic medical diagnosis. The method of attenuation estimation based on tracking of the mean frequency changes in a backscattered signal is presented in this paper. The attenuation estimates are characterized by high variance due to stochastic character of the backscattered ultrasonic signal and some special methods must be added to data processing to improve the resulting images. The following paper presents the application of Spatial Compounding (SC), Frequency Compounding (FC) and the combination of both. The resulting parametric images are compared by means of root-mean-square errors. The results show that combined SC and FC techniques significantly improve the quality and accuracy of parametric images of attenuation distribution.
3
Content available Tissue Attenuation Estimation from Backscattered Ultrasound Using Spatial Compounding Technique - Preliminary Results
Klimonda Z., Litniewski J., Nowicki A.
Archives of Acoustics
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2010
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Vol. 35, No. 4
643-651
EN
The pathological states of biological tissue are often resulted in attenuation changes. Thus, information about attenuating properties of tissue is valuable for the physician and could be useful in ultrasonic diagnosis. We are currently developing a technique for parametric imaging of attenuation and we intend to apply it for in vivo characterization of tissue. The attenuation estimation method based on the echoes mean frequency changes due to tissue attenuation dispersion, is presented. The Doppler IQ technique was adopted to estimate the mean frequency directly from the raw RF data. The Singular Spectrum Analysis technique was used for the extraction of mean frequency trends. These trends were converted into attenuation distribution and finally the parametric images were computed. In order to reduce variation of attenuation estimates the spatial compounding method was applied. Operation and accuracy of attenuation extracting procedure was verified by calculating the attenuation coefficient distribution using the data from the tissue phantom (DFS, Denmark) with uniform echogenicity while attenuation coefficient underwent variation.
4
Content available remote Spatial Resolution of Attenuation Imaging
Klimonda Z., Litniewski J., Nowicki A.
Archives of Acoustics
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2009
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Vol. 34, No. 4
461-470
EN
The attenuating properties of biological tissue are of great importance in ultrasonic examination even though its anatomical variability limits diagnostics effectiveness. We are currently developing a technique for parametric imaging of attenuation and we intend to apply it for in vivo characterization of tissue. The diagnostic usefulness of the proposed technique crucially depends on the precision of the attenuation estimate and the resolution of the parametric image. These two parameters are highly correlated, since the resolution is reduced whenever averaging is used to minimize the errors introduced by the random character of the backscatter. Here we report on the results of numerical processing of both, simulated and recorded from a tissue-mimicking phantom echoes. We have analyzed the parameters of the estimation technique and examined their influence on the precision of the attenuation estimate and on the parametric image resolution. The optimal selection of attenuation image parameters depending on its intended diagnostic use, was also considered
5
Content available Applications of image registration in parametric imaging
Rumiński J., Suchowirski M.
Journal of Medical Informatics & Technologies
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2006
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Vol. 10
47--53
EN
Applications of image registration in parametric imaging are investigated. The manual and automatic image registration methods have been used for image to image registration in sequences to correct movement artefacts in reconstructed parametric objects. Additionally the registration methods were used for multimodal visualisation of structural and parametric objects. The achieved results proved that the automatic image to image registration, for motion mechanisms correction, in the parametric model improves the quality of images. The multimodal visualisation of structural MRI images and parametric DSC-MRI images, enables to correlate the local dynamic changes with all morphological features.
6
Content available Registration and normalization of MRI/PET images
Rumiński J., Suchowirski M.
Journal of Medical Informatics & Technologies
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2005
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Vol. 9
159--166
EN
Parametric imaging is more and more popular in dynamic brain studies. It enables to quantitatively or semi-quantitatively estimate physiological state and processes in brain. Parametric images represent spatial distribution of parameter values calculated for chosen mathematical model of the process or object. This work compares different methods of geometrical transformations for image registration and normalization. Appropriate method for image registration and normalization (in reference to atlases) is extremely important for common visualization of structural and parametric images in MRI and PET studies. Rigid and elastic geometrical transformations are implemented and compared. Additionally Delaunay triangulation and image morphing methods are used. Manual and proposed automatic registration and normalization methods are presented and compared based on MRI/PET and Talairach atlas images. Concluding, the proposed automatic image normalization method is accurate and using the combination of Delaunay and morphing methods can produce even better results.
7
Content available Parametric imaging in dynamic glucose metabolism studies in brain
Rumiński J., Karczewski B.
Journal of Medical Informatics & Technologies
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2005
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Vol. 9
201--208
EN
Parametric imaging is more and more popular in dynamic brain studies. It enables to quantitatively or semi-quantitatively estimate physiological state and processes in brain. This work analyse the dynamic 18FDG-PET studies for estimation of brain glucose metabolism. The influence of the signal noise is analysed to estimate its influence on the final glucose metabolism parameter values. The LCMRGlc parameter is under investigation. It is based on three compartmental model proposed by Phelps. Using different 18FDG-PET data series obtained from independent sources the Gaussian noise was introduced (with different variance). Then the quality of the model fitting results were estimated. The final results clearly indicates than the noise is highly compensated in microparameter used in calculation of LCMRGlc. Concluding, it is possible to estimate the LCMRGlc parameter value even in the presence of noise.
8
Content available Limitations of DSC-MRI for quantitative brain perfusion
Rumiński J., Bobek-Billewicz B.
Journal of Medical Informatics & Technologies
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2004
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Vol. 8
MM49--58
EN
Synthesis of quantitative parametric images in DSC-MRI is presented. Critical review of major limitations of the DSC-MRI method is discussed. It includes investigation of measurement procedures/conditions as well as parametric image synthesis methodology. Simulations, as well as phantom studies were used to verify theoretical limitations of the DSC-MRI. Especially, estimation of the contrast (Gd-DTPA) concentration by EPI measurements, the role of a phantom and its pipes orientation, influence of a bolus dispersion, bolus arrival time, and other signal parameters on an image quality. As a conclusion testing software package is proposed.
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