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Techniki obrazowania rezonansu magnetycznego (MR)

Cichocka M.

Inżynier i Fizyk Medyczny

2015

Vol. 4, nr 6

313--318

Obrazowanie rezonansu magnetycznego (MR) pozwala nie tylko na uwidocznienie struktur ciała człowieka. Dzięki rozwojowi metody możliwe jest także określenie funkcjonalności mózgu (badania funkcjonalne, fMRI), nieinwazyjna ocena składu chemicznego tkanek (spektroskopia, MRS), obrazowanie dyfuzji wody (dyfuzja, DWI oraz tensor dyfuzji, DTI), a także pomiar perfuzji krwi przez poszczególne tkanki (perfuzja, PWI). Techniki te znajdują coraz szersze zastosowanie w różnych dziedzinach medycyny.

Magnetic resonance imaging (MRI) allows not only to visualize the structures of the human body. Thanks to the development of this method, it is also possible to determine the functionality of the brain (functional imaging, fMRI), non-invasively evaluate the tissues chemical composition (spectroscopy, MRS) image water diffusion (diffusion-weighted imaging, DWI and diffusion tensor, DTI), as well as to measure blood perfusion in individual tissues (perfusion-weighted imaging, PWI). These techniques are increasingly used in various fields of medicine.

A new approach to ballistocardiographic measurements using fibre Bragg grating-based sensors

Dziuda Ł., Skibniewski F. W.

Biocybernetics and Biomedical Engineering

2014

Vol. 34, no. 2

101--116

A method for acquiring a ballistocardiographic (BCG) signal from the feet of a standing person and the back of a sitting or lying patient is described. The measurements are carried out using in-house constructed fibre-optic sensors interrogated with a commercially available system. The sensor head consists of a fibre Bragg grating (FBG) attached to an elastic board that is placed between the monitored person's body and a soft surface, enabling the board to deform in an unobstructed way. The body's movements, including the BCG component, exert pressure on the board and make it deform along with the attached FBG. The changes to the Bragg wavelength are proportional to the body's movement and a BCG signal can be extracted from the obtained recording. The measuring capabilities of the sensors were evaluated by compar- ing the heart rate (obtained on the basis of the BCG signal) with the reference signal registered by an ECG recorder. An RMS value of the relative error is below 1.8% and statistical analyses show a satisfactory reconstruction of measurements. Tests carried out in the MRIenvironment proved the method to be immune to strong electromagnetic fields. The presence of the sensor in an MRI scanner does not affect the quality of imaging.

Novel statistical approach for segmentation of brain magnetic resonance imaging using an improved expectation maximization algorithm

Yang Y., Huang S.

Optica Applicata

2006

Vol. 36, nr 1

125-136

In this paper, an improved expectation maximization (EM) algorithm called statistical histogram based expectation maximization (SHEM) algorithm is presented. The algorithm is put forward to overcome the drawback of standard EM algorithm, which is extremely computationally expensive for calculating the maximum likelihood (ML) parameters in the statistical segmentation. Combining the SHEM algorithm and the connected threshold region-growing algorithm that is used to provide a priori knowledge, a novel statistical approach for segmentation of brain magnetic resonance (MR) image data is thus proposed. The performance of our SHEM based method is compared with those of the EM based method and the commonly applied fuzzy C-means (FCM) segmentation. Experimental results show the proposed approach to be effective, robust and significantly faster than the conventional EM based method.