Arūnas Lukoševičius

Specificity of transcranial sonography in parkinson spectrum disorders in comparison to degenerative cognitive syndromes

BackgroundHyperechogenicity of the substantia nigra (SN+), detected by transcranial sonography (TCS), was reported as a characteristic finding in Parkinsons disease (PD), with high diagnostic accuracy values, when compared mainly to healthy controls or essential tremor (ET) group. However, some data is accumulating that the SN + could be detected in other neurodegenerative and even in non-neurodegenerative disorders too. Our aim was to estimate the diagnostic accuracy of TCS, mainly focusing on the specificity point, when applied to a range of the parkinsonian disorders, and comparing to the degenerative cognitive syndromes.MethodsA prospective study was carried out at the Hospital of Lithuanian University of Health Sciences from January until September 2011. Initially, a TCS and clinical examination were performed on 258 patients and 76 controls. The General Electric Voluson 730 Expert ultrasound system was used. There were 12.8% of cases excluded with insufficient temporal bones, and 4.3% excluded with an unclear diagnosis. The studied sample consisted of the groups: PD (n = 71, 33.2%), ET (n = 58, 27.1%), PD and ET (n = 10, 4.7%), atypical parkinsonian syndromes (APS) (n = 3, 1.4%), hereditary neurodegenerative parkinsonism (HDP) (n = 3, 1.4%), secondary parkinsonism (SP) (n = 23, 10.8%), mild cognitive impairment (MCI) (n = 33, 15.4%), dementia (n = 13, 6.1%), and control (n = 71).ResultsThere were 80.3% of PD patients at stages 1 & 2 according to Hoehn and Yahr. At the cut-off value of 0.20 cm2 of the SN+, the sensitivity for PD was 94.3% and the specificity - 63.3% (ROC analysis, AUC 0.891), in comparison to the rest of the cohort. At the cut-off value of 0.26 cm2, the sensitivity was 90% and the specificity 82.4%.The estimations for the lowest specificity for PD, in comparison to the latter subgroups (at the cut-off values of 0.20 cm2 and 0.26 cm2, respectively) were: 0% and 33.3% to APS, 33.3% and 66.7% to HDP, 34.8% and 69.6% to SP, 55.2% and 82.8% to ET, 75% and 91.7% to dementia.ConclusionsThe high sensitivity of the test could be employed as a valuable screening tool. But TCS is more useful as a supplementary diagnostic method, due to the specificity values not being comprehensive.

Inertial sensor for objective evaluation of swimmer performance

In this paper, the development of an accelerometer based sensor and algorithms to extract useful information for evaluation of sportsman performance in swimming sport is presented. Several parameters were identified as useful and feasible to estimate from registered acceleration curves: ldquonumber of strokes per laprdquo, ldquoinstantaneous stroke raterdquo also durations of various swimming process intervals, periods and phases. Possible applications of extracted parameters were discussed.

Ensemble empirical mode decomposition based feature enhancement of cardio signals

This paper presents an application of ensemble empirical mode decomposition method for enhancement of specific biological signal features. The application for two types of cardiological signals is presented in this article. Detection of fiducial points is a routine task for analyzing these signals. In a clinical situation, cardiological signals are usually corrupted by artifacts and finding exact time instances of various fiducial points is a challenge. Filtering approach for signal to noise ratio enhancing is traditionally and widely used in clinical practice. Methods, based on filtering, however, have serious limitations when it is necessary to find compromise between noise suppression and preservation of signal features. The proposed method uses ensemble empirical mode decomposition in order to suppress noise or enhance specific waves in the signal. Performance of the method was estimated by using clinical electrocardiogram and impedance cardiogram signals with synthetic baseline-wander, power-line and added Gaussian noise. In electrocardiogram application, an average estimation error of QRS complex length was 2.06-4.47%, the smallest in comparison to the reference methods. In impedance cardiogram application, the proposed method provided the highest cross-correlation coefficient between original and de-noised signal in comparison to reference methods. When the signal to noise ratio of the input signal was -12 dB, the method provided signal to error ratio of 33 dB in this case. The proposed method is adaptive to template and signal itself and thus could be applied to other non-stationary biological signals.

Ranking of color space components for detection of blood vessels in eye fundus images

Most of the studies so far used the green component of RGB for blood vessel recognition in eye fundus images with some using luminance. However, no study was performed to justify in quantitative manner these choices. We aimed to investigate which color spaces (RGB, YIQ, HSV, HSL, XYZ’) can emphasize vasculature and vascular reflex in order to enable the usage of computationally and conceptionally simpler blood vessel detection methods.

Adjustment of ultrasound exposure duration to microbubble sonodestruction kinetics for optimal cell sonoporation in vitro.

Cell sonoporation enables the delivery of various exogenous molecules into the cells. To maximize the percentage of reversibly sonoporated cells and to increase cell viability we propose a model for implicit dosimetry for adjustment of ultrasound (US) exposure duration. The Chinese hamster ovary cell suspension was supplemented with microbubbles (MB) and exposed to US, operating at the frequency of 880 kHz, with a 100% duty cycle and with an output peak negative pressure (PNP) of 500 kPa for durations ranging from 0.5 to 30 s. Using diagnostic B-scan imaging we showed that the majority of the MB at 500 kPa US peak negative pressure undergo sonodestruction in less than a second. During this time maximal number of reversibly sonoporated cells was achieved. Increase of US exposure duration did not increase sonoporated cell number, however it induced additional cell viability decrease. Therefore aiming to achieve the highest level of reversibly sonoporated cells and also to preserve the highest level of cell viability, the duration of US exposure should not exceed the duration needed for complete MB sonodestruction.

Microbubble Sonodestruction Rate as a Metric to Evaluate Sonoporation Efficiency

The efficiency of sonoporation is directly related to microbubble cavitation and can be dependent on the microbubble sonodestruction rate. The objective of this study was to investigate whether the rate of microbubble sonodestruction can be used as a parameter to develop an implicit dosimetric method for sonoporation efficiency evaluation.

Network based clinical decision support system

Developed prototype of network based clinical decision support system consists of database of clinical data and web-based applications for signal and image analysis methods and algorithms. The methods for eye fundus image analysis and ECG P-wave morphology evaluation are the first methods covering two clinical specialties - cardiology and ophthalmology in the system. Network based database and combined analysis of the parameters obtained by means of implemented methods gives a possibility of holistic approach in clinical decision support.

New method of spatial superposition of attenuated waves for ultrasound field modelling

The objective of this work is the contrary issues of ultrasonic diagnostics in medicine when modern requirements for resolution are in conflict with strict safety issues. There is only one way to make progress by starting to take into account the attenuation in biological tissues and the wave diffraction phenomena. The aim of this work is to develop the flexible ultrasound field model implemented in routine algorithms of digital signal processing. The method consists of the calculation of plane wave propagation and the calculation of an ultrasound signal field. On the basis of the spatial impulse response of an aperture for calculation of space-spread ultrasound signals and the spectrum decomposition method for modelling plane wave propagation in lossy media, the modified method of spatial superposition of attenuated waves was developed. Using the method of equidistant line calculation the time and frequency features of the ultrasound signal field caused by the geometry and dynamics of the aperture, the attenuation and velocity dispersion in the medium are determined. The method was successfully applied to the investigation of the system for intracranial media monitoring, where a new measurement channel based on the changes of attenuation and dispersion in intracranial medium has been implemented.

Modification of drusen border detection algorithm based on flooding simulation

Drusen are white or yellow spots in eye fundus that consist of extracellular material. They are a sign of age-related macular degeneration (AMD) - the main cause of blindness in the developed countries and a third main cause of blindness in the whole world. Number and area of drusen are used to grade AMD. However, calculating them manually is time consuming. Thus various methods have been used to detect drusen automatically or semi-automatically. In this paper we propose an alternative method to find the borders of the drusen.

Courseware for ultrasonic medical diagnostics curriculum: system for on-site and remote laboratory experiments

The aim of this paper is to present the implementation approach of on-site and remote experimenting laboratory for ultrasound medical diagnostics curriculum. We demonstrate the implementation of such laboratory using virtual instrument that is built by using a standard computer, a ultrasonic transducer with a tissue like phantom, digitizer, function generator and the software package LabView. By controlling the virtual instrument it is possible to excite and receive ultrasound waves in the pulse echo mode, then process the received echographic signal and get the characteristics of the tissue like phantom. The tissue like phantom is characterized with thickness and density also with the speed of wave’s propagation and attenuation coefficient. The students are motivated by the assignment of the precise task - to identify the material from which the phantom is made. The implemented on-site experiments system is based on a virtual instrument, the remote experiments system and is tested using the LabView remote panel technology as well. This technology allows accessing the experiment system remotely using an internet browser. We expect the students will improve their knowledge of ultrasound medical diagnostics using our hands-on lab experiment system.