Andrius Sakalauskas

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.

Estimation of pulse arrival time using impedance plethysmogram from body composition scales

Long-term periodic monitoring of cardiovascular function in unobtrusive way has been a challenge in sensor research lately. This work presents the investigation of the method for pulse arrival time (PAT) estimation using body composition scales. It employs the electrocardiogram and the impedance plethysmogram (IPG) which are recorded from palm and plantar electrodes already integrated into body composition scales. Four subjects were involved in the experiment. The IPG was acquired from a single-foot and foot-to-foot and compared to the reference method - photoplethysmography. The range of correlation coefficient obtained in different methods varied from 0.7 to 0.94 showing that small PAT variations can be tracked using the IPG signals. Such results suggest that body composition scales could be supplemented with additional parameter for the assessment of arterial stiffness. This function will make them truly multi-parametric device for periodic health monitoring at home.

Noninvasive Evaluation of Portal Hypertension Using a Supervised Learning Technique

Portal hypertension (PHT) is a key event in the evolution of different chronic liver diseases and leads to the morbidity and mortality of patients. The traditional reliable PHT evaluation method is a hepatic venous pressure gradient (HVPG) measurement, which is invasive and not always available or acceptable to patients. The HVPG measurement is relatively expensive and depends on the experience of the physician. There are many potential noninvasive methods to predict PHT, of which liver transient elastography is determined to be the most accurate; however, even transient elastography lacks the accuracy to be a perfect noninvasive diagnostic method of PHT. In this research, we are focusing on noninvasive PHT assessment methods that rely on selected best-supervised learning algorithms which use a wide set of noninvasively obtained data, including demographical, clinical, laboratory, instrumental, and transient elastography measurements. In order to build the best performing classification meta-algorithm, a set of 21 classification algorithms have been tested. The problem was expanded by selecting the best performing clinical attributes using algorithm-specific filtering methods that give the lowest error rate to predict clinically significant PHT. The suggested meta-algorithm objectively outperforms other methods found in literature and can be a good substitute for invasive PHT evaluation methods.

RF Ultrasound Based Estimation of Pulsatile Flow Induced Microdisplacements in Phantom

Mechanical stimulus is key component to estimate tissue stiffness. Few techniques have been developed to induce external mechanical stimulus into tissues. We hypothesize that the natural tissue motion due to cardiovascular activity could be employed for this purpose and with decrease of tissue stiffness increase their motion amplitude. The assessment of elastic sub-millimeter tissue displacements is one of the leading developments for ultrasonic characterization of tissue stiffness. The objective of this study was to investigate the feasibility to parametrize the phantom material response to pulsatile flow. The displacements were evaluated in tissue-mimicking phantoms with known stiffness. The two agar phantoms, having vessel imitating channel with controlled pulsatile flow inside, were manufactured (agar concentrations 6 and 3 g/l in distilled water, predicted Young modulus was 10 and 7 kPa respectively). The pulse water flow in channel was produced by centrifugal pump MultiFlow (Gampt) with period of 1 s. The length of channel was 19 cm embedded in the tissue mimicking agarose gel. Linear array transducer L14-5 (5–14 MHz) driven by scanner SonixTouch (Ultrasonix) was used for the echoscopy of phantom and ultrasound (US) radiofrequency (RF) data acquisition. The collected beam formed B-mode RF data (120 fps) were used for the displacements estimation applying phase-correlation and sub-sample techniques. The pulsation of channel diameter and displacements of material were estimated at a few distances from channel border in all phantoms. The pulsation of diameter and displacements of material were parametrized extracting double amplitudes. Amplitudes of displacements of material were normalized respective to pulsation amplitude of channel diameter. The relation of amplitude parameters with concentration of agar was evaluated. It was determined that displacement is correlated with stiffness: with decrease of tissue stiffness the motion amplitude is increasing. The method may provide the technological background for future studies characterizing in vivo tissue stiffness from vascular pulsations generated displacements.

Transcranial Ultrasonographic Image Analysis System for Decision Support in Parkinson Disease: Transcranial US Image Analysis System for Parkinson Disease

Transcranial ultrasonography (US) is a relatively new neuroimaging modality proposed for early diagnostics of Parkinson disease (PD). The main limitation of transcranial US image‐based diagnostics is a high degree of subjectivity caused by low quality of the transcranial images. The article presents a developed image analysis system and evaluates the potential of automated image analysis on transcranial US.

Development of radiofrequency ultrasound based method for elasticity characterization using low frequency endogenous motion: phantom study

This paper presents developed radiofrequency (RF) ultrasound based strain elastography imaging method, which operates and could be adjusted in frequency domain. The method was verified by using agar-based tissue mimicking substitute. The phantom had 7 kPa stiffness background material and two inclusions of different stiffness 15 and 30 kPa. The displacements in the phantom material were induced by hand. The obtained strain contrast-to-noise ratio between the background material and two inclusions is 1.32 and 1.50 respectively. These results confirm the differentiation power of the method characterizing relative elasticity in-vitro.