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Vibration exercise (VE) has been suggested to improve muscle strength and power performance, due to enhanced neuromuscular demand. However, understanding of the most appropriate VE protocols is lacking, limiting the optimal use of VE in rehabilitation programs. In this study, the fatiguing effect of vibration at different frequencies was investigated by employing a force-modulation VE system. Twenty volunteers performed 12-s isometric contractions of the biceps brachii with a load consisting of a baseline force of 80% of their maximum voluntary contraction (MVC) and a superimposed sinusoidal force at 0 (control condition with no vibration), 20, 30, and 40 Hz. Mechanical fatigue was estimated by assessment of MVC decay after each task while myoelectric fatigue was estimated by analysis of multichannel electromyography (EMG) signals recorded during VE. EMG conduction velocity, spectral compression, power, and fractal dimension were estimated as indicators of myoelectric fatigue. Our results suggest vibration, in particular at 30 Hz, to produce a larger degree of fatigue as compared to control condition. These results motivate further research aiming at introducing VE in rehabilitation programs with improved training protocols.

This paper presents a noise-reconfigurable resistive feedback amplifier with current-reuse technique for fetal ECG monitoring. The proposed amplifier allows for both tuning of the noise level and changing the power consumption according to the signal properties, minimizing the total power consumption while satisfying all application requirements. The amplifier together with its amplitude detector and dynamical biasing circuit is implemented in a standard 0.18-μm CMOS process. Measurements demonstrate that the proposed current-reuse resistive feedback topology improves the power efficiency of the conventional resistive feedback amplifier, achieving at the same time a good noise efficiency factor (NEF =2.8) and an input impedance of 20 MΩ. The amplitude detector and the dynamical biasing circuit, which tunes the current in the amplifier according to the signal amplitude, save up to 40% of the total power consumption. The amplifier achieves a measured noise level of 0.34 μ Vrms in a 0.6-175-Hz band, consuming 6.3-μW power.

Angiogenesis plays a fundamental role in cancer growth and the formation of metastasis. Novel cancer therapies aimed at inhibiting angiogenic processes and/or disrupting angiogenic tumor vasculature are currently being developed and clinically tested. The need for earlier and improved cancer diagnosis, and for early evaluation and monitoring of therapeutic response to angiogenic treatment have led to the development of several imaging methods for in-vivo non-invasive assessment of angiogenesis. The combination of dynamic contrast-enhanced imaging with mathematical modeling of the contrast agent kinetics enables quantitative assessment of the structural and functional changes in the microvasculature that are associated with tumor angiogenesis. In this paper, we review quantitative imaging of angiogenesis with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), computed tomography (DCE-CT), and ultrasound (DCE-US).

Neoangiogenesis, which results in the formation of an irregular network of microvessels, plays a fundamental role in the growth of several types of cancer. Characterization of microvascular architecture has therefore gained increasing attention for cancer diagnosis, treatment monitoring and evaluation of new drugs. However, this characterization requires immunohistologic analysis of the resected tumors. Currently, dynamic contrast-enhanced ultrasound imaging (DCE-US) provides new options for minimally invasive investigation of the microvasculature by analysis of ultrasound contrast agent (UCA) transport kinetics. In this article, we propose a different method of analyzing UCA concentration that is based on the spatial distribution of blood flow. The well-known concept of Mandelbrot allows vascular networks to be interpreted as fractal objects related to the regional blood flow distribution and characterized by their fractal dimension (FD). To test this hypothesis, the fractal dimension of parametric maps reflecting blood flow, such as UCA wash-in rate and peak enhancement, was derived for areas representing different microvascular architectures. To this end, subcutaneous xenograft models of DU-145 and PC-3 prostate-cancer lines in mice, which show marked differences in microvessel density spatial distribution inside the tumor, were employed to test the ability of DCE-US FD analysis to differentiate between the two models. For validation purposes, the method was compared with immunohistologic results and UCA dispersion maps, which reflect the geometric properties of microvascular architecture. The results showed good agreement with the immunohistologic analysis, and the FD analysis of UCA wash-in rate and peak enhancement maps was able to differentiate between the two xenograft models (p <0.05).

OBJECTIVE: The role of angiogenesis in cancer growth has stimulated research aimed at non-invasive cancer detection by blood perfusion imaging. Recently, contrast ultrasound dispersion imaging was proposed as an alternative method for angiogenesis imaging. After the intravenous injection of an ultrasoundcontrast- agent bolus, dispersion can be indirectly estimated from the local similarity between neighboring time-intensity curves (TICs) measured by ultrasound imaging. Up until now, only linear similarity measures have been investigated. Motivated by the promising results of this approach in prostate cancer (PCa), we developed a novel dispersion estimation method based on mutual information, thus including nonlinear similarity, to further improve its ability to localize PCa.METHODS: First, a simulation study was performed to establish the theoretical link between dispersion and mutual information. Next, the method's ability to localize PCa was validated in vivo in 23 patients (58 datasets) referred for radical prostatectomy by comparison with histology.RESULTS: A monotonic relationship between dispersion and mutual information was demonstrated. The in-vivo study resulted in a receiver operating characteristic (ROC) curve area equal to 0.77, which was superior (p=0.21-0.24) to that obtained by linear similarity measures (0.74-0.75) and (p<0.05) to that by conventional perfusion parameters (0.70).CONCLUSION: Mutual information between neighboring TICs can be used to indirectly estimate contrast dispersion and can lead to more accurate PCa localization.SIGNIFICANCE: An improved PCa localization method can possibly lead to better grading and staging of tumors, and support focal-treatment guidance. Moreover, future employment of the method in other types of angiogenic cancer can be considered.

Item does not contain fulltext, INTRODUCTION: To overcome the limitations regarding transrectal ultrasound (TRUS)-guided biopsies in prostate cancer (PCa) detection, there is a focus on new imaging technologies. The Navigo system (UC-care, Israel) uses regular TRUS images and electrospatial monitoring to generate a 3D model of the prostate. The aim of this study was to compare cancer detection rates between the Navigo system and conventional TRUS, in patients without a history of PCa. METHODS: We performed a retrospective study by collecting data from all patients who underwent 12-core prostate biopsies from lateral peripheral zones between September 2013 and February 2015 at the Jeroen Bosch Hospital in 's-Hertogenbosch (Netherlands). RESULTS: A total of 325 patients met our inclusion criteria. 77.8 % of biopsy sessions were performed using the Navigo system. There was no statistically significant difference in PCa detection (39.9 vs 46.2 % with Navigo system and TRUS, respectively). Using the Navigo system for taking prostate biopsies proved not to be associated with the presence of PCa at biopsy, likewise for clinically significant PCa and for both subgroups. LIMITATIONS: The limitations of the study include its retrospective design, the limited number of patients in the conventional TRUS group, the statistically significant different number of biopsy sessions and the ones performed by an advanced physician in both groups. CONCLUSION: In our study, there is no added value of 3D TRUS using Navigo system compared to conventional 2D TRUS regarding PCa detection in biopsy-naive men and men with prior negative biopsy.

Decrease in muscle-fiber conduction velocity (MFCV) during sustained contraction has been widely accepted as myoelectric manifestation of muscle fatigue. Several methods have been proposed in the literature for MFCV estimation by analysing surface electromyography (EMG), e.g., cross-correlation (CC) function and maximum likelihood (ML). However, for all the available methods, windowing of the EMG signal and computationally demanding calculations are required, limiting the possibility to continuously monitor muscle fatigue in real time. In the present study, an adaptive scheme is proposed that permits real-time estimation of MFCV. The proposed scheme is based on a delay-locked loop (DLL). A second-order loop is adopted to track the delay variation over time. An error filter is employed to approximate a ML estimation in case of colored noise. Furthermore, the DLL system is extended for multichannel CV estimation. The performance of the proposed method is evaluated by both dedicated simulations and real EMG signals. Our results show the accuracy of the proposed method to be comparable to that of the ML method for much lower (1/40) computational complexity, especially suited for real-time MFCV measurements. Use of this method can enable new studies on myoelectric fatigue, possibly leading to new insight on the underlying physiological processes.

Fetal heart rate (fHR) monitoring is usually performed by Doppler ultrasound (US) techniques. For reliable fHR measurements it is required that the fetal heart is located within the US beam. In clinical practice, clinicians palpate the maternal abdomen to identify the fetal presentation and then the US transducer is fixated on the maternal abdomen where the best fHR signal can be obtained. Finding the optimal transducer position is done by listening to the strength of the Doppler audio output and relying on a signal quality indicator of the cardiotocographic (CTG) measurement system. Due to displacement of the US transducer or displacement of the fetal heart out of the US beam, the fHR signal may be lost. Therefore, it is often necessary that the obstetrician repeats the tedious procedure of US transducer positioning to avoid long periods of fHR signal loss. An intuitive US transducer positioning aid would be highly desirable to increase the work flow for the clinical staff. In this paper, the possibility to determine the fetal heart location with respect to the transducer by exploiting the received signal power in the transducer elements is shown. A commercially available US transducer used for fHR monitoring is connected to an US open platform, which allows individual driving of the elements and raw US data acquisition. Based on the power of the received Doppler signals in the transducer elements, the fetal heart location can be estimated. A beating fetal heart setup was designed and realized for validation. The experimental results show the feasibility of estimating the fetal heart location with the proposed method. This can be used to support clinicians in finding the optimal transducer position for fHR monitoring more easily.

We report on the first study demonstrating the ability of a recently-developed, contrast-enhanced, ultrasound imaging method, referred to as cumulative phase delay imaging (CPDI), to image and quantify ultrasound contrast agent (UCA) kinetics. Unlike standard ultrasound tomography, which exploits changes in speed of sound and attenuation, CPDI is based on a marker specific to UCAs, thus enabling dynamic contrast-specific ultrasound tomography (DCS-UST). For breast imaging, DCS-UST will lead to a more practical, faster, and less operator-dependent imaging procedure compared to standard echo-contrast, while preserving accurate imaging of contrast kinetics. Moreover, a linear relation between CPD values and ultrasound second-harmonic intensity was measured (coefficient of determination = 0.87). DCS-UST can find clinical applications as a diagnostic method for breast cancer localization, adding important features to multi-parametric ultrasound tomography of the breast.

Background Pulmonary transit time (PTT) is an indirect measure of preload and left ventricular function, which can be estimated using the indicator dilution theory by contrast-enhanced ultrasound (CEUS). In this study, we first assessed the accuracy of PTT-CEUS by comparing it with dynamic contrast-enhanced MRI (DCE-MRI). Secondly, we tested the hypothesis that PTT-CEUS correlates with the severity of heart failure, assessed by MRI and NT-proBNP. Methods and Results Twenty patients referred to our hospital for cardiac resynchronization therapy (CRT) were enrolled. DCE-MRI, CEUS, and NT-proBNP measurements were performed within an hour. Mean transit time (MTT) was obtained by estimating the time evolution of indicator concentration within regions of interest drawn in the right and left ventricle in videoloops of DCE-MRI and CEUS. PTT was estimated as the difference of the left and right ventricular MTT. Normalized PTT (nPTT) was obtained by multiplication of PTT with the heart rate. Mean PTT-CEUS was 10.5±2.4 s and PTT-DCE-MRI 10.4±2.0 s (P < 0.88). The correlations of PTT and nPTT by CEUS and DCE-MRI were strong; r=0.75 (P < 0.0001) and r=0.76 (P = 0.0001), respectively. Bland Altman analysis revealed a bias of 0.1 s for PTT. nPTT-CEUS correlated moderately with left ventricle volumes. PTT-CEUS and nPTT-CEUS correlated significantly with NT-proBNP; r=0.54 (P < 0.05) and r=0.68 (P < 0.01), respectively. Conclusions (n)PTT-CEUS shows strong agreement with that by DCE-MRI. Given the good correlation with NT-proBNP level, (n)PTT-CEUS may provide a novel, clinically feasible measure to quantify the severity of heart failure.

Motion artifacts (MA) have long been a problem in biopotential measurements. Adaptive filtering is widely used for optimal noise removal in many biomedical applications. However, the existing adaptive filtering methods involve the use of additional sensors, limiting the applicability of adaptive filtering for MA reduction. In the present study, a novel adaptive filtering method without need for additional sensors is proposed. In biopotential measurements, movement of the electrodes and their leads may cause variations not only in the skin and half-cell potential (motion artifacts), but also in the electrode-skin impedance. Such impedance variations may also cause power-line interference modulation (PLIM), resulting in additional spectral components around the power-line interference (PLI) in the frequency domain. Demodulation of the PLI may reflect the movement-induced electrode-skin impedance variation, and can therefore represent a reference signal for the adaptive filter. Preliminary validation on ECG measurements with seven volunteers showed a high correlation coefficient (R = 0.97) between MA and PLIM, and excellent MA removal by the proposed adaptive filter, possibly leading to improved analysis of biopotential signals.

Numerous age-related pathologies affect the prostate gland, the most menacing of which is prostate cancer (PCa). The diagnostic tools for prostate investigation are invasive, requiring biopsies when PCa is suspected. Novel dynamic contrast-enhanced ultrasound (DCE-US) imaging approaches have been proposed recently and appear promising for minimally invasive localization of PCa. Ultrasound imaging of the prostate is traditionally performed with a transrectal probe because the location of the prostate allows for high-resolution images using high-frequency transducers. However, DCE-US imaging requires lower frequencies to induce bubble resonance and, thus, improve contrast-to-tissue ratio. For this reason, in this study we investigate the feasibility of quantitative DCE-US imaging of the prostate via the abdomen. The study included 10 patients (age = 60.7 ± 5.7 y) referred for a needle biopsy study. After having given informed consent, patients underwent DCE-US with both transabdominal and transrectal probes. Time–intensity contrast curves were derived using both approaches and their model-fit quality was compared. Although further improvements are expected by optimization of the transabdominal settings, the results of transabdominal and transrectal DCE-US are closely comparable, confirming the feasibility of transabdominal DCE-US; transabdominal curve fitting revealed an average determination coefficient r2 = 0.91 (r2 > 0.75 for 78.6% of all prostate pixels) compared with r2 = 0.91 (r2 > 0.75 for 81.6% of all prostate pixels) by the transrectal approach. Replacing the transrectal approach with more acceptable transabdominal scanning for prostate investigation is feasible. This approach would improve patient comfort and represent a useful option for PCa localization and monitoring. Key Words Prostate cancer; Contrast-enhanced ultrasound; Ultrasound contrast agents; Dilution curve; Transabdominal ultrasound; Transrectal ultrasound; Perfusion

Currently, nonradical treatment for prostate cancer is hampered by the lack of reliable diagnostics. Contrastultrasound dispersion imaging (CUDI) has recently shown great potential as a prostate cancer imaging technique. CUDI estimates the local dispersion of intravenously injected contrast agents, imaged by transrectal dynamic contrast-enhanced ultrasound (DCE-US), to detect angiogenic processes related to tumor growth. The best CUDI results have so far been obtained by similarity analysis of the contrast kinetics in neighboring pixels. To date, CUDI has been investigated in 2-D only. In this paper, an implementation of 3-D CUDI based on spatiotemporal similarity analysis of 4-D DCE-US is described. Different from 2-D methods, 3-D CUDI permits analysis of the entire prostate using a single injection of contrast agent. To perform 3-D CUDI, a new strategy was designed to estimate the similarity in the contrast kinetics at each voxel, and data processing steps were adjusted to the characteristics of 4-D DCE-US images. The technical feasibility of 4-D DCE-US in 3-D CUDI was assessed and confirmed. Additionally, in a preliminary validation in two patients, dispersion maps by 3-D CUDI were quantitatively compared with those by 2-D CUDI and with 12-core systematic biopsies with promising results.

The objective was to study the effect of whole-body vibration (WBV) on strength, balance and pain in patients with peripheral neuropathies and to consider its significance for the rehabilitation of patients suffering from chemotherapy-induced peripheral neuropathy (CIPN). Using a broad search strategy, PubMed was searched for clinical trials on WBV interventions aimed at improving strength, balance or pain in patients with peripheral neuropathies, which were published in English until 5th June 2014. The search was performed by the first author and generated a total of 505 results, which yielded 5 articles that met the inclusion criteria, being studies: i) published in English; ii) involving adult human subjects’ peripheral neuropathies; iii) evaluating the effect of WBV as a therapeutic intervention; and iv) reporting findings for at least one of the following outcomes: strength, balance or pain. Methodological quality of included studies was assessed independently by first and second author, using the physiotherapy evidence database scale. The overall methodological quality of included studies was low. Two studies found a beneficial effect of WBV on neuropathic pain, but another study failed to find the same effect. One study found significant improvements in both muscle strength and balance, while another study found improvements only in some, but not all, of the applied tests to measure muscle strength and balance. The results of this literature search suggest insufficient evidence to assess the effectiveness for the effects of WBV on neuropathic pain, muscle strength and balance in patients with peripheral neuropathies. More high-quality trials are needed to guide the optimization of rehabilitation programs for cancer survivors with CIPN in particular.

Purpose : Surface electromyography (EMG) has been widely used to measure neuromuscular activity during vibration exercise (VE) to investigate the underlying mechanisms elicited by VE. However, the EMG spectrum recorded during VE shows sharp peaks at the vibration frequency whose interpretation remains controversial. Some authors considered those peaks as a result of motion artifacts, while others interpreted them as due to vibration-induced neuromuscular activity. The aim of the present study is to clarify the nature of those sharp peaks observed during VE. Methods : Three independent EMG measurements were performed during VE: in vitro (IVT), in vivo at rest ( IVV R ), and in vivo during voluntary contraction ( IVV C ). The amplitudes of the EMG vibration frequency components ( A VF ) were extracted for all measurements. The conduction velocity (CV) of the vibration frequency components and the full EMG spectrum were also estimated during voluntary contraction. Results : Our spectrum analysis revealed small A VF for IVT and IVV R , accounting for only 3.3 and 7.6 % of that obtained from IVV C . Moreover, the CV estimation indicated the EMG vibration components to propagate along the muscle fiber with CV ˜ 6.5 m/s, comparable to the CV estimated using the full EMG spectrum (5.7 m/s). Conclusion : We may therefore conclude that the sharp spectral peaks observed during VE are mainly due to vibration-induced muscle activity rather than motion artifacts.