Fast and Highly Sensitive Ionic-Polymer-Gated WS2 -Graphene Photodetectors.

The combination of graphene with semiconductor materials in heterostructure photodetectors enables amplified detection of femtowatt light signals using micrometer-scale electronic devices. Presently, long-lived charge traps limit the speed of such detectors, and impractical strategies, e.g., the use of large gate-voltage pulses, have been employed to achieve bandwidths suitable for applications such as video-frame-rate imaging. Here, atomically thin graphene-WS2 heterostructure photodetectors encapsulated in an ionic polymer are reported, which are uniquely able to operate at bandwidths up to 1.5 kHz whilst maintaining internal gain as large as 106 . Highly mobile ions and the nanometer-scale Debye length of the ionic polymer are used to screen charge traps and tune the Fermi level of the graphene over an unprecedented range at the interface with WS2 . Responsivity R = 106 A W-1 and detectivity D* = 3.8 × 1011 Jones are observed, approaching that of single-photon counters. The combination of both high responsivity and fast response times makes these photodetectors suitable for video-frame-rate imaging applications.

The role of N terminal pro-brain natriuretic peptide in the evaluation of left ventricular diastolic dysfunction: correlation with echocardiographic indexes in hypertensive patients.

UNLABELLED: The utility of N-Terminal pro Brain Natriuretic Peptide (NT-proBNP) and Brain Natriuretic Peptide (BNP) for detecting left ventricular (LV) diastolic dysfunction in hypertensive patients without heart failure symptoms is unclear. In this study, we investigated the relation between NT-proBNP plasma levels and LV diastolic dysfunction in hypertensive patients without systolic dysfunction. METHOD: We studied 40 ambulatory patients (26 women, mean age 52 +/- 5) with controlled hypertension. LV diastolic function was assessed with conventional Doppler, by means of mitral inflow and with tissue Doppler echocardiography by means of mitral annulus. The ratio of early diastolic transmitral E wave velocities to tissue Doppler mitral annulus early diastolic E' wave velocities (E/E'), was used to detect LV filling pressures. Patients were divided in three groups according to E/E' ratios < 10 (group I), E/E' ratios ''between'' 10 and 15 (group II) and E/E' ratios > 15 (group III). Plasma concentrations of NT-proBNP were measured by electro chemiluminescence's immunoassay. RESULTS: The NT-proBNP blood levels were positively correlated significantly with E/E' ratio (r = 0.80, P < 0.0001). Patients with elevated LV end diastolic pressure (LVEDP), defined as E/E' > 15 (n = 8) had highest NT-proBNP (203 +/- 75 pg/ml) levels. E/E' 10 to 15 group (n = 16) had a mean NT-proBNP level of 71 +/- 26 pg/ml, and those with E/E' < 10 (n = 16) had 39 +/- 20 pg/ml. A NT-proBNP value of 119 pg/ml had a sensitivity of 87%, a specificity of 100% for predicting E/E' > 15. CONCLUSION: The assessment of the blood concentration of NT-proBNP is of potential value for identification of those patients with hypertension to detect early cardiovascular changes, especially LV diastolic dysfunction.

Correlation between N-terminal pro B-natriuretic peptide and ultrasonic backscatter: implications for diastolic dysfunction in hypertension.

OBJECTIVE: This study was designed to determine how N-terminal pro brain-natriuretic peptide (NT-proBNP) levels correlate with cyclic variation of integrated backscatter (CVIBS) as a reflection of abnormal diastolic function in hypertension. PATIENTS: Forty essentially hypertensive patients were studied. CVIBS values were obtained from the septal wall in the parasternal long-axis view. Twelve had normal diastolic function, 18 had impaired relaxation, and 10 had pseudonormal pattern. RESULTS: Patients with normal diastolic function had a mean NT-proBNP concentration of 34 +/- 17 pg/ml and a mean CVIBS value of 7.1 +/- 0.9 dB; those with impaired relaxation had a mean NT-proBNP concentration of 71 +/- 25 pg/ml and a mean CVIBS value of 6.7 +/- 1.1 dB. Patients with pseudonormal pattern had the highest NT proBNP levels (206 +/- 75 pg/ml) and lowest CVIBS values (5.7 +/- 0.9 dB). An NT-proBNP value of 62 pg/ml had a sensitivity of 83% and a specificity of 91%; a CVIBS value of 7.2 dB had a sensitivity of 83.3% and a specificity of 66.7% for detecting diastolic dysfunction. An NT-proBNP value of 120 pg/ml had a sensitivity of 76% and a specificity of 96%; a CVIBS value of 6.1 dB had a sensitivity of 87.5% and a specificity of 75% for detecting severe diastolic dysfunction. A close correlation was found between the NT-proBNP and CVIBS values (r: 0.54, P < 0.05). CONCLUSION: Combinative use of NT-proBNP and CVIBS can detect the presence of diastolic abnormalities on echocardiography. A good correlation was found between the NT-proBNP and CVIBS values in detecting diastolic dysfunction in essentially hypertensive patients.

Ultrasound tissue characterization by integrated backscatter for analyzing Fluorouracil induced myocardial damage.

BACKGROUND: 5-Fluorouracil (5-FU) cardiotoxicity is a well-known clinical phenomenon whose pathophysiology remains controversial. Cyclic variation of integrated backscatter (CVIBS) assesses acoustic properties of myocardium that may reflect both contractility and structural changes. The aim of this study was to evaluate CVIBS alterations in cancer patients under high-dose leucovorin and infusional 5-FU (HDLV5FU) chemotherapy. METHOD: We prospectively evaluated 37 cancer patients under HDLV5FU treatment. Transthoracic echocardiography and CVIBS were performed at the 0th, 48th hours, and on day 15 of the first cycle. The parasternal long-axis view was preferred to obtain the image of integrated backscatter and mainly two regions of interest--interventricular septum (IVS) and posterior wall (PW)--were used. RESULTS: Clinical cardiotoxicity was observed in two patients. No significant differences were detected in pre- and posttreatment conventional echocardiography evaluations. However, both the IVS (9.3 +/- 1.0 to 8.1 +/- 1.2 dB, P < 0.001) and PW (9.1 +/- 0.7 to 7.8 +/- 0.9 dB, P < 0.001) CVIBS values significantly decreased in all patients. All values were returned to pretreatment levels (9.2 +/- 0.9 dB in the CVIBS-IVS and 8.9 +/- 0.6 dB in CVIBS-PW, respectively) on day 15 after the treatments. CONCLUSION: This study suggests that HDLV5FU may cause acute transient alterations in CVIBS values in the absence of clinical symptoms and signs of cardiotoxicity. The clinical value of CVIBS should be further studied in patients receiving 5-FU-based therapy.

Microalbuminuria is associated with reduced cardiac cyclic variation of integrated backscatter signal in severe hypertension.

OBJECTIVE: Microalbuminuria (MA) as a marker of systemic vascular disease and left ventricular (LV) hypertrophy is associated with increased cardiovascular mortality and morbidity in patients with essential hypertension. The aim of this study was to investigate changes in cardiac cycle-dependent variation of integrated backscatter signals (CVIBS) in hypertensive patients with MA. METHODS: Randomly selected 60 hypertensive patients (mean age 51 +/- 8) with uncontrolled blood pressure (BP) (>/=130 mmHg systolic and/or 85 mmHg diastolic) were included. All patients underwent urinary albumin excretion (UAE) measurements, 24-hour ambulatory BP monitoring, and LV echocardiographic examination. UAE was measured in two separate 24-hour urine collection and mean of two values was taken into consideration. Normotensive 20 healthy subjects served as controls. CVIBS values were obtained from mid-anteroseptal, mid-posterolateral, and mid-inferior areas at the papillary muscle level in the parasternal short-axis view. CVIBS was defined as the difference in integrated backscatter values between systole and diastole. CVIBS values in MA positive patients were compared with the values in MA negative patients and control subjects. RESULTS: Twelve patients had MA (UAE 30 to 300 mg/day) while 48 patients had normal UAE (<30 mg/day). The wall thickness (at septum and posterior) and left ventricular mass index (LVMI) values were all significantly higher in hypertensive patients with MA (P < 0.01). The CVIBS values in MA positive group were significantly lower than the CVIBS values both in MA negative hypertensive patients and control subjects (P < 0.01). CONCLUSION: This study demonstrates that in hypertensive patients a high LVMI is associated with reduced CVIBS values and MA appears to be a marker of hypertrophy.

Novel approach to measure myocardial performance index: pulsed-wave tissue Doppler echocardiography.

A simple, reproducible, noninvasive myocardial performance index (MPI) for the assessment of overall cardiac function has been described previously. The purpose of this study was to compare the MPI obtained by pulse Doppler method with the MPI obtained by tissue Doppler echocardiography (TDE) in normal subjects and patients with dilated cardiomyopathy (DCMP). Fifteen patients with DCMP and 15 healthy subjects were included. In order to calculate MPI by TDE, isovolumetric contraction (IVCT), relaxation time (IVRT), and ejection time (ET) were measured at two different sites of mitral annulus: septum and lateral. MPI was calculated by dividing the sum of IVCT and IVRT by ET at each site of measurement. The mean MPI value was found by dividing the sum of these MPI values into two. The same parameters were measured using the mitral inflow and left ventricular outflow velocity time intervals in pulsed Doppler method. At all sites measured, MPI by TDE correlated well with conventional MPI both in healthy subjects and patients with DCMP. The highest correlation was observed in mean values of MPI by TDE:r = 0.94, P < 0.0001in healthy subjects; andr = 0.95, P < 0.0001in patients with DCMP. In conclusion, this study clearly demonstrated that MPI could be measured by TDE and it correlated well with conventional MPI in normal and diseased heart.

Value of measuring myocardial performance index by tissue Doppler echocardiography in normal and diseased heart.

Myocardial performance index (MPI) is a simple and reproducible method for the assessment of overall cardiac function. In this study, we evaluated the applicability and usefulness of pulsed-wave tissue Doppler echocardiography (TDE) as a tool to calculate MPI in comparision with a conventional Doppler method. Twenty-five patients with previous myocardial infarction (MI) and 15 healthy subjects were included. In order to calculate MPI by TDE, isovolumetric contraction time (IVCT), isovolumetric relaxation time (IVRT), and ejection time (ET) were measured at four different sites in the mitral annulus: septum, lateral, anterior, and inferior. MPI was calculated by dividing the sum of IVCT and IVRT by ET at each site of measurement. The mean MPI value was found by dividing the sum of these MPI values into four. The same parameters were measured using the mitral inflow and left ventricular outflow velocity time intervals by a conventional method. MPI by TDE correlated well with conventional MPI in healthy subjects (r = 0.81, P < 0.0001). Although it continued to be statistically significant, the correlation between the two methods of measuring MPI, TDE and conventional, in patients with previous MI was not as high as it was in healthy individuals (P < 0.001, r = 0.62). This is due to the lesser degree of correlation between IVRT and IVCT values obtained by TDE and the conventional method (r = 0.49, P < 0.05; r = 0.56, P < 0.05; respectively). In conclusion, this study has demonstrated that MPI could be measured by tissue Doppler and that it correlated well with conventional MPI. Moreover, MPI by TDE has the advantage of assessing both regional and global myocardial performance.