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PubMed1998

Feedback systems for nontraditional medicines: a case for the signal flow diagram.

The signal flow diagram is a graphic method used to represent complex data that is found in the field of biology and hence the field of medicine. The signal flow diagram is analyzed against a table of data and a flow chart of data and evaluated on the clarity and simplicity of imparting this information. The data modeled is from previous clinical studies and nontraditional medicine from Africa, China, and South America. This report is a development from previous presentations of the signal flow diagram.1-4

Complementary Therapies↗

PubMed1999

Influence of instrument settings on flow signal and background noise in power Doppler US. An experimental study using a flow phantom with hyperechoic background.

OBJECTIVE: To determine the influence of various power Doppler instrument settings on intensities of flow signal and background noise in flow with a tissue-equivalent phantom. METHODS: Power Doppler images were obtained with changing wall filter level (low, medium, high, and maximum), pulse repetition frequency (PRF; 500, 700, 1000, 1500, 3000, and 6000 Hz), and Doppler gain (60%, 70%, 80%, 90%, and 100%) at different flow velocities (13.3, 26.5, and 49.8 cm/sec). To make a quantitative comparison of different settings, the authors measured the intensities of flow signal and background noise in obtained power Doppler images using the scanner and a computer program, calculated signal-to-noise difference (SND; intensity of flow signal--intensity of background noise), and evaluated the relation between SND and power Doppler settings. RESULTS: The intensities of flow signal and background noise were proportional to flow velocity and power Doppler gain but were inversely proportional to PRF and wall filter level. At constant wall filter level (medium), changes of PRF and Doppler gain to the same directions resulted in a high SND. At constant PRF (1000 Hz), changes of wall filter and Doppler gain to the same directions also resulted in a high SND. However, at constant Doppler gain (80%), a high SND was obtained with changing wall filter level and PRF to the opposite directions. CONCLUSIONS: Three Doppler instrument settings--wall filter level, pulse repetition frequency, and Doppler gain--have reciprocal influences on SND.

Blood Flow Velocity↗

PubMed1983

[Backward flow signal in the left atrium studied by Doppler echocardiography. Differentiation from mitral regurgitation].

A backward flow signal in the left atrium masquerading as mitral regurgitation was studied by a pulsed Doppler method. The subjects consisted of 20 normal volunteers, 12 cases with mitral valve prolapse syndrome, five cases with rheumatic mitral regurgitation, five cases with lone atrial fibrillation, four cases with asymmetric septal hypertrophy and three cases with the Björk-Shiley tilting disc valve in the mitral position. In two-dimensional echocardiography combined with pulsed Doppler method, a Doppler signal was recorded by locating a sample volume in the left atrium. In all of the cases with mitral valve prolapse syndrome and the cases with the prosthetic valve as well as in all of the normal subjects, the backward flow signal was observed in the left atrium. In three cases with mitral valve prolapse syndrome, it was differentiated from a transvalvular regurgitant flow signal. In all cases with rheumatic mitral regurgitation, the backward flow signal was masked by a turbulent flow signal representing regurgitation. In cases with mitral stenosis, the backward flow signal was scarcely recognized. The duration of the backward flow signal had no relationship with heart rate. The histogram of incidence on the scale of R-R interval revealed normal distribution with a mean value of 0.24 sec (+/- 0.09 sec). Therefore, in cases with tachycardia, the backward flow signal was seen throughout systole. The peak backward flow velocity of Doppler signals was correlated (r = 0.71, p less than 0.01) with the peak forward flow velocity in diastole. The faint backward flow signal seen in cases with mitral stenosis and post-extrasystolic potentiation of the backward flow signal were suggestive of the foregoing relationship. The mechanism producing the backward flow was postulated as a water hammer phenomenon caused by closure of the mitral valve.

Adult↗

PubMed2003

Residual flow signals predict complete recanalization in stroke patients treated with TPA.

BACKGROUND: Residual blood flow around thrombus prior to treatment predicts success of coronary thrombolysis. The authors aimed to correlate the presence of residual flow signals in the middle cerebral artery (MCA) with completeness of recanalization after intravenous tissue plasminogen activator (TPA). METHODS: The authors studied consecutive patients treated with intravenous TPA therapy who had a proximal MCA occlusion on pretreatment transcranial Doppler (TCD). Patients were continuously monitored for 2 hours after TPA bolus. Absent residual flow signals correspond to the thrombolysis in brain ischemia (TIBI) 0 grade, and the presence of residual flow signals was determined as TIBI 1-3 flow grades. Complete recanalization was defined as flow improvement to TIBI grades 4-5. RESULTS: Seventy-five patients with a proximal MCA occlusion had median pre-bolus NIHSS 16 (85% with > or = 10 points). TPA bolus was given at 141 +/- 56 minutes (median 120 minutes). Complete recanalization was observed in 25 (33%), partial in 23 (31%), and no early recanalization was seen in 27 (36%) patients within 2 hours after TPA bolus. Only 19% with absent residual flow signals (TIBI grade 0, n = 26) on pretreatment TCD had complete early recanalization. If pretreatment TCD showed the presence of any residual flow (TIBI 1-3, n = 49), 41% had complete recanalization within 2 hours of TPA bolus (P = .03). CONCLUSIONS: Patients with detectable residual flow signals before IV TPA bolus are twice as likely to have early complete recanalization. Those with no detectable residual flow signals have less than 20% chance for complete early recanalization with intravenous TPA and may be candidates for intra-arterial therapies.

Aged↗

PubMed1992

Value of acceleration flow signals proximal to the leaking orifice in assessing the severity of prosthetic mitral valve regurgitation.

To test the value of acceleration flow signals proximal to the leaking orifice in assessing the severity of prosthetic mitral valve regurgitation, 39 consecutive patients undergoing left ventriculography were examined by Doppler color flow imaging. Acceleration flow signals proximal to the regurgitant orifice were detected in 27 of the 31 patients who had prosthetic mitral regurgitation by left ventriculography (sensitivity 87%). All four patients without acceleration flow signals had mild prosthetic mitral regurgitation by angiography. No acceleration flow signals were detected in any patient without prosthetic regurgitation by left ventriculography (specificity 100%). Individual values of the maximal area of acceleration flow signals obtained from three orthogonal planes in seven patients with mild prosthetic mitral regurgitation by angiography ranged from 0 to 17 mm2 (mean 4 +/- 6). In 8 patients with moderate prosthetic mitral regurgitation by angiography, the maximal area of acceleration flow signals ranged from 21 to 58 mm2 (mean 33 +/- 15), whereas the maximal area of acceleration flow signals in 16 patients with severe prosthetic regurgitation ranged from 20 to 173 mm2 (mean 102 +/- 41). The maximal area of the acceleration flow signals from three planes correlated well with the angiographic grade of prosthetic mitral regurgitation. There was a significant difference in the maximal area of acceleration flow signals between mild and moderate (p less than 0.001), moderate and severe (p less than 0.001) and mild and severe (p less than 0.001) prosthetic mitral regurgitation. Thus, measurement of acceleration flow signals by Doppler color flow imaging is useful in assessing the severity of prosthetic mitral regurgitation.

Bioprosthesis↗

PubMed1990

Metabolic control analysis. An application of signal flow graphs.

In this paper the method of signal-flow graphs is used for calculating the Control Coefficients of metabolic pathways in terms of enzyme elasticities. The method is applied to an unbranched pathway (a) without feedback or feedforward regulation and (b) with feedback inhibition of the first enzyme by the last variable metabolite. It is shown that, by using a signal-flow graph, the control structure of a metabolic pathway can be represented in a graphical manner directly from the configuration of the pathway, without the necessity of writing the governing equations in a matrix form. From a signal-flow graph the various Control Coefficients can be evaluated in an easy and straightforward fashion without recourse to matrix inversion or other algebraic techniques. A signal-flow graph also provides a visual framework for analysing the cause-effect relationships of the individual enzymes.

Chemical Phenomena↗

PubMed1999

Cavernous sinus and inferior petrosal sinus flow signal on three-dimensional time-of-flight MR angiography.

BACKGROUND AND PURPOSE: Venous flow signal in the cavernous sinus and inferior petrosal sinus has been shown on MR angiograms in patients with carotid cavernous fistula (CCF). We, however, identified flow signal in some patients without symptoms and signs of CCF. This review was performed to determine the frequency of such normal venous flow depiction at MR angiography. METHODS: Twenty-five 3D time-of-flight (TOF) MR angiograms obtained on two different imaging units (scanners A and B) were reviewed with attention to presence of venous flow signal in the cavernous sinus or inferior petrosal sinus or both. Twenty-five additional MR angiograms were reviewed in patients who had also had cerebral arteriography to document absence of CCF where venous MR angiographic signal was detected, as well as to gain insight into venous flow patterns that might contribute to MR angiographic venous flow signal. Differences in scanning technique parameters were reviewed. RESULTS: Nine (36%) of the 25 MR angiograms obtained on scanner A but only one (4%) of the 25 obtained on scanner B showed flow signal in the cavernous or inferior petrosal sinus or both in the absence of signs of CCF. On review of 25 patients who had both MR angiography and arteriography, three patients with venous signal at MR angiography failed to exhibit CCF at arteriography. CONCLUSION: Identification of normal cavernous sinus or inferior petrosal sinus venous signal on 3D TOF MR angiograms may occur frequently, and is probably dependent on technical factors that vary among scanners. The exact factors most responsible, however, were not elucidated by this preliminary review.

Aged↗

PubMed1993

Rate of successful recording of blood flow signals in the middle cerebral artery using transcranial Doppler sonography.

BACKGROUND AND PURPOSE: To assess the usefulness of transcranial Doppler sonography, we investigated the rate of blood flow signal recording failure in the middle cerebral artery in Japanese subjects. Furthermore, we studied the effect of increased emitted power on the rate of successful recording in some of the patients in whom recording failure had been detected at the standard transducer power of 100 mW/cm2. METHODS: To evaluate the rate of successful recording, we measured blood flow signals in 597 patients (age range, 16 to 89 years) for screening of cerebrovascular disease by using a 2-MHz range-gated, pulsed-wave Doppler instrument at the standard transducer power. In 18 elderly patients with recording failure at the standard power, we assessed the effect of increased emitted power of 400 mW/cm2 on flow signal recording. RESULTS: Blood flow signals were recorded in 920 (77.1%) of the 1194 middle cerebral arteries of the 597 patients studied. The rate of successful recording of bilateral middle cerebral artery flow signals (70.9%; 423 of 597 patients) decreased with age, especially in females (17.0% in women aged 70 years or older). In 12 of 18 elderly patients with recording failure at the standard power, blood flow signals could be detected at the increased emitted power of 400 mW/cm2. CONCLUSIONS: The rate of successful recording of blood flow signals in Japanese subjects decreases with advancing age, especially in females. Increasing the emitted power markedly improves the successful recording rate.

Adolescent↗

PubMed2005

Comparison in values of color flow signals and vascular resistance of synovial vascularity demonstrated by Doppler sonography between knee and metacarpophalangeal joints of patients with rheumatoid arthritis.

Synovial vascularity of 12 patients with rheumatoid arthritis (RA) was examined by Doppler sonography for color flow signals and vascular resistance on knee joints and metacarpophalangeal (MCP) joints, and the results were compared with each other and with C-reactive protein (CRP) levels of the patients. A significant correlation was observed between knee resistance index (RI) and MCP-RI (P = 0.0140), but not between knee color flow signals and MCP color flow signals (P = 0.1029). A significant correlation was also observed between knee color flow signals and knee RI (P = 0.0107), and knee pulsatility index (PI) (P = 0.0146). On the other hand, no correlation was observed between MCP color flow signals and MCP-RI (P = 0.828), and MCP-PI (P = 0.434). There was no significant correlation between CRP levels and grades of color flow signals, RI, and PI for both knee and MCP joints. Doppler sonographic evaluation of RI, especially knee RI, could be a useful marker for estimating synovial inflammation in RA patients.

Journal Article↗

PubMed1995

Technical note: comparison of colour Doppler energy sonography with conventional colour Doppler sonography in detection of flow signal in peripheral renal transplant vessels.

The technical advantage of colour Doppler energy sonography (CDE) results in a higher sensitivity for blood flow detection than in conventional colour Doppler sonography (CDI). We compared the efficiency of CDE versus CDI in the detection of blood flow signals in asymptomatic patients after renal transplantation. 10 asymptomatic voluntary patients after renal transplantation were evaluated with CDI and subsequently with CDE by two examiners. Filter, scale and gate setting were kept constant, the Doppler gain was increased individually in every patient until background noise just did not derange the image. The assessment of blood flow signal was done using a self defined score system. CDI showed Doppler signal in the interlobar vessels in all 10 patients and blood flow signal in arcuate arteries and adjacent portions of interlobular vessels in nine of 10 patients. We were not able to detect blood flow related signal in the more peripheral medullary and cortical vessels. CDE obtained blood flow signal in interlobar and interlobular vessels in all patients. In addition, Doppler signal was observed in all patients in small medullary and cortical vessels. CDE increases detection of blood flow related signal in peripherally located small medullary and cortical vessels. There was no improvement in the evaluation of blood flow in interlobar vessels but marked improvement in blood flow detection in small peripherally located vessels. CDE cannot completely replace CDI in the sonographic evaluation of vascular complications in renal transplants, but should be used as an additional measure to rule out pathology in small peripheral renal vessels.

Adult↗

PubMed1986

Intravascular signal in MR imaging: use of phase display for differentiation of blood-flow signal from intraluminal disease.

Intravascular signal from flowing blood is frequently observed on magnetic resonance (MR) images and may be indistinguishable from partial or complete vascular occlusion caused by thrombus or tumor. With a phase-display reconstruction method, qualitative assessment of large-vessel patency within the abdomen was undertaken in 15 healthy subjects and 12 patients with angiographically or surgically documented intravascular thrombus or tumor. Computed tomographic (CT) scans were available in all patients for correlation. MR studies were performed with a multisection spin-echo pulse sequence and two-dimensional Fourier transform spatial encoding. Data acquired from a single sequence was reconstituted in two ways to provide both routine anatomic images and a pictorial representation of large-vessel flow on a phase-sensitive image. With this method, reliable and easy differentiation of intraluminal thrombus and tumor from blood flow signal within large vessels was achieved. Information from these phase-display images compared favorably with findings from angiography and contrast-enhanced CT in the determination of luminal patency and obstruction.

Blood Circulation↗

PubMed1998

Color Doppler ultrasound pulsatile flow signals of thoracic lesions: comparison of lung cancers and benign lesions.

Color Doppler ultrasound (US) was performed in 153 patients (including 102 with lung cancer and 51 with benign lesions) to assess pulsatile flow signals in thoracic lesions. The values of resistive index (RI) and pulsatility index (PI) of color Doppler US pulsatile flow signals in lung cancers and benign lesions were measured, analyzed, and compared. In the enrolled 153 patients with thoracic lesions, 61 lung cancers and 34 benign lesions had detectable color Doppler US pulsatile flow signals, and lung cancers had lower RI and PI values than benign lesions (RI: 0.70+/-0.03 vs. 0.79+/-0.04, p < 0.05; PI: 1.61+/-0.15 vs. 2.44+/-0.25, p < 0.005). However, overlapping RI and PI values in lung cancers and benign lesions somewhat limited color Doppler US pulsatile flow signals to differentiate lung cancers from benign lesions. Further analysis of RI and PI values in subgroups of lung cancers [squamous cell carcinoma (SCC, n = 34), adenocarcinoma (AC, n = 18), and small-cell lung cancer (SCLC, n = 6)] and benign lesions [cavitary benign lesions (CBL, n = 8), and noncavitary benign lesions (NCBL, n = 26)] revealed that all different cell types of lung cancers (SCC, AC, and SCLC), indeed, had lower RI and PI values than NCBL (for RI, all p < 0.01; for PI, all p< or =0.001). Moreover, the mean RI and PI values showed a significant incremental decrease from NCBL (mean RI, PI = 0.88, 2.94) toward SCC and AC (for SCC, mean RI, PI = 0.71, 1.68; for AC, mean RI, PI = 0.68, 1.67) and, finally, to SCLC (mean RI, PI = 0.62, 1.05). In contrast, CBL had relatively lower RI and PI values than AC and SCLC (for CBL, mean RI, PI = 0.53, 0.80; both p > 0.05 for RI and PI), and even a significant difference from SCC (p < 0.05 for RI and PI). We conclude that color Doppler US pulsatile flow signal is somewhat limited to differentiate lung cancers from benign lesions, but provides a noninvasive in vivo model to assess the neovascularity intensity of lung cancers.

Adenocarcinoma↗

PubMed1993

Enhancement of Doppler flow signals in the left heart chambers by intravenous injection of sonicated albumin.

OBJECTIVES: The objective of this study was to evaluate the effect of a transpulmonary contrast agent on Doppler flow signals in the left heart chambers. BACKGROUND: Echo contrast agents are good ultrasound reflectors and could be used as Doppler signal enhancers. Sonicated albumin microbubbles are transpulmonary echo contrast agents and could enhance left heart Doppler signals after peripheral venous injection. METHODS: Thirty-one patients with various heart diseases without intracardiac shunts were assessed with Doppler echocardiography before and after injection of sonicated albumin. RESULTS: After an intravenous injection, pulsed Doppler signals of transmitral flow became more intense in all 16 patients examined, although flow velocity itself was not changed. In Doppler color flow imaging, the maximal mitral regurgitant signal area increased from 312 +/- 405 mm2 to 434 +/- 465 mm2, an average increase of 59 +/- 40% in all 17 patients with mitral regurgitation (p < 0.01). These effects were considered to be due to improvement of signal to noise ratio by the enhancement of Doppler flow signals. The duration of enhancement of pulsed Doppler transmitral flow signals was significantly longer than that of the left ventricular echocardiographic opacification (44 +/- 11 s vs. 17 +/- 7 s, p < 0.01). CONCLUSIONS: Intravenous injection of sonicated albumin can enhance the Doppler flow signals in the left heart chambers. This effect may be useful to improve the sensitivity of the Doppler system for detecting abnormalities of left heart blood flow such as mitral regurgitation.

Atrial Function, Left↗

PubMed1993

Cardiac Doppler blood-flow signal analysis. Part 2. Time/frequency representation based on autoregressive modelling.

Doppler spectrograms obtained by using autoregressive (AR) modelling based on the Yule-Walker equations were investigated. A complex AR model using the in-phase and the quadrature components of the Doppler signal was used to provide blood-flow directions. The effect of model orders on the spectrogram estimation was studied using cardiac Doppler blood flow signals taken from 20 patients. The 'final prediction error' (FPE) and the 'Akaike's information criterion' (AIC) provided almost identical results in model-order selection. An index, the spectral envelope area (SEA), was used to evaluate the effect of window duration and sampling frequency on AR Doppler spectrogram estimation. The statistical analysis revealed that the SEA obtained from AR modelling was not sensitive to window duration and sampling frequency. This result verified the consistency of the AR Doppler spectrogram. The white-noise characteristics of the AR modelling error signal indicated that the Doppler blood-flow signal can be adequately modelled as a complex AR process. With appropriate model orders, AR modelling provided better Doppler spectrogram estimates than the periodogram.

Aortic Valve↗

PubMed1977

Tumour detection by ultrasonic Doppler blood-flow signals.

Ultrasonic Doppler blood-flow signals which seem to be associated with malignant tumour neovascularization have been detected in the female breast. No such signals have been detected from cysts. This discovery may lead to the development of a highspeed ultrasonic Doppler scanner which might make breast screening for cancer practicable.

Adenofibroma↗

PubMed1990

Origin and significance of diastolic Doppler flow signals in the left ventricular outflow tract.

Diastolic Doppler flow signals (greater than or equal to 0.2 m/s) in the left ventricular outflow tract have not been well characterized, and their origin and significance remain controversial. Fifty-nine patients (55 +/- 16 years of age) with technically good Doppler echocardiographic studies were studied prospectively. There were 14 normal subjects, 21 patients with left ventricular hypertrophy, 10 with dilated cardiomyopathy and 14 with other cardiac disease. The rhythm was sinus in 55 and atrial fibrillation in 4. Two distinct Doppler flow signals were detected in the left ventricular outflow tract during diastole. These were termed E' (early) and A' (active) because they occurred 40 to 100 ms after higher velocity mitral inflow E (passive filling) and A (atrial contraction) signals. Among 59 patients, E' signals were present in 48 (81%) and had a mean velocity of 0.41 +/- 0.23 m/s. In 55 patients with normal sinus rhythm, A' signals were present in 52 (95%) and had a mean velocity of 0.52 +/- 0.24 m/s. No A' signals were present in the four patients with atrial fibrillation. The E' and A' velocities by pulsed wave Doppler ultrasound were low at the left ventricular apex and increased along the basal septum in the left ventricular outflow tract. Prominent A' velocities (greater than or equal to 0.45 m/s) were seen in 62% of patients with left ventricular hypertrophy, 50% of normal subjects and 10% of patients with dilated cardiomyopathy. The A' velocity was higher in patients with left ventricular hypertrophy (0.63 +/- 0.26 m/s) than in those with a normal heart (0.45 +/- 0.16 m/s; p less than 0.05) or dilated cardiomyopathy (0.25 +/- 0.13 m/s; p less than 0.01). The major determinants of diastolic outflow tract velocity were the mitral inflow E and A velocities and left end-diastolic dimension, particularly when combined (r = 0.64, p less than 0.0001 for E'; r = 0.72, p less than 0.0001 for A'). Distinctive E' and A' Doppler outflow tract signals result from mitral inflow and may be detected in most patients with normal heart size. These E' and A' velocities increase from apex to base and are more prominent in patients with a small, normally contracting heart or left ventricular hypertrophy.

Blood Flow Velocity↗

PubMed2004

Comparison of limited monitoring using a nasal-cannula flow signal to full polysomnography in sleep-disordered breathing.

STUDY OBJECTIVES: Evaluate the utility of overnight monitoring limited to nasal cannula airflow and oximetry in the diagnosis of obstructive sleep apnea-hypopnea syndrome (OSAHS). DESIGN: Prospective randomized study, blinded analysis. SETTING: Sleep disorder center, academic institution. PARTICIPANTS: 56 patients with suspected OSAHS, 10 normal volunteers. MEASUREMENTS AND RESULTS: In-laboratory full nocturnal polysomnography (NPSG) and unattended ambulatory study with monitoring of only airflow and oximetry performed in randomized order. Obstructive respiratory events were scored on the full NPSG while visualizing all signals and then rescored on the full NPSG and on the ambulatory study while visualizing only airflow and oximetry signals. Respiratory disturbance indexes (RDI) for the limited studies (RDIFlowNPSG and RDIFlowAmbulatory) were calculated as the sum of the apneas and hypopneas (defined using airflow amplitude and O2 desaturation) divided by the valid flow-signal time. The reference RDIFullNPSG was calculated from the sum of the apneas and hypopneas (defined using flow amplitude, O2 desaturation and electroencephalographic arousal) identified on the full NPSG divided by the total sleep time. RDIFullNPSG was greater than RDIFlowNPSG (bias = 5.6 events per hour) and RDIFlowAmbulatory (bias = 10.9 events per hour), but the differences were mainly in subjects with an RDI > 40 events per hour. The diagnostic sensitivity and specificity for the diagnosis of OSAHS using a cutoff of 18 events per hour were 96% and 93% using the flow signal from the NPSG and 88% and 92% using the flow signal from the ambulatory study performed on a separate night. CONCLUSIONS: In subjects with OSAHS, analysis of the flow signal from a nasal cannula can provide an RDI similar to that obtained in a full NPSG.

Adult↗

PubMed2005

[Application of Burg algorithm in time-frequency analysis of Doppler blood flow signal based on AR modeling].

The Doppler blood flow signal is inherently a nonstationary Gaussian random process whose time-frequency representation associates with the time-varying velocity of blood flow and its variations. With the assumption that the signal being analyzed is stationary during a short time interval, we can not get Doppler time-frequency representations with satisfactory time and frequency resolution. AR modeling based on Levinson-Durbin algorithm has been used to generate time-frequency representations of Doppler blood flow signals. But the errors of the parameters computed by the algorithm will be aggrandized by the shortening of the time interval. Burg has advanced an algorithm, which computes the parameters by making the sum of forward and backward forecasting errors minimum. In the paper, time-frequency representations computed by Burg and Levinson-Durbin algorithm were compared with the theoretical representation. We found that the time-frequency representations computed by Burg algorithm are more similar to the theoretical representation, especially in frequency band.

Algorithms↗