Root-MUSIC analysis of nitric oxide-mediated changes in ophthalmic artery blood flow velocity waveforms

Clinical and experimental studies indicate that structural and functional changes in the microvasculature can predate or accompany risk factors for cardiovascular disease at the earliest stages in the disease process. In the current work, both simulated and actual Doppler ultrasound maximum blood velocity waveform envelopes recorded from the ophthalmic artery were analysed using a root-MUSIC and least squares fitting approach to determine amplitude frequency spectra. Both amplitude and frequency components of noise contaminated simulated waveforms were reliably determined indicating the robustness of the technique. The technique was then used to compare the spectral content of the ophthalmic artery blood velocity waveforms of normal controls in three test states: at baseline, following administration of GTN, a nitric oxide donor, and following administration of L-Name, a nitric oxide inhibitor. Principal components derived from root-MUSIC analysis discriminated between waveforms in baseline and non-baseline test states (p < 0.00001) and between GTN and non-GTN test states (p = 0.0002).     

Nearly automated analysis of coronary Doppler flow velocity from transthoracic ultrasound images: validation with manual tracings

Coronary flow velocity reserve is obtained by manual tracings of transthoracic coronary Doppler flow velocity profiles as the ratio of stress versus baseline diastolic peak velocities. This approach introduces subjectivity in the measurements and limits the information which could be exploited from the Doppler velocity profile. Accordingly, our goals were to develop a technique for nearly automated detection of Doppler coronary flow velocity profile, and automatically compute both conventional and additional amplitude, derivative and temporal parameters, and validate it with manual tracings. A total of 100 patients (17 normals, 15 patients with severe coronary stenosis, 41 with connective tissue disease and 27 with diabetes mellitus) were studied. Linear correlation and Bland–Altman analyses showed that the proposed method was highly accurate and repeatable compared to the manual measurements. Comparison between groups evidenced significant differences in some of the automated parameters, thus representing potentially additional indices useful for the noninvasive diagnosis of microcirculatory or coronary artery disease.     

彩色多普勒超声诊断胎儿单脐动脉的临床价值

目的探讨超声对胎儿单脐动脉的诊断意义。方法应用彩色多普勒超声连续观察21405例中晚孕期孕妇单脐动脉的发生情况并测量其脐动脉血流频谱（PI、RI及S/D比值）。结果共发现单脐动脉胎儿140例,99例单纯性单脐动脉,41例合并畸形,它们分别与正常胎儿的PI、RI、S/D值比较均无显著性差异（P〉0.05）。结论应用彩色多普勒超声可准确诊断胎儿单脐动脉的发生情况,为遗传生殖提供临床价值。     

Characteristics of the descending genicular artery blood flow velocity in patients with knee osteoarthritis

BackgroundIn patients with knee osteoarthritis (KOA), the descending genicular artery (DGA) showed abnormal angiogenesis. However, the non-invasive assessment method of DGA remains unclear. The aim of this study was to clarify the characteristics of blood flow velocity of the DGA in patients with KOA and to examine the factors involved in the changes.MethodsThe KOA group included 22 knees of 22 patients with KOA (4 males, 18 females; mean age, 72.3 ± 7.5 years) and the control group included 22 knees (4 males, 18 females; mean age, 71.3 ± 5.4 years) of 22 healthy adults. The peak systolic blood flow velocity (PSV) in each group was measured using ultrasonography. The KOA group was classified into the effusion group and the non-effusion group based on observed effusion, and the PSV was compared between the two groups. The relationships between PSV and suprapatellar bursa intracavitary distance, pain, femorotibial angle, Japanese Knee Osteoarthritis Measure were also investigated.ResultsThe PSV in the KOA group (51.5 ± 12.9 cm/s) was significantly higher than that in the control group (29.3 ± 4.4 cm/s) (P < 0.01). In the KOA group, PSV in the effusion group (55.5 cm/s (51.2–59.4 cm/s)) was significantly higher than that in the non-effusion group (39.1 cm/s (35.1–44.4 cm/s)) (P < 0.01). The PSV was positively and significantly correlated with both suprapatellar bursa intracavitary distance (r = 0.81: P < 0.01) and pain (r = 0.48: P < 0.05).ConclusionsThe PSV measurement in the DGA is useful for the evaluation of non-invasive synovitis of patients with KOA.     

Menorrhagia and uterine artery blood flow.

Menorrhagia is a significant problem in women of reproductive age. In half of the cases no specific aetiology is known. Vascular factors play a role but remain poorly understood. We chose to study whether any association exists between the flow impedance of uterine arteries and the amount of menstrual blood loss. The study population consisted of 60 spontaneously menstruating 35- to 49-year-old women without endometrial hyperplasia, polyps, or submucous fibroids. The pulsatility index (PI) from uterine arteries, arcuate arteries, and radial arteries was measured by transvaginal colour Doppler. Menstrual blood loss was measured by the alkaline haematin method. A significant inverse correlation was found between uterine artery PI and the amount of menstrual blood loss, suggesting that women with lower uterine flow impedance bleed more. A regression model confirmed that this association was specific and not explained by uterine size, fibroids or any other of the 11 potential confounders included in the model. The correlation between uterine artery PI and amount of menstrual blood loss suggests that vascular factors may be involved in the pathogenesis of menorrhagia.     

Twenty‐four‐hour non‐invasive monitoring of systemic haemodynamics and cerebral blood flow velocity in healthy humans

Acute short‐term changes in blood pressure (BP) and cardiac output (CO) affect cerebral blood flow (CBF) in healthy subjects. As yet, however, we do not know how spontaneous fluctuations in BP and CO influence cerebral circulation throughout 24 h. We performed simultaneous monitoring of BP, systemic haemodynamic parameters and blood flow velocity in the middle cerebral artery (MCAV) in seven healthy subjects during a 24‐h period. Finger BP was recorded continuously during 24 h by Portapres and bilateral MCAV was measured by transcranial Doppler (TCD) during the first 15 min of every hour. The subjects remained supine during TCD recordings and during the night, otherwise they were seated upright in bed. Stroke volume (SV), CO and total peripheral resistance (TPR) were determined by Modelflow analysis. The 15 min mean value of each parameter was assumed to represent the mean of the corresponding hour. There were no significant differences between right vs. left, nor between mean daytime vs. night time MCAV. Intrasubject comparison of the twenty‐four 15‐min MCAV recordings showed marked variations (P < 0.001). Within each single 15‐min recording period, however, MCAV was stable whereas BP showed significant short‐term variations (P < 0.01). A day–night difference in BP was only observed when daytime BP was evaluated from recordings in the seated position (P < 0.02), not in supine recordings. Throughout 24 h, MCAV was associated with SV and CO (P < 0.001), to a lesser extent with mean arterial pressure (MAP; P < 0.005), not with heart rate (HR) or TPR. These results indicate that in healthy subjects MCAV remains stable when measured under constant supine conditions but shows significant variations throughout 24 h because of activity. Moreover, changes in SV and CO, and to a lesser extent BP variations, affect MCAV throughout 24 h.     

多普勒超声观察创伤性寰枢椎不稳手术前后椎动脉血流的变化

目的探讨创伤性寰枢椎不稳患者内固定手术前后椎动脉血流的变化。方法32例创伤性寰枢椎不稳患者,其中男性22例,女性10例;年龄22～57岁,平均年龄38岁。手术前及内固定术后,均应用彩色多普勒超声测量颈椎1、2间和颈椎5、6间椎动脉血流速度、阻力指数。并对检查结果进行对比分析。结果32例创伤性寰枢椎不稳患者术前椎动脉血流39侧异常,25侧正常。内固定术后39侧异常者中35侧恢复正常,4侧无变化,3侧术前正常变为术后异常。结论创伤性寰枢椎不稳可导致椎动脉血流变化,手术复位内固定后增加了寰枢椎稳定性,可改善椎动脉血液供应。     

Can blood flow in separate small tubes be quantitatively assessed by high-resolution laser Doppler imaging?

A method is suggested for quantitative flow assessment of whole-blood perfusing tubes with diameters in the range from 500 μm to 1.5 mm, for velocities below 9 mm s⁻¹. The algorithm is based both on the Doppler broadening of backscattered laser light and the magnitude of the diameter of the perfused tube. A bandwidth-modified high-resolution laser Doppler perfusion imaging system is used to record the Doppler broadening. A flow model, consisting of a linearly narrowing tube (inner diameter 620–1330 μm), is connected to a precision infusion pump and perfused by human whole blood of volume flows ranging from 0 to 6.6 mm³ s⁻¹. empirical data are fitted into a regression model, and the parameters of the algorithm can be determined, resulting in a correlation coefficient of 0.975 between the predicted and true volume flows. Using this algorithm, volume flows in tubes of inner diameters of 500 μm, 750 μm and 1.4 mm are predicted, with accuracies corresponding to correlation coefficients of 0.994, 0.993 and 0.996.     

Influence of posture on middle cerebral artery mean flow velocity in humans

We determined middle cerebral artery, common carotid artery and temporal superficial artery Doppler derived flow velocities in ten subjects for 10 min after change in posture. Maximal changes were observed after about 3 min. The 10° head-down tilt position increased blood velocities in the common carotid artery by 13% (SD 4)% (P < 0.001), in the middle cerebral artery by,6% (SD 3)% (P < 0.001) and in the superficial temporal artery by 70% (SD 26)% (P < 0.001). In the standing position, there was an 18% (SD 9)% (P < 0.001) decrease in the common carotid blood velocities, with 14% (SD 6)% (P < 0.001) and 53% (SD 23)% (P < 0.001) reductions in the middle cerebral and superficial temporal artery velocities, respectively. At 9 min after the changes in posture, velocities in the middle cerebral artery were at the value of supine rest, whereas the common carotid blood velocity was not completely restored and deviations in the temporal artery velocity persisted. The data would suggest that cerebral blood flow is regulated with some delay and that such regulation is partially reflected in the common artery blood flow, since changes in a branch of the external carotid artery flow velocity remained.     

Middle cerebral artery blood velocity during rowing

Dynamic exercise increases the transcranial Doppler determined mean blood velocity in basal cerebral arteries corresponding to the cortical representation of the active limb(s) and independent of the concomitant rise in the mean arterial pressure. In 12 rowers we evaluated the middle cerebral artery blood velocity response to ergometer rowing when regulation of the cerebral perfusion is challenged by stroke synchronous fluctuation in arterial pressure. Rowing increased mean cerebral blood velocity (57 ± 3 to 67 ± 5 cm s^?1; mean ± SE) and mean arterial (86 ± 6 to 97 ± 6 mmHg) and central venous pressures (0 ± 2 to 8 ± 2 mmHg; P < 0.05). The force on the oar triggered an averaging procedure that demonstrated stroke synchronous sinusoidal oscillations in the cerebral velocity with a 12 ± 2% amplitude upon the average exercise value. During the catch phase of the stroke, the mean velocity increased to a peak of 88 ± 7 cm s^?1 and it was in phase with the highest mean arterial pressure (125 ± 14 mmHg), while the central venous pressure was highest after the stroke (20 ± 3 mmHg). The results suggest that during rowing cerebral perfusion is influenced significantly by the rapid fluctuations in the perfusion pressure.     

A field-programmable gate array based system for high frame rate laser Doppler blood flow imaging

This paper presents a general embedded processing system implemented in a field-programmable gate array providing high frame rate and high accuracy for a laser Doppler blood flow imaging system. The proposed system can achieve a basic frame rate of flow images at 1 frame/second for 256×256 images with 1024 fast Fourier transform (FFT) points used in the processing algorithm. Mixed fixed-floating point calculations are utilized to achieve high accuracy but with a reasonable resource usage. The implementation has a root mean square deviation of the relative difference in flow values below 0.1% when compared with a double-precision floating point implementation. The system can contain from one or more processing units to obtain the required frame rate and accuracy. The performance of the system is significantly higher than other methods reported to date. Furthermore, a dedicated field-programmable gate array (FPGA) board has been designed to test the proposed processing system. The board is linked with a laser line scanning system, which uses a 64×1 photodetector array. Test results with various operating parameters show that the performance of the new system is better, in terms of noise and imaging speed, than has been previously achieved.     

Intraluminal recording of cross-sectional blood velocity distribution of human ascending aorta by ultrasound Doppler technique

A pulsed Doppler ultrasound technique was used for mapping two-dimensional blood velocity profiles in the human ascending aorta during open-heart surgery. An electronic position-sensitive device was constructed and linked to an intraluminal 10 MHz Doppler ultrasound probe. From a plane perpendicular to the central direction of blood flow, velocity mapping was performed covering the entire cross-section of the ascending aorta 6–7 cm above the valve. This method is based on a sequential sampling of velocity from continuously changing locations during a stable haemodynamic period; typically velocity points are recorded from 150–300 beats. Further processing transformed data to suit a previously developed velocity distribution model for normal blood flow in the human ascending aorta, based on multiregression analyses. In this model, the time series of data from consecutive beats were computed into an average two-dimensional profile described through one cardiac cycle. This method allows high spatial resolution (1.5 mm), in addition to the high-frequency response (200 Hz) of the modified ultrasound Doppler meter. Together with the advantage of velocity directionality and minimal time interventions, this makes the method well suited for studies on normal flow conditions as well as flow velocity distribution distal to different heart valve prostheses.     

Feature extraction from Doppler ultrasound signals for automated diagnostic systems

This paper presented the assessment of feature extraction methods used in automated diagnosis of arterial diseases. Since classification is more accurate when the pattern is simplified through representation by important features, feature extraction and selection play an important role in classifying systems such as neural networks. Different feature extraction methods were used to obtain feature vectors from ophthalmic and internal carotid arterial Doppler signals. In addition to this, the problem of selecting relevant features among the features available for the purpose of classification of Doppler signals was dealt with. Multilayer perceptron neural networks (MLPNNs) with different inputs (feature vectors) were used for diagnosis of ophthalmic and internal carotid arterial diseases. The assessment of feature extraction methods was performed by taking into consideration of performances of the MLPNNs. The performances of the MLPNNs were evaluated by the convergence rates (number of training epochs) and the total classification accuracies. Finally, some conclusions were drawn concerning the efficiency of discrete wavelet transform as a feature extraction method used for the diagnosis of ophthalmic and internal carotid arterial diseases.     

Intra- and extracranial artery blood velocity during a sudden blood pressure decrease in humans

The intra- and extracerebral Doppler artery blood velocity responses to a 10-mmHg abrupt blood pressure (BP) decrease in ten healthy men were studied. This decrease was obtained using two cuffs placed over both thighs. First, cuffs were inflated to pressures greater than the arterial BP for 5 min. Next, they were deflated to 60 mmHg in order to prevent venous return from the legs. We obtained a decrease in mean arterial BP of from 101 (10) to 90 (10) mmHg [mean (SD), P < 0.01] without modifications in the heart rate [HR, 88 (14) beats min⁻¹]. Middle cerebral artery mean blood velocity (MCAmv) decreased immediately from 50 (10) to 42 (12) cm s⁻¹ (P < 0.05). Simultaneously, temporal superficial artery mean blood velocity (TSAmv) decreased from 11 (3) to 7 (2) cm s⁻¹ (P < 0.05) and common carotid artery blood flow (CCAbf ) decreased from 305 (23) to 233 (33) ml min⁻¹ (P < 0.05). After 5 s, MCAmv and CCAbf returned to baseline values, whereas TSAmv [8 (2) cm s⁻¹], mean arterial BP [86 (10) mmHg] remained low and HR increased [92 (12) beats min⁻¹]. TSAmv, BP and HR returned to baseline values in 1 min. These data confirm that cerebral blood flow (CBF) is very rapidly regulated but that blood flow in extracranial territories is not and that it follows the arterial BP changes. Accepted: 8 April 1997     

Increase of fetal arterial blood temperature by reduction of umbilical blood flow in chronically instrumented fetal sheep

The effect of reduced umbilical blood flow rate on fetal core temperature was investigated in five chronically instrumented fetal sheep (gestational age 124 days). On average, fetal-maternal temperature difference increased 0.13±0.02 °C when blood flow rate was decreased to about 1/3 of normal (248±69 ml min^–1) for 30 min. The small temperature rise is the consequence of predominant heat dissipation through the placenta, and of diminished oxygen consumption.     

Physiology: Description of circadian rhythm in uterine artery blood flow during the peri-ovulatory period

Uterine artery blood flow was assessed by transvaginal colourand pulsed Doppler ultrasound prospectively in six women duringthe peri-ovulatory period. All patients had regular ovulatorymenstrual cycles and a mid-luteal serum progesterone consistentwith spontaneous ovulation in the preceding cycle. Each patientunderwent serial transvaginal ultrasound examination and Dopplerassessment of blood flow in the uterine arteries. When the meanfollicular diameter was >16 mm or day –2 from the estimatedday of ovulation was reached, patients were scanned at 6 hourlyintervals at 0600, 1200, 1800 and 2400 h until follicular rupture.The pulsatility index (PI) and time averaged maximum velocity(TAMX) were calculated as Doppler indices of impedance to bloodflow and velocity respectively. A venous blood sample was takenat each visit for subsequent hormonal analysis. The mean uterineartery PI showed a marked daily fluctuation with a nadir occurringmost commonly at 0600 h. A comparison between the mean PI valuesat 0600 and 1800 h showed significantly lower results at 0600h in both dominant (P < 0.05) and non-dominant (P < 0.02)uterine arteries. Furthermore, mean uterine artery TAMX showeddaily fluctuations with peak values most commonly occurringat 0600 h with the nadir occurring during the afternoon andlate evening. There was no temporal relationship between thefluctuations in PI and changes in luteinizing hormone, folliclestimulating hormone, oestradiol or progesterone concentrations.These observations suggest that there is a circadian rhythmin uterine artery blood flow during the peri-ovulatory periodwhich appears to be independent from the hormonal changes.     

Diurnal variation in uterine artery blood flow in post-menopausal women on oestrogen hormone replacement therapy.

Doppler ultrasound was used to investigate circadian variations in uterine artery blood flow in 20 post-menopausal women in the oestrogen-only phase of combined oestrogen hormone replacement therapy with cyclical oral norethisterone or dydrogesterone. All women were examined between 0800 and 0830 h and then again between 1800 and 1830 h on the same day. Mean arterial blood pressure, heart rate and a blood sample for measurement of serum oestradiol were taken at each visit. Indices of uterine artery blood flow included the pulsatility index, resistance index, peak systolic velocity and time-averaged maximum velocity. No significant differences in the mean arterial blood pressure, pulse rate and oestradiol concentrations were detected between morning and evening visits. Significant fluctuation was observed in the pulsatility index (P < 0. 001), resistance index (P < 0.001) and time-averaged maximum velocity (P < 0.01). The assessment of uterine artery blood flow in post-menopausal women should take into account the presence of circadian variations to ensure accuracy and reproducibility of Doppler investigations.     

Temporal heterogeneity of the blood flow velocity at the middle cerebral artery in the normal human characterized by fractal analysis

The objective of this study is to characterize the temporal fluctuation of the axial blood flow velocity (BFV) at the middle cerebral artery (MCA). Biological observables such as BFV present complex oscillations. The irregularity of physiological systems may be assessed by fractal analysis by computing the fractal dimension (D_γ) and the corresponding temporal correlation (r_γ). The BFV at the MCA was registered with transcranial Doppler ultrasonography (TCD) in four adult volunteers. As fractal processes are assumed to have no absolute time scale, two time scales were compared. The digitized signal was averaged respectively at 1-s intervals and for each heart beat. D_γ and r_γ were determined using relative dispersion analysis. The results were D_γ= 1.24 ± 0.09 and r_γ= 0.45 ± 0.19 (mean ± SD) for the 1-s based time scale and D_r= 1.17 ± 0.09 and r_γ= 0.57 ± 0.20 for the heart-beat scale. We conclude that the temporal heterogeneity of the BFV at the MCA in the normal human has fractal properties. Fractal analysis of TCD data may become useful in clinical diagnosis because loss of complexity in physiological systems has been linked to senescence or disease conditions. Wide variations of the so called normal values of BFV measured by TCD have been reported. The physiological BFV fluctuations may explain, in part, the variability of values recorded during routine TCD diagnostic examinations. Our observations may also be of value for understanding the interaction of the vascular endothelium and the blood flow stream (shear stress).     

彩色多普勒超声测定胎儿大脑中动脉血流速度与围产儿预后的相关性研究

目的探讨应用彩色多普勒超声测定孕晚期胎儿大脑中动脉（MCA）血流参数与围产儿预后的相关性。方法通过运用彩色多普勒超声测定晚孕期胎儿MCA血流速度,并对胎儿预后进行随访观察。结果异常组胎儿MCA—ED显著高于正常组胎儿、MCA—PI、MCA—RI、MCA—S／D均显著低于正常组胎儿;以MCA—ED大于其正常值2个标准差、MCA—PI〈1．4、MCA—RI〈0．6、MCA—S／D值〈4．0为血流异常,预测胎儿预后不良的敏感性及特异性分别为26．39％和97．33％、62．50％和56．00％、12．50％和98．67％、65．28％和52．00％。结论彩色多普勒超声测定胎儿大脑中动脉血速度对预测围产儿预后具有一定的临床价值。