Reliable measurement methods for the isovolumic relaxation time: comparisons of dual gate Doppler and seven other methods

PURPOSE

Isovolumic relaxation time (IVRT) is a useful indicator of diastolic dysfunction. However, a measurement method for IVRT has not been established. The Dual Gate Doppler method, which can record two separate pulse-wave Doppler signals simultaneously using two sample gates, may be ideal for measuring IVRT. This study aimed to evaluate the accuracy of IVRT measured using conventional methods versus that measured using the Dual Gate Doppler method.

METHODS

A total of 104 patients (mean age 58 ± 21 years, 48 women) were examined using ultrasound equipment with Dual Gate Doppler at our hospital. In addition to Dual Gate Doppler method, IVRTs were measured using seven different methods: pulsed Doppler (PW method), continuous wave Doppler (CW method), and other methods. The IVRT values obtained using the Dual Gate Doppler method were compared with those measured using other methods.

RESULTS

All IVRTs measured using conventional methods showed a strong correlation with the that measured using the Dual Gate Doppler method. However, there were slight deifferences among the IVRTs depending on the method. The PW method and the PW time difference method using only the PW showed small statistical bias and were not complicated. The IVRT measured using the CW method was significantly longer than that measured using the Dual Gate Doppler method.

CONCLUSIONS

Among the conventional methods, the PW method was the simplest and most practical method for measuring the IVRT in any conditions as arrhythmias. It is important to recognize the characteristics of IVRTs based on the measurement method.

DOES FLOW-MEDIATED DILATION NORMALIZATION FOR BASE-SCALED SHEAR RATE IMPROVE ITS VALUE IN CORONARY ARTERY DISEASE DIAGNOSTICS?

The article presents a new normalization of flow-mediated dilation (FMD) in the radial artery, taking into account the parameter BSSR being equal to the ratio of the basal shear rate (BS) measured before the cuff inflation and post occlusive shear rate (SR). The in vivo usefulness of the new normalization algorithm was evaluated in two groups of patients. In group I, comprising 15 healthy volunteers, the normalized FMD/SR was (3.19 ± 1.4)•10^-4, while in group II, comprising 13 patients with stable coronary artery disease (CAD), it was (1.02 ± 0.76)•10^-4. We calculated almost 50% larger difference between the average values after normalizing FMD/BSSR. Specifically, the FMD/BSSR was equal to 28 ± 9.40 in group I and 6.01 ± 3.74 in group II. The prediction of CAD patients based on FMD/SR values had a sensitivity of 83.3% and a specificity of 84.6%, whereas the prediction of CAD patients based on the FMD/BSSR values revealed 100% sensitivity and specificity. These results confirm the usefulness of the novel normalization algorithm of the FMD in differentiation of normal patients from those with stable CAD.

Pulsed Doppler Echocardiography: An Historical Perspective

Over the past six decades, echocardiography has evolved into an important technique for not only imaging cardiac structures, but also, by employing the Doppler equation, for assessing cardiac blood flow and tissue velocities. This review focuses on pulsed Doppler echocardiography: its principles, early development, and clinical applications. Important clinical applications include: (1) measurement of flow velocities, stroke volumes, and regurgitant and shunt volumes; (2) assessment of time intervals, e.g., pulmonary artery acceleration time as a measure of pulmonary artery pressure and resistance or the timing of mitral regurgitation in hypertrophic cardiomyopathy; (3) detection of turbulent flow in regurgitation, stenoses, and shunts, enhanced by the implementation of color Doppler; and (4) evaluation of left ventricular diastolic function in conjunction with pulsed tissue Doppler and deformation (strain) measurements.

Directional Doppler in Cardiology: A 50-Year Journey

In 1968, while cardiologists were focused on cardiac structures imaged by ultrasound, Daniel Kalmanson in Paris, France, devised a new ultrasonic modality, directional continuous-wave Doppler, enabling him to record instantaneous cardiovascular blood flow velocities with recognition of their direction (relative to the transducer) in vessels. An innovative presentation of Doppler data also made velocity traces physiologically understandable. Following the noninvasive study of the arterial and venous beds, flow velocity in the right (1969) and left (1970) cardiac chambers was studied by means of a directional Doppler catheter. The curtain was then raised for the renewal of our pathophysiologic understanding of cardiac dynamics and the adoption of a new methodology. Technological evolution paved the way for clever researchers to pioneer important advances, diversifying the technique. Guided by the early principles, which are still valid in 2018, directional Doppler finally gained acceptance from the entire scientific community.

Pulsed Doppler fetal atrioventricular interval measurement: Assessment of a new image scoring method

OBJECTIVES

We propose an image scoring method to improve the quality and the reproducibility of measurement of the AV interval before establishing reference tables of the measurements and studies on the prevention and treatment of first-degree AV block especially if the first child has been diagnosed AV block.

METHOD

Prospective study from May 2015 to June 2016. Sonographers were asked to measure AV interval with pulsed Doppler in a five-chamber view in standard second-trimester screening before and after having received our image scoring method. Images were scored by 2 blinded reviewers.

RESULTS

The intra-class correlation coefficient (ICC) between the two reviewers for the overall score was 0.91. On average, the measurement quality increased by 2.5 points/10 (95% CI 1.0-4.0). In the second set of images, after the scoring method was given, the score stared at 6.50 for the first image, with a significant improvement of 0.18 (p = 0.016) per subsequent image comparing to a non significant improvement for the first set of image. There was a significant improvement in intra-observer reliability, ICC: 0.680 [95% CI 0.606-0.854] versus 0.458 [95% CI 0.140-0.651].

CONCLUSION

The use of this scoring method is simple, reproducible and improves image quality and reproducibility of AV interval measurement in a five-chamber view.

Pitfalls of Doppler Measurements for Arterial Blood Flow Quantification in Small Animal Research: A Study Based on Virtual Ultrasound Imaging

High-resolution Doppler is a popular tool for evaluating cardiovascular physiology in mutant mice, though its 1-D nature and spectral broadening processes complicate interpretation of the measurement. Hence, it is crucial for pre-clinical researchers to know how error sources in Doppler assessments reveal themselves in the murine arterial system. Therefore, we performed virtual Doppler experiments in a computer model of an aneurysmatic murine aorta with full control of the imaging and insonified fluid dynamics. We observed significant variability in Doppler performance and derived vascular indices depending on the interrogated flow, operator settings and signal processing. In particular, we found that (i) Doppler spectra in the upper aortic branches and celiac artery exhibited more broadening because of complex out-of-beam flow paths; (ii) mean frequency tracking outperforms tracking of the outer envelope, but is sensitive to errors in angle correction; and (iii) imaging depths deviating much from the elevation focus suffer from decreased spectral quality.

Defining the Collateral Flow of Posterior Tibial Artery and Dorsalis Pedis Artery in Ischemic Foot Disease: Is It a Preventing Factor for Ischemia?

BACKGROUND

Critical limb ischemia, a worldwide prevalent morbidity cause, is mostly secondary to vascular insufficiency due to atherosclerosis. The disease presents with intermittent claudication, which can progress to critical limb ischemia requiring amputation. Research has emphasized that the quality or existence of the pedal arch have a direct effect on wound healing and, therefore, on limb salvage, through the mechanism of collateral vascularization to the ischemic regions.

OBJECTIVES

This study aimed to determine the existence and, if present, grade of retrograde blood flow from plantar arch to dorsal foot artery (dorsalis pedis artery, DPA). The correlation between clinical symptoms and presence of collateral flow were also investigated.

PATIENTS AND METHODS

Study group consisted of 34 cases, which included patient group (n = 17, all male, mean age: 68 years) and control group (n = 17, all male, mean age: 66 years). After physical examination and lower extremity Doppler examination, spectral morphology of DPA flow was recorded, before and during manual compression of posterior tibial artery (PTA), for a period of 5 seconds. At the end, findings of Doppler ultrasound, computed tomography angiography, magnetic resonance angiography and, physical examination finding and symptomatology were gathered and analyzed.

RESULTS

In the patient group, 31 lower limb arteries, of total of 17 cases, were included. After compression maneuver, DPA in 11 cases (six right, five left) showed retrograde filling from plantar arch. This retrograde flow support was triphasic in three cases, biphasic in five cases, and monophasic in three cases. In other DPAs of these 20 limbs, PTA based retrograde collateral flow was not determined. In nine of these 20 limbs, with no or diminished retrograde filling, symptoms were worse than in other cases. Contrarily, only two of 11 limbs, with retrograde collaterals, have claudication during walking.

CONCLUSION

In cases with critical atherosclerotic disease of anterior tibial artery, PTA-based biphasic or triphasic retrograde collateral flow prevents ischemia, whereas monophasic support or no retrograde flow remains incapable.

Experimental verification of color flow imaging based on wideband Doppler method

The purpose of this study is to eliminate the aliasing in color flow imaging. The wideband Doppler method is applied to generate a color flow image, and the validity of the method is experimentally confirmed. The single beam experiment is carried out to confirm the velocity estimation based on the wideband Doppler method. The echo data for the conventional pulsed Doppler method and the wideband Doppler method are obtained using a flow model, and the estimated velocity for each method is compared. The color flow images for each method are also generated using several types of flow model. The generated images are compared, and the characteristics of the imaging based on the wideband Doppler method are discussed. The high velocity beyond the Nyquist limit is successfully estimated by the wideband Doppler method, and the availability in low velocity estimation is also confirmed. The aliasing in color flow images is eliminated, and the generated images show the significance of the elimination of the aliasing in the flow imaging. The aliasing in color flow imaging can be eliminated by the wideband Doppler method. This technique is useful for the exact understanding of blood flow dynamics.

Evaluation of testicular artery blood flow by Doppler ultrasonography as a predictor of spermatogenesis in the dog

The present study examines the relationship between reproductive and seminal characteristic with blood flow supply of the testis in male dogs by means of Doppler ultrasonography. Five male dogs were subject to a clinical examination, blood sampling, B-Mode and Doppler ultrasonography of the testis, semen evaluation at collections and after storage at 4°C for 24, 48 and 72 h in three replicates 30 days apart. Peak Systolic Velocity was positively correlated with testicular volume and negatively with live sperm at collections and after 24h. A negative correlation existed between Resistive Index and Pulsatility Index with total and progressive motility at collections and also after 24, 48 and 72 h. Resistive Index and Pulsatility Index were also negatively correlated with the percentage of membrane intact sperms with curled tails at collections while the latter was positively correlated with End Diastolic Velocity. Moreover, positive linear correlations of weight with bilateral testicular volume and total sperm concentration and also between age and abnormal sperm at collections and after 24h were established. The results suggest that the Resistive Index and Pulsatility Index seem to be potential markers of seminal quality in dogs.

Estimation of Doppler shift frequency using selected phase information for high frame rate color flow mapping

PURPOSE

We describe a new approach to processing signals used to estimate the Doppler shift frequency in high frame-rate color flow mapping with fewer pulse transmissions. When an ultrasound pulse is transmitted to a large number of scatterers, the echoes from the scatterers overlap and interfere with one another. This interference causes the phase of the received echo signal to fluctuate, thus disturbing the estimated shift in Doppler frequency. The technique proposed here eliminates this disturbed phase information, leaving the remaining information for use in estimating the shift in Doppler frequency. The instantaneous frequency of the echo signal can serve as an index of the influence of interference.

METHODS

To test this technique in vivo we used radio-frequency echo signals from the carotid artery for simulation and evaluated the error of the estimated Doppler shift frequency in several cases.

CONCLUSION

Performance was enhanced when the number of pulses transmitted was limited and this technique was used.