A mathematical basis for the application of the modified geometric method to maximum frequency estimation

Journal ArticleAbstract-The application of ultrasound in assessing the fetal cardiovascular system often requires the accurate estimation of maximum blood flow velocity waveforms using Doppler measurements. The modified geometric method estimates the maximum Doppler frequency as the frequency at which the vertical distance between the integrated spectrum and the reference line that connects the origin to the maximum value of the integrated spectrum is the largest. This paper presents amathematical formulation for a class of maximum blood flow velocity estimation algorithms that includes the modified geometric method. The analysis provides a rationale for the continued use of the modified geometric method for estimating the maximum frequency envelopes of Doppler signals. This paper also contains experimental results demonstrating the superiority of the modified geometric method over a commonly used threshold crossing method

Appraisal of different ultrasonography indices in patients with carotid artery atherosclerosis

In this study a semi-automated image-processing based method was designed in which the parameters such as intima-media thickness (IMT), resistive index (RI), pulsatility index (PI), dicrotic notch index (DNI), and mean wavelet entropy (MWE) were evaluated in B-mode and Doppler ultrasound in patients presenting with carotid artery atherosclerosis. In a cross-sectional design, 144 men were divided into four groups of control, mild, moderate and severe stenosis subjects. In all individuals, far wall IMT, RI, PI, DNI, and MWE of the left common carotid artery (CCA) were extracted using the proposed method. Our findings showed that the maximum far wall IMT, RI, PI, DNI in the CCA were significantly different in the patients with mild, moderate, and severe stenosis compared to control group (p-value 0.05). The proposed method can help physicians to better identify patients at risk of cardiovascular diseases

Appraisal of different ultrasonography indices in patients with carotid artery atherosclerosis

In this study a semi-automated image-processing based method was designed in which the parameters such as intima-media thickness (IMT), resistive index (RI), pulsatility index (PI), dicrotic notch index (DNI), and mean wavelet entropy (MWE) were evaluated in B-mode and Doppler ultrasound in patients presenting with carotid artery atherosclerosis. In a cross-sectional design, 144 men were divided into four groups of control, mild, moderate and severe stenosis subjects. In all individuals, far wall IMT, RI, PI, DNI, and MWE of the left common carotid artery (CCA) were extracted using the proposed method. Our findings showed that the maximum far wall IMT, RI, PI, DNI in the CCA were significantly different in the patients with mild, moderate, and severe stenosis compared to control group (p-value 0.05). The proposed method can help physicians to better identify patients at risk of cardiovascular diseases

Assessment of Hemodynamic Parameters in the Fetal and Utero-placental Circulation using Doppler Ultrasound

A short history of ultrasound in obstetrics and gynecology is given. So far there is no evidence that diagnostic ultrasound is harmful to the human fetus. However, it is known that ultrasound energy is partly absorbed by tissue and bony structures. As a result, temperature warming can be expected if during a considerable time the ultrasound beam is aimed at one particular spot. Modern ultrasound scanners are equipped with temperature index monitoring upon which the user may decide to use lower machine output settings or limit examination time to minimize any possible risk. The combination of the Doppler principle and two-dimensional ultrasound imaging enables blood flow velocity measurement in fetal blood vessels. This modality of ultrasound contributed to a better understanding of the physiology and pathophysiology of the fetal cardiovascular system. The aim of this Ph.D. study was to further improve our knowledge of the fetal and utero-placental circulation. To this purpose, fetal hemodynamic parameters were assessed and tested on spectral- and color Doppler derived data