Doppler Artifacts and Pitfalls

Respiratory Fluctuation of Peak Systolic Velocities in the Carotid Doppler Waveforms of Patients With Obstructive Airway Disease: Evidence of Pulsus Paradoxus With Experimental Validation

OBJECTIVES

To characterize fluctuations in peak systolic velocities (PSVs) in Doppler waveforms of the carotid artery in patients with and without obstructive airway disease and in volunteers subjected to incremental levels of airway resistance in an experimental model.

METHODS

The PSV variation in common carotid waveforms was measured in 100 patients who had had a carotid ultrasound examination and no respiratory or carotid disease. This was compared to that of patients who had this study during an admission for acute exacerbation of chronic obstructive pulmonary disease (COPD). The PSV variation was correlated with pulmonary function testing. In addition, 14 healthy volunteers were asked to breathe through 5 resistors. Simultaneous recordings were made of Doppler waveforms in the common carotid artery, cardiac activity, and respiration. Peak systolic velocity changes from inspiration to expiration were calculated.

RESULTS

Of the 100 patients without respiratory disease, the magnitude of the PSV variation averaged 6.3 cm/s. Of the 33 patients with COPD, the PSV variation averaged 16.5 cm/s. Nineteen of the 33 patients with COPD had concurrent pulmonary function testing; there was a statistically significant correlation between the PSV variation and forced vital capacity and forced expiratory volume indices. For the volunteers, mean velocity changes were 7.1, 6.6, 8.3, 15.1, and 16.1 cm/s for 0.00-, 2.15-, 3.27-, 3.58-, and 5.77-cm H₂ O/L/s levels of breathing resistance, respectively. There was a statistically significant relationship between an increasing airway load and the decline in PSV during inspiration (P = .02).

CONCLUSIONS

The PSV variation is greater in patients with increased airway resistance. Similar changes are evident in volunteers breathing into resistors. These findings likely reflect pulsus paradoxus.

Bone surface enhancement in ultrasound images using a new Doppler-based acquisition/processing method

Ultrasound (US) imaging has long been considered as a potential aid in orthopedic surgeries. US technologies are safe, portable and do not use radiations. This would make them a desirable tool for real-time assessment of fractures and to monitor fracture healing. However, image quality of US imaging methods in bone applications is limited by speckle, attenuation, shadow, multiple reflections and other imaging artifacts. While bone surfaces typically appear in US images as somewhat 'brighter' than soft tissue, they are often not easily distinguishable from the surrounding tissue. Therefore, US imaging methods aimed at segmenting bone surfaces need enhancement in image contrast prior to segmentation to improve the quality of the detected bone surface. In this paper, we present a novel acquisition/processing technique for bone surface enhancement in US images. Inspired by elastography and Doppler imaging methods, this technique takes advantage of the difference between the mechanical and acoustic properties of bones and those of soft tissues to make the bone surface more easily distinguishable in US images. The objective of this technique is to facilitate US-based bone segmentation methods and improve the accuracy of their outcomes. The newly proposed technique is tested both in in vitro and in vivo experiments. The results of these preliminary experiments suggest that the use of the proposed technique has the potential to significantly enhance the detectability of bone surfaces in noisy ultrasound images.

Triplex Doppler evaluation of the testes in dogs of different sizes

This study aimed to assess whether there are differences in Doppler velocimetry parameters between different sizes. Twenty dogs were equally divided into small and large groups used in this study. The dogs were evaluated using Triplex ultrasound. Testicular artery was located by Colour Doppler in the spermatic cord, marginal to the testes and intratesticular segments and then, spectral Doppler were used to calculate: peak systolic velocity (PSV), end diastolic velocity (EDV), resistance index (RI) and pulsatility index (PI). The mean testicular volume in the left side was significantly higher than the right side, in both groups. Doppler examination showed higher velocities (EDV) at spermatic cord in large dogs; marginal to the testes was observed higher velocities in small dogs; intratesticular region no differences were observed (P < 0.05) and within the groups differences between segments of the artery were also observed for each parameter. The results showed that there are differences in Doppler velocimetry parameters between different sizes.

Testicular Torsion: Twists and Turns

Testicular torsion is one of the common causes of acute scrotal pain. This review discusses the clinical and sonographic findings of intravaginal and extravaginal testicular torsion, including the normal sonographic and vascular anatomy of the testis. The role of color flow Doppler and spectral Doppler is also emphasized in the patient's complete, incomplete, and intermittent testicular torsion. Sonographic features of testicular torsion mimics, such as vasculitis, venous thrombosis, scrotal edema, and technical parameters, are also presented. A brief description of new developments such as contrast-enhanced ultrasound, dynamic contrast magnetic resonance imaging, and near-infrared imaging is included.