High-frequency Doppler Imaging Research Articles

Usefulness of Doppler sonography in aesthetic medicine.

IntroductionIn recent years, ultrasonography has been used in an increasing number of fields, such as dermatology, aesthetic medicine and cosmetology. For skin imaging, research has shown the usefulness of both classic scanners equipped with linear transducers, and high-frequency scanners with mechanical transducers. An increasing number of reports indicating high usefulness of Doppler sonography have been published recently. The aim of this study was to assess the usefulness of high-frequency Doppler imaging in the diagnosis of vascular complications after aesthetic procedures using tissue fillers.Materials and methodsA total of 12 women aged 19–48 years (mean age 36.08 years) who had undergone hyaluronic acid treatment were included in the study group. Ultrasound scans were performed using standard ultrasound scanners, i.e. Philips Epiq 5 with a linear transducer and Samsung RS85 with linear transducers and Doppler Microflow Imaging option. Ultrasound scans were performed to assess the presence of blood flow using Color Power Doppler (CPA). Pulsed-Wave Doppler was used only for arteries. If no blood flow was recorded with Color Power Doppler, Microflow Imaging was used.ResultsDoppler ultrasound showed normal blood flow despite reported symptoms in 3 cases. Vascular stenosis was found in 2 patients. In the other 7 patients, Doppler ultrasound showed no blood flow at the sites where complications developed.ConclusionsSkin ultrasound with Doppler options is a useful tool in the diagnosis of aesthetic medicine complications.

Effect of dual-frequency clutter suppression in harmonic Doppler detection

Background High-frequency Doppler imaging is highly potential for detection of blood flow in microcirculation. In a swept-scan system, however, the spectral broadening of tissue clutter limits the detectability of low-velocity flow signal. Conventionally, the scanning speed of transducer has to be reduced to alleviate the clutter interference but at the cost of imaging frame rate. For example, the blood velocity of 0.5 mm/s becomes detectable only with a scanning speed lower than 1 mm/s. In this study, an alternative method is examined by suppressing the clutter magnitude to reduce the interference to flow signal without sacrificing scanning speed. Methods The method of third harmonic (3 f 0) transmit phasing can suppress the tissue harmonic clutter by transmitting at the fundamental and the additional 3 f 0 frequencies to achieve mutual cancellation between the frequency-sum and the frequency-difference components of the second harmonic signal. With 3 f 0 transmit phasing, the cut-off frequency of wall filtering can be reduced to preserve low-velocity flow without compromising the frame rate. Results Our results indicate that the 3 f 0 transmit phasing effectively reduces the harmonic clutter magnitude and thus improves the flow signal-to-clutter ratio. Compared to the conventional counterpart, the clutter-suppressed color flow and power Doppler images show fewer clutter artifacts and is capable of detecting more low-velocity flow of microbubbles. The resultant color-pixel-density also improves with clutter suppression. Conclusion For the swept-scan high-frequency (>20 MHz) system, 3 f 0 transmit phasing is capable of providing effective clutter suppression. With the same achievable scanning speed, the resultant Doppler image has higher sensitivity for low-velocity flow and is less susceptible to clutter artifacts.

In vivo imaging of blood flow in the mouse Achilles tendon using high-frequency ultrasound

Objective Achilles tendinitis is a common clinical problem with many treatment modalities, including physical therapy, exercise and therapeutic ultrasound. However, evaluating the effects of current therapeutic modalities and studying the therapeutic mechanism(s) in vivo remains problematic. In this study, we attempted to observe the morphology and microcirculation changes in mouse Achilles tendons between pre- and post-treatment using high-frequency (25 MHz) ultrasound imaging. A secondary aim was to assess the potential of high-frequency ultrasound in exploring therapeutic mechanisms in small-animal models in vivo. Methods A collagenase-induced mouse model of Achilles tendinitis was adopted, and 5 min treatment of continuous-mode low-frequency (45 kHz) ultrasound with 47 mW/cm 2 maximum intensity and 16.3 cm 2 effective beam radiating area was applied. The B-mode images showed no focal hypoechoic regions in normal Achilles tendons either pre- or post-treatment. The Doppler power energy and blood flow rate were measured within the peritendinous space of the Achilles tendon. Conclusion An increase in the microcirculation was observed soon after the low-frequency ultrasound treatment, which was due to immediate induction of vascular dilatation. The results suggest that applying high-frequency Doppler imaging to small-animal models will be an invaluable aid in explorations of the therapeutic mechanism(s). Our future work includes using imaging to assess microcirculation changes in tendinitis between before and after treatment over a long time period, which is expected to yield useful physiological data for future human studies.

Quantitation of Hemodynamic Function during Developmental Vascular Regression in the Mouse Eye

Ultrasound biomicroscopy (UBM) utilizes frequencies higher than conventional diagnostic ultrasound and can noninvasively provide anatomic and functional information about mouse ocular structures in vivo at high resolution. Vascular development can also be assessed with high-frequency Doppler imaging, which permits detection and characterization of ocular blood flow not detectable at lower, conventional Doppler frequencies. The eyes of CD-1 mice were examined daily from the day of birth to postnatal day (P)16. Hyaloid vascular system anatomy was imaged with UBM and microcomputed tomography (microCT). Blood flow velocity was also measured with Doppler UBM imaging in the hyaloid artery, vasa hyaloidea propria, tunica vasculosa lentis, and retina. In the mouse, the hyaloid vasculature degenerated from a well-defined structure at birth by progressive loss of branches. Hyaloid regression coincided with a progressive decrease in blood velocity detected in the hyaloid vascular structures, which is thought to be one of the major triggering factors of the regression in these vessels. At P13, no further blood flow was detected in the CD-1 mouse hyaloid vasculature. An inverse relationship was also shown between peak blood velocity in the lens and retina. UBM imaging provides a valuable means of rapidly and noninvasively characterizing ocular development in vivo. MicroCT scans have also provided intralumenal images of hyaloid vascular structure. This is the first study of vascular structure and function during the dynamic process of hyaloid vascular regression during mouse neonatal eye development and the first three-dimensional images of the complex hyaloid vascular structure.

Detection of prostate cancer with high-frequency Doppler imaging

Objective: This study was performed to evaluate cancer detection with targeted biopsy of the prostate performed on the basis of high-frequency Doppler ultrasonographic imaging versus cancer detection with a modified sextant biopsy approach with laterally directed cores.

High-frequency doppler ultrasound examination of blood flow in the anterior segment of the eye

PURPOSE: To show that extending Doppler imaging into the high-frequency domain could allow detection and characterization of blood flow in small arterioles and capillaries. METHODS: A 40-MHz continuous wave Doppler system and a 60-MHz pulsed-wave Doppler system were constructed, tested, and used to examine the ciliary body region in two normal volunteers. RESULTS: Ciliary body circulation in the region of the great circle of the iris, which is undetectable by conventional 7.5-MHz duplex Doppler, was consistently and reproducibly detectable by high-frequency (40-MHz and 60-MHz) Doppler systems. CONCLUSION: High-frequency Doppler imaging may provide a unique new tool for the characterization and assessment of anterior segment ocular blood flow.