Strömungsmodell zur Untersuchung verschiedener Strömungsqualitäten in ihrer Auswirkung auf das Spektrum des Ultraschall-Doppler-Signals

Background —Ventricular assist devices (VADs) are an accepted therapy for patients with end-stage heart failure. The implantable devices that are available produce a pulsatile flow and are very large. In 6 patients, beginning in November 1998, we started to use the continuous-flow implantable DeBakey VAD device, which weighs 93 g. To detect the flow in peripheral vessels, we measured transcranial Doppler signals in patients after implantation. Methods and Results —Transcranial Doppler studies were performed with the MULTI-DOP X4 device with two 2-MHz probes (for the middle cranial arteries) in 4 patients for up to 12 weeks twice weekly after implantation. The blood velocity was measured, and the pulsation index (PI) calculated. The measured pump flow and rotations per minute were registered. The preoperative echocardiographic assessment values were compared with those acquired 6 weeks after implantation. The PI increased continually in all patients after VAD implantation, left ventricular (LV) ejection fraction did not improve, but right ventricular (RV) ejection fraction after implantation improved compared with preoperative values. The LV end-diastolic diameter after implantation decreased between 11% and 46% intraindividually. There was no correlation between PI and blood pressure or, except in 1 patient, between PI and blood flow through the VAD. Conclusions —The DeBakey VAD unloads the LV, which leads to a decrease in LV end-diastolic LV diameter and to the restoration of RV function. The unloaded LV and partially recovered RV provide a nearly physiological pulsatile flow despite the continuous flow of the VAD. Pulsatility is independent of peripheral vascular resistance. The first clinical experience with the DeBakey VAD was positive and has resulted in its continued use.

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Renal Allograft Torsion: US and CT Imaging Findings of a Rare Posttransplant Complication

Case Reports in Radiology ◽

10.1155/2016/4273780 ◽

2016 ◽

Vol 2016 ◽

pp. 1-3 ◽

Cited By ~ 1

Author(s):

Rohit Dewan ◽

Anil K. Dasyam ◽

Henke Tan ◽

Alessandro Furlan

Keyword(s):

Doppler Ultrasound ◽

Renal Allograft ◽

Color Doppler ◽

Color Doppler Ultrasound ◽

Imaging Findings ◽

Unenhanced Ct ◽

Doppler Signals ◽

History Of ◽

Normal Blood Flow

Vascular torsion is a rare renal transplant complication which requires prompt diagnosis and surgery to salvage allograft function. We report here a case of renal allograft torsion with interesting imaging findings on unenhanced CT and color Doppler ultrasound. A 60-year-old woman with a history of pancreas and kidney transplant presented to the emergency room with nausea, vomiting, abdominal pain, and minimal urine output. Unenhanced CT of the abdomen demonstrated an enlarged and malrotated renal allograft with moderate hydronephrosis. Color Doppler ultrasound demonstrated lack of vascularity within the allograft. The patient was taken urgently to the operating room where the renal allograft was found twisted 360 degrees around the vascular pedicle. After the allograft was detorsed, the color of the kidney returned and the Doppler signals for arterial flow improved. Intraoperative biopsy showed no evidence of infarct or acute cellular rejection. The detorsed kidney was surgically fixed in position in its upper and lower poles. Follow-up ultrasound 1 day later demonstrated normal blood flow to the renal allograft and the serum level of creatinine returned to normal.

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Laser Doppler Velocimetry Signal Processing Based on Spectral Refinement and Correction

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.383-390.6319 ◽

2011 ◽

Vol 383-390 ◽

pp. 6319-6323

Author(s):

Nian Long Song ◽

Da Zhang ◽

Qi Li

Keyword(s):

Signal Processing ◽

Laser Doppler Velocimetry ◽

Operation Time ◽

Laser Doppler ◽

Doppler Signal ◽

Doppler Velocimetry ◽

Basic Principles ◽

Doppler Signals ◽

Sinusoidal Signals ◽

Ratio Correction

In order to improve the accuracy of signal processing in Laser Doppler Velocimetry, a method based on the association of spectral refinement and correction is presented. Zoom-FFT and ratio correction are adopted to realize this method. Basic principles of zoom-FFT and ratio correction are expounded. FFT and the method are adopted to process sinusoidal signals and simulated laser Doppler signals with different frequencies separately in circumstance of MATLAB 7.0. Comparisons between the results of FFT and the method are carried out. The comparisons show that this method has the capability to improve the accuracy of laser Doppler signal processing significantly and the operation time is acceptable for LDV system.

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ANALYSIS OF CAROTID ARTERIAL DOPPLER SIGNALS USING STFT AND WIGNER–VILLE DISTRIBUTION (WVD)

Journal of Mechanics in Medicine and Biology ◽

10.1142/s0219519409002845 ◽

2009 ◽

Vol 09 (01) ◽

pp. 49-62

Author(s):

MELLE SEDDIK AMINA ◽

M. BEREKSI REGUIG FETHI

Keyword(s):

Power Spectra ◽

Doppler Imaging ◽

Time Frequency ◽

Ultrasound Frequency ◽

Doppler Signals ◽

Cross Terms ◽

Noticeable Reduction ◽

Doppler Power ◽

Short Time

The study presented in this paper is concerned with the analysis of the ultrasound Doppler signal of the carotid arteries in the time-frequency domain using the short time Fourier transform (STFT) and the Wigner–Ville distribution (WVD). This study is carried out in order to investigate the behavior of the spectral broadening index (SBI) derived from spectra obtained using these methods. The variations in the shape of the Doppler power spectra as a function of time are presented in the form of sonograms in order to determine the degree of primitive carotid artery stenosis. The obtained results show a qualitative improvement in the appearance of the sonograms generated using the WVD over the STFT. However, despite this qualitative improvement the WVD suffers from some drawbacks: the presence of the cross terms which are primarily due to its quadratic nature. The application of the Choi–Williams distribution (CWD) in this analysis shows a noticeable reduction of these cross terms, improving therefore the quality of the sonograms. From these generated sonograms, the ultrasound frequency envelopes are extracted. The maximum and the mean frequencies in these envelopes are used to determine the SBI. The magnitude of the CWD-SBI is significantly greater than that of the STFT-SBI. In addition, there is a correlation between the SBIs obtained using the STFT and the CWD and the degree of severity of stenosis measured by 2D Doppler imaging.

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