Doppler scanning

A 64-year-old man with giant cell arteritis was given prednisolone 60 mg/day. Within 5 days he developed double vision and agitation and became drowsy and confused. A cranial MRI scan showed recent cerebral lesions and a Doppler scan showed high-resistant blood flow in both vertebral arteries. He had an episode of complete loss of vision and was given dexamethasone... 

Fig. 1.7 A Mossbauer transmission spectrum produced by Doppler scanning, and the factors influencing it.

Resonant absorption of the 129-4-keV y-ray was first demonstrated in an on-off experiment in which the y-transmission was measured at 20 K and 65 K [85]. Initial attempts to observe the 129-keV resonance by Doppler scanning using Au/Cu and Au/Ir sources with platinum absorbers at... 

A 24-year-old woman had vaginal bleeding at 15 weeks gestation. She received 2 units of packed erythrocytes and then 3 units of oxytocin through a cannula on the back of the hand. Within 30 minutes the hand had become edematous and cyanotic. Extravasation was apparent. The radial and ulnar pulses were not palpable and were faint on a Doppler scan. The hand was elevated and the symptoms gradually abated, with improvement of the pulses. 

In colour Doppler, similar processing is applied across the image. The colour Doppler signals are shown as an overlay conventionally coded in shades of red for flow towards, and blue for flow away from the transducer (Fig. 1.3). Another way to display flow information depicts only the Doppler signal intensity as a power Doppler scan. It has higher sensitivity than frequency-based colour Doppler but lacks directional information and so is more useful for the small vessels, for example, in tumours, than for the portal vein where flow direction is important. 

Fig. 10.6. Color Doppler of hepatocellular adenoma. Color Doppler scan reveals the presence of arterial vessels within the lesion with arterial spectrum...

The brief history, operation principle, and applications of the above-mentioned techniques are described in this chapter. There are several other measuring techniques, such as the fluorometry technique. Scanning Acoustic Microscopy, Laser Doppler Vibrometer, and Time-of-flight Secondary Ion Mass Spectroscopy, which are successfully applied in micro/nanotribology, are introduced in this chapter, too. 

Laser Doppler Vibrometry (LDV) is a sensitive laser optical technique well suited for noncontact dynamic response measurements of microscopic structures. Up to now, this technology has integrated the micro-scanning function for... 

Evaluation Perform computed tomography (CT) scan and MRI for evaluation of acute event. Perform magnetic resonance angiography for asymptomatic infarction. Perform transcranial Doppler to detect abnormal velocity and identify high-risk patients. Perform electroencephalography if there is a history of seizure. 

To analyze the data, first perform the vx- and ty-corrections and the time-to-speed transformation to make the velocity volume element the same for all data points, and then normalize each Doppler-selected TOF spectrum according to the averaged ID Doppler profile from several independent scans, I vz) = )T)(, vyS(vy vx 0,vz)dvy. Due to the large exothermicity of this reaction, the problematic density-to-flux transformation is not negligible (despite the large probe laser size used to minimize its effects) and needs to be accounted for (the wy-correction , see Sec. 3.3). By combining all the resulting TOF spectra, the product 3D velocity flux contour... 

The branching ratios into the various 0(3Pj) states were surprisingly difficult to measure. The power dependence of the ionizing laser at the center of the Doppler profile was measured before each scan of the Doppler profile to provide proper normalization of the power dependence. It was found that the combination of our laser power and sample concentration put... 

In order to dissipate the recoil energy Mossbauer was the first to use atoms in solid crystal lattices as emitters and also to cool both emitter and absorber. In this way it could be shown that the 7-ray emission from radioactive cobalt metal was absorbed by metallic iron. However, it was also found that if the iron sample were in any other chemical state, the different chemical surroundings of the iron nucleus produce a sufficient effect on the nuclear energy levels for absorption no longer to occur. To enable a search for the precisely required absorption frequency, a scan based on the Doppler effect was developed. It was noted that a velocity of 102 ms-1 produced an enormous Doppler shift and using the same equation (7) it follows that a readily attainable displacement of the source at a velocity of 1 cms-1 produces a shift of 108 Hz. This shift corresponds to about 100 line-widths and provides a reasonable scan width. 

Figure 5.4 In order to cover all possible transitions in the absorbing nucleus, the energy of the source radiation is modulated by using the Doppler effect. For 57Fe the required velocities fall in the range between -I and +1 ctn/s. In Mfissbauer emission spectroscopy, the sample under investigation is the source, and a single line absorber is used to scan the emission spectrum.

Figures 24 and 25 demonstrate the success of deconvolution beyond the Doppler limit. Trace (a) in both figures is the undeconvolved data and represents the result of signal averaging over a large number of scans to produce a signal-to-noise ratio of approximately 300 1. The spectra were base-line corrected using a 0% absorption corresponding to the apparent base line between lines and a 100% absorption level was assumed, which gave reasonable relative intensities for the range of J values observed. The...

Fig. 24 Tunable-diode-laser spectrum of RQ0 of v9 of ethane. Trace (a) is the average of 250,000 scans and exhibits linewidths of 0.0022 cm-1 (the Doppler width is 0.0018 cm-1). Trace (b) results from the deconvolution of the data in trace (a) using a gaussian with a FWHM of 0.0022 cm-1 as a response function. Trace (c) is the Q branch calculated using a model that includes torsional splitting effects Av = 1.95 mk. Trace (c) is calculated for Av = 0.00075 cm-1, which is less than one-half the 300 K Doppler width.

In laser Doppler vibrometry (SLDV), surfaces are slightly vibrated by mechanical activation while the vibrometer scans the object producing 2- or 3D maps of velocity, amplitude, and phase, which allow the detection and mapping of structural defects [15]. 

Castellini P, Esposito E, Marchetti B, Paone N, Tomasini EP (2003) New applications of scanning laser doppler vibrometry (SLDV) to non-destructive diagnostics of artworks mosaics, ceramics, inlaid wood and easel painting. J Cult Herit 4 321s-329s. 

Photons from a tunable dye laser are absorbed by a metastable state of the ion. Spontaneous emission at several wavelengths follows. The ionizing electron energy is varied over the region of interest. At each setting the laser is frequency scanned across the Doppler profile of the io.i-beam... 

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