Doppler sonography


Catalog excerpts

Doppler sonography - 1

vascular diagnosis innovative medical products

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Doppler Sonography in Vascular diagnosi Amongst angiologists, the great importance of Doppler sonography in vascular diagnosis has been undisputed for many years. For example, in his preface to a collection of papers published by Thieme in 1978, Bol linger/Zurich wrote: "Ultrasound Doppler technology represents the greatest enhancement in angiological diagnostics in the last 10 years". In the preface to his book "Praktische Dopplersonographie (Practical Doppler sonography)" published in 1984, M. Marshall/Munich demanded ."...that this method should be adopted as widely as In the meantime,...

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Table of contents Table of contents 1. 1.1. 1.2. 1.3. 2. 2.1. 2.2. 2.3. 2.4. 2.5. 2.6. 3. 3.1. 3.2. 3.3. 4. 4.1. 4.2. 5. 5.1. 5.1.1. 5.1.2. 5.1.3. 5.2. 5.3. 6. 6.1. 6.2. 6.3. 7. 7.1. 7.2. 7.3. 7.4. 7.5. 7.6. 8. Physical Principles The Nature of Sound Generating Ultrasound The Doppler Effect Equipment Unidirectional Continuous Wave Doppler Bidirectional Continuous Wave Doppler Frequency Spectrum Analysis Pulsed Doppler The Duplex System The Colour Duplex System Methods The Correct Transmission Frequency The Probe Position The Characteristics of Sound Peripheral...

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Physical principles Sound waves - or mechanical waves in general - are usually generated by an oscillating body, for example the resonance bow of a string instrument or the oscillating prongs of a tuning fork. As shown in Fig. 1.1.1, during an outward oscillation, the oscillating prongs of the tuning fork briefly compress the molecules in their immediate vicinity. A defined area of increased molecule density is created (excess pressure zone}. This excess pressure zone spreads in the direction of the oscillation in a kind of chain Whilst this area of excess pressure is spreading, the prongs...

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Physical principles 1. The speed at which waves spread or the speed of sound depends on the elasticity and molecule density of the medium. Here are some examples: Air Water Soft tissue Bone 330 1.480 approx. 2.700 — 1.540 4.100 m/s m/s m/s m/s Sound waves - created by oscillating bodies — spread in the form of cyclical pressure differences and the speed at which they spread is material specific. If a body is oscillating quite slowly, the distance between the pressure zones, the so-called wave length, is large. The human ear picks up this oscillation as a deep note. In contrast, a body which...

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Physical principles 1. Generating Ultrasound 1.2. Thin slices made of quartz crystal are used to generate the extremely high frequencies between 1 and 10 MHz used for medical diagnostic purposes (Fig. 1.2.1). Fig. 1.2.2. Changes in spatial expansion of a quartz crystal grid by changing voltage polarity The mechanical movements of the crystal follow the voltage polarity virtually with no inertia. If a constantly reversing polarity is generated using an alternating current generator, the crystal changes size in the rhythm of the alternating voltage. The crystal therefore is turned into an...

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Physical principles 1. equipment, whereby the form of the crystal can differ. Fig. 1.2.4 Transmission and reception technology of ultrasound using a quartz crystal (piezo effect) Doppler sonography in vascular diagnosis Page 4 of 67

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Physical principles The Doppler Effect The Doppler effect is named after the Austrian mathematician and physicist Christian Johann Doppler (1805-1853). Doppler had observed that the light spectrum of a celestial body which is approaching the observer was displaced to the blue end of the spectrum, i.e. it reached the Earth with a short wavelength, whereas the light spectrum of the same celestial body which was now moving away from the observer was displaced to the red end of the spectrum and therefore arrived at the Earth with a longer wavelength (Fig. 1.3.1). Based on this observation, in...

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Physical principles starting position Displacement ot (he frequency Que lo a decrease or increase in wauele direcllon ol movement relative to the recipient. Mie displacement in treg The next example shows the starting position of the tuning fork which is moving to the right tuning fork are oscillating to the outside and generating the excess pressure zone Ih due the movemenl ol the iransmiiter RM>. Depending on tlie labelled with "1" and which is now spreading through the medium at the speed of sound. One millisecond later the prongs of the tuning fork are swinging outwards again and are...

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Physical principles labelled with “2“. Due to its inherent speed the tuning fork has moved 5.5 cm with the same period of 1 millisecond. This means that the 2nd area of pressure was generated 5.5 cm to the right relative to the starting position. Therefore the wavelength on the right hand side is decreased by 5.5 cm to only 27.5 cm. In contrast, the wavelength on the left hand side increases by 5.5 cm to 38.5 cm. If the tuning fork stays at the same speed, a sound field is generated on the right hand side, the wavelength of which is only 27.5 cm, whereas a sound field is created on the left...

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Physical principles 1. Fig. 1.3.4 Negative frequency displacement when the recipient moves away from the transmitter. Even though it is not irrelevant whether the transmitter or recipient are moving towards or away from each other when calculating the frequency displacement, a simplified equation can be specified due to the relatively low speed of the recipient or transmitter in relation to the speed of sound: Fo ⋅V C Here: Fd = Frequency displacement in Hz Fo = Transmission frequency in Hz V = Velocity in m/sec C = Speed of sound in m/sec Therefore Fd is proportional to the transmission...

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Physical principles 1. but the sound transmitted is deflected by a moving reflector. In this case, a double Doppler displacement occurs. The first displacement occurs when the sound hits the reflector and a second displacement occurs when this sound is reflected at an already increased frequency (Fig. 1.3.6). Fig. 1.3.7 — Analogy for the Doppler effect: The size of the frequency displacement (here an approaching train) depends on the angle between the reflector (train) and the transmitter / recipient (observer) Fig. 1.3.6 Double frequency displacement in the case of sound reflection via a...

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