Vascular Sonography

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Vascular Sonography

Introduction

Sonography is defined as a diagnostic medical procedure, which uses high frequency sound waves to produce dynamic visual images of organs, blood flow, and tissues. At this point, Sonography is increasingly being used in the detection and treatment of heart attack, heart diseases, and vascular diseases that can lead to stroke. Vascular sonography is, therefore defined as the process of using high-pitched sound waves to study the blood vessels in the body. As a matter of fact, an ultrasound image provides an essential way of evaluating the circulatory system of the body. The images are captured in real-time thus helping radiologists to monitor the blood flow to organs/tissues all over the body. In addition, the ultrasound sound images help radiologists to locate and identify blockages and abnormalities like blood clot, emboli, and plaque thereby facilitating a plan for effective treatment.

Background

Vascular refers to the blood vessels that carry blood from the heart to the other body organs and vice versa. Vascular diseases are unhealthy changes that occur in blood vessels. The circulatory system is very complex in function and structure. The flow of blood is influenced by a number of factors among them are elasticity of the vessel walls, vascular injuries, and the tone of vascular smooth muscle. Individuals with vascular injuries as a result of penetrating or blunt trauma can be divided into those which have direct clinical signs of arterial/venous injury and those with indirect signs. Trauma without direct signs represents a particular challenge as a result of the undetected vascular injury. In the past century, there was a conflict regarding the management of vascular trauma because many people advocated for aggressive surgical exploration. The approach led to a high rate of unnecessary surgery thus generating the need for selective diagnostic imaging to establish if operative intervention is required.

The potential for using the reflection of sonography in the visualization of the internal organs of the human body started in the late 1930s. Austrian neurologist Dussik K.T developed a sonographic transmission technique in order to visualize cerebral ventricles. When a particle is activated to vibrate in its equilibrium position, the vibration is transmitted to a neighboring molecule in the medium.

In this manner, kinetic energy is propagated from one molecule to the other thereby spreading through the medium in what is similar to sine wave pattern. The sound waves compresses and expands the medium as it travels through. An ultrasound image is created thus revealing any abnormality in the blood.

Sonography guided vascular access

Vascular access is an essential procedure that clinicians have to master. Injuries, obesity, intravenous drug use, and chronic medical conditions can make placements of vascular catheters in both peripheral and central veins time-consuming and challenging. In the recent years, there have been dramatic improvements in portable sonar technology, which includes the development of relatively inexpensive machines with adequate resolution to guide needle placement through tissues.

Transducer selection

Transducer characteristics such as shape and frequency determine sonar image quality. For the purpose of vascular access, it is essential to use high frequency as well as small footprint transducers. As a matter of fact, the high-frequency linear array transducer offers a higher resolution of the superficial areas of soft tissues that includes veins and arteries.

Modes

The color Doppler and B-mode are the main ultrasound modes that can used to access venous tissues. The B-mode produces recognizable 2D gray scale images. Color Doppler can applied to characterize blood flow. The mode detects optimal flow of blood when the transducer is parallel to the flow. However, when the transducer is perpendicular to the vessel, the detection of flow is worst.

Optimizing image quality

Best visualization of target vessels calls for an optimal machine setting. Generally, proper transducer selection and the selection of pre-programmed vascular sonography settings offer acceptable quality of images. Moreover, other controls that can further enhance the quality of the image are focus, depth, gain, and frequency.

Proper depth adjustment offers a better target vessel imaging. Furthermore, it facilitates the tracking of equipment used through the tissue. When the depth setting is increased, the target vessel becomes smaller. Contrary, when the depth is too shallow, significant structures that surround the target vessels may be lost. That is to say, it is necessary to select the appropriate depth for the target vessel.

The brightness of an image on the screen is directly controlled by the gain setting of the sonar machine. Furthermore, it depends on the selected gains. By increasing the gain of the machine, the image is made brighter thereby easy to study. However, when the gain is decreased, the image becomes darker thus very difficult to analyze. Actually, the highest resolution of any image displayed is at the focal zone. With the use of sonar machines, it is essential to put the focus at the level of the target vessel of interest.

Physical Principles of Sonography: Doppler Effect

During the examination of blood vessels, the moving blood cells act as the reflectors. To specific, the red blood cells act as the reflectors as a result of their great majority in the blood cells. The difference between the frequency of the reflected and transmitted sound is known as Doppler-frequency-shift. If the direction of the blood flows to the transducer, then Doppler-shift is positive. Nevertheless, if the direction of blood flow is away from the probe, the Doppler-shift is negative.

The Doppler-shift can be displayed in a number of ways, which depend on the Doppler technique. The use of spectral mode is popular because Doppler tracing can be seen. Moreover, color/Doppler mode can be used. This mode displays the Doppler-shift as shades of one or more color inside the color box.

Spectral Doppler Sonography

Spectral Doppler techniques display consists of two types: pulsed and continuous wave Doppler modes. Pulsed wave Doppler mode is used in peripheral/abdominal vascular studies while continuous wave Doppler is to measure high velocities. A pulsed wave transducer contains one piezoelectric crystal.

In connection the above point, the crystal transmits pulses at regular intervals. The same crystal receives reflected signal and compares it with the transmitted reference. Pulsing the waves allow Doppler measurements to be taken from a specific region within the image field thereby allowing velocity measurements from the selected vessels. A pulsed wave allows precise localization of the volume of tissue from, which the Doppler blood flow signal is sampled in contrast with the continuous wave technique.

Duplex imaging uses pulsed wave Doppler with a two-dimensional real-time image. Normally, the location of the target volume is displayed on the B-scan tomogram. At this point, the sampling gate can be moved to the lumen of the vessel as highlighted on the real-time image. The velocity changes, which occur in each cardiac cycle, can be displayed graphically. The running time is placed on the horizontal axis. If the cursor is aligned parallel to the blood vessel, the velocity of the moving cells can be seen on the vertical axis.

During a duplex Doppler examination, the Doppler-shift can be displayed graphically or in audible form. The arteries have swish-like sounds while veins have continuous wind-blow-like sounds. The intensity of the audible sounds is directly proportional to the quantity of moving blood cells. The higher of the velocity of the flowing blood, the higher the audible sound is. In effect, pulsed wave Doppler sonography promotes the assessment of the direction, presence, and velocity of blood flow in the sample volume.

The most commonly used methods for measuring the blood flow velocity in a vessel are the maximum velocity method and uniform insonation method. In the uniform insonation method, the entire lumen of the vessel is incorporated into the gate. Nevertheless, maximum velocity method is where a small sample volume is placed in the placed in the centre of the vessel.

Color Doppler imaging

The basics of color Doppler imaging are almost similar to pulsed wave Doppler mode; however, it has a number of multiple sample volumes inside a circumscribed region known as a color box rather a visible one. The position and size of the color box on the B-mode image is determined by the operator. This type of sonography displays the two-dimensional flow information in color superimposed on the B-mode image of the vessel as well as the surrounding tissue.

Inside the color box, all the points are in a shade of red or blue rather than a shade of gray. The direction of flow relative to the transducer is illustrated on a color bar adjacent to the image. By convection, the flow the move towards the transducer is red whereas the flow away from the transducer is blue.

Color Doppler sonogram technique offers movement-information regarding a large part of the image. In point of fact, color Doppler flow imaging promotes the assessment of the presence, quality, and direction of blood flow more quickly than it does in other noninvasive technique.

 

Planes and Views

For the purposes of vascular access, two types of planes are used: longitudinal and transverse views. In the transverse view, the transducer plane is placed in cross section of the target vessel and the vessel is displayed on the screen as a circle. However, in a longitudinal view, the transducer plane is placed parallel to the one another and the vessel is displayed on the screen as a long tube running across the screen. On the whole, a longitudinal view allows visualization of the entire vessel of interest but requires that needle, transducer beam, and the target vessel to be held parallel to one another.

Differentiating vein and artery

Differentiating between vein and artery is important to safely perform sonography guided vascular access. The simplest way to differentiate between artery and vein is the compressibility of veins. Basically, veins compress with minimal pressure while arteries retain much of their original shape and appearance despite a heavy pressure. While performing an internal jugular vein placement, it is necessary to visualize the influence of respiratory variation on the vein diameter. Trendelenberg positioning and valsalva maneuvers make vein larger; however, it has a minimal impact on the carotid artery.

Scanning techniques

The guidance of vascular access using sonogram can be grouped as dynamic or static. In the static use of sonogram, providers apply sonogram to localize the vein and mark the site of the needle insertion on the skin. The dynamic guidance entails the use of sonogram in real-time with continuous visualization of the needle insertion throughput the procedure. The success rate for dynamic guidance is higher than those of static technique.

Sonographic examination of blood vessel

The Rise and Grandeur of Qing Dynasty

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The Rise and Grandeur of Qing Dynasty

Summary of the development

The Qing dynasty was the last Chinese dynasty with began in 1644 and ended in 1912. It began after the decline of Ming dynasty which had ruled for 276 years. Qing dynasty was being ruled by a bordering nomadic clan known as Manchus. The Manchus forcefully entered Beijing to seize the throne from the Ming rulers. After crossing the walls of Beijing, the Manchu forces engaged in a fight against the Li Zicheng’s army. They succeeded and eventually managed to take the throne and that marked the beginning of the Qing Dynasty. The establishment of the Qing Dynasty marked the beginning of a period of growth for the Chinese and Manchu people. The public works sector significantly added to the growth of the cities and the living standards of people improved due to increased trade and lower taxes on people. Western missioners, who came to China at the time, brought about Christianity and also influenced the Chinese in science. Politically, positions were shared among the Manchu and Chinese people. They had well organized military units which especially played an important role in the success of the dynasty.

Historical context of the rise and grandeur of the Qing dynasty

The establishment of the Qing dynasty was preceded by a period in which the Ming government was weak due to their inability to address famine, natural disasters and economic instability in the empire. People were then convinced that the Ming had lost the Mandate of Heaven. Rebellions then erupted from the Mongols and Jurchens. It is the invasions of the Mongolians and attacks from the Manchus that led to the eventual fall and rise Ming and Qing dynasties respectively. Just before the Ming dynasty was overthrown and Qing dynasty established, China’s economy was undergoing one of the greatest expansions in history. New markets were being established and merchants were expanding their trade activities as far as the South China Sea. Through the ‘Ming Voyages’, Chinese merchants were able to reach Southeast Asia and were actively involved in businesses. The economic growth (dynamic, commercialized) continued through the Qing dynasty period until the eruption of the Opium wars. In 1900, a group of rebels in southern China carried out rebellion against the Qing Dynasty. The success of the revolt saw the establishment Republic of China and the end of Chinese dynastic system.  

Significant contingent factor(s) relating to the rise and grandeur of Qing dynasty

The most significant contingent factors relating to the rise and grandeur of the Qing dynasty include the decline of the Ming dynasty, favorable policies and also the strong economic foundation that preceded the Qing dynasty period. The prominent problems as economic instability, natural disasters weakened the Ming dynasty and that acted as an important factor in influencing the Mongolians and Manchu’s to rebel and finally overthrow the government. That gave rise to the Qing Empire. Favorable policies allowed for lower taxes and improved living standards of the people who in turn gained confidence on the leadership of the Qing dynasty.  Such policies allowed for active providence of public goods to improve the economic well-beings of the people of China and Manchu. The economic foundation laid in the pre-Qing dynasty period allowed for more growth and stability in the empire and largely contributed to its continuity through to the 20th century.

Historical Complexity

The Manchus (rulers of the Qing Dynasty) received much resistance because they were non Han Chinese. They had to adopt Chinese cultures and Ming institutions to be able to dominate over the empire and to reduce resistance. They, for example, sustained the Confucian temple rituals, court practices and civil service. To quell the ever inherent internal rebellion and foreign invasions, Qing rulers subdued China Proper and went beyond the borders to conquer Outer Mongolia, Central Asia (Tibet) and Taiwan, among other neighbouring states. In this way, they were able to eliminate threats both from within and from outside China Proper. Qing rulers were always suspicious of the Han Chinese. As a result, they implemented measures to ensure that the relatively fewer Manchus rulers were not absorbed into the Han Chinese population that was dominant. Such measures included outlawing intermarriage between the two groups and forbidding Chinese migration into the Manchu mainland, among others.

Significance of the rise and grandeur of Qing dynasty in the world today

The significance of the Qing dynasty is evident in the world today. First, it was a period that to a large extent lay foundation for the Republic of China particularly in terms of social and cultural ideals. Economically, the period influenced trade across the world and shaped trade trends that are still in effect even in the world today such as those established between China and Europe. It was the time in which religious constructs took shape in terms of the introduction of the world religions that exist in the world today. Missioners brought Christianity into China, a fact that has continued to influence people within and without the country. The Qing dynasty period is also well known as the period for the development of art in form of paintings and sculpturing. Much of the styles and principles of the arts at the time have had great influences on the art pieces in the contemporary world. Many artists today have borrowed specific techniques and styles from the paintings of the Qing dynasty period. Also, the period also gave rise to the Chinese culturalism and self-sufficiencywhich still forms an important ideal for the Chinese government today.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Works Cited

‘China’s Last Empire: The Great Qing’. Choice Reviews Online 47.07 (2010): 47-3974-47-3974. Web.

Hall, Eleanor J. Ancient Chinese Dynasties. San Diego, CA: Lucent Books, 2000. Print.

Udry, Stephen P. ‘China’s Last Empire: The Great Qing – By William T. Rowe’. Historian 73.3 (2011): 603-604. Web.

Wang, Wensheng. ‘China’S Last Empire: The Great Qing , By William T. Rowe . Cambridge MA: Harvard University Press, 2012 (Paperback Edition). [Viii] + 360 Pp. US$18.95 (Paperback).’. The China Journal 71 (2014): 285-288. Web.

Zhang, Wei-Bin. The Rise And Fall Of China’s Last Dynasty. New York: Nova Science Publishers, 2011. Print.