Ultrasound Physics

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  • hello I am working on Ph.D thesis it is about the ultrasound and I need to make sure of some concept. is the high density material reflects the ultrasound waves as echo more than the low density material? thanks for reply (wmamj@yahoo.com) , (+9647705865940)
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  • dear sir
    u r ppt is very good

    pls mail me
    'santhosh4665@gmail.com'
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  • Stem cells are “non-specialized” cells that have the potential to form into other types of specific cells, such as blood, muscles or nerves. They are unlike 'differentiated' cells which have already become whatever organ or structure they are in the body. Stem cells are present throughout our body, but more abundant in a fetus.
    Medical researchers and scientists believe that stem cell therapy will, in the near future, advance medicine dramatically and change the course of disease treatment. This is because stem cells have the ability to grow into any kind of cell and, if transplanted into the body, will relocate to the damaged tissue, replacing it. For example, neural cells in the spinal cord, brain, optic nerves, or other parts of the central nervous system that have been injured can be replaced by injected stem cells. Various stem cell therapies are already practiced, a popular one being bone marrow transplants that are used to treat leukemia. In theory and in fact, lifeless cells anywhere in the body, no matter what the cause of the disease or injury, can be replaced with vigorous new cells because of the remarkable plasticity of stem cells. Biomed companies predict that with all of the research activity in stem cell therapy currently being directed toward the technology, a wider range of disease types including cancer, diabetes, spinal cord injury, and even multiple sclerosis will be effectively treated in the future. Recently announced trials are now underway to study both safety and efficacy of autologous stem cell transplantation in MS patients because of promising early results from previous trials.
    History
    Research into stem cells grew out of the findings of two Canadian researchers, Dr’s James Till and Ernest McCulloch at the University of Toronto in 1961. They were the first to publish their experimental results into the existence of stem cells in a scientific journal. Till and McCulloch documented the way in which embryonic stem cells differentiate themselves to become mature cell tissue. Their discovery opened the door for others to develop the first medical use of stem cells in bone marrow transplantation for leukemia. Over the next 50 years their early work has led to our current state of medical practice where modern science believes that new treatments for chronic diseases including MS, diabetes, spinal cord injuries and many more disease conditions are just around the corner.
    There are a number of sources of stem cells, namely, adult cells generally extracted from bone marrow, cord cells, extracted during pregnancy and cryogenically stored, and embryonic cells, extracted from an embryo before the cells start to differentiate. As to source and method of acquiring stem cells, harvesting autologous adult cells entails the least risk and controversy.
    Autologous stem cells are obtained from the patient’s own body; and since they are the patient’s own, autologous cells are better than both cord and embryonic sources as they perfectly match the patient’s own DNA, meaning that they will never be rejected by the patient’s immune system. Autologous transplantation is now happening therapeutically at several major sites world-wide and more studies on both safety and efficacy are finally being announced. With so many unrealized expectations of stem cell therapy, results to date have been both significant and hopeful, if taking longer than anticipated.
    What’s been the Holdup?
    Up until recently, there have been intense ethical debates about stem cells and even the studies that researchers have been allowed to do. This is because research methodology was primarily concerned with embryonic stem cells, which until recently required an aborted fetus as a source of stem cells. The topic became very much a moral dilemma and research was held up for many years in the US and Canada while political debates turned into restrictive legislation. Other countries were not as inflexible and many important research studies have been taking place elsewhere. Thankfully embryonic stem cells no longer have to be used as much more advanced and preferred methods have superseded the older technologies. While the length of time that promising research has been on hold has led many to wonder if stem cell therapy will ever be a reality for many disease types, the disputes have led to a number of important improvements in the medical technology that in the end, have satisfied both sides of the ethical issue.
    CCSVI Clinic
    CCSVI Clinic has been on the leading edge of MS treatment for the past several years. We are the only group facilitating the treatment of MS patients requiring a 10-day patient aftercare protocol following neck venous angioplasty that includes daily ultrasonography and other significant therapeutic features for the period including follow-up surgeries if indicated. There is a strict safety protocol, the results of which are the subject of an approved IRB study. The goal is to derive best practice standards from the data. With the addition of ASC transplantation, our research group has now preparing application for member status in International Cellular Medicine Society (ICMS), the globally-active non-profit organization dedicated to the improvement of cell-based medical therapies through education of physicians and researchers, patient safety, and creating universal standards. For more information please visit http://www.neurosurgeonindia.org/
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Ultrasound Physics

  1. 1. Ultrasound Physics
  2. 2. Characteristics of Sound • Requires medium for its transmission. • Compression and rarefaction. • Propagation.
  3. 3. Ultrasound waves • Range • Longitudinal waves • Length of wave • Wave once generated continue in original direction until it is either reflected, refracted or absorbed
  4. 4. Velocity of Sound • Independent of frequency • medium How velocity is related to: • Compressibility • Density • Intensity
  5. 5. Transducers • Converts an electrical signals into ultrasonic energy that can be transmitted to tissues & vice versa • Constituents :- 1. Piezoelectrical crystals 2. Two electrodes 3. Backing block 4. Acoustic insulator(rubber ) 5. Plastic housing
  6. 6. • Two basic modes of transducers 1. Continuous mode – doppler studies 2. Pulse mode
  7. 7. Curie temperature Resonant frequency Transducer Q factor •Two characteristics- purity of sound & length of sound •High Q transducer •Low Q transducer
  8. 8. Advantage of High frequency over low frequency Depth resolution is superior & near zone is long Dis-advantage Tissue absorption increases with increased frequency
  9. 9. Interaction between ultrasound & matter 1. Reflection 2. Refraction 3. Absorption
  10. 10. Reflection • Reflected wave sound produces image • It depends on 1. Acoustic impedance 2 Angle of incidence
  11. 11. Acoustic impedance • Impedance is product of tissue density with velocity of sound in the material. Angle of incidence Higher the amount of angle less is the amount of sound reflected Specular interface Examples diaphragm,walls of the vessels boundaries of many organs
  12. 12. Refraction • Bending of waves as they pass from one medium to another is called refraction • Interfaces that are either smaller than the wavelength or not smooth are nonspecular interface • Example Rbc,liver parenchyma
  13. 13. Absorption • It means conversion of ultrasonic to thermal energy • It depend on 1. Frequency of sound 2. Viscosity of medium 3. Relaxation time
  14. 14. Ultrasonic display • A Mode– displayed as spikes projecting from baseline. Spike height is proportional to echo intensity. It is static one- dimensional mode. • TM Mode– echoes produced by moving structures as dots. • B Mode– produces a picture of a slice of tissue. Echoes displayed as dots. • Gray scale Imaging– It’s a B mode type displaying large amplitude of echoes arising from tissues as varying shades of gray
  15. 15. • Real time imaging– produces multiple images in a very short period • Two types 1. Mechanical– Oscillating & Rotating wheel 2. Electronic array– Linear array & phased or steered array
  16. 16. PRINCIPLES OF DOPPLER ULTRASOUND
  17. 17. BASIC PRINCIPLE • Doppler ultrasound is a technique for making non-invasive velocity measurements of blood flow. • Christian Doppler was the first to describe the frequency shift that occurs when sound or light is emitted from a moving source. • Ultrasound is transmitted into a vessel and the sound that is reflected from the blood is detected. Because the blood is moving, the sound undergoes a frequency (Doppler) shift.
  18. 18. Uses of doppler • Determination of anatomy. • Determination of small vessel flow distribution. • Detection of vascular dilatation, obstruction. • Evaluation of intravascular disease and evaluation. • Detection of extra vascular flow.
  19. 19. 1) Continuous wave doppler • Without B MODE imaging 2) Pulsed wave doppler • Pulsed Doppler ultrasound is a technique for measuring the velocity of blood in a small sample volume • Used in general & obstetric ultrasound & also used to provide data for doppler sonograms & colour flow images. Disadvantage – “Aliasing” 3) Color Doppler
  20. 20. DOPPLER INDICES

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