Information AboutUltrasound |
| CATEGORIES ABOUT ULTRASOUND | |
| hearing | |
| acoustics | |
| ultrasound | |
| medical physics | |
| medical ultrasoundhearing | |
| acoustics | |
| ultrasound | |
| medical physics | |
| medical ultrasound | |
| acoustics | |
| sound | |
| medical physics | |
|
Ultrasound is a cyclic Sound pressure with a Frequency greater than the upper limit of human hearing, this limit being approximately 20 Kilohertz (20,000 hertz). ABILITY TO HEAR ULTRASOUND The upper frequency limit in humans (approximately 20 kHz) is caused by the Middle Ear , which acts as a Low-pass Filter . If ultrasound is fed directly into the skull bone and reaches the Cochlea without passing through the middle ear, much higher frequencies can be heard. This effect is discussed in Ultrasonic Hearing . Carefully-designed scientific studies have been performed and confirmed what they call the Hypersonic Effect - that even without consciously hearing it, high-frequency sound can have a measurable effect on the mind. It is a fact in company has used this to create ring signals supposedly only able to be heard by younger humans "A Ring Tone Meant to Fall on Deaf Ears" (New York Times article); but many older people claim to be able to hear it, which is likely given the considerable variation of age-related deterioration in the upper hearing threshold. Some animals – such as Dog s, Dolphins , Bat s, and Mice – have an upper frequency limit that is greater than that of the human Ear and thus can hear ultrasound. DIAGNOSTIC SONOGRAPHY "]] See Also: Medical ultrasonography Medical sonography ('''ultrasonography''') is an ultrasound-based diagnostic Medical Imaging technique used to visualize muscles, tendons, and many internal organs, their size, structure and any pathological Lesion s with real time tomographic images. They are also used to visualize a fetus during routine and emergency Prenatal Care . Ultrasound scans are performed by medical health care professionals called Sonographer s. Obstetric Sonography is commonly used during Pregnancy . Ultrasound has been used to image the human body for at least 50 years. It is one of the most widely used diagnostic tools in modern medicine. The technology is relatively inexpensive and portable, especially when compared with modalities such as Magnetic Resonance Imaging (MRI) and Computed Tomography (CT). As currently applied in the medical environment, US poses no known risks to the patient. {Link without Title} Ultrasound is generally described as a "safe test" because it does not use ionizing radiation, which imposes hazards, such as cancer production and chromosome breakage. However, ultrasound energy has two potential physiological effects: it enhances inflammatory response; and it can heat soft tissue. Watson, T. (2006). "Therapeutic Ultrasound". (see here for a pdf version with the author and date information) Ultrasound energy produces a mechanical pressure wave through soft tissue. This pressure wave may cause microscopic bubbles in living tissues, and distortion of the cell membrane, influencing ion fluxes and intracellular activity. When ultrasound enters the body, it causes molecular friction and heats the tissues slightly. This effect is very minor as normal tissue perfusion dissipates heat. With high intensity, it can also cause small pockets of gas in body fluids or tissues to expand and contract/collapse in a phenomena called cavitation (this is not known to occur at diagnostic power levels used by modern diagnostic ultrasound units). The long-term effects of tissue heating and cavitation are not known. There are no known harmful effects associated with the medical use of sonography. Widespread clinical use of diagnostic ultrasound for many years has not revealed any harmful effects. Studies in humans have revealed no direct link between the use of diagnostic ultrasound and any adverse outcome. Although the possibility exists that biological effects may be identified in the future, current information indicates that the benefits to patients far outweigh the risks.[http://www.aium.org/patient/aboutExam/safety.asp Obstetric ultrasound can be used to identify many conditions that would be harmful to the mother and the baby. For this reason many health care professionals consider that the risk of leaving these conditions undiagnosed is much greater than the very small risk, if any, associated with undergoing the scan. According to Cochrane review, routine ultrasound in early pregnancy (less than 24 weeks) appears to enable better gestational age assessment, earlier detection of multiple pregnancies and earlier detection of clinically unsuspected fetal malformation at a time when termination of pregnancy is possible. {Link without Title} Ultrasound is used routinely in obstetric appointments during pregnancy, but the FDA discourages its use for non-medical purposes such as fetal keepsake videos and photos, even though it is the same technology used in hospitals. Obstetric ultrasound is primarily used to:
Unfortunately, results are occasionally wrong, producing a false positives (the Cochrane Collaboration is a relevant effort to improve the reliability of health care trials). False detection may result in patients being warned of birth defects when no such defect exists. Sex determination is only accurate after 12 weeks gestation in Obstetrics and Gynecology 1999 . When balancing risk and reward; there are recommendations to avoid the use of routine ultrasound for low risk pregnancies [ACOG]. In many countries ultrasound is used routinely in the management of all pregnancies. According to European Committee of Medical Ultrasound Safety (ECMUS) "Ultrasound examinations should only be performed by competent personnel who are trained and updated in safety matters. Ultrasound produces heating, pressure changes and mechanical disturbances in tissue. Diagnostic levels of ultrasound can produce temperature rises that are hazardous to sensitive organs and the embryo/fetus. Biological effects of non-thermal origin have been reported in animals but, to date, no such effects have been demonstrated in humans, except when a microbubble contrast agent is present" {Link without Title} . A study on rodent fetus brains that are exposed to ultrasound showed signs of damage. Speculation on human fetuses can be in a range of no significant complications to variety of mental and brain disorder. The study shows that rodent brain cells failed to grow to their proper position and remained scattered in incorrect parts of the brain. The conditions of this experiment are different from typical fetal scanning because of the long dwell times. Institute of Neurological Disorders; Proceedings of the National Academy of Sciences . Care should be taken to use low power settings and avoid pulsed wave scanning of the fetal brain unless specifically indicated in high risk pregnancies. It should be noted that obstetrics is not the only use of ultrasound. Soft tissue imaging of many other parts of the body is conducted with ultrasound. Other scans routinely conducted are cardiac, renal, liver and gallbladder ( Hepatic ). Other common applications include musculo-skeletal imaging of muscles, ligaments and tendons, Ophthalmic ultrasound (eye)scans and superficial structures such as Testicle , Thyroid , Salivary Glands and Lymph Nodes . Because of the Real Time nature of ultrasound, it is often used to guide interventional procedures such as fine needle aspiration FNA or Biopsy of masses for Cytology or Histology testing in the breast, thyroid, liver, kidney, lymph nodes, muscles and joints. Ultrasound scanners using pulsed wave and colour Doppler are used to visualize arteries and veins. Figures released for period 2005-2006 by UK Government (Department of Health) show that non-obstetric ultrasound examinations contributed to more than 65% of the total number of ultrasound scans conducted. BIOMEDICAL ULTRASOUND APPLICATIONS Ultrasound also has therapeutic applications, which can be highly beneficial when used with dosage precautions:''Essentials of Medical Ultrasound: A Practical Introduction to the Principles, Techniques and Biomedical Applications'', edited by M. H. Rapacholi, Humana Press 1982
INDUSTRIAL ULTRASOUND cracking]] Ultrasonic Testing is a type of Nondestructive Testing commonly used to find flaws in materials and to measure the thickness of objects. Frequencies of 2 to 10 MHz are common but for special purposes other frequencies are used. Inspection may be manual or automated and is an essential part of modern manufacturing processes. Most Metal s can be inspected as well as Plastics and Aerospace Composites . Lower frequency ultrasound (50 kHz to 500 kHz) can also be used to inspect less dense materials such as Wood , Concrete and Cement . Ultrasound can also be used for heat transfer in liquids.Milton B. Larson, ''Study of the Effects of Ultrasonic Vibrations on Convective Heat Transfer in Liquids'', (1960) Researchers recently employed ultrasound in dry corn milling plant to enhance ethanol production {Link without Title} . ULTRASOUND FLOW METER See Also: Ultrasound flow meter ULTRASONIC CLEANING Ultrasonic Cleaner s, sometimes mistakenly called '' Supersonic cleaners'', are used at frequencies from 20-40 KHz for Jewellery , Lenses and other optical parts, Watch es, Dental Instrument s, Surgical Instrument s and Industrial parts. An ultrasonic cleaner works mostly by energy released from the collapse of millions of microscopic Cavitation s near the dirty surface. The bubbles formed by Cavitation collapse forming tiny jets directed at the surface. Home ultrasonic cleaners are available and cost about US $60 or more. ULTRASOUND AND ANIMALS Bats Bats use a variety of ultrasonic ranging ( Echolocation ) techniques to detect their prey. they can detect frequencies as high as 100,000 hz(HERTZ) Dogs The Dog Whistle is used to call to a Dog . It emits ultrasound at a Frequency in the range of 15hz to 30,000hz which Dog s can hear.. Dolphins and Whales It is well known that some whales can hear ultrasound and have their own natural Sonar system. Some whales use the ultrasound as a hunting tool (for both detection of prey and as an attack). Fish |
|
|