8/8/2023 0 Comments Sonogram vs ultrasound![]() The real-time nature of ultrasound imaging is useful for the evaluation of physiology as well as anatomy (e.g. There are few (if any) contraindications to the use of ultrasound, compared with MRI or contrast-enhanced CT Ultrasound is straightforward to perform portably, unlike CT/MRI Ultrasound examination is less expensive to perform than CT or MRI In most centers, ultrasound is more readily available than more advanced cross-sectional modalities such as CT or MRI Ultrasound uses non-ionizing sound waves and has not been associated with carcinogenesis - this is particularly important for the evaluation of the fetal and gonads Ultrasound continues to evolve additional functions, including 3D ultrasound imaging, elastography, and contrast-enhanced ultrasound using microbubbles. This is invaluable for evaluation of some structures such as blood vessels or the heart ( echocardiography). Doppler ultrasound, for instance, can detect a frequency shift in echoes, and determine whether the tissue is moving toward or away from the transducer. Some characteristics of returning echoes from tissue can be selected out to provide additional information beyond a grayscale image. ![]() The echoes contain spatial and contrast information. The concept is analogous to sonar used in nautical applications, but the technique in medical ultrasound is more sophisticated, gathering enough data to form a rapidly moving two-dimensional grayscale image. It sends an ultrasound pulse into tissue and then receives echoes back. TransducerĪn ultrasound transducer operates based on the physical principles of ultrasound. The loss of 3 decibels will reduce the sound intensity by half 2. ![]() Meanwhile, relative sound intensity is measured by decibels, which compares the relative intensity of two sound beams 2. The intensity/loudness/amplitude of ultrasound is measured as watts cm -2. The lower the compressibility (or higher the stiffness), or the lower the density, the higher the velocity of ultrasound 2. Compressibility (or stiffness) of the material and density of the material affects the veolocity of the ultrasound wave. During the change in velocity, the wavelength changes while the frequency remains constant 2. The velocity of transmitted wave can be either be higher or slower than the incident wave depending on the type of material it passes through 2. The angle of the transmitted sound waves (refracted waves) is governed by Snell's law 2. Differences between the acoustic impedance of the two mediums govern the proportions of reflected and transmitted sound waves 2. Acoustic impedance is a physical property of a tissue in which how much resistance it offers to stop the transmission of an ultrasound beam 2. The amount of attenuation of ultrasound is described by the attenuation coefficient. These properties cause attenuation of ultrasound that is used to localize and characterize different tissue types 2. Ultrasound images are produced by relying on properties of acoustic physics (reflection, refraction, absorption 2, and scattering). In contrast, the upper range of audible frequencies for human is around 20 thousand cycles per second (20 kHz) 2. The frequency of the sound waves used in medical ultrasound is in the range of millions of cycles per second (megahertz, MHz). Regions of high pressure and density are called "compressions" while regions of low pressure and density are called "rarefactions" 1. Sound wave transmits their energy mechanically, through pressure variations on the particles. It is a useful and flexible modality in medical imaging, and often provides an additional or unique characterization of tissues, compared with other modalities such as conventional radiography or CT.Ī sound wave is transmitted through liquids as a longitudinal wave, in which the movements of particles in a medium are parallel to the direction of propagation of the sound wave 2. Ultrasound ( US) is an imaging technology that uses high-frequency sound waves to characterize tissue.
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