Fundamentals of Ultrasound: Physics Primer

Welcome to the Fundamentals of Ultrasound:  A Physics Primer.   Diagnostic ultrasound is one of the most versatile non-invasive imaging modalities available worldwide.   We will begin with an introduction to the basic physical properties of ultrasound, how they interact and influence one another.     Thank you for your interest in ultrasound.   So, let us get started! Congratulations. You have just finished the online course, A Physics Primer. Listed below are the key points. Take time now to review the material here and in the glossary that follows before proceeding to the final quiz. Link to the Detailed Course Review. Identify fundamental sound wave frequency ranges Understand the piezoelectric principle Discuss echolocation Relate penetration and resolution to frequency, pulse, and wavelength Understand how impedance and incidence impacts reflected echoes     Earlier we learned that sound waves transport energy as they travel through a medium. This transfer of energy weakens the ultrasound signal as it passes further into the body interacting with organs and tissue. The signal integrity of pulses degrades with distance traveled. Knowing that signal integrity of pulses degrades with distance traveled, higher frequencies attenuate and do not travel as far as low frequencies.   Now, select learn more below for more information.     Frequency, Penetration, and Resolution Learn how frequency influences resolution and penetration. The reproduction, transmission or distribution of this training or its contents is not permitted without express written authority. Offenders will be liable for damages.   All names and data of patients, parameters and configuration dependent designations are fictional and examples only. All rights, including rights created by patent grant or registration of a utility model or design, are reserved.   Copyright © Siemens Healthcare GmbH, 2020.   Please note that the learning material is for training purposes only!   For the proper use of the software or hardware, please always use the Operator Manual or Instructions for Use (hereinafter collectively “Operator Manual”) issued by Siemens Healthineers. This material is to be used as training material only and shall by no means substitute the Operator Manual. Any material used in this training will not be updated on a regular basis and does not necessarily reflect the latest version of the software and hardware available at the time of the training.   The Operator Manual shall be used as your main reference, in particular for relevant safety information like warnings and cautions. Note: Some functions shown in this material are optional and might not be part of your system. The information in this material contains general technical descriptions of specifications and options as well as standard and optional features that do not always have to be present in individual cases.   Certain products, product related claims or functionalities described in the material (hereinafter collectively “Functionality”) may not (yet) be commercially available in your country. Due to regulatory requirements, the future availability of said Functionalities in any specific country is not guaranteed. Please contact your local Siemens Healthineers sales representative for the most current information.     Infrasound is inaudible, and a very low-frequency sound of less than 20 Hz.  Human ears can perceive sound frequency in a range from 20 Hz to 20,000 Hz this is audible sound.  Ultrasound is above the audible sound range; the sound frequency that is greater than 20,000 Hz.  Ultrasound is a short wave occurring at a higher frequency.   Learn more below.   Audible and Inaudible Sound Learn more about infrasound and ultrasound.   The transducer beam should be perpendicular or have normal incidence to the tissue interfaces and organs to create the best image.   Select learn more about normal and oblique incidence below.   Normal Incidence Learn how normal or oblique incidence affects the echo. Learn more wavelength, impedance, and attenuation in soft tissue below. Impedance Learn more about the impedance. Attenuation Learn more about the attenuation. Frequency and Wavelength Learn more about frequency and wavelength. Upon successful completion of this course, you will be able to:   Identify fundamental sound wave frequency ranges Understand the piezoelectric principle Discuss echolocation Relate penetration and resolution to frequency, pulse, and wavelength Understand how impedance and incidence impacts reflected echoes The piezoelectric properties of the elements or ‘crystals’ contained within the transducer are the sound source and create the ultrasound waves.  Learn more below.   Sound Source Learn more about the sound source. Diagnostic ultrasound imaging mostly uses short segments of pulsed ultrasound waves to transmit signals into the body. Learn more about echolocation below. Echolocation Learn more about echolocation. References and Glossary Glossary Glossary Glossary Acoustic Impedance- Impedance is a property of a medium that impedes the movement of the sound wave through the media. Acoustic impedance is the product of the density of the medium and the propagation speed of the medium. Axial Resolution –The ability to display two closely spaced targets as two individuals in the vertical direction.  Frequency and wavelength determine the axial resolution.  Frequency- Relates to how many cycles of wave vibrations occur and is measured in Hertz or Hz. Echoes-The signals that return from the organs and tissue interfaces. Echolocation- Locating objects by reflected sound is called echolocation. Elements- Another name for the piezoelectric crystals. The construction and properties can be natural occurring or manmade. Frequency- the number of cycles per second measured in Hz. Human Hearing- Sound frequency between 20Hz and 20,000Hz. Infrasound- Sound frequency below 20Hz. Lateral Resolution - The minimum separation of structures that can be resolved in the direction perpendicular to the beam. Mapping- Using greyscale to assign strengths of returned echoes to the display. Piezoelectric- The crystals within the ultrasound transducer can convert electric signal to a mechanical pulse and convert a mechanical pulse into an electric signal. This phenomenon is called Piezoelectric effect. Propagation Speed – The speed that sound travels through a medium. Transducer- The transducer is the handheld potion of the ultrasound system and interfaces with the tissue. Ultrasound- Sound frequency greater than 20,000Hz.  Used in diagnostic medical ultrasound imaging. References References 1.             Hertz, H., Electric Waves, in University of Bon. 1893. 2.             Ramsayer, K., Infrasonic Symphony. Science News, 2004(165): p. 22-28. 3.             Griffin, D.R., The mechanism by which bats produce supersonic sounds. Anat Rec, 1946. 96(4): p. 519. 4.             Edelman, S.K., Understanding Ultrasound Physics. 4 ed. 2016, Woodlands: Elsevier. 5.             J. Serway, J.W.J., Soundwaves, in Physics for Scientist and Engineers, T.B.a. Cole, Editor. 2004. p. 1296. 6.             Kremkau, F.W., Sonography: principles and instruments. 9 ed. 2016, St. Louis: Elsevier. 7.             Society, F.R.o.I.T.i., Propagation Speed in Tissue, Zurich43, Editor. 2018. 8.             J.A. Zagzebski, J.A., Essentials of Ultrasound Physics. 1996, St. Louis: Mosby. 9.             Hedrick, W., Technology for diagnostic sonography. 2013, St. Louis, MO: Elsevier. 10.           Miele, F.R., Ultrasound Physics and Instrumentation. 5 ed, ed. F.R. Miele. 2013: Pegasus Lectures Inc. 11.           Lord, M. and D.M. Smith, Static response of a simple piezoelectric load cell. J Biomed Eng, 1983. 5(2): p. 162-4. 12.           Fleischer, M., D. Stein, and H. Meixner, New type of piezoelectric ultrasonic motor. IEEE Trans Ultrason Ferroelectr Freq Control, 1989. 36(6): p. 614-9. 13.           Z.Zhang,et.al, Design and comp. PMN-PT single crystals and PZT ceramics based medical phased array ultrasonic transducer. Sensor and Actuators, 2018. 1: p. 273-281. 14.           in Webster's Third New International Dictionary, Unabridged B.D. Learning, Editor. 2017. 15.           Havemeyer, H. Unit Juggler. 16.           Havemeyer, H. How to conert meters per second to miles per hour. Physics Fundamentals 2017  April 24, 2017]. 17.           Rokuro, H., et al., Measurement of Speed of Sound in Skull Bone and Its Thickness Using a Focused Ultrasonic Wave. Japanese Journal of Applied Physics, 2002. 41(5S): p. 3327. 18.           F.J. Fry, J.E.B., Acoustical Properties of the Human Skull. Journal Accoustic Society of America, 1977(May): p. 1576-1590. 19.           Kremkau, F.W., Doppler color imaging. Principles and instrumentation. Clin Diagn Ultrasound, 1992. 27: p. 7-60. 20.           Francisco Neto, M.J., et al., Advances in lung ultrasound, J Einstein (São Paulo). 2016. 14: p. 443-448. 21.           Saraogi, A., Lung ultrasound: Present and future. Lung India : official organ of Indian Chest Society, 2015. 32(3): p. 250-257. 22.           Banholzer, P., et al., [Sonographic changes in the size of the kidneys in type I diabetes as a method of early detection of diabetic nephropathy]. Ultraschall Med, 1988. 9(6): p. 255-9. 23.           Dulchavsky, S.A., et al., Thoracic Ultrasound Diagnosis of Pneumothorax. 1999. 47(5): p. 970. 24.           Michel Claudon, F.T., David H. Evans, Frédéric Lefèvre, Jean Michel Correas, Advances in Ultrasound. European Radiology, 2002. 12: p. 7-18. The number of waves that occur over one second is the frequency of sound and measured in Hertz (Hz) named after Heinrich Rudolf Hertz. Dr. Hertz was a German physicist who proved the existence of electromagnetic waves and was the first to measure their length and velocity.  Sound waves behave much the same as light waves. However, sound can only travel through material or media. Sound waves transport energy as they travel through a medium or media. Sound travels through a medium. The speed or propagation speed is the rate that sound travels through the medium or media. There are different propagation speeds or the speed that sound travels through a medium.   Select learn more below. Propagation Speed Learn more about propagation speed. Sound Travel Learn more about sound travel.