Basic physics of ultrasound imaging
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Ultrasound imaging is a cost-effective, portable, and radiation-free technique that provides real-time cross-sectional views for medical interventions. The document discusses the basic physics of ultrasound, emphasizing its properties such as frequency, acoustic impedance, and the behavior of ultrasound waves as they interact with different tissues. Key points include the attenuation of waves, piezoelectric crystals' role in generating ultrasound, and the importance of frequency for imaging resolution.
Basic physics of ultrasound imaging
- 1. Basic Physics of ultrasound imaging
- 2. Why ultrasound? • Inexpensive • Portable • Safe, devoid of radiation risk • Real time, cross sectional views • Interventions, regional anesthesia “dr. karl theo dussik austrian neurologist” TITANIC Crit care med 2007 vol.35,no.5(suppl)
- 3. Ultrasound • Audible range 20hz – 20khz • SOUND: waves travelling parallel to the energy progression • SOUND has work, energy and power • Decibles – ratio measurement (logarithmic) • Velocity – m/sec • Sound velocity in body 1540 m/sec. Crit care med 2007 vol.35,no.5(suppl)
- 5. Ultrasound • Frquency: 2-10Mhz • Propagarion speed: tissues • Pulsed ultrasound • Angle of incidence • Attenuation
- 6. Ultrasound • Pulsed ultrasound: means of emitting ultrasound waves from a source. • depth of resolution • pulses are a millisecond or so long on Crit care med 2007 vol.35,no.5(suppl)
- 7. Ultrasound • Interaction with tissues: • Reflection: echo • Acoustic impedence: physical property of the tissue resistance offered by a tissue to the ultrasound beam while traversing through - Depends on density of the tissue and velocity of the ultrasound wave Z = d x c
- 9. Ultrasound • Same acoustic impedence between two tissues no image is produced • Large difference: soft tissue and bone – produce large echos, may cause not enough ultrasound waves beyond the tissue • Crit care med 2007 vol.35,no.5(suppl)
- 10. Ultrasound
- 11. Ultrasound Deviation of the ultrasound wave from straight line that depends on the velocity of the sound wave across the boundary between tissues
- 12. Ultrasound
- 13. Ultrasound • Attenuation: • The intensity of the beam is reduced by refection, refraction, scattering and absorption - Reflection and refraction at surface of the tissue - Objects lesser than the wavelength of the US scattering occur - Final eventual fate of US is absorption and transforming heat in the tissues - Crit care med 2007 vol.35,no.5(suppl)
- 14. Ultrasound • Piezoelectric crystals: interconnected electronically and vibrate in response to an applied electric current • 1880 Curie brothers : piezoelectric effect and reverse piezoelectric effect • Frequency, wavelength, amplitude • Atlas of Ultrasound-Guided Procedures in Interventional Pain Manag ement
- 15. Ultrasound • US waves wavelength and frequency are inversely related • High frequency - Better penetration of tissues – good resolution of deeper structures • Low frequency probes used for superficial structures visualization • Higher frequency waves are more attenuated than lower frequency for a given distance • 1-20Mhz probes • Atlas of Ultrasound-Guided Procedures in Interventional Pain Manag ement
- 16. Ultrasound • Pulsed wave: Ultrasound waves are generated in pulses (intermittent trains of pressure) that commonly consist of two or three sound cycles of the same frequency • PRF: pulse repeteation frequecy • 1-10khz • Atlas of Ultrasound-Guided Procedures in Interventional Pain Manag ement
- 18. Ultrasound • Specular reflection: incident ultra sound pulse encounters a smooth and large interface of different acoustic impedance the sound wave reflects back to transducer
- 19. Ultrasound • Conclusion: 1.Ultrasound is a sound wave out of range of audible range of human being 2. Sound wave undergoes changes while travelling through the tissues 3.Resoution of the image depends on the reflexion,rarefaction and attenuation of the waves in the tissues.
- 20. • ENERGY NEITHER BE DESTROYED NOR BE CREATED CAN BE TRANSFORMED INTO ANOTHER FORM OF ENERGY. THANK YOU