Partial preview of the text
Download biomedical lecture note and more Lecture notes Biomedical Engineering in PDF only on Docsity!
Ultrasonic Imaging Lis) @ Safe and inexpensive(CT and MR) @ Visualization of internal structures and the disgnosis of disease - Diagnosis of cysts and tumors - Measuring bloodflow - Analysis of cardiac cycle - Evaluation of fetal development - Applications in neurology and opthalmology @ Ultrasound waves are vibrations or disturbances in the physical medium such as gas, liquid, or solid matter. - Acoustical wave above the range of human hearing(20-30 KHz) ~ 1 MHz - 20 MHz - Low power(average power level of 0.01 to 200 mW/cm” @ Amplitude and time delay of echoes -> Image formation Doppler shift -> Movement of structures and bloodflow Generation of Ultrasound @ Piezoelectric effect - Deformation by mechanical pressure or strain applied in certain directions causes electrical poralization of the crystals. (Polarity and magnitude of the charges depend on the direction and the amount of pressure) - The application of an electric field to a crystal produces mechanical deformation. (The charge densities produced are directly proportional to the strain in the crystal.) - Transducres can be used both to transmit and to receive sound waves. Ultrasound is generated by exciting vibrations of the piezoelectric transducer by an alternating electric field of appropriate frequency. * When an acoustic wave hits the transducer, the pressure waves cause the crystal to vibrate, causing a changing voltage to be measured across the crystal. Metal: Goniet * d y 4 Variable Fj applied ~ tage 7 Quartz ¥ crystal e-cut) Time —> 
