Basic Physics of Medical Ultrasound   2 

   Ultrasound is defined as the high-frequ high-frequency vibration that travels through tissue at high speed, approximately 1540 m/s Frequency range In medical ultrasound used is 1 to 50 MHz.

Ultrasound vibration travels as a pressure waveform.

Ultrasound can be generated and detected by piezoelectric

crystals contained in small hand-held transducers.

Echoes produced by transmitted ultrasound pulses at tissue interfaces are the basic source of information in diagnostic ultrasound.

Material.                                                       Speed (m/s)

Air.                                                               330

Fat.                                                            1450

Water (20°C).                                           1480

Soft tissue.                                               1540

Liver                                                          1550

Blood.                                                         1570

Muscle.                                                      1580

Bone.                                                          3500     

                         Speed of ultrasound and acoustic impedance

The speed of ultrasound in soft tissue depends on its rigidity and density

The more rigid a material, the higher the speed.

The vibration produced by the transducer is a flow of energy through the tissue