Volume I Companion Presentation Frank R. Miele Pegasus Lectures, Inc. Ultrasound Physics & Instrumentation 4th Edition Volume I Companion Presentation Frank R. Miele Pegasus Lectures, Inc. Pegasus Lectures, Inc. COPYRIGHT 2006

License Agreement Pegasus Lectures, Inc. All Copyright Laws Apply. This presentation is the sole property of Pegasus Lectures, Inc. No part of this presentation may be copied or used for any purpose other than as part of the partnership program as described in the license agreement. Materials within this presentation may not be used in any part or form outside of the partnership program. Failure to follow the license agreement is a violation of Federal Copyright Law. All Copyright Laws Apply. Pegasus Lectures, Inc. COPYRIGHT 2006

Volume I Outline Pegasus Lectures, Inc. Chapter 1: Mathematics Chapter 2: Waves Chapter 3: Attenuation Level 1 Level 2 Chapter 4: Pulsed Wave Chapter 5: Transducers Chapter 6: System Operation Pegasus Lectures, Inc. COPYRIGHT 2006

Chapter 3: Attenuation - Level 2 Pegasus Lectures, Inc. COPYRIGHT 2006

Fig. 21a: Anechoic Mass (Cyst) in the Liver (Pg 160) No Echogenicity Fig. 21a: Anechoic Mass (Cyst) in the Liver (Pg 160) Pegasus Lectures, Inc. COPYRIGHT 2006

Fig. 21b: A Small (5-6 mm) hypoechoic Mass in the Liver (Pg 160) Low Echogenicity Fig. 21b: A Small (5-6 mm) hypoechoic Mass in the Liver (Pg 160) Pegasus Lectures, Inc. COPYRIGHT 2006

Hyperechoic Pegasus Lectures, Inc. High Echogenicity Fig. 21c: Transverse View Through a Normal Liver with a Hyperechoic Area from the Ligamentum Teres (Pg 160) Pegasus Lectures, Inc. COPYRIGHT 2006

Calcified Pegasus Lectures, Inc. Strongly echogenic, usually with acoustic shadowing Fig. 21d: Calcified Plaque with Acoustic Shadowing at the Origin of the ICA (Pg 161) Pegasus Lectures, Inc. COPYRIGHT 2006

Complex Pegasus Lectures, Inc. Mixed Echogenicity with or without acoustic shadowing Fig. 21e: Complicated Plaque with Multiple Levels of Echoes at the Origin of the ICA (Pg 161) Pegasus Lectures, Inc. COPYRIGHT 2006

Attenuation Rates Pegasus Lectures, Inc. Attenuation rates through various media have been empirically determined to be approximately as follows: Note that attenuation already implies a decrease. The fact that the rates are specified in decibels demonstrates that the attenuation is a non-linear process. Attenuation increases exponentially with both depth and transmit frequency. Soft Tissue: 0.5 dB/(cm * MHz) Muscle: 1.0 dB/(cm * MHz) Blood: 0.125 dB/(cm * MHz) Pegasus Lectures, Inc. COPYRIGHT 2006

Fig. 22a: Specular Reflection from the Humeral Head in the Shoulder (Pg 165) Pegasus Lectures, Inc. COPYRIGHT 2006

Specular Reflection Pegasus Lectures, Inc. Fig. 22b: Specular Reflection from the Anterior Leaflet of the Mitral Valve and Aortic Valve Cusp (Pg 165) Pegasus Lectures, Inc. COPYRIGHT 2006

Fig. 22c: Specular Reflection from a Prosthetic Mitral Valve (Pg 166) Pegasus Lectures, Inc. COPYRIGHT 2006

Specular Reflections Pegasus Lectures, Inc. Fig. 22d: Specular Reflections from Spiny Processes and the Cranial Bone (Pg 166) Pegasus Lectures, Inc. COPYRIGHT 2006

Scattering Pegasus Lectures, Inc. Fig. 23a: Coarse Speckle Pattern (loss of definition between muscle and gland) (Pg 168) Fig. 23b: Fine Speckle Pattern (neck muscles visible anterior to thyroid) (Pg 168) Pegasus Lectures, Inc. COPYRIGHT 2006

Reflection – Equation Applied In Level 1 of this Chapter, we learned that the amount of reflection from a boundary is determined by the acoustic impedance mismatch. We will now apply the reflection equation to a specific imaging situation. Pegasus Lectures, Inc. COPYRIGHT 2006

Acoustic Impedance Mismatch between PZT and Tissue Fig. 24: (Pg 170) Pegasus Lectures, Inc. COPYRIGHT 2006

The Use of a Matching Layer Tissue Fig. 25: Impedance Matching (pg 171) The use of a matching layer is to improve the transmission efficiency by reducing the acoustic impedance mismatch of the high impedance of the crystal and the low impedance of the tissue. Pegasus Lectures, Inc. COPYRIGHT 2006

High Impedance Mismatch with Air Fig. 26: (Pg 172) The impedance mismatch to air is enormous, resulting in very poor transmission into and out of the patient. The use of gel is to eliminate the air that would otherwise be trapped on the surface of the patient between the skin and the matching layer of the transducer. Pegasus Lectures, Inc. COPYRIGHT 2006

Small Impedance Mismatches Fig. 27: (Pg 173) Small impedance mismatches may result in the inability to visualize a structure in the body, even if the structure is relatively large. Pegasus Lectures, Inc. COPYRIGHT 2006

Shadowing from Bone Pegasus Lectures, Inc. High reflectivity from large acoustic impedance mismatch and high absorption rate results in signal dropout (shadowing) below the bones (in this case from the vertebral spinous process bone) Fig. 28: (Pg 173) Pegasus Lectures, Inc. COPYRIGHT 2006

Fig. 29: Lateral Displacement Caused by Refraction (Pg 176) Effects of Refraction Refraction can result in a lateral displacement of structures within an image as demonstrated in the associated figure. Fig. 29: Lateral Displacement Caused by Refraction (Pg 176) Pegasus Lectures, Inc. COPYRIGHT 2006

Determining Refraction Direction As seen in the animation of page 154, the direction of in which the beam refracts can be determined by drawing the change in speed of the wavefront at the interface between the two media. In this case, C2 is greater than C1, resulting in the refraction as shown in the figure. Fig. 30: (Pg 177) Pegasus Lectures, Inc. COPYRIGHT 2006

Lateral Displacement from Refraction Fig. 32: Where a structure would appear from a bent path length with a change in propagation speed (Pg 177) Pegasus Lectures, Inc. COPYRIGHT 2006

Refractive Shadowing and the Critical Angle Fig. 33: (Pg 178) Pegasus Lectures, Inc. COPYRIGHT 2006

Notes: