Penetration depth and resolution Factors affecting ultrasound transmission: cycle length: (wavelength λ [mm]) frequency: (frequency f [Hz]) Speed: (propagation velocity c [m/s]) in the respective medium The relationship of these parameters is described by the wave equation: c = λ × f λ = c / f longer wavelengths penetrate further than shorter wavelengths Image resolution cannot be greater than one wavelength the higher the ultrasound frequency, the better the image resolution
Types of resolution Axial resolution Lateral resolution Elevational resolution
Modes 1-A mode 2-B mode 3-M mode 4-2D Echogenicity
The difference between the emitted frequency and the received frequency is called: Doppler shift (fd ) Blood flow V = fd × c/2 × f0 × cos α For practical application in Doppler echocardiography: the emitted frequency (f0) is known and the velocity of sound (c/2) is constant at 1540 m/s. Therefore, the velocity causing the Doppler shift can be calculated by: V = fd × cos α
TDI Speckle Tracking: non-Doppler, angle- independent quantification of myocardial deformation, by tracking the displacement of the speckles during the cardiac cycle, strain and the strain rate can be measured offline.
Recommended books 1-Practical approach to transesophageal echocardiography(Perrino) 2-Core topics in echocardiography (Rob Fenneck) 3-Atlas of multiplane transesophageal echocardiography (Martin Dunitz) 4-transesophageal echocardiography in anesthesia and intensive care (BMJ) 5-Pocket atlas of echocardiography (Thieme) 5-Essential echocardiography (Humana press)