Infographics / Ultrasound Physics

Tissue harmonic imaging (THI)

Two frequency spectra compare the transmitted pulse, a single peak at the fundamental f0, with the received signal, where a band-pass filter keeps only the second harmonic 2f0 and rejects the fundamental. A depth curve shows the harmonic is weak in the near field and builds up with nonlinear propagation, and a beam diagram shows the 2f0 beam is narrower than the f0 beam. A summary lists why harmonic imaging reduces artefacts and improves resolution and contrast.

Tissue harmonic imaging: transmit at the fundamental, receive the second harmonic Two frequency spectra compare the transmitted pulse, a single peak at the fundamental f0, with the received signal, where a band-pass filter keeps only the second harmonic 2f0 and rejects the fundamental. A depth curve shows the harmonic is weak in the near field and builds up with nonlinear propagation, and a beam diagram shows the 2f0 beam is narrower than the f0 beam. A summary lists why harmonic imaging reduces artefacts and improves resolution and contrast. Tissue harmonic imaging (THI) Transmit at the fundamental f0; image using the second harmonic 2f0 generated in tissue. Transmitted pulse amplitude f0 frequency single peak at the fundamental Received signal f0 2f0 band-pass 2f0 kept f0 filtered image formed from the harmonic 2f0 only Harmonic builds with depth harmonic amp. depth weak near field nonlinear build-up Narrower effective beam f0 beam 2f0 beam Why harmonic imaging helps • Harmonics are integer multiples of f0 from nonlinear propagation; the 2f0 harmonic is used • Broad-bandwidth probe: transmit f0, receive 2f0 • Pulse inversion cancels the fundamental • 2f0 has a shorter wavelength → narrower beam, lateral resolution maintained or improved • Harmonics weak in near field → less reverberation and side-lobe clutter; better contrast
Practise Ultrasound PhysicsDownload SVG

More in Ultrasound Physics

Practice the Physics paper

FRCRX is a Part 1 Physics question bank: true/false items with explanations, timed mocks and topic analytics.

Start question practiceSee plans