Second harmonic imaging is a recently developed concept where distorted ultrasound waves (due to tissue) are partly returned back at a frequency twice that of the fundamental (normally emitted) frequency. This returned wave frequency is the second harmonic frequency. Newer machines are now able to disable the fundamental frequency and only analyze the second harmonic frequency. The advantages are -
The advantages are many as you can see, but there remains a disadvantage.
Valve structures can appear thicker than usual, and hence second harmonic imaging should ideally be avoided if echo is indicated for assessment of valve structure and function.
Second harmonic imaging is also used with contrast imaging. Microspheres in the contrast media reflect the ultrasound frequency as second harmonics rather than the fundamental frequency. This is not so with red blood cells or with tissue and thus helps analyze jet velocities clearly.
References
1. Mark Monaghan Second-harmonic imaging: a new tune for an old fiddle? Heart 2000;83:131-132
- Clearer visualization of deeper tissues
- Reverberation artifacts (eg. from ribs) are eliminated
- Clearer endocardial definition and hence good to use in stress echo
- Useful for patients with poor visualization windows and obese patients.
The advantages are many as you can see, but there remains a disadvantage.
Valve structures can appear thicker than usual, and hence second harmonic imaging should ideally be avoided if echo is indicated for assessment of valve structure and function.
Second harmonic imaging is also used with contrast imaging. Microspheres in the contrast media reflect the ultrasound frequency as second harmonics rather than the fundamental frequency. This is not so with red blood cells or with tissue and thus helps analyze jet velocities clearly.
References
1. Mark Monaghan Second-harmonic imaging: a new tune for an old fiddle? Heart 2000;83:131-132
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