Cardiac Imaging Using Ultrasonography

Cardiac ultrasound is called echocardiography. It uses a transducer to send and receive ultrasound waves and produces real-time images of the heart.

Basic Arrangement

Ultrasound Probe
      ↓
Chest Wall
      ↓
Heart Structures
      ↓
Reflected Echoes
      ↓
Probe
      ↓
Beamformer / Processor
      ↓
B-mode + Doppler Image

Procedure

1. The patient is positioned, commonly in a left lateral decubitus position for transthoracic imaging.
2. Acoustic gel is applied to remove air between the probe and skin.
3. A phased-array transducer is placed at standard acoustic windows such as parasternal, apical, subcostal and suprasternal positions.
4. Short ultrasound pulses are transmitted into the chest.
5. Echoes from myocardium, valves and blood interfaces return to the probe.
6. B-mode creates real-time anatomical images.
7. M-mode can measure rapid valve and wall motion along a selected line.
8. Doppler measures blood-flow velocity and direction.
9. Color Doppler maps flow over the anatomical image.

Important Measurements

Echocardiography can assess:

• Chamber size.
• Wall thickness and motion.
• Valve structure and function.
• Blood-flow velocity.
• Ventricular function and ejection fraction.
• Abnormal flow such as regurgitation or stenosis.

Advantages

• Real-time imaging.
• No ionizing radiation.
• Portable and relatively inexpensive.
• Can assess both anatomy and blood flow.
• Useful for repeated examinations.

Limitations

Image quality can be reduced by obesity, lung air, ribs and other acoustic barriers. Operator skill and correct acoustic windows are important.

Conclusion

Echocardiography combines B-mode, M-mode and Doppler techniques to evaluate cardiac anatomy, motion and blood flow in real time.