3D ultrasound is a medical ultrasound technique, often used in fetal, cardiac, trans-rectal and intra-vascular applications. 3D ultrasound refers specifically to the volume rendering of ultrasound data and is also referred to as 4D (3-spatial dimensions plus 1-time dimension) when it involves a series of 3D volumes collected over time.
When generating a 3D volume the ultrasound data can be collected in 4 common ways. Freehand, which involves tilting the probe and capturing a series of ultrasound images and recording the transducer orientation for each slice. Mechanically, where the internal linear probe tilt is handled by a motor inside the probe. Using an endoprobe, which generates the volume by inserting a probe and then removing the transducer in a controlled manner. The fourth technology is the matrix array transducer that uses beamsteering to sample points throughout a pyramid shaped volume.
Risks
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The risks in outlined Medical ultrasound#Risks and side-effects in the Medical ultrasound page also apply to 3D Ultrasound. Essentially ultrasound is considered safe. While other imaging modalities use radioactive dye or ionizing radiation, for example, ultrasound transducers send pulses of high frequency sound into the body and then listen for the echo.
In summary, the primary risks associated with ultrasound would be the potential heating of tissue or cavitation. The mechanisms by which tissue heating and cavitation are measured are through the standards called thermal index (TI) and mechanical index (MI). Even though the FDA outlines very safe values for maximum TI and MI it is still recommended to avoid unnecessary ultrasound imaging.
Applications
Fetal
Cardiac
Regional Anesthesia
Real-time three-dimensional ultrasound is used during peripheral nerve blockade procedures to identify relevant anatomy and monitor the spread of local anesthetic around the nerve. Peripheral nerve blockades prevent the transmission of pain signals from the site of injury to the brain without deep sedation, which makes them particularly useful for outpatient orthopedic procedures. Real-time 3D ultrasound allows muscles, nerves and vessels to be clearly identified while a needle or catheter is advanced under the skin. 3D ultrasound is able to view the needle regardless of the plane of the image, which is a substantial improvement over 2D ultrasound. Additionally, the image can be rotated or cropped in real time to reveal anatomical structures within a volume of tissue. Physicians at the Mayo Clinic in Jacksonville have been developing techniques using real time 3D ultrasound to guide peripheral nerve blocks for shoulder, knee, and ankle surgery.
References
External links
- The History of Ultrasounds (including 3D ultrasounds)
- The Endowment for Human Development provides numerous 4D ultrasounds that can be viewed online.
- Scans uncover secrets of the womb BBC News
- About the discovery of medical ultrasonography
- Learn how to perform 3D/4d Ultrasounds
- Safety Concerns Details a number of health concerns over this unregulated practice
- 3D Ultrasound Clinic and Education Facility A 3D Ultrasound clinic in Sacramento, CA that specializes in performing 3D ultrasound and training sonographers.
