Foetuses in 3D

Parents-to-be might soon wear 3D glasses in the ultrasound lab to see their developing foetuses in the womb, according to researchers at Duke University's Pratt School of Engineering.

The same Duke team that first developed real-time, three-dimensional ultrasound imaging says it has now modified the commercial version of the scanner to produce an even more realistic perception of depth. Paired images seem to pop out of the screen when viewed with the special glasses.

The researchers created an updated version of the image-viewing software found on clinical ultrasound scanners, making it possible to achieve a stereo display with no additional hardware.

‘To our knowledge, this is the first time it's been made possible to display real-time stereo image pairs on a clinical scanner,’ said Stephen Smith, a professor of biomedical engineering at Duke. ‘We believe all 3D scanners could be modified in this way with only minor software changes.’

The new imaging capability can improve the early diagnosis of certain kinds of birth defects of the face and skull and improve surgeons' depth perception during ultrasound-guided medical procedures, including tumour biopsies and robot-assisted surgeries done through "keyhole" incisions.

The Duke team, which also includes Joanna Noble, an undergraduate student, and Matthew Fronheiser, a graduate student in Smith's laboratory, reported the findings in an issue of the journal Ultrasonic Imaging dated July 2006, but published in April 2007.

Human depth perception is largely the result of stereo vision -- the slightly different perspectives of the same scene that are observed by the left and right eyes, Smith said. The brain processes the information to produce a sense of depth, a phenomenon that can't be achieved when viewing a single, flat image.

Stereoscopic images solve that problem by taking two "snapshots" of the same object from slightly different angles, mimicking the normal difference between left and right eye views.

Special glasses or goggles can then be used to fuse the two images into one, gaining a 3D effect. With practice, some people can "defocus" their eyes and fuse the paired images without the aid of any special viewing device.

To demonstrate the new capability, the researchers first generated stereo ultrasound images of a small metal cage. They then advanced to ultrasound images in living animals of a heart valve and blood vessels and needle biopsies of the animals' brains and oesophagi.

The researchers have since recorded ultrasound images of a model human foetus that is traditionally used in the testing of foetal ultrasound imaging devices. (Watch the video, including paired images of both the cage and model foetus, here).

‘Thousands of 3D ultrasound systems in clinics could be upgraded with such new software, and stereoscopic goggles could be issued to them as well,’ Smith said. ‘Keepsake DVDs of the foetal exam could also be viewed at home in 3D stereo.’

The goggles would soon become obsolete, he added. New monitors capable of fusing stereo 3D images without them are now in development.