Ultrasound Gone Wild

Imaging animals in the womb

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At three months, the elephant embryo is approximately 2 centimeters in size. Even at this early stage in the elephant's 22-month gestation period, the heart is beating and the embryo can move independently. (National Geographic Channel)

The elephant fetus' head is 40 percent of the total body length at the five-month point of gestation. (National Geographic Channel)

By 12 months, the elephant fetus can use its trunk, curling it right up into its mouth and over its head. (National Geographic Channel)

At two months, the dolphin's tail, or fluke, begins to form. (National Geographic Channel)

By nine months, the color of the dolphin's skin is similar to that of an adult dolphin: a dark gray upper body and a whitish underside. (National Geographic Channel)

Did You Know?

• Regardless of size, age or breed, all dogs are pregnant for approximately 63 days.
  Because a dog's eggs are not immediately ready for fertilization when released, individual puppies within the same litter can have different fathers.
• In contrast with many other mammals, dolphins are born with their eyes open and senses alert, with enough muscular coordination to follow their mothers

immediately.

Female dolphins have one calf at a time and wait about four years for the calf to become independent before they become pregnant again. Males are not involved in parental care.

Dolphins have a 320-degree field of vision, and they can use each eye independently.

The elephant's 22-month gestation period is the longest of all mammals.

A normal fertilized elephant egg weighs under a thousandth of a gram. A full-grown elephant weighs close to five tons.

Elephants can swim more than 15 miles without stopping, by using their trunks to breathe above the water line.

Elephant brains have almost the same memory capacity as human brains, with the ability to remember locations of food and water over a 20-year period.

— National Geographic Channel

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In 2006, using this 4-D imaging technology on pregnant human mothers, the National Geographic Channel (NGC) aired a special production titled, "In the Womb." Building on the interest generated from that production, NGC recently developed a two-hour show featuring expectant mothers not in a human's doctor office, but in a veterinarian's office, instead.

"In the Womb: Animals" highlights state-of-the-art visual effects, computer graphics and real-time, moving 4-D ultrasound imagery to shed light on the unique world of animal fetal development. For the first time on television, viewers are led inside the wombs of three mammals – an elephant, dolphin and dog – to trace their vastly different paths from conception to birth and uncover evolutionary clues to their ancestral past by observing the fetuses in utero.

A New Dimension

Veterinarians have been using traditional, diagnostic ultrasound technology since the early 1980s to diagnose diseases in small animals. Over the years, it has been used in veterinary hospitals and teaching centers as a noninvasive, painless way of evaluating soft tissue, including the kidneys, liver, pancreas, bladder, urinary tract, gallbladder and heart. Ultrasound is particularly useful in animal pregnancy because fetal heartbeats are difficult to identify early in pregnancy. Thanks to the advanced imaging technology, experts are able to learn more about the fetus' activities and its ancestors.

Unlike the 3-D ultrasound that shows only length, width and depth in a single still frame, the 4-D ultrasound shows length, width and depth over a period of time to produce a video of the moving fetus. With this additional dimension, activities of the fetus can be clearly seen and identified.

As for the risks of repeated exposure to ultrasounds, NGC claims that, after 50 years of extensive use and testing, ultrasound has not been shown to cause any harm to a human or animal fetus. And there is not a greater risk associated with the additional dimensions either, as the same ultrasound waves are used in 2-D, 3-D and 4-D ultrasound scans.

Unlocking the Gates

When performing an ultrasound on a dog, according to the NGC, there is little preparation. The veterinarian simply cuts back some of the fur at the area to be scanned, because ultrasound technology cannot scan through the hair. The dog remains awake through the entire procedure and is not sedated unless it becomes anxious or aggressive. As in an ultrasound of a human, a water-soluble coupling gel is placed on the skin surface, and the transducer is moved in a circular motion to scan the organs.

Ultrasound has confirmed pregnancy on a dog as early as 12 days after fertilization. Even though a dog's gestation period is only approximately 63 days, experts recommend waiting until 25 or 30 days to scan a pregnant dog when attempting to count the number of pups she is expecting.

Ultrasound technology has been used with elephants for approximately six years in many zoological studies. To perform an ultrasound on an elephant, some preparation is involved. First, the veterinarian dispenses an enema to remove all feces in the rectum and clears the path for the ultrasound transducer to be placed. Although the elephant is not typically sedated, it is held in place by a rope or chain. With shoulder-length gloves and other appropriate gear, the veterinarian inserts the probe into the elephant's rectum to view its liver and other internal organs.

Due to the massive size of the elephant and its organs, only partial views of the organs can be seen on the ultrasound screen. In terms of confirming pregnancy, ultrasound has been able to detect an elephant fetus as early as 16 weeks into its 22-month gestation period.

According to NGC reports, performing an ultrasound on a dolphin may be the easiest procedure of the three. The dolphin is trained to float on its side in preparation for the procedure. The veterinarian or trainer stretches the dolphin out in the water and runs the transducer probe over the area to be scanned. Ultrasound technology has confirmed a dolphin pregnancy as early as four months into its 12-month gestation period.

Tracking Activities

Performing these ultrasonic procedures allows imaging professionals to track the animals' pregnancies from conception to birth. Imaging captures a single cell – less than half a millimeter across – as it develops into a baby elephant weighing more than 260 pounds. The new 4-D imaging captures video of the dolphin fetus as it learns to swim in the amniotic fluid of the womb at two months; the dog fetus begins to show signs of panting at the 40-day point; and the elephant fetus exhibits a slow, running-type motion at five months.

Learning these characteristics in the womb is essential for survival on land. For example, walking and standing are imperative functions for an elephant to reach its mother's milk. Also, for dogs, panting is essential for regulating body heat, as they have limited sweat glands. And, a dolphin must be able to swim out of the womb and get its first breath at the surface.

Imaging into the Past

Being able to capture clear pictures of animal fetuses with 4-D imaging allows experts to identify clues into the ancestry of certain species. For example, 4-D documentation of the elephant's growth shows that it develops ducts normally found in freshwater fish, suggesting its ancestors once swam in seas. Similarly, one month into the dolphin's gestation, leg-like limb buds appear, but then retract and vanish completely within two weeks. Scientists believe this is evidence that the dolphin's ancestors once lived on land.

Imaging reveals interesting differences between the three animals' pregnancies and how they've adapted through evolution. For instance, because a dog's eggs are not immediately ready for fertilization when released, sperm will attach to the uterine wall, waiting approximately two days for the eggs to mature. Scientists believe this is an adaptation due to the dog's wild relatives' limited amount of time with and access to the dominant mating female.

Also, imaging shows scientists that hairs lining the elephant's uterine wall actually wave in unison to propagate the sperm to reach the egg on the last stretch inside the uterus. Experts believe that this, too, is an adaptation due to the six feet – compared to a human's three inches – that a sperm must travel to fertilize the egg.

Professionals Behind the Images

Rae Stone, DVM, provided consult on the dolphin portion of the NGC show. Stone, founder of Dolphin Quest – a chain of animal care facilities that offer dolphin reproduction programs, veterinary expertise and education – pioneered the use of diagnostic ultrasound in dolphins and other marine mammals, and specializes in noninvasive aquatic animal diagnostic techniques.

Stone began exploring the benefits of veterinary ultrasonography for marine mammals at Marineland in Palos Verdes, Calif. Today, she is a guest lecturer at veterinary colleges, an author of papers and chapters in scientific presses and an active member of and presenter at numerous veterinary medical professional associations.

A portion of the "In the Womb: Animals" video features Thomas Hildebrandt, DVM, of the Berlin-based Institute of Zoo and Wildlife Research, imaging a pregnant golden retriever. Hildebrandt is a specialist in veterinary ultrasonography and one of the few people in the world that can capture 4-D images of animals in the womb.

The other consulting professionals involved in the "In the Womb: Animals" production include: Dennis Schmitt, DMV, PhD, DACT; Hans Thewissen, PhD; Jay Sweeney, VMD; Howard Evans, PhD; and Drew Noden, PhD.

After this special on animal imaging aired, 4-D ultrasound took center stage again with an "In the Womb: Multiples" television special that takes viewers into the world of twins, triplets and quadruplets, as they develop in utero. The advanced imaging techniques provided by 4-D ultrasound images reveal how the multiples grow and compete for resources.

Click here to check out a clip of video captured by 4-D ultrasound technology.

Editor's Note: "In the Womb: Animals" will air a rebroadcast on May 25 at 9 p.m. (ET/PT) on the National Geographic Channel.

— Amy Storer is the online editor of RT Image. Questions and comments can be directed to astorer@rt-image.com.