Tag Archives: computer tomography

image CT scan

Inside the human body in real time: GIFs demo the power of CT scan

image CT scan

The skull and the Circle of Willis – a structure which supplies blood to the brain and surrounding area.

Computed Tomography (CT) is based on the x-ray principal: as x-rays pass through the body, they are absorbed or attenuated (weakened) at differing levels creating a matrix or profile of x-ray beams of different strength. But while x-rays can only be used to image the outlines of bones and organs, CT creates three-dimensional images of the body one narrow slice at a time.

ct scan

The abdomen and the aorta.

A CT scanner basically looks like a square shaped doughnut fitted with an x-ray tube mounted on one side and the banana shaped detector mounted on the opposite side. As the frame rotates, it takes timely snapshots of whatever or whoever rests inside it. Each time the x-ray tube and detector make a 360° rotation, an image or “slice” has been acquired and by stacking each slice atop another you eventually get a full 3-D image. If all this sounds familiar, it’s because CT is very similar to functioning magnetic resonance imaging (fMRI). Some key differences are that fMRI exploits powerful magnet and pulsing radiowaves, which do not emit potentially harmful radiation, unlike CT.

CT scan

Where CT shines, however, is in its ability to image tissue inside the body otherwise unapproachable using other methods. All of the GIFs in this post were made from computer images taken using General Electric’s  Revolution CT, first introduced in 2013. The device is designed to emit less radiation and provide more comfort. Guts, veins, brains and hearts have now been imaged in the gruesomest detail ever.

CT scan

Another view of the Circle of Willis. It is located at the base of the brain and forms a circle of arteries around it.

CT scan

Another view of the Circle of Willis.

An image of a complete heart in just a single heartbeat.

An image of a complete heart in just a single heartbeat.

BONUS: still, high definition images taken with the Revolution CT

The skull and carotid arteries.

The skull and carotid arteries.

An image of the abdomen and pelvis.

An image of the abdomen and pelvis.

The rib cage, the heart and the chest cavity. The Revolution CT can image the heart in a single heartbeat.

The rib cage, the heart and the chest cavity. The Revolution CT can image the heart in a single heartbeat.

The whole aorta and kidneys.

The whole aorta and kidneys.

CT and 3D printing combined to reproduce fossilized dinosaur bones

 

  • Most fossils are very fragile, difficult to handle and transport
  • Researchers conducted CT scans on fossils still trapped in sedimentary material, creating 3D models
  • The models were then 3D printed – an accurate, non invasive method to replicate fossils for schools, museums and other researchers

 

Doctors and dinosaurs

Being a paleontologist and working with dinosaur fossils is a rewarding, but tough job. You have to work with a very limited amount of fossils, it’s difficult to share them with researchers from other sites of the world, and the samples are very fragile – making transportation quite risky. But researchers have found a way to work around that problem: 3D printing dinosaur bones.

A 3D print of vertebral body created using the CT dataset. Copyright: all images were taken from the article.

A 3D print of vertebral body created using the CT dataset. Copyright: all images were taken from the article.

Researchers at Berlin’s Charité Campus Mitte have combined data from computed tomography (CT) scans with 3D printing technology to make it possible to print any number of accurate 3D reproductions from virtually any dinosaur (and not only) bone, without any negative effect on the original sample.

Valuable fossils are often stored in protective jackets (or casts), from which they are removed only when they are actually studied. The removal of the plaster and the sediment surrounding it could result in loss of material or significant deterioration. Quite often, you find fossils clumped in material from which it is very difficult to safely remove them, so this is a big problem.

The 3D-printed vertebral body next to the original unprepared and erroneously labeled plaster jacket.

The 3D-printed vertebral body next to the original unprepared and erroneously labeled plaster jacket.

A research team led by Ahi Sema Issever, M.D., has found a way to gain access to a fossil’s secrets without destroying its protective environment – they took an unidentified fossil from the Museum für Naturkunde in Berlin (the natural science museum), and subjected it to a CT scan with a 320-slice multi-detector system. The bone and surrounding material have very different radiation absorption rates, so the team was able to construct an accurate depiction of a fossilized vertebral body. The CT scan itself provided valuable insights not only helping paleontologists identify it, but also providing information about its condition and integrity.

Axial CT scans of fossil. Notice the fissures.

Axial CT scans of fossil. Notice the fissures.

But the team didn’t stop here. They used the CT scan to produce a 3D model that was printed using selective laser sintering, an additive manufacturing that uses a powerful laser to fuse together powder material in the desired shape and size; basically, they 3D printed it.

This method has two major advantages: you don’t have to remove the fossil when it is tightly attached to its surrounding material, thus eliminating the risk of damage to the fossil, and you can make as many copies of it as you want. This is much less time consuming than traditional fossil replication and makes it possible for museums, schools and other institutions to share unique fossils, without letting the original out of their hands.

“Just like Gutenberg’s printing press opened the world of books to the public,” says Dr Issever, “digital datasets and 3-D prints of fossils may now be distributed more broadly, while protecting the original intact fossil.”

Scientific Reference: Reviving the Dinosaur: Virtual Reconstruction and Three-dimensional Printing of a Dinosaur Vertebra. René Schilling, MD, Benjamin Jastram, Dipl-Ing, Oliver Wings, Dr rer nat, Daniela Schwarz-Wings, Dr rer nat, Ahi Sema Issever, MD

Internal anatomy of V. cardui as it develops within the chrysalis. The tracheal system is blue, the midgut is red, the air lumen is green, and the Malpighian tubules (part of the excretory system) are orange. (c) Lowe et al

CT scan images caterpillar to butterfly metamorphosis in 3-D

Internal anatomy of V. cardui as it develops within the chrysalis. The tracheal system is blue, the midgut is red, the air lumen is green, and the Malpighian tubules (part of the excretory system) are orange. (c) Lowe et al

Internal anatomy of V. cardui as it develops within the chrysalis. The tracheal system is blue, the midgut is red, the air lumen is green, and the Malpighian tubules (part of the excretory system) are orange. (c) Lowe et al

Metamorphosis

Serving as one of the strongest metaphors nature has to offer, at the later stages of its evolution the caterpillar – a soft bodied, not very pretty, ground based insect – morphs into a butterfly – a majestic flying insect of varying coloring and shape. What exactly goes inside the chrysalis the caterpillar wraps itself with for the many weeks required for metamorphosis remains a mystery, though.

Recently, a mixed team of entomologists and geologists used high resolution computer tomography (CT) to image in real time the development stages of the painted lady butterfly (Vanessa cardui), mapping each individual change as it happened.

“The crucial thing in this case is that they examined live material,” said Rolf Beutel, a professor of entomology at Friedrich Schiller University of Jena in Germany, who was not involved in the study. “This is really exciting.”

Saying that researchers had no idea what happens during metamorphosis isn’t exactly fair. The process is very well documented and its stages have been rather well defined many years ago through means of dissection. Traditionally, a biologist looking to study an insect’s metamorphosis will collect many specimens of the same species and dissect their pupae at varying stages of development. But never before has metamorphosis been observed “in situ”. Of course, dissecting them also kills them, which is not only sad for the insects, but may alter the scientific information. This is why scientists wanted to observe it “live”.

V. cardui chrysalis at day 16 of development, showing many aspects of adult butterfly anatomy.

V. cardui chrysalis at day 16 of development, showing many aspects of adult butterfly anatomy.

Studying dead specimens offers a pretty reliable snapshot of the insect’s development stages, however there are many fine details that can only observed in living specimens and this is where CT came really in handy. The researchers  did scans on nine painted lady chrysalises throughout their development while leaving one chrysalis alone as a control, all while trying to be very careful to keep the chrysalises healthy. CT radiation can interfere with their well being, and indeed four specimens scanned in their earliest stages of development perished, but the researchers accounted this to heat given off by the machine rather than radiation exposure.

“It’s basically the first time a CT has been used to look at the development of a single individual,” said Russell Garwood of the University of Manchester, a geologist who usually studies fossil insects and an author of the paper.

Eventually, one of the specimens stood out as having the most complete set of scans, so the researchers focused on assembling its data, comparing it with scans of other specimens to rule out any anomalies. As expected, no startling surprises occurred. Traditional dissection did a very good job at accurately describing metamorphosis.  “We’re filling in the details rather than rewriting the story,” Garwood said.

What would prove to be truly interesting is performing CT scans of the insects while still in caterpillar form, however this proves to be extremely challenging since CT scans work poorly for subjects that tend to move all the time. Beutel is currently experimenting with using CT scans on anesthetized cockroaches.

Findings were reported in a paper published in the Journal of the Royal Society Interface via The Scientist.