Tuesday, 16 February 2010

Twice crowned in fire

 Gorgeous visible and ultraviolet composite of Saturn and its aurora from Spacetelescope.org
I've just been admiring the luscious production values of NASA's Hubblecast, as superbly displayed by their most recent video which looks at the aurorae of Saturn.  Formed in the same way as Earth's Northern and Southern lights, the aurorae of Saturn circle both poles of the planet and rise more than a thousand miles above the cloud tops. 

Hubble image of Saturn showing both poles with aurorae, and the planet's rings edge-on, from Spacetelescope.org

The gas giant recently moved into a position where the light shows of both poles are visible simultaneously.  Fortuitously, this coincides with the planet's equinox, allowing scientists to make a direct comparison between the two displays, as the two poles are recieving an equal influx of charged particles from the sun.  Interestingly this has shown up a subtle difference in activity, which implies that the magnetic field of the planet is not evenly distributed.  I'm intrigued to find out where this goes with further observation. 

In the meantime, the beautiful video of fluttering, coruscating curtains of light encircling the planet's poles has really inspired me to create some jewellery - I'll share if it works!

Monday, 8 February 2010

Submarines to sprogs

Dr Mark Lythgoe gave me another generous helping of food for thought the other morning, with episode three of his Images That Changed the World series, considering the foetal ultrasound scan.


Ultrasound imaging (also known as sonography) is an incredible tool for safe and non-invasive investigation of the soft tissues of the body. It can reveal the presence of an embryo at a very early stage in development, as well as show the foetus in sufficient detail not only to let its digits be counted, but to look further inside and resolve abnormalities in the internal organs.  Dr Joseph Woo has put together a fantastic site on the usage and history of ultrasound in obstetrics, including an amazing gallery of images.

Twin pregnancy at 10 weeks from Obstetric Ultrasound - A Comprehensive guide
Ultrasound images are such a routine part of obstetrics now that it's hard to imagine a time without them. Historically, however, the 9 month journey from bundle of cells to wriggling sprog was shrouded in mystery, punctuated by unseen movement and illustrated only by the unsettling sight of cold, grotesque pickled embryos and foetuses in jars. The programme explored the impact on parents of having even a scruffy little black and white outline of their offspring-in-progress, but what caught my ear was the history of the development of ultrasound imaging technology.

Towards the end of the 18th Century, Italian experimental biologist Lazzaro Spallanzani concluded that the uncanny ability of bats to orient themselves without the use of sight is related to their hearing. 140 years later Donald Griffin recorded their inaudible cries using the first ultrasound microphone and completed the picture. Bats emit sharp sounds above the range of human hearing ('ultrasound' begins just beyond what we can hear, about 20 kilohertz), and listen for the echoes, using the timing and volume of the echo to guage the distance and nature of obstacles and prey. The resolution of echolocation is dependent on the frequency of the sound used, so the extremely high-pitched squeaks of bats allows them to detect tiny prey insects on the wing. I found a great page from the Western Ecological Research Center, with modified recordings of the sounds various species of bat use to investigate their surroundings – there's even one which is low enough for humans to hear without modification.

Bat in flight by Arnold Song at Brown University, who was researching the aerodynamics of their flight

Other species also use echolocation, from cave-dwelling swiftlets to the tiny shrew, but perhaps the most well-known are the toothed whales, including dolphins. Greater sound transmission in the liquid medium apparently allows a dolphin to resolve a golfball a football field away, but that's far too sporting a measure for me. Let's just say that it beats a bat's ~17 meter range.

It wasn't until the Titanic was rusting on the sea bed, however, that humans really took up the act.  In 1913 Alexander Behm patented the echo sounder, a device intended to prevent future disasters by detecing icebergs.  It proved much more effective at locating the sea-bed though, and has been a huge aid to shipping since.

During WWI the threat of enemy submarines drove further research into the potential of echoes, culminating in the invention of ASDIC (later renamed 'SONAR' by the Americans), the piercing 'ping' of which is a familiar staple of tense, dank aquatic thrillers. Reflected sound was also used to detect far smaller dangers, when engineers used ultrasound to examine the internal structures of aircraft wings for stress-induced cracks.

Submarine Sonar Operator's Manual - a fantastic piece of online archive material, training operators of the US's state-of-the-art sonar equiment at the end of WWII - from the Maritime Park Association

In the wake of WWII, obstetrician Professor Ian Donald returned home and began to wonder about the application of this technology to his own profession.  Armed with an ultrasound transducer, he began experimenting on tumours and cysts removed from patients, to see whether they could be differentiated from other tissues, such as muscles (represented by slices of beef). In 1958 he published his work, and so began the application of ultrasound imaging to medicine.

While it has used the same basic principle of reflected sound waves for the past 50-odd years, sonography has evolved into a vital medical tool.  Imaging resolution has improved hugely, structures can be viewed in realtime (cue videos of waving foetal hands and wrinkling noses) and shown 3D rather than cross-section.  Ultrasound can even reveal blood flow in the arteries by analysing the doppler shift of the echoes.  It can also be used in more active ways, such as in controlled powerful bursts to break up kidney stones into easily passed fragments. 

From submarines in the watery deeps to foetuses immersed in amniotic fluid - not a bad bit of lateral thinking, and one that has had a huge impact on medicine and pregnancy.

Monday, 1 February 2010

The Death Inside

This morning I've been listening to yet another fascinating piece of radio from the BBC.  Images That Changed The World is a series of 15 minute programmes presented by Dr Mark Lythgoe examining the history of medical imaging, and how five leaps in imaging technology impacted popular culture at the time.

The first X-ray image of the hand of Röntgen's wife (who exclaimed something along the lines of "It's like seeing the death inside me"), taken from the mesmerising Dream Anatomy gallery at the NIH's NLM

When in 1896 Wilhelm Conrad Röntgen presented his discovery of X-rays, the ghostly depiction of his wife's hand which illustrated the work took only days to reach newspaper and magazine covers around the world.  Never before had the deep, delicate structures within the body been seen in their living context, and the new technology went straight to the public's imagination. X-ray machines were installed in big department stores and fairgrounds, and the public flocked to have their pictures taken.  There were even fads for X-ray family portraits, and the possibility of buying lead-lined underwear to protect a lady's modesty.

Coin operated X-ray machine c1900, taken from A Short History of Amusement Arcades

An anecdotal tale of a woman's diamond engagement ring being revealed as a fake or 'paste' gem led me off at slight tangent.  I've heard the term before many times in venerable works of detective fiction, but the word 'paste' did not call to mind anything you could mistake for the sparkle of finest emeralds.  It turns out that 'paste' gems are a form of heavy glass with a high refractive index, which when cut well can imitate gemstones.  'Paste' refers to the method of manufacture: powdered silica, soda and lead or other metal oxides are combined with water to ensure even mixing, before being heated in a kiln until fused.  [This page on gem creation is a good read if you have any interest in jewellery and gemology.] A more common name for a paste gem which you might recognise is 'rhinestone', widely used in costume jewellery.

 Radiograph of a diamond ring from Myth busting – in the world of x-rays

Being amorphous, fused glasses rather than single, grown crystals of gemstone, paste gems have subtly different optical properties, meaning that the expert can distinguish them just by looking (an important plot point!).  Even an untrained eye, however, can spot when the diamond they expect to appear as a faint smudge appears completely opaque in an X-Ray image - hence the woman's outrage at the X-ray image's revelation. 


Within a year of the announcement of Röntgen's announcement reaching Britain, school student Russell Reynolds completed the building of his own X-ray apparatus.  Home machines like these became widespread, with enthusiastic amateurs able to bring cutting-edge scientific equipment to their parlours.  Experiencing the glee of examining everything within reach with a microscope makes it easy to imagine excited Victorians X-raying hands, feet, cats, frogs, and indeed anything that they could get their hands on.

Unfortunately however this orgy of discovery came at a price - the following years revealed the dangers of overexposure to the ionising radiation - burns, ulcers, cancers and amputations.  The grisly vignette of a conference of radiologists unable to cut up their food due to the loss of one or both hands puts a chilling dampener on the joy of discovery.

X-ray images revolutionised medicine by enabling the harder structures within the body to be viewed non-intrusively for the first time, revealing everything from broken bones to tuberculosis.  Understandably, the X-ray machine above has been selected by curators at the Science Museum in London as the item in its collection that had made the biggest impact on human history. 

Nowadays X-ray images of the human body are familiar, but along with less familiar portraits of plants, animals and everyday objects the can be fascinating and beautiful, as well as instructive.  I highly recommend you check out the incredible work of Albert Koetsier and Nick Veasey, but be warned you may be there some time.