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Archive for August, 2010

NASA Flies Plane Into Hurricane Earl

August 31, 2010 2 comments

Photo: NASA

NASA, in its ongoing effort to study just about, well, everything, has outdone themselves this time.

They flew a DC-8 into Hurricane Earl in an effort to study how hurricanes and tropical storms form. SWEEEET!

They also got this really cool satellite image of Hurricane Danielle (northern one) and Hurricane Earl (southern one) in the same image.

Photo: NASA Click for Large version

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The Physics Of X-Ray Imaging

August 31, 2010 3 comments

So here is Part One of my series of the “Physics Of” medical imaging. First up is the most recognizable: X-ray Radiography.

Radiography (which uses x-rays, but the images are generally called “X-Rays”) are the most common form of medical imaging, and are incredibly useful. Thousands of images are performed everyday and medicine was revolutionized when this non-invasive means to study the body was discovered.

But how exactly do we get x-rays and use them for imaging?

Lets start with a bit of history. The first X-ray image was created by a guy named Wilhelm Rontgen in 1895.

Wilhelm Rontgen

Rontgen called them “X” rays because they were an “unknown” type of radiation, and the name kind of stuck.

The first image was of Rontgen’s wife’s hand, and is pretty cool because you can actually make out her wedding ring.

First image using X-rays of Wilhelm Rontgen's wife's hand

I actually find this a bit funny. I just picture a crazy looking physicist saying “Honey! C’mere! Stick your hand in front of this radiation for a second!”

Luckily for Mrs. Rontgen, x-rays, in small doses, are not very dangerous. So what exactly are x-rays?

X-rays are electromagnetic waves just like visible light, radio waves and microwaves. They have a wavelength range of roughly 0.01 to 10 nanometers (1 nanometer = 1 billionth of a meter).

When talking about x-ray imaging, however, its easier to think of x-rays in terms of photons. Photons are like tiny wave “packets” and electromagnetic waves can be described as a big collection of photons.

X-rays are generated in an x-ray tube (unsurprisingly). Basically, a bunch of electrons are shot at a piece of metal (usually tungsten, the same metal used in old school incandescent light bulbs). Now what happens next is a little complicated, but really cool…

So the electron travels at a certain speed toward the piece of tungsten; it has kinetic energy, which is the energy of motion. But as it gets close to the Tungsten it will run into an electric field produced by the metal, and will actually slow down.

X-ray Tube

Now, in physics there is principle called the conservation of energy. Basically this just says that energy can never be created or destroyed, it can only change form. So when the kinetic energy (energy of movement) of the electron drops (when it slows down) that lost energy has to go somewhere. Where it goes, in fact, is in the generation of an x-ray. The electron will actually emit an x-ray when it gets slowed down by the tungsten. Pretty sweet eh?

Schematic of X-ray tube. Electrons come in from the bottom, strike the tungsten target (the anode) and emits x-rays

This is actually a type of radiation called Bremsstrahlung, which is German for “braking radiation”.

Schematic Diagram of Bremsstrahlung

Ok, so now we got x-rays, how do we make an image?

Well, if we fire x-rays at, oh lets say, YOU! the x-rays will interact with your body. How you ask?

Well when an x-ray passes through the body, it may get absorbed or scattered by the body. An x-ray gets absorbed when the x-ray hits an electron in our body, and the electron “jumps” out of the atom. This is called the photoelectric effect.

The Photoelectric Effect

The x-ray may also get scattered. This just means that the x-ray will get close to the nucleus of an atom and get kind of turned in another direction due to the electric field of the nucleus. This is known as Compton Scattering.

Compton Scattering Effect

In spots of our body that very dense like bones, the x-rays have a much higher chance of getting absorbed or scattered than if they pass through muscle or fat, which are less dense. So if we were to stick a piece of film which is sensitive to x-rays behind someone getting a radiograph, you would get lots of x-rays hitting the film when they pass through muscle or fat, but very few pass through bones (or metal, if you’re really unlucky).

So on the radiograph muscles and fat show up dark, and bones show up white. BAM! Radiograph!

Chest Radiograph

See, now that wasn’t so bad was it? Pretty interesting if you ask me.

The next installment of my “Physics Of” medical stuff  series will be something that takes x-rays to the next level: Computed Axial Tomography, commonly called “CAT” scans.

Hummingbirds in Slo-Mo and HD! OMG!

August 30, 2010 Leave a comment

I know, I’ve been slacking this weekend. Why?

Well it was Alison’s birthday on Friday. So I did the boyfriend thing and took her out for a nice sushi dinner etc. She has the full details of the evening on her blog, so feel free to read them here.

Also, I just bought StarCraft II.

I been waiting for this for all of the 15 years Blizzard has been keeping us all in suspense (its awesome too, btw). So that ate up most of my weekend.

So I’ll be back in full form this week. But to get you started, here’s a video I came across on the weekend.

Its some pretty remarkable footage of hummingbirds which I read about on Mental_Floss. The footage is from a Nature documentary which aired on PBS.

I’ve always found hummingbirds really interesting; being able to hover in mid-air and then dash away like a UFO is pretty sweet.

(Protip: You can watch the video in HD on YouTube.)

The parts I find really interesting are the “flower-view” of the hummingbird eating, as well as when it catches an insect in mid-air in a fraction of a second. Seeing a hummingbird as a predator is something I never could have imagined.

So I hope you enjoy this, my brief foray into blogging about Ornithology. Birds have never been my main interest, but c’mon,  hummingbirds in slow motion? Awesome!

Woo Hoo! Isotopes Rule!

August 27, 2010 Leave a comment

Gotta love the Isotopes!

After a 15 month hiatus, the Chalk River nuclear reactor in Ontario, Canada, is starting to once again produce isotopes used for medical  imaging.

The Chalk River reactor produced one third of medical isotopes used for imaging procedures all over the world. Namely, it produced Molybdenum-99, which is created as a fission product in the nuclear reaction.

The Molybdenum-99 isotope is unstable, and will decay into Technetium-99m. The Technetium can then be injected into a patient to perform medical scans.

Molybdenum-99 is kept in specialized containers while it decays into Technetium-99m

Now, I did my Masters thesis on Magnetic Resonance Imaging, so these medical procedures bring back some good memories for me. As such, I am going to start a series of posts describing the “Physics Of…” various medical techniques.

These will include things like X-Rays, PET scans, CAT scans, etc. So look forward to that, its a subject I hold very dear to my heart.

Hurricane Katrina As Seen From Space: 5 Years Later

August 26, 2010 Leave a comment

Its been almost 5 years since the disaster of Hurricane Katrina.

The city of New Orleans has not yet fully recovered from the devasting effect of the hurricane, which made landfall in the United States on August 29, 2005, and the failure of the levees which were supposed to protect the historic city.

As a way of reminding us all of the terrible impact the hurricane had, NASA has released this retrospective video. It contains images and analyses from a wide variety of satellites which imaged the hurricane as it developed, travelled through the Gulf of Mexico, hit the city of New Orleans, and finally it shows the amount of flooding which occured after the hurricane hit.

From a scientific standpoint, it is very interesting to see how the hurricane progressed in its development. Unfortunetly, the images of those trapped on rooftops are still burned into my memory, so the knowledge gained from studying this hurricane is somewhat bittersweet.

Dinosaur Found in Sewer by My House!

August 25, 2010 Leave a comment

Yup, its totally true.

A city worker in Edmonton, Alberta (not far from yours truly) was having a regular, shitty day at work in the sewer. Thats gonna be my only sewer joke, I swear.

So this young man named Aaron Krywiak found what he described as “an interesting shaped rock.” Well that rock turned out to be the tooth of an Edmontosaurus. But thats not all.

Aaron Krywiak

Upon further investigation, Aaron found a “motherlode” of dinosaur bones belonging to Edmontosaurus and Albertosaurus.

Edmontosaurus

Albertosaurus

I love living here. Its pretty cool to be so close to such world class dinosaur research and sites.

I still haven’t made it to the Royal Tyrell Museum though, which is where these fossils are going to be taken. Not to worry, I’ll get there soon and you’ll be sure to hear about it!

Sumo Wrestlers Getting Free iPads Because Hands Too Fat

August 24, 2010 Leave a comment

Yup, its not a joke.

Japan’s governing body of Sumo wrestling is going to distribute iPads to the various “stables”, which is where the wrestlers train (seriously, THATS not a joke either!) so that they can communicate with each other more easily.

Apparently the wrestlers struggle with cell phones because their hands are simply too large to work the keypads.

Well, using an iPad is a bit more high-tech than a dialing wand. I would expect nothing less from the technology geniuses in Japan.