Archive
If Your Bandage is Glowing, That’s Bad…
A polymer and fluorescent dye work together to cause a bandage to glow in the presence of infection.
A team of researchers at the University of Sheffield has developed an interesting way of detecting bacteria in a wound (I know, gross).
The researchers found that a polymer attached to a fluorescent dye on bandage can detect when bacteria or other harmful organisms come into contact with the wound. The polymer changes shape when the bacteria are present, activating the dye and emitting ultraviolet light.
The technique was mainly developed with military applications in mind. Being able to easily and quickly identify infected wounds on the battlefield could help significantly reduce the severity of injuries.
“If you know you’ve got infection it’s going to change how you treat your soldiers, it’s going to change how you’re going to treat those patients in the home,” Sheffield researcher Sheila McNeil said. [UPI.com]
At the moment, the technique has only been applied to artificial tissues. However, it currently takes several days to confirm the presence of infection, so there is quite an interest in expanding the technique to human trials.
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Ryan
50th Anniversary of the Discovery of Stem Cells
In the early 1960s, two Canadian scientists by the names of James Till and Ernest McCulloch at the University of Toronto made the discovery of stem cells.
Stem cells, put simply, can be thought of as “blank slates”; cells which can divide differentiate in a variety of cell types. They can now be used to grow human tissues and may even one day be able to grow entire organs which can be transplanted into human subjects.
The medical implications of this discovery are incredible. To help celebrate, the Ontario Science Center has an exhibit open until October 2, 2011, depicting the wonders of stem cells.
So if you live in the Toronto area, be sure to check it out!
(Thanks to @DiscoveryCanada for bringing this to my attention)
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REMINDER: This blog is moving! The new location is http://www.aquantumofknowledge.com/
Remember to update your subscriptions! This site will go dead on September 30, 2011.
Thanks!
Ryan
Vaccines (once again) Found Safe. Not That Anti-Vaxxers Care…
The Institute of Medicine has released a comprehensive report on the safety of vaccines. They looked at a wide range of vaccine types and various adverse affects known to be associated, and thought to be associated, with vaccines.
The report looked at claims which were submitted to the National Vaccine Injury Compensation Program (VICP), which was setup in 1986 to compensate those who were injured by vaccines.
They then looked for a causal relationship between the administration of the vaccine and the adverse effect reported in the claim.
In short, the committee found that most issues with vaccines were rare and mild.
Additionally, evidence favors rejection of five vaccine-adverse event relationships, including MMR vaccine and autism and inactivated influenza vaccine and asthma episodes.
A summary of the report very aptly states:
Despite much media attention and strong opinions from many quarters, vaccines remain one of the greatest tools in the public health arsenal. Certainly, some vaccines result in adverse effects that must be acknowledged. But the latest evidence shows that few adverse effects are caused by the vaccines reviewed in this report.
Of course, this doesn’t sway the staunch anti-vax supporters. Age of Autism, a group which is hell-bent on rejecting any scientific evidence showing that vaccines do not cause autism, had this to say about the study:
The IOM report took two years to produce, mostly behind closed doors, and was paid for by the Department of Health and Human Services, the government agency which is also a defendant against the vaccine-injured in the government’s vaccine court
Their arguments are as predictable as the sun rising in the east. It is a government agency, therefore they don’t accept the research.
If people want to keep their heads buried in the sand that is one thing, but the problem is that it is children who end up suffering when people don’t accept the science behind one of the greatest medical advances in history.
But I guess I shouldn’t be surprised. Though that doesn’t mean I can’t be disappointed.
Does TV Watching Make You Sick? Not Exactly…
Beware! It might kill you! Photo Credit: Istvan Takacs
I’m a little annoyed with some headlines hitting a few news websites today:
TV Watching Raises Risk of Health problems, dying young
Excess TV time linked to early death
TV time tied to death, diabetes risk
The stories are talking about a study getting published this week in the Journal of the American Medical Association.
The study is a meta-analysis of 8 studies over the past 40 years which look at the correlation between watching television and risk of diabetes and cardiovascular disease.
The study found, unsurprisingly, that increased television watching was correlated with an increased risk of type 2 diabetes and heart disease.
The pooled relative risks per 2 hours of TV viewing per day were 1.20 (95% CI, 1.14-1.27) for type 2 diabetes, 1.15 (95% CI, 1.06-1.23) for fatal or nonfatal cardiovascular disease, and 1.13 (95% CI, 1.07-1.18) for all-cause mortality.
In layman’s terms, this means that for each 2 hours of television watched per day, risk of type 2 diabetes increased by about 20%, risk of developing fatal or non-fatal heart disease increased by about 15%, and risk of dying of any cause increased by about 13%.
So does watching TV make you sick? Not exactly.
I’m not doubting the results of the study, though they should be taken with the usual grain of salt that should be taken with all epidemiological studies.
They are observational studies, not controlled studies in a lab. There are many variables which can influence the results.
That being said, the results of the study are not surprising and I have every confidence that there is truth in there.
But the media takes these types of studies, gives them a sensationalized headline and doesn’t put them in the proper context.
Watching TV does not make you sick; being lazy makes you sick. What this study is really showing is that watching TV correlates to a lazy lifestyle.
There’s nothing wrong with kicking back and watching some Star Trek reruns or even *groan* Dancing with the Stars. Just make sure you go out for a jog now and then. Or play some basketball. Or just do anything that isn’t sitting around and being lazy!
I’m sure snacking is a big factor in the results of this study as well. No doubt increased time in front of the TV leads to eating more unhealthy foods.
But if you sit in front of the tube and eat baby carrots or oatmeal, then you are probably not at a huge risk of developing heart disease or diabetes.
So if you watch a lot of TV, you’re not necessarily going to die young because TV doesn’t make you sick.
But if you eat a lot of junk food and don’t exercise, then you might die young. But then again, THAT’S not exactly news, is it?
Measles Outbreak Hospitalizes Four Children
Yes, and it could have been prevented.
The outbreak happened in the Twin Cities area of Minneapolis. Since measles immunization is highly effective at preventing measles, how is it a that an outbreak like this could have occurred?
According to the Minnesota Department of Health, a recent outbreak of measles in the Twin Cities area was caused in part by former doctor and medical researcher Andrew Wakefield’s influential but fraudulent study suggesting a connection between child vaccination and autism.
So why weren’t the children vaccinated?
Several of the parents informed the Health Department they had avoided the mumps, measles, and rubella (MMR) vaccine out of concerns their children would be at risk of autism.
If you read this blog at all (or any other skeptic blog, for that matter) you know this already. But once more, with feeling…
Not only has Wakefield’s original study been shown be of poor quality, it has also been alleged to be fraudulent. Many larger studies have shown absolutely no correlation between vaccines and autism.
None. Zero. Nada. Zilch. Nil.
Ok, I’m starting to get worked up. It happens when I talk about vaccines especially.
Why? Well usually when a scientist’s outlandish claims get debunked it is an “I told you so!” situation.
But when children (or anyone) get hurt or hospitalized as a result of those outlandish claims, it becomes a “Bang your head against the wall because this could have been prevented” situation.
Maybe we could call this a “Wakefield” situation; a “When Are Kids Ever going to Forgive us for letting Idiots Endanger their Lives with Debunked science” situation.
The reality is starting to set in, as Dr. William Schaffner, chair of the Department of Preventive Medicine at Vanderbilt University, lays out:
Hospitalizations and deaths have occurred—all preventable, had the children been immunized. In the U.S., some parents withhold vaccines; others stretch out the vaccination schedule, leaving children susceptible to disease for longer than they should.
I don’t know if the damage caused by that original Wakefield paper will ever be fully undone. But that doesn’t mean we can’t try to undo as much as possible.
The Globe and Mail Fails Again
The Globe continues its descent from decent reporting to tabloid-like fear mongering. The culprit this time is a completely unskeptical article containing a condensed interview with Paul Connet, “a U.S. academic and public-health advocate”. He has recently penned a book called ‘The Case Against Fluoride’.
The article is available here, but I was so disappointed with the article’s lack of counter evidence or even discussion, that I feel the need to provide such commentary here. Let’s look at a few of the questions that were asked:
Before you became involved in this issue, you were skeptical that fluoride was harmful and thought critics of the practice were misguided. What changed your mind?
There were two things. The first was that fluoride interfered with hydrogen bonds, which are common in proteins and other important molecules in our bodies. That sent alarm bells ringing through my head. The second was that the level in mothers’ milk was incredibly low. When you see what nature’s take on it is, which is don’t give the baby much fluoride, then I felt this doesn’t make any sense to add it to water.
Hydrogen bonding is a form of attraction between the positive hydrogen atom and an electronegative atom. Connet is referring to a paper written in 1981 in the Journal of the American Chemical Society. The paper found that hydrogen bonds are quite strong in a fluoride-amide solution and that this may affect proteins. Amides also appear in proteins, and he believes that this will have some kind of biological effect. I have not found, however, any papers finding that this effect can be extended to fluoride detrimentally affecting human proteins in vivo. In fact, it is fluoride’s effect on hydrogen bonding that may be part of the reason it is beneficial to tooth enamel.
His second reason for fearing fluoride just seems silly. It’s not in breast milk therefore we should not use it? This just flat-out doesn’t make sense. We have evolved to a point where we can use medicine and vaccines to improve our health beyond that which has naturally occurred through evolution. To deprive an infant of these advantages because they are not in mother’s milk is ridiculous.
In the case of fluoridation, the water supply is being used as a drug-delivery mechanism to treat a medical condition. Why is this wrong, in your view?
It violates people’s right to informed consent, which has always been the strongest argument against fluoridation. We’ve never done it with other drugs. Since fluoridation began in 1945, not one other substance has been added to the water to address a health concern. You shouldn’t use the water supply to deliver medication, for obvious reasons. You can’t control the dose. You can’t control who will get it. There is no individual supervision. The whole practice doesn’t make sense from a medical point of view.
True, we have never use water to deliver other drugs. But we have in salt. Iodised salt was introduced in the United States in 1924 to help prevent goiters and iodine deficiency. I don’t hear anyone complaining about the lack of goiters.
Dose control is a noble concern, but not relevant. So long as the fluoride concentration is controlled and tested regularly (about 0.5 to 1 mg/L), it would take an unfeasible amount of water ingestion to even have a chance of causing any detrimental health effects.
The right to informed consent is actually the one argument I think has merit. However, people are always informed if fluoride is added to their water supply and do have the option to get a water filter to remove the majority of it if they wish.
The first U.S. fluoridation trial began in the mid-1940s. Would fluoridation pass a modern, drug-style clinical trial or risk assessment?
There is no way on planet Earth that you could get fluoridation through today. It’s only because it’s been an inherited practice and so much credibility is at stake for the medical community that keeps it going.
This is just flat-out wrong. Studies on the effect of fluoride have never stopped and continue to be updated. The consensus remains the same: fluoride is an effective and safe means of preventing dental caries.
What are the health dangers from fluoridation?
I think we’re going to pay a huge price. I’m convinced, based on animal studies, clinical trials and epidemiological studies, that drinking fluoridated water for a whole lifetime will increase your risk of arthritis and also increase your risk of hip fractures, which is very serious in the elderly. The reason for these problems is that half the fluoride people ingest is stored in the bone. We may also have a problem with it lowering the IQ of children. There are 23 studies from four countries that have found a possible association between drinking naturally fluoridated water and lower IQ in children.
Regions which have artificially fluoridated water, that is, water in which the fluoride concentration is controlled, show no significant correlation between arthritis or hip fractures. The statement that “half the fluoride ingested is stored in the bone” is not necessarily true. 75-90% of ingested fluoride is absorbed and in adults about 60% of absorbed fluoride is retained. Connet’s concern about the IQ of children comes from studies of naturally fluoridated water, that is, water which does not have the fluoride added by the city, but comes from natural sources or fluoride pollution. These naturally fluoridated waters supplies usually have much, much higher concentrations of fluoride than artificially fluoridated sources.
A lot of these concerns are based on flimsy evidence and straw man arguments. There are however, a couple of things I do actually agree with:
1. Naturally fluoridated water supplies are a problem because the concentration are too high and may cause adverse health effects. However, this concern should not be unfairly extended to artificially fluoridated water supplies.
2. The argument about informed consent is a valid one. But if you don’t want fluoride in your water because of this reason, don’t argue it based on health effects; argue it based on an informed consent platform.
Oh and one more thing. I am actually worried about the fluoride in MY water supply. The reason is because Calgary has voted to remove it.
I will definitely be making sure there is fluoride in my toothpaste.
Cell Phones, Your Brain, and the Media
Usually, when a scientific study gets this much media attention, it has something quite impactful to report.
But when the study has nice, media-friendly buzz-words like “radiation” and “brain activity”, you get a firestorm of media coverage. Even if your study doesn’t say all that much.
The study I am referring to is called “Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucose Metabolism” which was recently published in the Journal of the American Medical Association.
The study looked at 47 healthy volunteers; a relatively small study. The researchers took these volunteers and gave them all PET scans on their brains. They had also strapped two cellphones on either side of their head. One cell phone was on, and the other was turned off.
During a 50 minute phone call, they compared the two sides of their brain to see if there was any change in glucose uptake.
What did they find?
Whole-brain metabolism did not differ between on and off conditions. In contrast, metabolism in the region closest to the antenna (orbitofrontal cortex and temporal pole) was significantly higher for on than off conditions (35.7 vs 33.3 μmol/100 g per minute; mean difference, 2.4 [95% confidence interval, 0.67-4.2]; P = .004). The increases were significantly correlated with the estimated electromagnetic field amplitudes both for absolute metabolism (R = 0.95,P < .001) and normalized metabolism (R = 0.89; P < .001). [JAMA]
So basically, whole-brain metabolism was the same whether the phone was on or off. However, in regions close to the phone’s antenna, the metabolism was “significantly higher”. It is important to point out that in this context, “significantly” means statistical significance, not a large increase. In fact, the increase was only about 7%.
Brain imaging physicist Dardo Tomasi of Brookhaven National Laboratory, who co-authored the study, said that’s several times less activity than visual brain regions show during an engaging movie. [Wired]
Ok, so now the important question: what does this mean for our health? Nora Volkow, the study’s lead author commented:
Volkow says it is too early to tell whether this is good or bad for the brain. “Much larger fluctuations in brain activity occur naturally,” says Patrick Haggard at University College London. In fact, being able to increase activity might boost the brain’s connectivity, and could even be useful therapeutically, Volkow suggests. [New Scientist]
So although the study was published as a “Preliminary Communication”, and that the study itself concludes:
This finding is of unknown clinical significance. [JAMA] (emphasis mine)
there is still a large number of news outlets which reported on the study. Why?
Well we know why already. That “unknown” word in the above quote carries a lot of baggage.
Cell phones are the new danger to health, of course. Despite there being no conclusive evidence that cell phones even have the ability to cause cancer, and the fact that even with the explosion of cell phone use in recent years, cancer rates have not increased, people are still scared of their cell phone.
This is thanks to poor media coverage, and a few crackpots out there who are determined to prove that technology is going to destroy us all.
And as a result this small, preliminary study with a result that, while interesting, is completely benign, gets extensive media coverage. Not only that, but some news sites give thinly veiled comments suggesting that the results somehow show that cell phones are dangerous, like this one:
The unusual finding, published on Tuesday in the Journal of the American Medical Association, is likely to lead to new calls for stricter regulation of radiation emissions from the ubiquitous phones. The government currently assumes the signals have no effects other than a harmless warming of tissues near where they’re held. [The Globe and Mail]
or this one:
Some studies have linked cell phone exposure to an increased risk of brain cancers, but a large study by the World Health Organization was inconclusive. [MSNBC]
Of course they used the word “inconclusive” in the above quote, when it should really read “it showed no correlation”. Scicurious points out that this is probably because “‘inconclusive’ sounds scarier”.
So nobody panic. This study does not show that cell phones are dangerous. It may show that the electric field from the antenna somehow increases metabolism of glucose, but those findings need to be corroborated by other labs. Let’s wait until their findings are duplicated on a larger scale and a mechanism by which this effect happens can be discovered before we decide what, if any, impact this study should have.
Calgary Falls to Fluoride Fear
In a huge skeptic fail, the city of Calgary has announced that it will remove fluoride from its water supply.
The move comes after the city council voted 10-3 in favour of stopping the addition of fluoride to the city’s water.
And now, Fluoride Action Network, based in the U.S. but which has spearheaded the anti-fluoride movement in Canada and has succeeded in Waterloo and now Calgary, is moving its fight against reason to London, Ontario.
I live in Calgary now, and I used to go to school in London. Is this a personal attack against me!?
The Fluoride Action Network has a lot of similarities with the anti-vaccine movement. They are claiming that they are “are just pushing for a review that’s badly needed after decades of conventional wisdom.”
Yet the first thing you see on their homepage, in large font: “TAKE ACTION! A Reduction in Fluoride Levels is Not Enough: Tell HHS to End Fluoridation Completely”
As the CBC reports today, the city council acted without any input from Calgary’s citizens:
Earlier in the day, city council considered and rejected by a vote of 8-5 putting the fluoride issue to a plebiscite in the 2013 municipal election.
And this was my favourite quote:
Council also rejected referring the matter to an expert panel.
*FACEPALM*
So the City Council basically said “No, no. We won’t ask an expert. We know what direction the wind is blowing and we will go along with it.”
People are motivated by fear. A couple of months ago there was this piece in Maclean’s magazine about Canadians reacting to these fear tactics, including fluoride:
the Waterloo regional council voted to stop the 43-year practice of adding fluoride to the municipal drinking water, after two local residents complained that it was making them sick. Forget the fact that the only known side effect from water fluoridation—from too-high fluoride levels, specifically—is something called dental fluorosis, a.k.a. stained teeth, and that the ban was implemented despite strong opposition from the very people who stand to benefit most from the ban, namely, local dentists. Waterloo residents are now revealed as the Birthers of dental hygiene, sticking to their thesis precisely because it is so implausible.
But anti-fluoriders stick to their convictions, saying that it is not the Government’s job to maintain the health of its people, which is a crock. The government is in place to do whats best for its people. They police the streets, they manage public transportation and they plow the roads. If adding a bit of fluoride to the water is in our best interest, why shouldn’t they do it?
Not convinced? You want some science? Well as stated above, the only side effect of excess fluoride is stained teeth. Fear-mongerers attempt to convince us that fluoride consumption is correlated with bone cancer. But that study was not peer reviewed, and only looked at a small subset of the data. When compared with the entire population, that correlation disappeared. The authors of that study themselves noted that it had serious limitations.
But there are several reviews of actual peer-reviewed research stating that fluoride is perfectly safe at the levels maintained in public water supplies:
- Water fluoridation. Parnell C, Whelton H, O’Mullane D. Eur Arch Paediatr Dent. 2009 Sep;10(3):141-8. (Conclusion: Water fluoridation, where technically feasible and culturally acceptable, remains a relevant and valid choice as a population measure for the prevention of dental caries.)
- Systematic review of water fluoridation. McDonagh MS, Whiting PF, Wilson PM, Sutton AJ, Chestnutt I, Cooper J, Misso K, Bradley M, Treasure E, Kleijnen J.BMJ. 2000 Oct 7;321(7265):855-9. (Conclusion: The evidence of a beneficial reduction in caries should be considered together with the increased prevalence of dental fluorosis. There was no clear evidence of other potential adverse effects.)
- Water fluoridation in Australia. Spencer AJ, Slade GD, Davies M.Community Dent Health. 1996 Sep;13 Suppl 2:27-37. (Conclusion: Community water fluoridation continues to be the most effective and socially equitable measure for caries prevention among all ages by achieving community-wide exposure to the caries preventive effects of fluoride.)
- Risk-benefit balance in the use of fluoride among young children. Do LG, Spencer AJ. J Dent Res. 2007 Aug;86(8):723-8. (Conclusion: Exposure to fluoridated water was positively associated with fluorosis, but was negatively associated with caries. Using 1000-ppm-F toothpaste (compared with 400- to 550-ppm-F toothpaste) and eating/licking toothpaste were associated with higher risk of fluorosis without additional benefit in caries protection.)
- An update on fluorides and fluorosis. Levy SM.J Can Dent Assoc. 2003 May;69(5):286-91. (Conclusion: Water fluoridation and use of fluoride dentifrice are the most efficient and cost-effective ways to prevent dental caries; other modalities should be targeted toward high-risk individuals.)
Thankfully, residents of London Ontario seem to be approaching the issue with the right amount of skepticism.
“They refer to fluoride as being the equivalent of a poison or a toxin,” said Pollett, London’s top public health official. “These fears are not substantiated but nonetheless they raise concerns in people’s minds.”
Fluoride levels in London water “pose no risk to health,” he added.
London has had fluoride in its water since 1967. It costs about 40 cents per year per Londoner to put it in the system.
In another article written today by Ian Gillespie, his similar feeling about the absurdity of fluoride fears is quite apparent:
When asked about the benefits of adding fluoride to our drinking water, London Coun. Denise Brown said, “If you do any research on the Internet, you’ll find scientists believe there are health risks.”
Yes, that’s right.
And if you do more Internet “research,” you’ll also discover “experts” who argue that aliens hijacked the Voyager 2 spacecraft, Paul McCartney died in a 1966 car crash, Elvis Presley is alive and the Apollo moon landing was a hoax.
C’mon folks. Give your head a shake.
Yes, City Councilors are listening to whatever fringe group is loudest to make their decisions now it seems. They also believe that by doing “research on the internet” (what skeptics like to call ‘attending the University of Google’) they can get accurate and unbiased information.
So if you are a resident of London, please check out the real information about fluoride. Decades of credible research show that it is perfectly safe, over 90 Health organizations all over the world, who routinely review the scientific evidence, all endorse the use of fluoride in water.
The United States Center for Disease Control sees fluoride in public water supply as one of the 10 greatest public health achievements of all time.
Since water fluoridation has been around for so long, people forget what happens when you remove it.
“(Officials in) Dorval, Que., took the fluoride out in 2003,” [Dr. Lynn Tomkins, president of the Ontario Dental Association] says. “And the rates of dental decay in pre-schoolers there have doubled. That’s pretty alarming.”
So if you live in Calgary, you might want to start getting better dental coverage. Because fluoridation of water is of course “the most monstrously conceived Communist plot we have ever had to face.”
The Physics of MRI
MRI being performed. Via Wikimeda Commons
Phew. I know, right?!
I’ve been saying I’ll write a post about the physics of MRI for months. Never got around to it. Mostly because I knew that since magnetic resonance imaging (MRI) was my field of research, that I would want to go into a lot of detail. I loved the time I spent doing MR research, and now I’ll finally share with all of you how it works.
Let’s start at the beginning.
We are all made of atoms. Atoms consist of a nucleus (made of neutrons and protons) orbited by electrons. The most common atom in our bodies is Hydrogen, which is a single proton orbited by a single electron. It is the simplest atom in nature, and it is quite fitting that it makes up the majority of our bodies.
We are mostly made of hydrogen because we are mostly water. Water has 2 hydrogen atoms and 1 oxygen atom (H20). When we do an MRI, what we are actually taking an image of is the hydrogen in our bodies.
How is that done? Well protons have charge, a positive charge. Any particle that has charge also has what is called a magnetic moment. A magnetic moment is essentially a measure of the strength and direction of the magnetic field of particle. For a proton, the magnetic moment looks like this:
A proton (red circle) and it's magnetic moment (arrow)
Usually, all the magnetic moments in your body are jumbled about in all directions. That’s why you are not magnetic. When this is the case, we say that your net magnetic moment is zero.
Normally, all the magnetic moments in your body are jumbled around. Thus, your net magnetic moment is zero.
But if we apply a magnetic field from the outside, we can get the moments in your body to line up with the field, like so:
If we apply a magnetic field in a certain direction (blue arrow) the magnetic moments in your body will tend to align with the magnetic field.
In order to do that, we need BIG MAGNETS. That’s why MRI’s are so strong; you need that strong magnetic field to get the moments in your body to line up. (The diagram above is an exaggeration; in reality, only 1 in a million of the magnetic moments will line up with the field, on average).
How strong is an MRI magnet? Magnetic fields are measured in units of Tesla (in honour of Nikola Tesla). A typical MR scanner has a field of 1.5 Tesla. For comparison, this is about 30 000 times stronger than the Earth’s magnetic field, the field that makes a compass needle point north.
Now your body has what is called a net magnetization. This means that the magnetic moments have lined up and you are a little bit magnetic.
But that’s only half the battle. Next, we have to get some kind of signal from your body to make an image. How do we do that?
Well, have you ever swiped a credit card in a machine? What would happen if you just held it still? Would it still work?
The answer is no. Your credit card only works because the black strip in the back is magnetic. When you swipe it through the machine, it creates an electric current. This is due to Faraday’s Law, which says that a changing magnetic field in a loop of wire will create an electric current in that wire.
When you swipe a credit card through a credit card machine, you induce an electric current in the machine.
We can apply this concept to your body too now that its been magnetized by the MRI machine. You see, MRIs actually have a radio transmitter/receiver inside of them as well. How does THAT help?
Unlike a credit card, we can’t swipe YOU through the MRI machine. That’s not feasible. But we can manipulate the fact that you are now magnetized. This can be done using a radio-frequency pulse. Basically this is just a short, intense burst of radio waves at your body. This will actually make your net magnetic moment spin.
If your net magnetic moment is now spinning, it creates the exact same effect as if we were to swipe you through the MRI machine: it generates an electric current in a receiver in the MRI. Cool eh?
Ok so now we have a signal from your body by magnetizing it, and then making that net magnetization vector spin. How does that make an image?
So we made your net magnetization spin by using a radio-frequency pulse. How fast it spins depends on how strong the magnetic field is. So what MR scanners do is they make the magnetic field a bit different at each point in your body. That way, the magnetization from each part of your body spins at a different rate (or frequency) and we can then determine what part of your body is giving the signal.
Confused? Think of it this way:
Let’s say you had a piano. You hit a key on the left side of the piano and what happens? It makes a deep, low-frequency sound. Now you hit a key on the other end of the piano and you get a high-pitched, high frequency sound.
Different keys on the piano make different frequencies of sound. You can get an idea of what key someone hit from the frequency of the sound, without actually seeing the piano.
Now pretend you weren’t looking at the piano at all, and someone else hit a key. If you hear a low-frequency sound, you know they hit a key on the left side of the piano. If you hear a high frequency sound, you know it came from the right side. You were able to determine the position of the key by its frequency.
Its the exact same idea in MRI. Using the frequency of the signal we get, we can determine where in your body that signal came from. We then put all those signals from all parts of your body together, and we get an MRI image.
MRI of the head (Photo: NASA)
I know, there’s a lot of steps to MRI, so I’ll recap:
- We magnetize your body by using a really big, strong magnet.
- We make your net magnetization spin using a radio-frequency pulse.
- This spinning magnetization generates an electric current in the radio receiver in the MRI machine.
- We can tell where in your body this signal came from by its frequency.
- Putting all the signals from all over your body together, we can make an image.
So there you go. Simple right?
If you want some more information you can check out the MRI article on HowStuffWorks.
Or if you want something a little more technical and goes a bit deeper into MR theory (e.g. relaxation, pulse sequences), check out this online book by J.P. Hornak, or the Wikipedia page on the physics of MRI.
Happy learning!
Does VitaminWater Prevent the Flu?
That is what an advertisement for vitaminwater is suggesting.
The ad has raised the concern of the National Consumers League (NCL), which has filed a complaint with the Federal Trade Commission.
They state that the poster advertisement, as well as a TV commercial for vitaminwater give false statements concerning the efficacy of vitaminwater for preventing the flu.
In the TV ad, a cartoon woman brags about how she can use her sick days to hang out with her boyfriend because she drinks vitaminwater. A transcript of the commercial goes like this:
I love skipping work, especially when I’m feeling great. Layin’ in my pj’s searching Netflix for a guilty pleasure marathon. And since it’s Friday, I’ve got a nice little three-day staycation package. One of my secrets? vitaminwater power-c. It’s got vitamin C and zinc to help support a healthy immune system. So I can stay home with my boyfriend – who’s also playing hooky. What a coincidence.
The NCL’s letter to the FTC states their concern:
The Commission should immediately take enforcement action to halt such claims because such misinformation constitutes an imminent public health hazard. Discouraging members of the public from getting a flu shot as recommended by government health authorities is not only deceptive, but dangerous.
They go on to talk about how vitaminwater projects an image of a healthy beverage, yet it still contains a decent amount of sugar and has 125 calories per serving.
Oh, did I mention that there is no conclusive scientific evidence that increased Vitamin C or Zinc intake can prevent contracting influenza?
The letter cites precedent of other lawsuits for similar complaints in which the FTC ruled that there was indeed false and misleading statements. Those cases have many things in common with the NCL’s complaints about vitaminwater.
As reported by the Boston Globe, a spokesperson for Glaceau, the manufacturer of vitaminwater (and a Coca-Cola subsidiary) responded to the complaints:
vitaminwater has always had a fun, humorous, and engaging personality — and our ads reflect that.
I don’t know about you, but I’m getting the impression that vitaminwater is more concerned with producing a good-tasting, trendy beverage that makes money than with the health of its consumers.
It reminds me a bit of Sunny Delight, which advertised itself as a healthy drink for kids, when really it has as much sugar as soda and is merely spiked with a couple of vitamins.
I have tried some vitaminwater drinks, and they do taste pretty good. I can’t say that I felt any healthier, although some of my college friends claimed that it was great for relieving hangovers.
Of course there is no scientific data to back me up, but it sounds like an over-hyped placebo effect to me.
A Quantum of Knowledge 