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Detecting Chemicals Through Bone

Unknown Lamer posted about 9 months ago | from the full-of-poison dept.

Medicine 23

MTorrice writes "To understand the brain and its chemical complexities, researchers would like to peer inside the skull and measure neurotransmitters levels as the brain at work. Unfortunately, research methods to measure levels of chemicals in the brain require drilling holes in the skull, and noninvasive imaging techniques, such as MRI, can't detect specific molecules. Now, as a first step toward a new imaging tool, chemists report they can detect molecules hidden behind 3- to 8-mm-thick bone."

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Drill, baby, drill (5, Funny)

Travis Mansbridge (830557) | about 9 months ago | (#45500773)

Trepanning always gets a bad rap.

Re:Drill, baby, drill (0)

Anonymous Coward | about 9 months ago | (#45501093)

Zombie president agree. Will sign trepanning bill if Congress pass. Must. Have. Braaaaains.

Re:Drill, baby, drill (1)

camperdave (969942) | about 9 months ago | (#45502133)

Trepanning always gets a bad rap.

Bad rap? You're trying to imply that there's such a thing as good rap?

Re:Drill, baby, drill (0)

Anonymous Coward | about 9 months ago | (#45502593)

Trepanning always gets a bad rap.

I'd let 'em drill, if the money were right. With reasonable assurances, contractually. And payment up front, assigned to my heirs, should something go really wrong.
 
Hell, if you believe my ex-wife, it's not as though I'm actually USING my brain for anything she thought was important *grin*.
 
Captcha: fevered. Yup, that's about right!

Question (3, Interesting)

excelsior_gr (969383) | about 9 months ago | (#45500789)

Isn't MRI practically NMR? NMR is used for chemical analysis. Then how come MRI machines can't be programmed to do the same?

It's NUCLEAR magnetic resonance (3, Interesting)

localroger (258128) | about 9 months ago | (#45500849)

NMR only reports the presence of (certain isotopes of) nuclei. With most biochemicals of interest being made almost entirely of the same four atoms (carbon, hydrogen, oxygen, and nitrogen) there's nothing to tell the MRI which particular large molecule the atoms are part of.

Re:It's NUCLEAR magnetic resonance (3, Informative)

Anonymous Coward | about 9 months ago | (#45500895)

NMR only reports the presence of (certain isotopes of) nuclei. With most biochemicals of interest being made almost entirely of the same four atoms (carbon, hydrogen, oxygen, and nitrogen) there's nothing to tell the MRI which particular large molecule the atoms are part of.

Are you sure you know what you're talking about?

NMR spectroscopy perhaps the most powerful analytic technique in modern organic chemistry -- it works on molecules as simple as hydrocarbons and as complex as proteins. Information is extracted from the fact that the resonant frequency of a hydrogen atom changes slightly depending on the nearby atoms. This has to do with the shielding of the nuclei by electrons. It's really amazing what it can do -- you can detect not only the different functional groups, but also their relative numbers and positions in the molecule.

The relatively small "alphabet" of biomolecules is certainly no barrier to NMR spectroscopy.

The answer to the GP's question, by the way, is that NMR spectroscopy requires a pure substance. If you tried to do NMR spectroscopy on someone's head, you would probably just get the overlapping spectra of every molecule in the head. Not too helpful.

Re:It's NUCLEAR magnetic resonance (0)

Anonymous Coward | about 9 months ago | (#45500939)

Speaking of not knowing what one is talking about, apparently I don't either:

The answer to the GP's question, by the way, is that NMR spectroscopy requires a pure substance. If you tried to do NMR spectroscopy on someone's head, you would probably just get the overlapping spectra of every molecule in the head. Not too helpful.

Well, you do get the overlapping spectra of every molecule in the target area, but apparently, they can actually get some useful information out of that -- it's called in vivo magnetic resonance spectroscopy [wikipedia.org] . Pretty remarkable.

Re:It's NUCLEAR magnetic resonance (4, Interesting)

venicebeach (702856) | about 9 months ago | (#45500927)

The summary is overly dismissive of existing techniques.

In addition to MR spectroscopy, [wikipedia.org] chemical activity in the brain can be measured with techniques like PET [wikipedia.org] and SPECT [wikipedia.org] .

All of these techniques have their advantages and disadvantages, and its certainly always great to have new options.

Re:It's NUCLEAR magnetic resonance (1)

ColdWetDog (752185) | about 9 months ago | (#45501031)

When I first read TFS I thought the researchers had come up with a new way to look at in vivo molecules without 'tags' - molecules introduced into the organism to trigger whatever probe technology you were using. If I'm reading the article correctly, this doesn't seem to be the case - you do have to introduce some tag, presumably into the brain for neuro imaging. Thus, it doesn't have the utility of say an NMR that can read the sample directly (albeit in a tiny glass tube).

It is more like PET / SPECT and similar imaging techniques. Maybe useful, but similar.

Re:Question (1)

umafuckit (2980809) | about 9 months ago | (#45500887)

Isn't MRI practically NMR? NMR is used for chemical analysis. Then how come MRI machines can't be programmed to do the same?

I think they have/are been: http://www.ncbi.nlm.nih.gov/pubmed/9339439 [nih.gov] http://www.ncbi.nlm.nih.gov/pubmed/23494381 [nih.gov] http://www.ncbi.nlm.nih.gov/pubmed/12891651 [nih.gov] http://web.mit.edu/newsoffice/2010/brain-imaging-0301.html [mit.edu]

Re:Question (1)

femtobyte (710429) | about 9 months ago | (#45501223)

NMR for chemical structure and MRI for imaging both rely on the same physics principles (signals emitted by polarized nuclei precessing in a magnetic field). However, there will be significant differences in the hardware optimized for each task (not a software matter of "reprogramming the machine"). Imaging (MRI) hardware is primarily interested in answering the question "where are the nuclei located?", while chemical NMR is about getting an extremely precise measurement of "how fast are the nuclei precessing" to see the tiny frequency shifts caused by interactions with electron structure. A typical imaging MRI hardware system will have nowhere near the sensitivity to fine chemical frequency shifts to indicate much more than the most crude chemical environment differences (not picking up trace levels of particular molecules). For a rough analogy, consider the difference in hardware for triangulating where a radio signal is coming from, versus decoding a message in a radio transmission --- hardware optimized for one task won't be "reprogrammable" to do another. Of course, as NMR/MRI technology improves, people are able to get more and more precise chemical composition information at the same time as measuring the position/density of nuclei.

Re:Question (1)

K. S. Kyosuke (729550) | about 9 months ago | (#45502843)

Of course, as NMR/MRI technology improves, people are able to get more and more precise chemical composition information at the same time as measuring the position/density of nuclei.

You'd need tremendous weak signal detection capabilities for that. I believe this is a case of "either X or Y" situation, or perhaps the best we can hope for is meeting somewhere in the middle: by integrating a signal from larger areas, you regain some measure of "chemical" resolution at the cost of some spatial resolution. (A bit like the color graphics mode on ZX Spectrum. :-))

Re:Question (1)

femtobyte (710429) | about 9 months ago | (#45502875)

Yes, it's a difficult tradeoff, and what you can tell with position information is nothing close to what you can get from a dedicated high resolution instrument (with a tiny sample volume). Note this highly informative post [slashdot.org] further down the thread by a working MRI physicist, indicating some level currently obtainable, from which one might expect gradual improvements with fancier instrumentation (squids! squids everywhere!).

Re:Question (1)

K. S. Kyosuke (729550) | about 9 months ago | (#45502815)

Isn't MRI practically NMR? NMR is used for chemical analysis. Then how come MRI machines can't be programmed to do the same?

Perhaps it's a difference in wiring rather than a difference in programming. NMR chemical analysis gives you high resonance frequency resolution but couldn't care less about spatial resolution. MRI attempts to project the whole 4D thing into high contrast, high spatial resolution imagery instead, while the molecular recognition abilities are sacrificed. (Chemical analysis via NMR integrates the signal for sparsely concentrated molecules over a large area, how would you reconcile that with high spatial resolution anyway?) It's like a difference between a digital camera and a spectrograph. Just because both use photons and CCDs doesn't necessarily mean you can "program" a camera to become a spectrograph.

Honestly, the only way is to (-1)

Anonymous Coward | about 9 months ago | (#45500847)

Chamfer my butt....

I detect sperm in my bone! (-1)

Anonymous Coward | about 9 months ago | (#45501053)

I also detect my bone in your mouth!

Misleading headline (1)

Wdi (142463) | about 9 months ago | (#45501285)

The reported method requires that specially coated nanoparticles are first injected though the bone. That is just drilling a smaller hole.

Spectroscopy with MRI (3, Informative)

DrLudicrous (607375) | about 9 months ago | (#45501307)

Disclaimer: I am a physicist who works in MRI. MRI can be used to measure concentrations of certain biochemicals. MRI is sensitive enough to different proton-containing species that the frequency difference between fat and water causes image artifacts that can pose great difficulty. Not all biomolecules are sufficiently concentrated in the brain, or have a spectrum that is unique enough to be measured in vivo. A good example of a brain chemical that can be measured is N-acetyl aspartate (NAA), which has a proton peak at around 2 ppm that doesn't overlap with much else. Magnetic resonance spectroscopy is very difficult, and is most easily accomplished on research scanners operating at 3 tesla or higher. The reason for this is that rather than letting all hydrogen nuclei contribute to one signal that is then spatially located, one must parse what kinds of nuclei (i.e. what their chemical shift is) within each voxel. This not only imposes technical difficulties, but reduces the signal to noise ratio, potentially requiring more signal averaging in order to see sufficient signal above the noise floor.

Why not just drilling holes in living animals ? (0)

Anonymous Coward | about 9 months ago | (#45501359)

It's not like it has never been done before [wikipedia.org] or it's not being done in secret right now [wikipedia.org] in the name of the Great Science, our god.

Re:Why not just drilling holes in living animals ? (0)

Anonymous Coward | about 9 months ago | (#45505713)

Shouldn't you be choking on vegan food and bitterness?

MR Spectroscopy (2)

Qwerpafw (315600) | about 9 months ago | (#45501705)

The article summary is incorrect. MR Spectroscopy (MRS) is used today to measure molecules inside the brain. Resolution is not great for 3D MRS in clinical applications (due to the tradeoff between SNR and resolution, acquisition times are slow), but it's more than high enough to distinguish between different regions of the brain. And it's very common to perform single-voxel imaging and only get the spectroscopy for a given piece of tissue - for example, where a tumor is located.

MRS easily detects metabolites and ratios, like choline, NAA, as well as things like lipids, and alcohols. It requires expensive scanners, but it works and is used routinely in brain imaging today. The article mentions something that does not work clinically, and is being demonstrated in a lab with a piece of meat. The technology in the article is not a "first step" to understanding molecules in the brain, because we already have that technology today with MRS.

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