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Detecting Chemicals Through Bone
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."
Trepanning always gets a bad rap.
Isn't MRI practically NMR? NMR is used for chemical analysis. Then how come MRI machines can't be programmed to do the same?
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.
Brackets contain world's first nanosig, highly magnified:[.]
The reported method requires that specially coated nanoparticles are first injected though the bone. That is just drilling a smaller hole.
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.
It's not like it has never been done before or it's not being done in secret right now in the name of the Great Science, our god.
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.
I thought this was supposed to be a safer alternative?