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Mapping the brain August 10, 2008

Posted by tomography in fMRI, MRI, Radiology.
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Researchers at Massachusetts General Hospital in Boston are experimenting with a new technique called diffusion spectrum imaging that could help us map the network of axons in the human brain. The basic concept is that MRI is very sensitive to water molecules, and as water molecules are diffusing through the axons, their signals may be picked up using this method.

Scientists can use these diffusion measurements to map the wires, creating a detailed blueprint of the brain’s connectivity.

This could help us make risky surgical operations safer, and it could probably help us better understand how the brain works so that diseases such as schizophrenia and autism may be treated some day. Its worth keeping track of these folks’ work!

Further information:

– Andras

fMRI Predicts Again April 1, 2008

Posted by tomography in fMRI, Radiology.
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Almost all cancers metastasize to the liver leading to slow but certain organ failure and death. Such metastases do not leave too many options for the clinician. Most of the time treatment is only palliative, but in certain cases treatment may be achieved and the patient’s life prolonged.

One such treatment option is transarterial chemoembolization (TACE). Researchers from Johns Hopkins University and Northwestern University say that the effects of TACE on liver metasteses from neuroendocrine tumors may be predicted by fMRI.

“Naik and colleagues enrolled 21 patients with HCC who underwent TACE and intra/postprocedural 1.5T gadolinium-enhanced T1-weighted MR and DWI with follow-up at one and three months. The investigators found DWI changes did occur a few weeks after treatment began and they were useful to predict TACE effects two months before they actually took place and became evident on imaging.

In another study, interventional radiology fellow Dr. Josephina A. Vossen and colleagues at Johns Hopkins evaluated 19 patients with unresectable primary (n = 11) and metastatic (n = 8) liver tumors treated with TACE. Patients underwent unenhanced/contrast-enhanced MRI and MR spectroscopy before and after a single treatment. Two radiologists interpreted results by consensus.

They found 11 patients with successful tumor embolization showed loss of choline peak on MR spectroscopy, significant increase in apparent diffusion coefficient values (22%, p = 0.004), and significant decrease in tumor arterial and venous enhancement (43%, p = 0.005 and 40%, p = 0.002, respectively). Patients with no evidence of tumor response had a stable choline concentration, tumor enhancement, and ADC.”

These functional findings preceded tumor regression in size, and may be utilized to detect early therapeutic response

Vossen said.

Conclusion: Contrast enhancement and metabolic changes detected with functional MR imaging can be used to anticipate the effects of transarterial chemoembolization on primary and metastatic tumors of the liver.

Read the article here.

– Andras

fMRI: Reading your mind March 8, 2008

Posted by tomography in fMRI, MRI, Radiology.
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The brain is the largest consumer of oxygenated blood in the human body. When neural activity increases in certain areas of the brain, during talking or pondering a problem for example, perfusion of those areas are hence increased. This change in blood supply can be detected by fMRI or functional magnetic resonance imaging thanks to two phenomena:

  • the different signals of oxyhemoglobin and deoxyhemoglobin,
  • and the increased local perfusion.

With the BOLD (blood oxygen level dependent) technique it is possible to map a patient’s brain before a risky surgery so that important areas such as Broca’s or Wernicke’s can be spared.

(Broca’s area activated in four patient’s. Source: Journal of Young Investigators.)

Just recently, in a research paper published in Nature, scientists at The University of California at Berkeley claim to have figured out a way to predict the image that their subject is looking at.

Their experiement consisted of two phases. In the first phase the subjects were asked to view 1750 images and their brain activity was monitored with fMRI. This means that every 4 seconds a MRI scan was obtained. During the second phase the subjects were shown 120 novel images, and the software, based on previous experience, “guessed” what image the subjects were looking at.

How accurate was the software? In some cases it was correct 9 out of 10 times. In others its performance was very low; about 0,8%. How can these results contribute to scientific development?

Our results suggest that it may soon be possible to reconstruct a picture of a person’s visual experience from measurements of brain activity alone. Imagine a general brain-reading device that could reconstruct a picture of a person’s visual experience at any moment in time.

So, in the near future it might be possible to decode and store dreams for further viewing with this technique. I can think of one practical use: that is to help people suffering from PTSD verbalize their traumatizing experiences.

Further reading:

– Andras