Tuesday, July 28, 2009

Hybrid Linac-MRI System

This is rather fascinating.

A new medical device is being proposed that combines two existing technologies - MRI with medical linear accelerator.

A more robust way to guide radiotherapy would be to image the entire tumor continuously and adjust the radiation beams accordingly. Fallone and his colleagues are testing a prototype Linac-MR system they built to do just that.

Linacs (short for linear particle accelerators) are basically devices that use radio waves to accelerate electrons to high speeds and crash them into a solid metal target -- typically tungsten -- producing high-energy X-rays in the collision. These high-energy X-rays destroy cancerous cells by causing irreparable damage to the cells' DNA, MRIs, familiar because of their ubiquity in modern hospitals, are very good at imaging soft tissue and would be an ideal technology for combining with Linacs because most cancers occur in soft tissue.

The problem is making MRIs and Linacs work together. Normally, each one would interfere with the other. Linac systems emit radio waves, which interfere with MRI hardware -- so much so that most hospital MRIs are placed in shielded rooms that specifically block radio waves. At the same time, MRIs employ strong magnets that can interfere with Linac systems.

That's what I thought when I first read this. These are two systems that one seldom thought would be compatible with each other, since they both produces effects that the other doesn't want. I think this is more of a technical or engineering issue that needs to be carefully solved. Certainly, I don't see any showstopper that would stop the progress here. It would be an amazing and important development if one could image and perform the treatment simultaneously. In fact, if one could even detect where the x-ray is actually being deposited as the treatment is being done, that would be as important.


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