Saturday, February 7, 2009

Pinpoint Radiation Treatment with Constructive Interference

Radiation can be used to attack cancerous tumors non-invasively from outside the body. One large problem with this method, however, is that the radiation destroys healthy tissue in the process.

If one were to synchronize and focus multiple radiation beams that are relatively weak and innocuous, they could intersect inside the body at the tumor, and their waveforms could constructively interfere to deliver a powerful dose of radiation with pinpoint accuracy.

This may already be practiced in oncology...not sure. Let me know in the comments if you know!

CATEGORY: Medicine / Technology


  1. It's called stereotactic radiation therapy.


  2. Proton therapy is another option here, the protons expend most of their energy at the target as opposed to the surrounding tissue as it passes through. I was working on one of these projects when I left BJC. From the Still River website

    Conventional high-energy x-rays (photon radiotherapy) deposit dose along the entire energy beam path to the tumor as well as beyond the depth of the tumor. Radiation oncologists employ several techniques to minimize collateral damage to adjacent tissue: targeting the tumor from different angles, tailoring the beam to conform to the shape of the tumor, and modulating the intensity of the radiation delivered to different parts of the tumor.

    How is proton radiotherapy different?
    Proton radiotherapy deposits most of its energy at a specific depth and then stops entirely. This allows the physician to tailor the deposition of dose to the specific depth and shape of the tumor while simultaneously reducing the damage to surrounding normal tissue. The advantages of proton radiotherapy over conventional radiotherapy are emphasized in areas of the body with critical adjacent structures (e.g. eye, brain, base of the skull, spine, and prostate) as well as in pediatric tumors.


  3. very interesting - thanks for the info Ryan.

  4. I don't believe what you are proposing is done and I doubt that it could be. Stereotactactic conformal radiotherapy delivers a differential dose to the target volume (tumour) and organs at risk by shaping the x ray beam at a macroscopic level using lead leaves arranged in the shape of the tumour as seen from the beam's eye view; and by choosing a number of beam angles. The X ray beam zooms straight through the surrounding tissue, into the target volume and out the other side, being absorbed to some extent by all of the tissue along its path.., and kind of like the performer on stage at the royal variety performance under multiple spotlights, the thing of most importance gets the most irradiation (only in this case they have one beam and use it multiple times in sequence).

    What's tricky is when the target volume is closely surrounded by organs at risk (brain stem, optic nerve etc.) which you really don't want to give a high dose to any portion of, obscuring a direct view of the complete target from most if not all angles.

    I think what you were suggesting is the notion that occurred to me before I googled and found your blog entry. I think you were suggesting that you could carefully arrange linear accelerators to create inteference patterns that would allow a further degree of intensity modulation to increase or decrease the dose at a given point. I'm no Einstein, but with my knowledge of physics I would suggest that the problems with this would be a) for inteference to work you need a very narrow waveband (e.g. laser) which is not typical of current arrangements, and may be at odds of producing sufficiently high energy beams; b) you need multiple synchronous beams (not impossible, but not the norm) and then the main showstopper would be the disparity between the complexity and scale of the 3d arrangement of target volume and organs at risk versus the scale and flexibility of producing inteference patterns.

  5. A single monochromatic beam passed through the appropriate aperture will create an interference pattern. Probably can't get the necessary pattern with such short wavelength, though. Darn!