Gamma Rays and Laser Guns!


“Where does the radiation shoot out from? Is it a little cone with rings and a round knob at the end?”

“If the radiation hits you in the wrong spot, it will hurt you, right? Then why don’t we have laser/radiation guns?”

Paul (age 11) and I were brainstorming questions to ask my radiation oncologist, Dr. Loiselle, and my neurosurgeon, Dr. Monteith.

James (age 9) wanted to know what would happen in an earthquake. Or if you need to sneeze.   And why doesn’t the laser hurt you on the way into your brain?  How does it just zap the tumor?

Let’s start with the fun stuff.

There IS such thing as a radiation laser gun. It’s called a cyberknife. Dr. Loiselle showed me a picture.


The cyberknife works like a gun, pointing radiation where you point the knife.   But creating that laser knife demands that you generate temperatures of about 2,000 degrees Celsius.  Yeah.  HOT!  And it takes a huge room of equipment to cool things back down.

Plus, the weight of the protective casing for the radiation would be huge and hard to carry.

“But they could still create canons, right?”  asks Paul.

Hmmmm… More questions for the next visit.

OK.  On to James’ question.

A Gamma Knife is not a Cyber Knife.  (I’m pretty confused on capitalization here.  Are these brand names or products?  Kleenex or tissue?)


A gamma knife is actually a kind of half-spherical helmet with 192 pieces of cobalt emitting radiation.  The knife acts on the radiation rays like a magnifying glass would act with the rays of the sun.

(The magnifying glass is Dr. Loiselle’s metaphor.)

Remember using a magnifying glass to burn your initials into leather or kill ants?    If that magnifying glass was too close to the leather or ant, nothing happened.  If it was too far away, nothing happened.  There is a focal point created by how the lense bends the light rays.

The gamma knife works in a similar way.    It works like a lense, moving that focal point to exactly where it is needed.

Then they just zap the tumor, bit by bit, voxel by voxel.

Remember when it was cool for all of us to learn Photoshop because there weren’t really any other good options out there for amateurs?  Remember how we (some of us) could only use it to correct red eye by making the picture so large you could see the pixels and then by changing the color of each pixel, one by one?

Well that’s what they do with the Gamma Knife.  They have a very detailed picture of my brain and they zap the tumor voxel by voxel.  A voxel is a three dimensional pixel.

Anyway, the gamma radiation from the individual rays coming into the helmet are not strong enough to do any damage.  You need those  192 rays all focused together at one point.

Cool, right??!!

The science behind this treatment is really the only thing to talk about because the treatment itself is probably, statistically, the most effective tool ever been used so far on my cancer.  Success rates are in the high 90%.    Because my oncologist, Dr. Wahl, has been so proactive, the scans available allowed the team to identify very small tumors and other possible threats very early.   Therefore, there will be practically NO SIDE EFFECTS.

Cancer treatment without side effects.  How cool is that?

I’m not supposed to put my head between my legs and then swing it upright for a day.  I’m not supposed to lift heavy stuff for a day.

I can’t drive for a day due to sedatives they give.

And I need to take steriods before and after the procedure to help reduce the risk of swelling.

Steriods make me MOODY, so I’ll just warn you all to ignore me for a week.

That’s it.  Boring, right?

Turns out the screws they put in my head to place the helmet don’t even go into my skull.   They just push into the skin a bit.   And the reason they keep you awake for the procedure is that the entire process is so painless and uneventful that it’s simply not needed.  It’s just a long MRI session, but quieter and with a hat.

I *do* have an interesting “spot” in my brain,  though, that I will tell you all about next time.

Gamma Knife day is Thursday, July 7th and I’ll be getting lots of scans the day before.

Oh!  Oh!  Oh!  And the BEST part?  There’s a PHYSICIST on the medical team!!  If your brain’s health depends on the team’s ability to get their math right, it’s really great to have a physicist on board.

Francois (my personal physicist) said I should ask for his grades from graduate school,though, to be sure.





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