George,

The Cyberknife (which uses an accelerator) works somewhat like the Gammaknife (which uses 201 cobalt-60 sources of approximately 30 curies (1.1 TBq) each), in that it *intersects* a great many relatively low intensity beams at the target point(s) – the difference being that the Gammaknife only combines beams in space (firing them all at once), while the Cyberknife combines beams using both space and time – it only has a single beam to work with at any one time, so needs to move it around constantly, to achieve the same effect as the Gammaknife.....

(there is a nice video of the Cyberknife here in Montreal – in French: http://www.youtube.com/user/chumontreal#p/search/0/zRawBnQQGF0 )

Given all the motion and relatively low beam intensity, it seems impractical to use detectors to stop a treatment procedure.

But maybe they do – I don’t know.

Certainly there must be a variety of safety features included with such machines – not to mention extensive training for the operators.

But things can still go wrong....

Jaro

^^^^^^^^^^^^^^^^^^^^^^^^^

From: cdn-nucl-l-admin@mailman1.cis.McMaster.CA [mailto:cdn-nucl-l-admin@mailman1.cis.McMaster.CA] On Behalf Of George Stanford
Sent: January-24-10 12:45 PM
To: Jerry Cuttler
Cc: Canadian Nuclear Discussion List
Subject: Re: [cdn-nucl-l] Radiation Offers New Cures, and Ways to Do Harm

Question: At the cost of more complexity, could there not be
an array of radiation detectors on the other side of the patient,
programmed to shut the accelerator off if the dose gets too high?

-- George

~~~~~~~~~~~~~~~~~~~~~~~~~~~`

At 09:30 AM 1/24/2010, Jerry Cuttler wrote:
I think the driving force of this complexity is minimizing the damage to healthy cells.

LNT believers assume that any exposure increases the number of mutations, and hence increase the incidence of new cancers. However, low doses reduce the number of mutations, even in Muller's fruit flies. A high dose would be expected to increase the number of mutations. The additional mutations might develop into cancers after another ten to twenty years, which would increase the incidence of cancer (in the recovered paients) at that time.

In reality, healthy tissue recovers (heals) from overdoses. Those Chernobyl fire fighters who tried to extinguish the fire in Unit 4 received large radiation overdoses. 134 of them were hospitalized for acute radiation syndrome, and 28 of them died. 106 recovered. In the subsequent 19 years, 20 of those that recovered died. The mortality of unexposed workers is ~ 1% per year, which is about the same as the mortality of these recovered workers.

During my assignment to address the Y2K issue of cancer therapy machines, I learned that:
- the weakness of radioisotope machines is that you cannot turn off the source. This leads to the problem of orphan cobalt-60 sources (a la Taiwan).
- the weakness of accelerators is software (and mechanical) complexity and the operator-machine interface.

Jerry

----- Original Message -----

From: Rod Adams

To: Canadian Nuclear Discussion List

Sent: Sunday, January 24, 2010 9:10 AM

Subject: Re: [cdn-nucl-l] Radiation Offers New Cures, and Ways to Do Harm

It seems to me that part of the cautionary tale is the value of simplicity. Many of the reported accidents occur due to machine failures and software glitches.

Makes me wonder just why we have moved so far away from simple sources with focus lenses to provide correct gamma exposure based on time and distance.

Why has the medical device industry developed such complex and expensive equipment to substitute for what is essentially a simple and predictable process, like the decay of radioactive isotopes?

Rod Adams

On Jan 24, 2010, at 8:59 AM, Jerry Cuttler wrote:

The hazard in radiation therapy is not from low dose, but from overdose cause by human error.

http://www.nytimes.com/2010/01/24/health/24radiation.html?hp=&pagewanted=print

http://www.nytimes.com/interactive/2010/01/22/us/Radiation.html?hp

January 24, 2010

The Radiation Boom

Radiation Offers New Cures, and Ways to Do Harm

By WALT BOGDANICH

As Scott Jerome-Parks lay dying, he clung to this wish: that his fatal radiation overdose — which left him deaf, struggling to see, unable to swallow, burned, with his teeth falling out, with ulcers in his mouth and throat, nauseated, in severe pain and finally unable to breathe — be studied and talked about publicly so that others might not have to live his nightmare.

snip ...

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RE: [cdn-nucl-l] Radiation Offers New Cures, and Ways to Do Harm

Radiation Offers New Cures, and Ways to Do Harm