X-Message-Number: 3283 Date: 17 Oct 94 14:30:14 EDT From: yvan Bozzonetti <> Subject: SCI.CRYONICS Brain scanning, answer to B. Wowk Re: your message # 3271, Sat. 15 Oct. 94. About the impossibility of brain scanning with ionising radiations and high definition MRI. Thank you for your computation about X-rays, I have read before about the impossibility of high definition CAT scan X-ray tomography, now we have a quantitative argument, thanks for it Brian. On the other side, I must recall I considered only X-ray holography, tomography works effectively by absorbing photons (it is a particle technology), contrairy to holography, a wave technology based on interferences. In the visible range, holography works by mixing a beam from a laser with another beam of the same laser reflected by an object. In the X-rays domain, few materials are good reflectors, so it is the phase shift generated by refraction who is used. An absorbed photon is lost and the wavelength must be choosen so that there is as litle absorbtion than possible. To see a small computation, assume the refractive index of a neuron is 10^-6 above or under what is found in the surrounding, that is, the speed of X-ray is shifted by 300 m/s (One millionth of 299972 Km/s). Assume the neuron componement to be looked for is .3 micrometer, or a travel time near 10^-15 second for the wave. At 300 m/s, the displacement will be 3. 10^-13 m. Now, a 100 kev X-ray has a wavelength near 10^-11 m, so the shift is somewhere near 1/30 th of wavelength. Interferometric systems can detect a shift of 10^-6 wavelength, 30 000 times smaller than my example. A superficial reader could ask: who is right? Brian or me? The answer is both: Brian solution applies to imaging by X-ray absorbtion, my one by X-ray phase shift. Well, there is no perfect system and even with a holographic setting, some photons will be lost by absorbtion, producing some irradiation, but this is only a residual effect with low doses. I have spoken about holography because it is a well known technology today, in fact I don't think it is the real best solution, my taste will tip toward quantum non demolition, a subject not included in my original paper because it is a seed for controversies. Some readers may (must) have been somwhat baffled at my historical introduction to nuclear fusion devices. I have said they are the only system able to generate long coherence X-rays for holography of bulky object. That is true, but the rays are radiated by nonlinear process in multi-beams of correlated photons, and there is really the interest of the system. May be some readers know about the Aspect's experiment on quantum Bell's inequalities. To reduce everything at some lines, quantum mechanics predicts than, when a photon, in a correlated pair or set, is perturbed, the other feels the effect instantaneously. Practical experiments strongly suggest this is indeed the way real world applies physics. Now, a nuclear device radiates more than one hundred beams, all correlated between them. Assume for example there are 201 beams, one is targeted to the brain, 100 are sent on as many detectors and 100 "handled in a special way". Looking at one photon in each beam for the shake of simplicity, the brain photon undergoes many effects on its direction, polarization, energy... Now, each photon sent to a detector will test one possibility by yes or no, the 100 yes/no answers give a 100 digits number, that is, there are up to 10^30 possibilities for the state of the photon sent to the brain, as tested in the 100 correlated others, an enormous quantity of information has so been retrived from a single photon. Next, with the 100 remainning photons, a no/yes system can produces the complementary number of the one detected before, that will constrain the state of the last photon, the brain going one, to revert to its initial state. Every particle knocking it has generated is so undone and there is strictly no radiation effect. This is allowed by the physics laws but remains hard to swalow for many, so I discussed only holography but included all the backgroud on nuclear system to go one step fruther. I go now to MRI: Well Brian, you seems right. Definitively no high resolution picture at the micron scale or beyond. I give you the point but... (I have not the exact reference in mind). In July 86 or 87, on the cover of the scientific magazine Nature there was the picture of a cell produced by high gradient MRI with many details down to micron or less. Inside the issue, was a "letter to Nature" paper and a "News and view" article on the subject. What must I think about? If that was an untimely April fool joke, I think I was not the only victim... But looks at these papers, you have at most 8 Nature covers to look at in the nearest library to find them, may be they was serious after all... Yvan. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=3283