X Ray photon?
Article Stereotactic Convergent Beam Radiosurgery Versus Stereotacti...
I am pretty sure this is a comparison between Gamma Knife and Linac based radiosurgery. Gamma Knife has 201 cobalt sources which all converge at a point and the patients "condition" is located at this converging beam point for the delivery of treatment illustrated http://images.elektagallery.com/famain.asp?customerId=476&sKey=45ETMKVK&action=viewimage&cid=99&imageid=479&hasSrchMode=1
Several papers have explored whether there are differences between Gamma Knife and Linac based radiosurgery and seem to concluded that there aren't any. Varian (linac vendor) provides a bibliography of papers http://newsroom.varian.com/SRS_equivalency
I am also pretty sure about the sources Lindsay picked up. But he forget one instrument the so called "Cyber knife". The main difference is that such a small 6MV linac on a robot arm can be used for target volumes some where in the body and not only in the brain. In both cases the beams are collimated using lead or tungsten apertures with different diameters. In the Gamma knifethere are 201, in the Ciber knife a set of different apertures. The ciber knife follows the movement of the patient eg. breathing, the patient has not to be fixed on the table.
Apparently you have not understood my question, I mean as they achieve a unique convergent X-ray beam.
Ok starting again..... this is a simple case of terminology. Becker et al have not magically created an individual converging radiation beam ( LINAC-based convergent beam radiosurgery) but use the term in the of the Gamma Knife, remember my link, the illustration on the RHS show the beams "pointing/intersecting" at one location. In both linac based radiosurgery and gamma knife the beams are well collimated and do not significantly diverge over the distances involved. Becker et al was comparing an established stereotactic process (Tübingen radiosurgery system...illustration..... http://link.springer.com/chapter/10.1007%2F978-3-7091-9399-0_10#page-1) with their own developed (DKFZ) method. With respect to Hanno, whilst Cyber Knife is now in the field, I guess it wasn't considered by Becker et al as it was pretty much still at Stanford as a prototype.
Terminology is not, I'm asking for a real convergent X ray photon beam for use in radiotherapy.
Rodolfo, if I am to understand your last post, you actually want to know a method by which you can cause a x-ray photon beam to be convergent rather than its normal divergent state. Whilst it may be possible to get a reasonably tightly collimated beam from a stereo cone it certainly isn't convergent and the process by which the radiation is generated in a linac is divergent anyway. What you are asking is not possible.
To ensure the last answer of Lindsay,
to produce X-rays on a target by a small needle beam of electrons you get a diverging photon beam (bremsstrahlung coil). No chance to change it. The higher the energy is the smaller is the diverging angle. What you can do is to use a smart collimating system (small apertures or slits) which scatter the photons by comptonscattering back from the tube walls, so you get a nearly parallel photon beam with good half beam shadow. If this "parallel beam hits on tissue you again get compton scattering with diverging beam coil in the patient.
You can get a very well collimated, 'pencil-like' x-ray beam by Thomson backscattering of optical (laser) photons from a relativistic electron beam. But this is technically quite challenging and needs expensive infrastructure.
@Günter,
could you please provide a paper about Thomson scattering of laser photons?
Thanks and regards
Hanno
voilà: http://arxiv.org/abs/1208.2801
Photons are emitted in the direction of the electron beam. The opening angle of the photon beam cone scales with the inverse gamma factor of the electrons.
Microfocus ion beams can be generated in an Ion Accelerator but to get a convergent photon beam can only be done through repeated collimation. That may be easy for soft Xrays bur difficult for hard Xrays.
@Narendra: Could you give me some concrete idea (scetches, principle, underlying interactions) who to focus photons by multiple repeated collimation? Thanks in advance Hanno
In our case we achieve with high energy electrons (6 MeV) through a thin anode spherical impact and suitable filtering and / or collimated.
So far we have done this with a Monte Carlo Simulation code are designing the first prototype to generate a converging beam of high energy (CONVERAY) Pat pending.
In radiation teraphy a convergent beam of photons X, generates a dose peak in the target similar to hadron therapy, but with a small budget very many more. We are open for collaboration in this work thematic
I read it, but I do not really understand. Would you mind to show a scatch and some experimental results please?
Thanks Rodolfo,
I´ll read and try to understand. No sorrow for your patent.
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