Roy and Niels

Roy and Niels
Showing posts with label protons. Show all posts
Showing posts with label protons. Show all posts

Thursday, March 6, 2014

A Stopping Power App for Android



We (as in APTG) have just released the dE/dx Android app on Google Play!

Screnshot of the dE/dx app, ver. 1.0 from my LG Nexus 4 phone.

The app is written by student Casper Cristensen in collaboration with the Dept. of Physics and Astronomy and the School of Engineering at Aarhus University. The app is based on the stopping power library libdEdx-1.2.1  which was presented in an earlier blog entry here.

The cool thing about the app is that all tables are stored locally on phone (this is why it needs access to USB memory), so no network access is necessary - useful if you want to look up stopping power while working in a shielded area with no network.

In summary the features are:
  • ICRU 49 and ICRU 73 (revised version) electronic stopping power tables
  • MSTAR tables provided by Helmut Paul
  • BETHE_EXT00, a generic algorithm as used in SHIELD-HIT12A. Applicable for any ion to all 278 ICRU compounds (beware, use with care, can be off at lower energies), .
  • no network access needed after installation
  • calculation of CSDA range of particle in target material
  • inverse CSDA lookups possible (if you need to figure out what specific energy is needed to produce a certain range in a material.

Disclaimer: of course we do not claim correct reproduction of any of the data, use at own responsibility!

Thanks to:

  • Casper Christensen (programming this app)
  • Jesper Rosholm Tørresø (being Casper's supervisor and our contact person to the engineering school)
  • Jakob Toftegaard (writing most of the libdEdx backend and dedx.au.dk webpage)


Enjoy! :-)

Wednesday, November 21, 2012

SHIELD-HIT12A demo version released

Here is a little sneak-preview of the upcoming release of SHIELD-HIT12A.

Pimp my Niva... (artist's impression of SHIELD-HIT12A).

SHIELD-HIT12A is a Monte Carlo particle transport code capable of transporting heavy ions through arbitrary media. The -A fork was made in 2010 from SHIELD-HIT08, and since then we have added plenty of new features, solved many bugs, increased calculation speed and optimized the nuclear models to new data on carbon-12 fragmentation.

A free demo version where the random seed and statistics are fixed to 10.000 particles can be downloaded from the project development page. There are builds for Linux and Windows systems (32- and 64 bit). It is a beta-release, but we would like to bring this demo version to a broader community, and thereby hopefully also fix some more bugs before we release the full version.

The new features in SHIELD-HIT12A are:
  • New simplified material and beam parameter parser in free format and extensible without breaking downward compability.
  • Including 279 ICRU default materials and elements, it has never been so easy to specify a material.
  • New beam model: divergence and focus distance can now be specified (thanks to Uli Weber from Marburg).
  • Arbitrary starting beam directions now possible.
  • New routine for Vavilov straggling, 5-6 times faster than the original one by Rotondi and Montagna which was used in Geant3.21. In total, this alone means a speed improvement of roughly 30-40%.
  • Ripple filter has two modes of operation, Monte Carlo type or Modulus type.
  • Logarithmic energy binning in SPC files for TRiP
  • Full howto for generating DDD files for TRiP
  • Now only three input files are needed to setup a run.
  • Improved documentation.
  • Scoring by zones using detect.dat (complementary to Cartesian mesh and cylindrical scoring)
  • Alanine response model included, so SHIELD-HIT12A can directly calculate the dose equivalent response in alanine.
  • Flat circular and square beams can be defined
  • Neutron data for natural Argon was added (needed for detailed simulations of air)
  • Another ton of bug fixes.
Of course SHIELD-HIT12A includes the features from SHIELD-HIT10A (which was never released):
  • Totally new (parallelizable) scoring system:
    • Arbitrary Mesh and Cylindrical scoring
    • Lots of detectors such as energy, fluence, dose-averaged LET, track-averaged LET, average velocity (beta), dose to medium (where medium can be changed if you want to calculate stopping power ratios) etc....
  • finally SHIELD-HIT10A is parallelizable
  • New random number generator, which gives a massive performance boost
  • New adjusted inelastic cross sections for carbon ions based on recent data
  • Fine tuning of the fermi-breakup parameters
  • SHIELD-HIT10A can be configured without accessing the source code anymore, so no programming knowledge required to use SHIELD-HIT10A.
  • SHIELD-HIT10A is installable
  • Runs on linux again, even when compiling with code optimizations, ok with GNU gfortran, Intel and Portland compilers.
  • Many bug fixes
Enjoy! And please drop me a line when you find bugs in the software and errors in the manual, they are there, but we hid them well. :o)


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Friday, June 1, 2012

Don't Mention the War

Last year the Danish government announced that it will finance a national particle therapy facility together with some private funding agencies. Two applications were submitted for evaluation:

and of course there is a strong interest from each side to host this project. Naturally, since I am part of the Aarhus Particle Therapy Group, I will right out admit I am naturally in favour of our project in Aarhus.

The plan is now that an international expert commission is being setup by the ministry of health. That commission will then evaluate those two applications and give a suggestion where to place such a facility.

If you compare those two applications, you will see that they both apply for a 3-gantry treatment facility. Copenhagen lock themselves on a cyclotron solution, where we in Aarhus are also open to a synchrotron based solution.

Basically the differences can be summarized here:

Copenhagen Aarhus
3 treatment rooms with 2 gantries 3 treatment rooms with 2 gantries,
+1 research room
3rd gantry will be installed later 3rd gantry will be installed later,
a fourth treatment room with gantry can be added
ProtonsProtons
CyclotronCyclotron or Synchrotron
1000 patients per year1000 patients per year


So basically what we apply for is rather similar.

What about the costs? If you compare those budgets, you will note that the prices of the equipment and the building are comparable too.

Copenhagen Aarhus
Equipment450 mio. DKK 475 mio. DKK
Building382 mio. DKK 295 mio. DKK
Supply systems and lines195 mio. DKK (incl. in building)
Purchase and demolition of Rockefeller Building147 mio. DKK (none)
Total1174 mio. DKK 770 mio. DKK
Optional 3rd gantry(not mentioned) 75 mio. DKK

Copenhagen need to build in the middle of the city, whereas we in Aarhus have a pristine green field adjacent to the New University Hospital. This means that the expenses for the Copenhagen proposal are significantly higher than the Aarhus solution, since a building has to be demolished first (they have simply a lack of space in Copenhagen). The "supply lines" cover, as far as I heard, establishing extra power for the facility, please correct me if I am wrong here. The annual operational costs are also similar.

There has been a few articles in the Danish press about the two applications. None of the Journalists managed to actually compare the two budgets, so basically the message was that Aarhus offeres particle therapy at dumping prices. Yeah right.

In addition, I hear a lot of weird arguments, e.g. such a facility MUST be build in Copenhagen, since it is the capital city, and it has a proximity to the airport.

Huh?

How many of the existing facilities are located in capital cities? Lets pick some of the most famous ones: HIT is in Heidelberg (147.000 inhabitants, 1hours drive to next airport). PSI is in Villingen. The Swedish facility is built in Uppsala, and not Stockholm. Why is that so? These research institutions simply had the longest track record in terms of particle therapy! I don't get the point of the closeness of an airport either, since you can reach any point within a few hours in DK by car, and sorry guys... particle therapy is not that acute.

Now, today this conflict took a very curious turn, as Copenhagen announced in Dagens Medicin that they will cut the price 75 % (login required to view link). What is going on?
It seems that Copenhagen suddenly decided to go for a single gantry facility by Mevion, formerly known as StillRiver. To me this looks like a very poor decision. The Mevion facility has been controversial for a long list of reasons. In a scientific article by Schippers and Lomax they list some of the issues with this facility:

  • the very compact design of the cyclotron, may lead to large beam losses and resulting activation. 
  • repetition frequency of synchrocyclotrons are typically 1kHz which limits applicability of the different pencil beam scanning methods.
  • There is no beam analysis and no magnets in the beam path, in other words an energy selection system is missing. This means that the beam will have a poor distal edge, always looking as if it traversed 25-30 cm of material, e.g. when treating head an neck cancers. This limits possible treatment planning techniques, such as patch fields.
  • Neutron contamination may be an issue, due to the proximity of the degrader, modulator and collimator(s). 
To this, I might add that the construction of the prototype is still awaiting FDA approval, and we have not seen any data on how this machine operates. We are just in the middle of a never ending scandal about a couple of diesel IC4 trains ordered from AnsaldoBreda a decade ago, where the trains still are not functional and with a significant risk that they never will be. Billions of taxpayer money are lost here. Most Danes are therefore allergic to order unproven technology abroad.

Update: Mevion just got their FDA approval.

Another update: it's a "Premarket Notification" and not a "New Device Approval". Read it here. Thanks to Klaus Seiersen for pointing this out.

The recent article in Dagens Medicin does not even mention that cutting 75% of the price leads to a single-gantry facility, which means the patient numbers needs to be adjusted down, perhaps by 2/3rds.

Finally, if you need three treatment rooms, then measured in costs per treatment room, a conventional solution is cheaper than the Mevion solution, according to Schippers.

I am very astonished, it seems that Copenhagen just scored an own goal. However, I fear this may delay the decision process even more. In the end this is about patients, and if the money is there, we should not be satisfied with giving our patients the most inferior kind of proton therapy, and rely on unproven technology.

Monday, January 31, 2011

Making Bubbles: The Particle Way

BTI BubbleTech Industries manufacture neutron detectors intended for personal dosimetry. Theses devices contain a polymer gel holding very small droplets of a superheated gas. When a neutron interacts with these superheated droplets, a phase transition happen from liquid phase to gas phase expanding the volume dramatically - a bubble appears.

The video below demonstrates how such a detector responds to a (weak) Americium-Beryllium neutron source:



The activity of the AmBe source was 2.64E+4 neutrons per second. The detectors we had were calibrated against ICRP-60 in terms of dose equivalent, according to BTI. The sensitivity of the particular detector shown in the video above was about 0.7 bubbles / µSv dose equivalent.

The detectors come with an integrated piston which repressurizes them, so they can be reused, however not indefinitely. We used our detectors rarely, and kept them refrigerated. However, after two years the encapsulation/pressurization system leaked.

The bubble detectors can be bought with varying sensitivity ranges and BTI even offers a set of detectors which are sensitive above a varying energy threshold. Deconvoluting the counts in each detector of this set will yield a coarse energy spectrum, in e.g. 6 energy bins.

We have used the these bubble detectors in our antiproton beam line at CERN in order to get a coarse measure of the amount of fast neutrons emitted from the antiproton annihilation. We used both the personal dosimeter type and the BDS spectrometer.



The picture above show how multiple personal dosimeter detectors are places at a certain distance from the annihilation vertex.

Unfortunately we had some trouble interpreting the results from the spectrometer. The BDS spectrometer counts seemed to be simply unphysical and a spectrum could not be deconvoluted. The readings from the personal dosimeter also seemed to be off by an order of magnitude.

After some investigations we started to suspect that these bubble detectors were not only sensitive to fast neutrons, but also to charged particles, such as protons. From the antiproton annihilation we do get a similar amount of protons and a threefold multiplicity of energetic pions, which have a long range, far beyond the position of the bubble detectors.

A paper in NIM B, which was published a few years ago by us, lists our findings. Basically we conclude that the sensitivity (# of neutrons per bubble) is quite comparable to that for protons, and perhaps a bit less for pions. The proton part we could test at our storage ring, ASTRID, which we have in the basement of our Physics Department in Aarhus.

In the video you are about to see, we extract a few million protons at about 50 MeV from the synchrotron. The bubble detector here is immersed in a water bath.



The range of the protons are clearly visible. A distinct Bragg peak does not really form, the effect is primarily related to nuclear interaction cross sections.