Problem running Lu-177 simulation

Not sure if this falls in this category.

I am trying to duplicate a paper simulation for Lu-177, just a surface source of 2.5mm diameter sphere.

While my simulation results the dose drop-off seems much quicker than the paper.

I run some point source and seems mean range and max penetatrion are shallower.

I attached my code and wondering did I set something wrong?


Lu177Surface.flair (2.2 KB)

Lu177Surface.inp (1.8 KB)

I also simulated a point source in water, the max range seems off (less than 1mm). Really confused on what the problem is.

Lu177MeanMax.flair (2.2 KB)
Lu177MeanMax.inp (1.6 KB)

I simulate a 497keV electron isotropic source, which is the mean beta energy for Lu-177 decay. The result is very similar to the publication. But the Lu-177 simulation is off. Is something wrong here?

It seems like the Fluka decay scheme for Lu-177 is not correct.

I had an earlier thread and now I sampled the beta spectrum and it seems the Fluka data is wrong.

Betas from 177Lu (6.734 d 12)
Eb endpoint (keV) Ib (%) Decay mode
176,98 12.2 7 b-
248,63 0.053 22 b-
385,35 9.1 13 b-
498,3 78.6 11 b-


the Lu-177 decay data in FLUKA is actually correct, as indicated by the resulting spectrum (thanks to @pschoofs)

where the peaks are photons and the background, extending towards the ~500 keV endpoint, is due to electrons. Note that the energy you took above is in fact the endpoint of the ~80% emission, which is not at all representative of the spectrum, being three times higher than the respective mean beta energy.

Thank you so much, really appreciate.

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