I have a problem calculating the surface dose when simulating the Gamma Knife machine

Hi Experts,
I am simulating a source of the Gamma Knife machine projecting onto a spherical phantom. The water phantom contains a tumor (4cmx4cmx4cm). I calculated the horizontal surface dose on the tumor. I have done simulations with phits and Geant4. I run 10e9 particles.

But the result of the dose horizontally ​in Geant4 got the error. I checked the geometry, materials, physics library, and particle generation. And I referenced the gamma knife simulation in the Geant4 example for the particle generation and physics library.
Can you suggest where the problem occurs in the program?
Many thanks

Hi duydhust
Could you please explain how did you score lateral dose?

Hi keyvantabaei
I use class G4ScoringManager to score.

Hi duydhust,
sorry,I have not experienced G4ScoringManager a lot, I have done lateral dosimetry before by using G4Parametriation and SensitiveDetectors, It may be because of your number of bins if you have assigned them low, I hope someone else would help you

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