1. GAMOS tutorial X-ray Exercises
Pedro Arce Dubois
CIEMAT

2. X-ray simulation Exercises
Ex. 1: X-ray tube
Ex. 2: Writing phase space
Ex. 3: Score dose in phantom
Ex. 4: Score lateral dose
The exercises are sequential
Use the commands of the previous exercise (only change what indicated)
GAMOS radiotherapy tutorial
Pedro Arce

3. Exercise 1: X-ray tube geometry
Tube of inner diameter 60 mm, length 100cm. Wall of 2 mm of pyrex. Filled with vacuum (G4_Galactic material). The tube is placed rotated -90 degrees around the X axis
The tube has a window hole of 2.5 cm length and 2.5 cm width, placed at phi 90 degree (so that after rotation it will end at the positive Z side). In the middle of the window hole there is a foil of 125 microns of berilium at Z positive. The centre of the window foil is placed at position (0,0,0)
The tube is surrounded by a shield 2 cm thick of lead. In it there is also a hole at the position than the tube
GAMOS radiotherapy tutorial
Pedro Arce

4. Exercise 1: X-ray tube geometry
The anode is built from an alloy of 90% tungsten and 10 % rhenium. It is a polycone of width 10 mm, radius 20 mm at one side and 5 mm at the other side. The surface has an inclination of 12 degrees. The anode axis coincides with the tube axis and it is placed at 80 mm from the tube wall, with the smaller radius towards the tube center
The source of electrons is a cylinder of air of 5 mm radius and 10 microns thick, placed so that its centre is in front of the centre of the anode inclined surface, at mid-distance of radius (=12.5 mm out of centre), and at 50 mm along the tube axis coordinate
The primary particles are electrons of 150 keV homogenously distributed in the source cylinder and with initial direction along the Y axis
Physics is low energy electromagnetic one
GAMOS radiotherapy tutorial
Pedro Arce

5. Exercise 1: study gamma propagation
Plot the initial kinetic energy and direction theta angle of all gammas created
Plot the kinetic energy and direction theta angle of all gammas when they reach the inner side of the tube (or the window hole inner side)
Plot the kinetic energy and direction theta angle of all gammas when they exit the shield
Plot the total length that primary electrons travel inside the anode
GAMOS radiotherapy tutorial
Pedro Arce

6. Exercise 2a: write phase space
Use setup of exercise 1 and write a phase space of the particles that reach a Z plane situated 10 cm below the tube window foil
GAMOS radiotherapy tutorial
Pedro Arce

7. Exercise 2b: use bremsstrahlung splitting
Same as exercise 2a, but use Z-plane bremsstrahlung splitting
Z plane defined at 10 cm from window foil and size 15 X 15 cm
Try splitting 100 times and see bias in phase space
GAMOS radiotherapy tutorial
Pedro Arce

8. Exercise 3a: score dose in phantom
Use the phase space created in exercise 2
Run events, reusing phase space file
Score dose in phantom voxels
Use test_64x64x39.g4dcm
Print a report of the dose in each voxel, with errors
Make histograms of dose in voxels (PDD, profiles)
Write dose in a file, with dose squared, to allow summation of files
GAMOS radiotherapy tutorial
Pedro Arce

9. Exercise 3b: place a protection before phantom
Repeat exercise 3a, but placing a protection of 2cm of Cerrobend, 10 X 10 cm wide, at the centre of the phantom, touching it
Compare dose distributions
Plot length of tracks traversing protection
GAMOS radiotherapy tutorial
Pedro Arce

10. Exercise 4a: Calculate lateral dose
Read phase space from exercise 2
Use point detector scorer to calculate dose in three points
At the Z of the window foil at Y = 25.1 cm (1 mm from phantom)
At Z 1 meter below the window foil at Y = 25.1 cm
At Z 1 meter above the window foil at Y = 25.1 cm
GAMOS radiotherapy tutorial
Pedro Arce

11. Exercise 4b: Calculate dispersion in patient
Same as exercise 4a, and place patient of exercise 3
Compare equivalent dose in each of the three points
GAMOS radiotherapy tutorial
Pedro Arce