Table 3.
Beam attenuation due to PMMA base plate (12 mm) without air gap and carbon fiber base plate
| Gantry angle (degree) | Path length (mm) PMMA | PMMA base plate on the phantom % attenuation | Path length (mm) Carbon fibre | Carbon fiber plate on the phantom % attenuation |
|---|---|---|---|---|
| 0 | 12.00 | 4.85 | 8.0 | 3.68 |
| 10 | 12.185 | 5.19 | 8.12 | 3.70 |
| 20 | 12.77 | 5.28 | 8.51 | 3.93 |
| 30 | 13.856 | 5.78 | 9.23 | 4.23 |
| 40 | 15.66 | 6.28 | 10.44 | 5.00 |
| 50 | 18.67 | 7.81 | 12.44 | 6.22 |
| 60 | 24.00 | 10.55 | 16.0 | 7.98 |
| 70 | 35.00 | 10.31 | 0.0 | 0.00 |
| 80 | 0.0 | 0.00 | 0.0 | 0.00 |
| 90 | 0.0 | 0.00 | 0.0 | 0.00 |
It is to mention that half of the beam is passing through the PMMA base plate at gantry angle 70 degree