Presentation Transcript
Clinical Electron beam characteristics :Clinical Electron beam characteristics p.Senthil kumar
m.sc(medical physics)
Linear accelerator head :Linear accelerator head
Electron source :Electron source
Slide 4:Central axis depth dose
Absorbed dose build-up :Absorbed dose build-up
Slide 6:Absorbed dose at surface Depth in water in cm
Slide 7:Isodose curves
Range concept :Range concept
Electron beam energy specification :Electron beam energy specification The most probable energy Ep,0
Ep,0 = 0.22 + 1.09Rp + 0.0025Rp ²
The mean electron energy E0
E0¯ = CR50
where C = 2.33 MeV/cm for water.
Ez, the mean energy at a depth z in a water phantom, is related to the practical range Rp by the Harder equation as follows
Ez = E0 (1 – z/Rp)
Slide 10:TYPICAL DEPTH DOSE PARAMETERS OF ELECTRON
BEAMS
Energy R90 R80 R50 Rp E0 Surface dose
(MeV) (cm) (cm) (cm) (cm) (MeV) (%)
6 1.7 1.8 2.2 2.9 5.6 81
8 2.4 2.6 3.0 4.0 7.2 83
10 3.1 3.3 3.9 4.8 9.2 86
12 3.7 4.1 4.8 6.0 11.3 90
15 4.7 5.2 6.1 7.5 14.0 92
18 5.5 5.9 7.3 9.1 17.4 96
Field size dependence :Field size dependence
Back scattering of electrons :Back scattering of electrons
Field shaping :Field shaping Electron beam applicators
Shielding and cut-outs
Electron applicators :Electron applicators
Slide 15:Shielding and cut-outs LEAD THICKNESS (mm) REQUIRED FOR
VARIOUS TRANSMISSION LEVELS FOR A 12.5 × 12.5 cm2 ELECTRON FIELD
Energy (MeV)
Transmission
(%) 6 8 10 12 14 17 20
50 1.2 1.8 2.2 2.6 2.9 3.8 4.4
10 2.1 2.8 3.5 4.1 5.0 7.0 9.0
5 3.0 3.7 4.5 5.6 7.0 8.0 10.0
Clinical applications of electron beam therapy :Clinical applications of electron beam therapy
Slide 17:Thank you