719 / 1542
0
20
40
60
80
100
120
0
5
10
15
20
25
> 1913
> 1951
> 1952
Dose
Depth [cm]
early days
1895: discovery X-rays
1913: 140 kV, Coolidge: vacuum tube, heated kathode
1921: 200 kV
1925: 300 kV
1951: first cobalt treatment unit
1952: first clinical linear accelerator (Increase Energy
→
reduce skin dose)
orthovoltage
Reason 1) before 1951 many beams to reduce skin dose