Which technological advancement enabled the transition from orthovoltage to megavoltage radiation therapy?

Answer

The linear accelerator

The development of the linear accelerator, or linac, along with Cobalt-60 teletherapy units, revolutionized radiation treatment by producing megavoltage beams. Unlike previous orthovoltage machines that generated low-energy beams capable of burning the skin without reaching deep tissues, megavoltage photons can travel through the skin with minimal surface damage and deposit energy deep within the body where tumors are located.

Which technological advancement enabled the transition from orthovoltage to megavoltage radiation therapy?
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