Orthovoltage X-rays
（重定向自Orthovoltage）
Orthovoltage x-rays are produced by x-ray generators operating at voltages in the 200–500 kV range, and therefore an energy in the 200–500 keV range (see external beam radiotherapy for an explanation of the maximum and mean energies as a function of voltage). They have more energy than the x-rays used for radiography, and are used in medicine in external beam radiotherapy to treat cancer and tumors. When used to treat patients, radiation oncologists find that they penetrate to a useful depth of about 4–6 cm. That makes them good for treating skin, superficial tissues, and ribs, but not for deeper structures such as lungs or pelvic organs.