Same, just different source

In “Seeing the whole picture” (Health Scan, February 4), Prof. Yujiang Fang, a visiting professor at Rambam Medical Center, is quoted as saying: “Radiation therapy uses high-energy X-rays and other particles, such as gamma rays, to destroy cancer cells.”

X-rays and gamma rays are the same particles – both are photons. X-rays are usually a by-product of electrons impinging on a metallic target, while gamma rays are usually created in radioactive sources, but they are identical particles. YIGAL HOROWITZ

Beersheba The writer is emeritus professor of radiation physics at Ben-Gurion University of the Negev.