BEIJING, Oct. 23 (Xinhua) -- Chinese nuclear physicists have developed a medical treatment for destroying malignant tumors more than 2.1 cm below the skin surface through the use of heavy ion beams.

    Zhan Wenlong, the country's leading nuclear physicist, said the research carried further an earlier accomplishment made by the same scientists in January. It also used heavy ion beams to treat tumors 2.1 cm or less below the body surface.

    Compared with light ion beams, such as gamma rays and X-rays used in traditional radiotherapies, heavy ion beams are considered the most effective, so far, in accurately moderating the amount of radiation and minimizing the damage done to healthy cells, said the Beijing-based scientist.

    He explained the new treatment used stronger heavy ion beams that reached 400 mega electron volts (MeV) at their highest level that could travel farther into the human body to kill deeper tumors.

    The Heavy Ion Research Facility in Lanzhou -- Cooler Storage Ring (HIRFL-CSR), a 300 million yuan (about 44 million U.S. dollars) national science project built in the northwest Gansu Province capital, is playing a key role in generating the beams.

    Its internally developed heavy ion beams used in the January tests were 100 MeV, which limited the treatment to shallow tumors only, said a researcher.

    Zhan explained in contrast to the traditional light ion beam treatment, in which the amount of ions diminished along the way as a beam travels, the amount of ions in the heavy ion beam treatment peaked when getting to the deep tumors; they became strong enough to kill tumors and better protect the healthy cells along the path.

    At the CAS Institute of Modern Physics, Zhan and his research team have produced a broad spectrum of heavy ion beams. They range from 80 to 400 MeV, which can be used to treat both shallow and deep-seated tumors.

    Scientists were now optimizing the system software to pave the way for clinical testing in the near future, he added.

    With this medical goal achieved, China followed Germany, Japan and the United States in becoming the fourth country to use heavy ions in cancer therapy.

    The HIRFL-CSR, which was officially completed in July, included a main ring, an experimental ring, a radioactive beam separator, an experimental detector and a radiation protection system.