. >> and joining me now, dr. otishief medical officer of the american cancer society and a good friend of the program. thanks for joining us. >> thanks for having me. >> i find this confusing as a physician. this idea of who should get screened with psa testing and then what to do about it. what do you think of this idea of using an mri, as well? >> well, for men who have actually been diagnosed with a prostate cancer, i'm excited about the technology of using an mri, still experimental and we still need to develop it and maybe we're going it be able to watch a group of men who have a localized prostate cancer and say this tumor is not growing over time. therefore, this is a man who does not need to be treated. from men who have localized prostate cancer have perhaps have or maybe even 60% don't need to be treated because that tumor will never bother them. i want to be able to treat the guys who need to be treated and the mri may help me. >> that's the interesting point. so, someone has an elevated psa, this prostate