Devices and related methods are provided for irradiating a portion of a body. A device according to one embodiment can include a radiation needle, a fluorescent target, and an x-ray transmitting window. The radiation needle can include a radiation conduit having a first and second end for passing primary x-rays. An x-ray generator can generate the primary x-rays and pass the primary x-rays from the first end to second end. The fluorescent target can connect to the second end for absorbing the primary x-rays and produce by fluorescence secondary x-rays for irradiating a predetermined portion of the body. The fluorescent target having a surface for absorbing the primary x-rays to fluoresce and emit said secondary x-rays. The x-ray transmitting window can be positioned adjacent to the fluorescent target such that the secondary x-rays exit through the x-ray transmitting window. The secondary x-rays can irradiate target tissue within the body.