The invention provides a method for generating medical isotopes, the method comprising contacting a primary radiation beam with a converter for a time sufficient to produce a secondary beam of gamma particles, and contacting the beam of gamma particles to a target, where the cross section dimension of the beam of gamma particles is similar to the cross section dimension of the target. Both the converter and target are small in diameter and very closely spaced. Also provided is a system for producing medical isotopes, the device comprising a housing having a first upstream end and a second downstream end, a radiotransparent channel (collimator) with a first upstream end and a downstream end, wherein the upstream end is adapted to receive a radiation beam, a target positioned downstream of the downstream end of the channel and coaxially aligned with the channel, wherein the target has a cross section that is similar to the cross section of the channel.