An apparatus and method for in vivo and ex vivo control, detection and measurements of radiation in brachytherapy accomplished through scintillating material detection. One example includes scintillating fibers placed along a delivery guide such as a catheter for measuring applied radiation levels during brachytherapy treatments, sensing locations of a radiation source or providing feedback of sensed radiation. The catheter may also be a mammosite type catheter. The scintillating fibers provide light output levels correlating to the levels of radiation striking the fibers. The output may then be used to measure and compute radiation distribution maps using Monte Carlo reconstruction simulation. Adjustments to a radiation treatment may be made as needed based on actual and measured applied dosages. Characteristics of a radiation source may also be measured using scintillating materials.