A catheter system adapted for navigating, guiding and implanting a catheter or a plurality of catheters in a spatially-defined implantation within the tissue of a patient is provided. The system can include a tissue navigation system and a probe to inform the navigation system to guide emplacement of the catheters within a target tissue. The probe can provide images, such as fiberoptic visual images, or ultrasound images, or can provide radiolocation data, to guide the catheter emplacement. The catheters supply a pressurized liquid including a bioactive agent, such as can be used in the treatment of cancer, for example 123I- or 125I-IUDR. The system and methods provided can be used in the treatment of locally advanced tumors, such as cancers of the brain, head or neck, esophagus, prostate, ovary, liver, pancreas, bladder or rectum.