**6. Conclusion**

Accumulation of radiopharmaceuticals at diseased cells through one or variety of localization mechanisms describes the specificity and efficacy of the tracer agent. The description of different localization mechanisms in above sections, helps in developing new radiopharmaceuticals for theranostics. However, the success of the radiopharmaceutical depends on the accumulation of radiopharmaceutical at specific target cells in term of per cent of injected dose per gram organ or tissue. According to the survey of literature, which has been cited in this chapter, different localization processes are quite promising but the receptor based localization of radiopharmaceuticals is the most successful nuclear medicine procedure both in diagnosis and therapeutic treatments of global fatal diseases.
