The spatial distribution of the absorbed dose still remains a great challenge for boron neutron capture therapy (BNCT). Knowledge of the dose is a fundamental element for the correct planning of radiotherapy treatment and the subsequent effects produced by the treatment. In BNCT, the radiation field has many components, which makes gaining knowledge of the dose even more complex. Currently, it is not possible to account for this complexity in in vivo dosimetry. Treatment plans refer to the absorbed dose at the macroscopic level calculated through kerma, under charged particle equilibrium (CPE) conditions. Most techniques developed to date to determine the absorbed dose distribution in vivo are reviewed in this chapter, concluding with the most recent work carried out by our group at Pavia University on PG-SPECT or BNCT-SPECT systems using semiconductor detectors as photon sensors.