Reconstruction of doses absorbed by radiotherapy patients by means of EPR dosimetry in tooth enamel

The objective of this study was verification of actual doses absorbed by teeth enamel in patients undergoing radiotherapy treatment. The retrospective dosimetry was based on ex vivo   measurements of electron paramagnetic resonance (EPR) signals in teeth extracted from six patients during dental treatment within a few years after radiotherapy with 60Co60Co photons and high-energy photon and electron beams. The measured doses were compared to those calculated by radiotherapy treatment planning (RTP) algorithm (CadPlan 3.1). The total accuracy of dose reconstructions based on EPR measurements was 5–9%. The discrepancy between the planned and measured doses ranged from a few percent (for teeth positioned within the irradiated field) up to about 120% (for teeth located outside the primary beam). Such significant differences between results of RTP calculations and EPR measurement can be explained by changes in geometry of tissues within patient's oral cavity during the treatment, which cannot be accounted for by RTP based on radiotherapy simulation procedure preceding the treatment.