Brachytherapy is an effective local treatment for early-stage head and neck cancers. Mold irradiation is a method in which the source is placed in the oral cavity in sites where the soft tissue is thin and an irradiation source cannot be implanted. However, dose calculations based on TG-43 may be subject to uncertainty due to the heterogeneity of tissues and materials used for the irradiation of head and neck cancers.

In this study, we investigated the basic physical properties of different materials and densities in the molds, retrospectively analysed patient plans and verified the doses of intraoral mold irradiation using a dose verification system with MC simulations specifically designed for brachytherapy, which was constructed independently.

Dose–volume histograms were obtained with a treatment planning system (TG-43) and MC simulation and revealed a non-negligible difference in coverage of high-risk clinical target volume (HR-CTV) and organ at risk (OAR) between calculations using computed tomography values and those with density changes. The underdose was 10·6%, 3·7% and 5·6% for HR-CTV, gross tumour volume and OAR, respectively, relative to the treatment plan. The calculations based on the differences in the elemental composition and density changes in TG-43, a water-based calculation algorithm, resulted in clinically significant dose differences. The validation method was used only for the cases of complex small source therapy.

The findings of this study can be applied to more complex cases with steeper density gradients, such as mold irradiation.

To compare the image-based three-dimensional treatment planning using AcurosTM BV and AAPM TG-43 algorithm for intracavitary brachytherapy of carcinoma cervix.

Twenty-seven patients with cancer cervix, stage IIB or IIIB with vaginal involvement limited to the upper third of the vagina was included into the study. Intracavitary treatments with the patient in this study done with computed tomography and magnetic resonance imaging compatible ring applicator. Groupe European de Curietherapie and European Society for Therapeutic Radiology and Oncology recommended doses to target volumes and organs at risk compared using dose volume histogram.

The mean value of Point ‘A’ dose was compared between AcurosTM BV and TG-43, which indicates 0·13% difference. The differences in the mean dose to gross tumour volume for various volumes are V100% 0·28%, V150% 1·22% and V200% 1·03%; all volumes showed small difference but statistical significant (p<0·05). The mean dose of high-risk clinical target volume (HRCTV) D90 using AcurosTM BV was 8·47 Gy, which was 1·63% less compared with TG-43. The mean point A dose using AcurosTM BV is 1·04 times the dose to D90 of mean HRCTV. The same difference was observed in comparison with TG43. D2cc and D0·1cc of the bladder, rectum and sigmoid showed a statistically significant difference (p<0·05) in comparison with TG-43.

The differences in dosimetric parameters between the AcurosTM BV and TG-43 proved to be statistically significant. The difference is very small, and they are clinically insignificant.