[Dosimetric comparison of model-based and conventional calculation algorithms in high-dose-rate brachytherapy of head and neck tumours].

AIM: To investigate the effect of a model-based calculation algorithm that takes into account tissue inhomogeneities and real scattering conditions, on dose-volume parameters in brachytherapy for head and neck tumours.

METHODS

We recalculated the treatment plans of twentyfour patients treated with brachytherapy using the modelbased Advanced Collapsed Cone Engine (ACE) algorithm. High-dose volumes in the target and volumes irradiated with lower doses were determined. We calculated the doses to the organs at risk for the small volumes receiving high doses and the average doses.

RESULTS

The conventional calculation algorithm calculated higher doses than ACE for almost all parameters. The difference was less than 1% for V100 and D90. Among the volumes enclosed by the isodose surfaces, the difference was greater between the high-dose volumes and the low-dose volumes. The doses to the mandible were 2-3% lower with ACE, while the doses to the skin were 4-7% lower. The difference to the salivary glands was between 5-8%, while the doses to the spinal cord were the same.

CONCLUSIONS

When treating head and neck tumours, the traditional calculation algorithm overestimates the doses to the target volume and organs at risk. The introduction of the new calculation algorithm into clinical practice is not yet recommended.