Evaluation of spinal cord risk during HDR brachytherapy in patients with nasopharyngeal cancer

Abstract

Aim

Use of Rotterdam applicators was analysed for the purpose of ascertaining the average dose to the spinal cord at the point of greatest load.

Materials/Methods

20 procedures carried out on patients treated in the brachytherapy department were evaluated. Rotterdam nosopharynx applicators were positioned and localised according to the “box technique”. The radiographs were used to reconstruct the applicator in PLATO NPS version 14.1.3 treatment planning system. The position of spinal cord points were inserted according to the radiographs. The highest-loaded points were chosen to analyze.

Results

Points were localized (along the cord) to within an average accuracy of 0.52 mm. A comparison of doses in the cord at these points was carried out and the average dose using geometrical optimization (on distance) was 19.7% of the reference dose while without optimisation the average was 18.7% of the reference dose.

Conclusions

From the study undertaken, it appears that the calculated doses in the spinal cord, at the points of greatest load, are as described in the published data. The Rotterdam applicator may be used equally for radical treatment and for locally increasing the dose (boost) because of an acceptable spinal cord dose.