Whole CNS radiotherapy – a modification of the lower spinal field to reduce organ doses in the abdominal cavity

Abstract

Introduction

A modification of the lower spinal field in the whole CNS irradiation technique was introduced at the Radiotherapy Department, University Children's Hospital of Kraków. We developed a modification of the standard technique since we were not able to use high-energy electron beams wanted to obtain maximum protection of healthy tissues in the irradiated children.

Materials and methods

7 patients (2 girls and 5 boys) have been subjected to radiation treatment by a modified technique since 2002. The changes involved rotation of the gantry and the table column in the lower spinal field.

Results

A more homogenous dose distribution in the spinal canal volume (in the area of the spinal field junction) was achieved. The maximum liver dose was reduced by 5 Gy. The total maximum and mean ovarian doses however increased by 0.6 Gy and 0.4 Gy, respectively. The mean dose to the intestines increased by 2 Gy, which was due to the larger volume of the organ covered by the radiation field in the modified technique. The doses to other organs were similar in both techniques.

Conclusions

The modified technique made it possible to decrease the dose delivered to the liver and to achieve homogenous dose distribution in the spinal canal volume. This modification, however led to an increase in the mean dose to the intestines by 2 Gy and the total maximum and mean ovarian doses by 0.6 Gy and 0.4 Gy, respectively. Therefore the modified technique is recommended for boys rather than girls.