Application of intensity-modulated radiotherapy for carniospinal irradiation with multi-ISO centers planning method

Abstract

Objective To explore the application value of multi-ISO center planning method in intensity-modulated radiotherapy for carniospinal irradiation. Methods Ten patients treated with craniospinal irradiation with helical tomotherapy were selected. For these patients, new plans were designed with multi-ISO centers planning method on the treatment planning system (TPS) named Eclipse 11.0. Dose distribution to the tumor, OARs and normal tissue, the treatment time and the monitor units (MUs) of the two plans were compared. Results The plans designed in two groups satisfied all clinical requirements. For the tumor target (PTV), the difference of D95% between two groups was not statistical significant, while D98%, D2% and HI in HT group were superior to M-ISO group(t=2.822, 2.333, 4.743, P<0.05), D50%, Dmean and CI in M-ISO group were superior to HT group (t=5.259, 3.685, 8.835, P<0.05). The dose of OARs such as cochlea, parotid, submandibular gland, thyroid gland and kidney in HT group was lower than M-ISO group (t=4.365, 5.416, 2.674, 3.077, 2.782, 2.607, 4.659, P<0.05), and the dose of pancreas and small bowel was higher than M-ISO group(t=5.265, 5.935, P<0.05). Differences were not significant for V5 of normal tissue between two groups; while V10, V20 and V36 of normal tissue in M-ISO group were lower than HT group (t=3.57, 3.701, 2.602, P<0.05). M-ISO group reduced 41.0% of the treatment time by average and reduced 94.1% MUs by average. Conclusions Intensity-modulated radiotherapy for carniospinal irradiation with multi-ISO centers planning method not only met the requirements of clinical dosimetry, but also shorten the treatment time, reduced the damage to the machine. Multi-ISO centers planning method might be promoted as a new design scheme. Key words: Multi-ISO center planning method; Craniospinal system; IMRT; Helical tomotherapy