Comparison of TomoTherapy and RapidArc in Hippocampus Sparing Brain Radiotherapy in Pediatrics

Background and Objectives: Both TomoTherapy and RapidArc have been examined in hippocampus sparing whole brain irradiation in adults. We aim to compare both techniques in pediatrics with relatively smaller brain volume. Patients and Methods: The hippocampus, the whole brain and the eyes were manually contoured in 3 pediatric patients. TomoTherapy plan was created aiming at adequate brain coverage and as low as possible hippocampus dose, RapidArc was challenged to achieve similar or better plan results. The prescription dose was 36 Gy in 20 treatment fractions to the whole brain. Results: TomoTherapy was able to achieve a mean hippocampus dose of 13.6 Gy with brain homogeneity index [HI] of 0.14 Using RapidArc [single arc], the same hippocampus dose was not achievable without compromising the brain HI significantly. By using 2 arcs, similar results to the TomoTherapy plan were achieved. The treatment time for TomoTherapy was 3.5 minutes while it was 1.2 minutes for single arc and 2.4 minutes for two arcs. Conclusions: TomoTherapy can achieve better target coverage with lower doses to the hippocampus compared to single arc RapidArc technique, while using 2 arcs RapidArc can achieve similar results with shorter treatment time.