Dosimetric comparison of conformal radiotherapy and volumetric modulated arc therapy in craniospinal radiotherapy

Craniospinal radiotherapy is a complex radiotherapy technique which mostly used in childhood brain tumors. Right along with different radiotherapy techniques, in recent years volumetric arc therapy (VMAT) is prefered because of the dose coverage advantages. In this study 6 infants medulloblastoma patients are planned with conformal and VMAT technique and these techniques are compared dosimetrically. In VMAT technique cranium, superior and inferior spinal fields are used and in each field 2 arcs were used. Between each field there is 1,5-2 cm junction. In conformal techniue again cranium, superior and inferior spinal fields were used. For the minimization of possible hot and cold spots feathering technique was used. Technique is based on table shifting between fractions. For the comparison of the 2 techiques: left- right lenses maximum doses, esophagus mean and maximum doses, heart mean dose, spinal cord maximum dose and dose of %1 volume, lung volumes of 5Gy and 20 Gy, total Monitor Unit (MU), conformality index, homogenity index, maximum dose of whole body, oral cavity mean dose, right-left kidney mean doses, liver mean dose, whole body volume receiving 18-24-40 Gy are considered. Right-left lens doses, total MU values are lower in conformal technique and this difference is statistically significant (p=0.028). Esophagus mean and maximum doses, heart mean dose, spinal cord maximum dose and dose of %1 volume, conformality index, homogenity index, maximum dose of whole body, liver mean dose, whole body volume receiving 18-24-40 Gy are lower in VMAT technique (p<0.05). Lung volume of 5Gy is lower in conformal technique (p=0.028), lung volume of 20Gy is lower in VMAT techique (p=0.028). For right-left kidney mean doses the difference between 2 tecniques is not statistically significant (p=0.075)