Effect of Halo-Vest on dose distribution of radiotherapy for primary cervical spine malignant tumors / 中华放射医学与防护杂志

ABSTRACT

Objective:To investigate the effect of Halo-Vest on the dose distribution of different radiotherapy techniques for primary cervical spine malignant tumors.Methods:Ten patients with primary cervical spine malignancies who underwent radiotherapy after Halo-Vest surgery were retrospectively studied. The IMRT and VMAT plans were designed on the contoured CT images including Halo-Vest delineations using Monaco planning system. The IMRT and VMAT plans with the same field parameters were duplicated to the CT images without the Halo-Vest delineations, and the dose distribution was recalculated. The dose distribution of the target, organs at risk and normal tissues was analyzed and compared for the plans with and without the Halo-Vest delineation.Results:For most dosimetric parameters of VMAT plans, the mean deviations induced by the Halo-Vest were less than 1%, except for PGTV 107%. Without Halo-Vest delineation, the mean maximum dose of spinal cord and spinal cord-PRV increased by 0.38 Gy and 0.42 Gy ( Z=-2.803, -2.803, P<0.05), respectively. The mean Dmean of spinal cord and spinal cord PRV increased by 0.35 Gy and 0.37 Gy, respectively ( Z=-2.703, -2.701, P<0.05). The maximum deviation observed in the mean V5, V30, and Dmean of mucosa, thyroid, parotid gland, mandible, mandibular joint, and normal tissues was 0.74%. For IMRT plans, larger dosimetric deviations than VMAT plans were observed in PTV and PGTV, most of which were more than 1.0% and the maximum deviation was 4.55%. The absence of Halo-Vest delineation increased the mean maximum dose of spinal cord and spinal cord-PRV by 0.48 Gy and 0.59 Gy ( P>0.05), respectively. The mean Dmean of spinal cord and spinal cord PRV increased by 0.57 Gy and 0.59 Gy, respectively ( Z=-2.293, -2.293, P<0.05). The maximum deviation of other organs at risk was 1.98%. Conclusions:There are no clinically significant dose differences for VMAT planning with or without Halo-Vest delineation on the CT images. But the dosimetric impact of absent or partial Halo-Vest delineation on IMRT planning is relatively large and should be considered.