Image guided radiotherapy enhances the precision of radiotherapy for vertebra metastasis / 中华放射肿瘤学杂志

ABSTRACT

Objective To evaluate the precision of image guided radiotherapy (IGRT) for vertebra metastasis.Methods Cone-beam computed tomography (CBCT, ELEKTA SynergyTM) scanning was performed to 15 patients with vertebra metastasis treated with three dimensional conformal radiation therapy (3DCRT) or intensity modulated radiation therapy (IMRT).CBCT images were then compared with corresponding planning images to calculate the position errors.The isocenter was adjusted based on the errors calculated , CBCT scanning was re - performed , and the new - errors were then calculated .Results Compared to the firstly collected CBCT images, the average errors of 4 cases of cervical bone metastases in x (left-right), y (cervical-caudal), and z (anterior-posterior) directions were 1.8 mm, 0 mm and 3.6 mm respectively.After adjusting the isocenter, the new-errors were reduced to 0.1 mm, 0.4 mm and 0.3 mm.For 11 cases of thoracic and lumbar bone metastases, the average errors in x, y, and z directions were 1.9 mm, 0.1 mm, and -2.1 mm, respectively.While the new-errors were reduced to 0.9 mm, 0.5 mm and -0.3 mm.Conclusions IGRT can improve the precision of radiotherapy for vertebra metastasis to less than 2 mm, which provides a possibility of dose escalation in GTV while reduce the dose in the spinal cord.