Dosimetric characteristics of tomotherapy and threedimensional conformal radiotherapy for head and neck cancer

Background: this study aims to evaluate and compare three-dimensional conformal radiotherapy (3d-crt) versus helical tomotherapy (ht) based on treatment planning and selection of the most appropriate method to reduce side effects. materials and methods: treatment planning was performed on images of 20 patients with head and neck cancer with lymph node involvement by ht and 3d-crt techniques in seyed al-shohada hospital, isfahan, iran. the quality of target coverage, the exposure of normal tissue, and radiation delivery efficiency in two studied methods were compared. results: tomotherapy showed significant improvement over 3d-crt in terms of d2%, d50% dmean, v95%, ci (conformity index), and hi (homogeneity index) for ptv (planning target volume) and in terms of d2%, d98%, dmean, v95%, ci and hi for ptv nodal. the mean dose received by 98% of ptv (d98%) increased in ht compared to 3d-crt. whereas, higher doses received in organs at risk (oars) in 3dcrt compared to ht. conclusion: results showed improvements in target quality for ht over 3d-crt, including dosimetric coverage of target volumes, homogeneity and conformity indices, and reduction of the volume of cold and hot spots. tomotherapy also performed better than that of 3d-crt in oars. overall, with the satisfactory results obtained here, ht technique has considerable promise for treating head and neck cancers with the involvement of regional lymph nodes.