Dosimetric comparison between TomoDirect and Helical Tomotherapy in total body irradiation / 中华放射医学与防护杂志

ABSTRACT

Objective@#To investigate the dosimetric differences between TomoDirect (TD) and Helical Tomotherapy (HT) in total body irradiation (TBI), as well to evaluate the plan quality and delivery efficiency of TD.@*Methods@#Eight patients with acute leukemia at an average height of about 120 cm who had undergone TBI in the first affiliated hospital of Zhengzhou university were retrospectively reviewed and replanned with the TD and HT techniques for dosimetric comparison. Identical planning parameters were configured for both techniques except that TD plans were designed with 2-12 equally spaced odd number fields and with an initial angle of 180 or 0 degree. Dosimetric differences in mean dose of plan target volume (PTVDmean), homogeneity index (HI), dose of organs at risk (OARs), as well as delivery time were compared between the TD and HT plans.@*Results@#The TD plans with 9 fields or more had similar PTVDmeanand HI compared with HT plans, while TD plans with less than 9 fields had a significant different PTVDmean(t=-3.12, -5.41, -20.33, -4.56, -7.22, -11.27, P<0.05) and HI (t=-2.94, -5.18, -15.66, -4.31, -5.51, - 9.13, P<0.05) compared with those of HT. In terms of OARs, the TD plans with 7 fields or more had no significant dosimetric differences in the mean dose of left and right lung compared with the HT plans. The TD plans with 3 fields had significant different maximum dose in the left lens plan risk volume(PRV) (2.14±0.60) Gy and the right lens PRV (3.05±0.10) Gy (t=0.77, 0.63, P<0.05) compared with the HT plans. No significant difference in delivery time was observed. The initial angle of the TD plans had no effects on PTVDmean, HI, OAR dosimetry and delivery time.@*Conclusions@#The TD plans with 9 fields or more can achieve similar plan quality in terms of target coverage, OAR sparing and delivery time, but have an advantage in the maximum dose to lens PRV compared with the HT plans.