ABSTRACT
Objective:To preliminarily investigate the effects of tumor treating field (TTF) arrays on the positioning accuracy of radiotherapy setup in the treatment of glioblastoma.Methods:The kilovolt cone-beam CT (CBCT) and an X-ray volumetric imaging (XVI) system were used to verify the radiotherapy setup of 29 patients treated with conventional radiotherapy and 12 patients treated with TTF concurrent radiotherapy, respectively. The errors of radiotherapy position isocenter and treatment plan isocenter were evaluated in six directions, namely lateral (Lat), head pin (Lng), dorsoventral (Vrt), roll, pitch, and rotation (Rtn). Then, the plan isocenter was redetermined according to the setup error data. Moreover, the dose distribution was recalculated without changing the radiation field parameters. Finally, the V40, Dmean, D98% and D2% of both PTV and CTV and the Dmean, D20 cm 3, and D30 cm 3 of scalp tissue were evaluated. Results:When patients were treated with TTF concurrent radiotherapy wearing TTF arrays, the setup errors increased by 2 mm and 1.3 mm on average (maximum: 3.5 mm and 2.7 mm) toward the foot and dorsal directions, respectively. In addition, the setup errors in both Roll and Rtn directions increased by about 1.1° toward one side. The V40 and D98% of PTV decreased by up to 4.78% and 6%, respectively. The Dmean, D20 cm 3, and D30 cm 3 to scalp tissue increased by up to 2.6%, 3.2%, and 3.5%, respectively. The errors of other dose parameters for both CTV and PTV were within 2%. Conclusions:TTF arrays have significant effects on the setup errors of patients in the Lng and Vrt directions and increase the setup difficulty in the Roll and Rtn directions, while there is no significant error in the Lat and Pitch directions. Moreover, too large setup errors can significantly reduce the dose to PTV.
ABSTRACT
Objective To explore a new method of comparing the references images first to enhance the precision of the central point of the radiation treatment planning(RTP), try to establish a reference standard for this method in the nasopharyngeal cancer(NPC)and carcinoma of utercin cervix in the work of position verification. Methods For 50 RTPs of NPC and 20 RTPs of carcinoma of utercin cervix, the reference-CT-images in set-up and in position verification were compared, and to measure the difference between the two images. Then, in the same way, compare and measure the difference in the central-pointimages. Results For NPC, there was over 90% RTPs in which every difference measured was less than 2 mm;for carcinoma of utercin cervix, over 80% RTPs meet the criterion:the value of △MU1 ' or △MU2' was less than 5 mm and the others are less than 3 mm. Conclusions By comparing the references-CT-images in set-up and in position verification, the precision of the central point of the RTP is enhanced. The marks on the skin become more credible. So, it is feasible to perform the criterions in the work of position verification:for NPC every difference measured is less than 2 mm;for carcinoma of utercin cervix the value of △MU1 ' or △MU2 ' is less than 5 mm and the others are less than 3 mm.