Impact of transducer arrays on deep-seated dosimetry in radiotherapy with concurrent TTFields for glioblastoma (extreme analysis).

OBJECTIVE

To study the impact of transducer arrays on the deep-seated dosimetry of radiotherapy with concurrent tumor treating fields (TTFields) for glioblastoma.

METHODS

Firstly, the covering style of transducer arrays to CIRS-038 phantom was designed to simulate the "extreme situation": four arrays were attached to the phantom as a style similar with that in clinical scene and, meanwhile, to assure that layer of interest of CIRS-038 was surrounded by twelve electrodes (three in each array). Then, eight patients undergone glioblastoma radiotherapy were selected, and the planed dose of each patient was delivered to the phantom with dosimetry film inside without and with transducer arrays. For the phantom with arrays, CBCT was used to check the dedicated covering style before dose delivery. Finally, Gamma-based consistency analysis was performed for two dose distributions for each plan (without/with arrays).

RESULTS

The covering style of the TTFields array met the requirements in 8 cases before dose delivery. Gamma indexes under the four criteria (2%/2 mm, 2%/3 mm, 3%/2 mm and 3%/3 mm) were (93.16 ± 5.16)%, (96.08 ± 3.49)%, (96.77 ± 2.54)% and (97.96 ± 1.61)%, respectively.

CONCLUSION

Even in extreme situation (twelve electrodes covering the same cross-section), the perturbation of the TTFields arrays to the deep-seated dose distribution of the radiotherapy for glioblastoma is weak and acceptable.