KEY POINTS
- This technical note used a solid-water slab phantom, a 6-megavolt Varian TrueBeam linear accelerator, and an Optune 3 × 3 ceramic transducer array to quantify dose perturbation during photon irradiation.
- Dose at depth was measured at 1.5, 5, and 10 cm with a Farmer-type ionization chamber; surface dose was measured with diodes, metal-oxide-semiconductor field-effect transistor detectors, and radiochromic film.
- The array caused statistically significant attenuation at depth, with dose reductions of approximately 2%–4% up to 10 cm.
- Surface dose increased substantially: diode and metal-oxide-semiconductor field-effect transistor measurements showed enhancement factors of 1.87 ± 0.07 and 1.81 ± 0.11, while radiochromic film showed 2.89 ± 0.09.
- Repositioning the array by one transducer diameter reduced peak surface dose by up to 40% and reduced localized film hotspots by 24%, but residual surface dose remained about 1.6–2.3 times baseline.
CLINICAL TAKEAWAY
Tumor treating field arrays can meaningfully perturb photon dose delivery, especially at the scalp surface, when used concurrently with radiotherapy. Array repositioning helps reduce localized hotspots, but it does not normalize surface dose and may redistribute elevated dose across a broader area. This is technically relevant for glioblastoma radiotherapy workflows, but the evidence is phantom-based and should inform treatment-specific dosimetric evaluation rather than clinical outcome claims.