Volumetric modulated arc therapy (VMAT) for hippocampal-avoidance whole brain radiation therapy: planning comparison with Dual-arc and Split-arc partial-field techniques

Abstract

Background: Although whole brain radiation therapy (WBRT) provides palliation and prophylaxis, reduces local recurrence probability and improves overall survival, it is evident that WBRT is associated with neurocognitive deficits due to radiation induced damage of the hippocampus. Therefore, minimizing hippocampal dose to the least possible level is of high clinical relevance. In dual-arc conventional volumetric modulated arc therapy (dac-VMAT), the large irradiation field for whole brain planned target volume (PTV) requires a wide jaw opening in which substantial low dose volume to the hippocampus may be produced due to suboptimal multi-leaf collimator (MLC) movements. The present study investigates the potential of a radiation therapy technique with split-arc and reduced field size, namely split-arc partial-field volumetric modulated arc therapy (sapf-VMAT) to spare the hippocampus during WBRT. Methods: Computed tomography and magnetic resonance images of 20 patients with brain metastases were retrieved in this retrospective planning study. The hippocampus was manually delineated by single radiation oncologist strictly following the RTOG 0933 atlas definition. Plans delivering 30 Gy in 10 fractions were generated for each patient using dac-VMAT and sapf-VMAT. Dosimetric parameters from both techniques were compared by paired t-test. Results:The results demonstrated that radiation dose to the hippocampus was significantly reduced using sapf-VMAT relative to dac-VMAT plans. sapf-VMAT (7.86Gy, p = 0.001) had significantly lowered average D 100% compared to dac-VMAT (9.23 Gy). Decrease in hippocampus D max using sapf-VMAT (13.23 Gy, p = 0.001) was statistically significant when compared to dac-VMAT (16.33 Gy). The resulting mean dose to the hippocampus was 9.16 Gy for the for sapf-VMAT. Mean dose of sapf-VMAT was significantly lower than dac-VMAT (10.85 Gy, p < 0.05). In both eyes, sapf-VMAT demonstrated significantly lower D mean compared to dac-VMAT (p < 0.05). Whole brain PTV coverage was not compromised in both techniques. Conclusion: sapf-VMAT has demonstrated significant dose reduction to the hippocampus and both eyes compared to dac-VMAT.

Treatment planning of volumetric modulated arc therapy and positioning optimization for hippocampal‐avoidance prophylactic cranial irradiation

“…Recently, Yuen et al have decreased the max hippocampal dose to 44% PD for HA-WBRT using complex VMAT techniques, such as split-arc and partial field. 18 In the present study, we employed four coplanar full arcs and reduced the max hippocampal dose to 35% of the PD (even lower than the HT plans) while maintaining a high plan quality. The planning method we used is mainly improved from the following aspects.…”

Hybrid split-arc partial-field volumetric modulated arc therapy: an improved beam arrangement for linear accelerator-based hippocampal-avoidance whole brain radiation therapy

“…The sapf-VMAT plans were created with reference to previous publication of our oncology centre [ 2 ]. Four VMAT arc fields of 179.9° were employed with collimator angle of 85°, 95°, 15° and 345°, respectively.…”

“…S1 ) [ 1 ]. Recently, our oncology centre has employed both split-arc and partial-field techniques together to eliminate scatter radiation and overcome multileaf collimator (MLC) limitations in WBRT volumetric modulated arc therapy (VMAT) planning [ 2 ]. This technique has shown to be more advantageous in sparing hippocampus compared with conventional dual-arc VMAT, while the target coverage has not been compromised.…”

Jurnal Review: Pengobatan Klinis Tumor Otak pada Orang Dewasa

“…Sumber radiasi (akselerator linier) berputar mengelilingi meja dalam bentuk busur, mengirimkan balok dari sudut yang berbeda. Komputer mengontrol intensitas pancaran untuk membantu menjaga radiasi tetap fokus pada tumor dan radiasi yang diberikan dalam waktu yang lebih sedikit di setiap sesi pengobatan (Yuen et al, 2020).…”