158. Retrospective analysys of volumetric modulated arc therapy treatments: Correlation between plans complexity and dosimetric accuracy

Abstract Background Total scalp irradiation presents technical and dosimetric challenges. While reports suggest that HyperArc, a new stereotactic radiosurgery planning technique, is associated with high conformity and rapid dose fall-off, the performance of HyperArc plans for cancers of the head and neck regions has not been explored. The current study aimed to compare the dosimetric performance of HyperArc plans with those of non-coplanar volumetric-modulated arc therapy (VMAT) plans in angiosarcoma of the scalp.Methods Six patients with angiosarcoma of the scalp were included in this study. Performance of three different non-coplanar plans administered using TrueBeam Edge was compared. Three plans were employed namely VMAT using flattening filter (FF) beams (VMAT-FF), HyperArc using FF beams (HyperArc-FF), and HyperArc using flattening filter free (FFF) beams (HyperArc-FFF). The dose distribution, dosimetric parameters, and dosimetric accuracy for all plans were evaluated.Results The three plans showed no statistically significant differences in target volume coverage, conformity, and homogeneity. With regard to the normal brain tissue, the received volume doses were significantly lower for the HyperArc-FF and the HyperArc-FFF plans than for the VMAT-FF plans. Mean brain doses were 17.56 ± 5.70 Gy, 12.88 ± 3.36 Gy, and 13.24 ± 3.55 Gy in the VMAT-FF, the HyperArc-FF, and the HyperArc-FFF plans, respectively. There were almost no differences in sparing the organs at risk between the HyperArc-FF and HyperArc-FFF plans. The HyperArc-FF and HyperArc-FFF plans provide a shorter beam-on time than does the VMAT-FF plan. The 3%/2 mm gamma test pass rates were above 95% for all plans.Conclusions Our results suggested that the HyperArc plan can be potentially used for radiation therapy of target regions with large and complicated shape, such as the scalp, and that there are no advantages of using FFF beams.

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Novel strategy with the automatic non-coplanar volumetric-modulated arc therapy for angiosarcoma of the scalp.

10.21203/rs.3.rs-27984/v2 ◽

2020 ◽

Author(s):

Shoki Inui ◽

Yoshihiro Ueda ◽

Shingo Ohira ◽

Haruhi Tsuru ◽

Masaru Isono ◽

...

Keyword(s):

Organs At Risk ◽

Volumetric Modulated Arc Therapy ◽

Target Volume ◽

Pass Rates ◽

Flattening Filter Free ◽

Arc Therapy ◽

Dosimetric Accuracy ◽

Planning Technique ◽

Flattening Filter ◽

Novel Strategy

Abstract Background: Total scalp irradiation presents technical and dosimetric challenges. While reports suggest that HyperArc, a new stereotactic radiosurgery planning technique applied to non-coplanar volumetric-modulated arc therapy (VMAT) technique, is associated with high conformity and rapid dose fall-off, the performance of HyperArc for total scalp irradiation has not been explored. The current study aimed to compare the dosimetric performance of HyperArc plans with those of non-coplanar VMAT plans in angiosarcoma of the scalp. Methods: Ten patients with angiosarcoma of the scalp were included in this study. The performance of three different plans administered using TrueBeam Edge were compared: non-coplanar VMAT using flattening filter (FF) beams (VMAT-FF), HyperArc using FF beams (HyperArc-FF), and HyperArc using flattening filter free (FFF) beams (HyperArc-FFF). The dose distribution, dosimetric parameters, and dosimetric accuracy for each of these plans were evaluated. Results: The three plans showed no statistically significant differences in target volume coverage, conformity, and homogeneity. The HyperArc-FF and HyperArc-FFF plans provided significantly lower mean brain doses (12.63 ± 3.31 Gy and 12.71 ± 3.40 Gy) than did the VMAT-FF plans (17.11 ± 5.25 Gy). There were almost no differences in sparing the organs at risk between the HyperArc-FF and HyperArc-FFF plans. The HyperArc-FF and HyperArc-FFF plans provided a shorter beam-on time than did the VMAT-FF plan. The 3%/2 mm gamma test pass rates were above 95% for all three plans. Conclusions: Our results suggest that the HyperArc plan can be potentially used for radiation therapy of target regions with large and complicated shapes, such as the scalp, and that there are no advantages of using FFF beams.

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