Abstract
PurposeWith the new mode of Tomotherapy, irradiation can be delivered using static ports of the TomoDirect mode. The purpose of this study was to evaluate the characteristics of TomoDirect plans compared to conventional TomoHelical plans.MethodsTomoDirect and TomoHelical plans were compared in 46 patients with a prostate, thoracic wall or lung tumor. The mean target dose was used as the prescription dose. The minimum coverage dose of 95% of the target (D95%), conformity index (CI), uniformity index (UI), dose distribution in organs at risk and treatment time were evaluated. For TomoDirect, 2 to 5 static ports were used depending on the tumor location.ResultsFor the prostate target volume, TomoDirect plans could not reduce the rectal dose and required a longer treatment time than TomoHelical. For the thoracic wall target volume, the V5Gy of the lung or liver was lower in TomoDirect than in TomoHelical (p = 0.02). For the lung target volume, TomoDirect yielded higher CI (p = 0.009) but smaller V5Gy of the lung (p = 0.005) than TomoHelical. Treatment time did not differ significantly between the thoracic wall and lung plans.ConclusionProstate cancers should be treated with the TomoHelical mode. Considering the risk of low-dose radiation to the lung, the TomoDirect mode could be an option for thoracic wall and lung tumors.
Highlights
The Tomotherapy Hi-Art system (Accuray Inc, Sunnyvale, CA, USA) is a radiation delivery system that combines dynamic intensity-modulated radiation therapy (IMRT) and an on-board imaging systems [1,2]
All eligible patients seen during the period, i.e., 46 adults treated for prostate cancer, thoracic wall metastasis and lung tumor, were studied
In the thoracic wall plans (Figure 1), the conformity index (CI) in TomoDirect plans was worse than that in TomoHelical (p = 0.004), D95% in TomoDirect was better than that in TomoHelical (97 ± 1% vs. 96 ± 1%, p = 0.04)
Summary
The Tomotherapy Hi-Art system (Accuray Inc, Sunnyvale, CA, USA) is a radiation delivery system that combines dynamic intensity-modulated radiation therapy (IMRT) and an on-board imaging systems [1,2]. Treatment is usually delivered with 360-degree rotation of the 6-megavolt linear accelerator gantry. This conventional treatment mode is called TomoHelical. A new system upgrade named TomoDirect has been introduced [3,4]. TomoDirect allows the delivery of radiation at preestablished discrete angles with a fixed gantry. This new system is expected to reduce treatment time and reduce
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