Abstract
A software tool is developed, given a new treatment plan, to predict treatment delivery time for radiation therapy (RT) treatments of patients on ViewRay magnetic resonance image‐guided radiation therapy (MR‐IGRT) delivery system. This tool is necessary for managing patient treatment scheduling in our clinic. The predicted treatment delivery time and the assessment of plan complexities could also be useful to aid treatment planning. A patient's total treatment delivery time, not including time required for localization, is modeled as the sum of four components: 1) the treatment initialization time; 2) the total beam‐on time; 3) the gantry rotation time; and 4) the multileaf collimator (MLC) motion time. Each of the four components is predicted separately. The total beam‐on time can be calculated using both the planned beam‐on time and the decay‐corrected dose rate. To predict the remain‐ing components, we retrospectively analyzed the patient treatment delivery record files. The initialization time is demonstrated to be random since it depends on the final gantry angle of the previous treatment. Based on modeling the relationships between the gantry rotation angles and the corresponding rotation time, linear regression is applied to predict the gantry rotation time. The MLC motion time is calculated using the leaves delay modeling method and the leaf motion speed. A quantitative analysis was performed to understand the correlation between the total treatment time and the plan complexity. The proposed algorithm is able to predict the ViewRay treatment delivery time with the average prediction error 0.22 min or 1.82%, and the maximal prediction error 0.89 min or 7.88%. The analysis has shown the correlation between the plan modulation (PM) factor and the total treatment delivery time, as well as the treatment delivery duty cycle. A possibility has been identified to significantly reduce MLC motion time by optimizing the positions of closed MLC pairs. The accuracy of the proposed prediction algorithm is sufficient to support patient treatment appointment scheduling. This developed software tool is currently applied in use on a daily basis in our clinic, and could also be used as an important indicator for treatment plan complexity.PACS number(s): 87.55.N
Highlights
51 Liu et al.: ViewRay treatment delivery time prediction processes into very complex procedures during the past two decades.[4]. The ViewRay System (VRS) (i.e., MRIdian system;ViewRay Inc., Oakwood Village, OH) is an integrated magnetic resonance (MR) image-guided radiation therapy system designed to provide simultaneous MR imaging (MRI) and external-beam radiation therapy (EBRT) treatment.[5]. The first commercial ViewRay system was installed in our institution.[6]. It has three cobalt-60 treatment heads, 120° apart, and each head provides a nominal dose rate of 1.85 Gy / min at isocenter.[7,8,9]
The total beam-on time attributing to the total treatment time is decided by the last finished beam at one of three treatment heads during each gantry position simultaneous delivery. (iii) Cobalt-60 sources decay. (iv) The VRS reorders the planned gantry positions according to the current gantry angle left from the previous patient treatment delivery so that VRS rotates
The scheme of our algorithm With the understanding of the treatment delivery procedure, we model the total treatment delivery time in four components: 1) the treatment initialization time; 2) the total beam-on time; 3) the gantry rotation time; and 4) the MLC motion time
Summary
51 Liu et al.: ViewRay treatment delivery time prediction processes into very complex procedures during the past two decades.[4]. The main motivation of this paper is to predict the total treatment delivery time at the completion of or during treatment planning in order to effectively schedule patient treatment appointments. VRS total treatment deliver time is a complex function of source decay, the order of beam deliveries, the gantry and MLC motions, and the final gantry position of the previous delivery. (ii) There are three cobalt-60 treatment heads to allow simultaneous beam delivery. The total beam-on time attributing to the total treatment time is decided by the last finished beam at one of three treatment heads during each gantry position simultaneous delivery. (iv) The VRS reorders the planned gantry positions according to the current gantry angle left from the previous patient treatment delivery so that VRS rotates The total beam-on time attributing to the total treatment time is decided by the last finished beam at one of three treatment heads during each gantry position simultaneous delivery. (iii) Cobalt-60 sources decay. (iv) The VRS reorders the planned gantry positions according to the current gantry angle left from the previous patient treatment delivery so that VRS rotates
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