Abstract
Reducing the treatment time for IMRT patients is highly desirable. The objective of this work was to evaluate the new clinical Siemens KonRad inverse treatment planning system (TPS) and compare it to the CMS XiO TPS with special emphasis on the segmentation efficiency. For head and neck, liver and prostate cancer patients, step‐and‐shoot IMRT plans were designed using both CMS XiO and Siemens KonRad TPS. Number, direction and energy of beams used were the same in the plans from both systems for each treatment site. The plans were optimized to achieve the same clinical objectives concerning dose to the target volume and to the relevant organs‐at‐risk (OARs). The number of intensity levels were minimized until the clinical objectives could not be achieved anymore. Dose‐volume histograms (DVHs), mean and maximum doses were compared, as well as the number of beam segments and monitor units (MUs). The beams of each plan were delivered individually on a MapCheck device to verify the agreement between calculations and measurements to be less than 3%–3 mm distance‐to‐agreement. Plans optimized with KonRad resulted in fewer segments and lower number of MUs and therefore reduced delivery time on average by 28% or 3.6 min, while achieving similar dose distributions. CMS XiO plans exhibited a slightly steeper dose fall‐off outside the target volumes; however the difference was not clinically significant. DVHs to OARs were comparable. All calculated dose distributions passed the 3%–3 mm verification check.PACS numbers: 87.55.D
Highlights
Intensity modulated radiation therapy (IMRT) delivers increasingly conformal radiation fields to tumors with sharp dose-gradients around the target volume while allowing better sparing of healthy tissue
Because the field is composed of smaller segments the total number of monitor units (MUs) is larger, and more importantly the time for moving the multi-leaf collimator (MLC) leaves and subsequent need for record and verify cycles add a significant overhead to the total treatment time
Reducing the number of beam segments and MUs is a prerequisite for shortening the delivery time of step-and-shoot IMRT
Summary
Intensity modulated radiation therapy (IMRT) delivers increasingly conformal radiation fields to tumors with sharp dose-gradients around the target volume while allowing better sparing of healthy tissue. In the static or step-and-shoot IMRT approach each IMRT field is composed of several overlaying segments with different weights and shapes, designed by the segmentation algorithm of the treatment planning system. The fields of each segment are shaped by the multi-leaf collimator (MLC) and delivered sequentially. As compared to 3D conformal radiation therapy, the treatment time to deliver a similar dose is typically longer. Because the field is composed of smaller segments the total number of monitor units (MUs) is larger, and more importantly the time for moving the MLC leaves and subsequent need for record and verify cycles add a significant overhead to the total treatment time.
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