IMRT of prostate cancer

Abstract

Background and Purpose: Intensity-modulated radiation therapy (IMRT) has shown its superiority to 3D conformal radiotherapy in the treatment of prostate cancer. Different optimisation algorithms are available: algorithms which first optimise the fluence followed by a sequencing (IM) and algorithms which involve the machine parameters directly in the optimisation process (DSS). The aim of this treatment planning study is to compare both of them regarding dose distribution and treatment time.Patients, Material and Methods: Ten consecutive patients with localized prostate cancer were enrolled for this planning study. The planning target volume (PTV) and the rectum volume, urinary bladder and femoral heads as organs at risk (OAR) were delineated. Average doses, the target dose homogeneity H, D 5 , D 95 , monitor units per fraction and the number of segments were evaluated. Results:While there is only a small difference in the mean doses at rectum and bladder, there is a significant advantage for the target dose homogeneity in the DSS-optimised plans compared to the IMoptimised ones. Differences in the monitor units (nearly 10% less for DSS) and the number of segments are also statistically significant and reduce the treatment time. Conclusion:Particularly with regard to the tumor control probability the better homogeneity of the DSS-optimised plans is more profitable. The shorter treatment time is an improvement regarding intrafractional organ motion. The DSS-optimiser results in a higher target dose homogeneity and, simultaneously, in a lower number of monitor units. Therefore it should be preferred for IMRT of prostate cancer.

Volumetric‐modulated arc therapy and intensity‐modulated radiation therapy treatment planning for prostate cancer with flattened beam and flattening filter free linear accelerators

“…The IMRT planning followed26 using seven equispaced beams with gantry angles of 0°, 51°, 103°, 154°, 206°, 257°, and 309°. The collimator was set to 0°.…”

Evaluation of volumetric modulated arc therapy (VMAT) with Oncentra MasterPlan® for the treatment of head and neck cancer

“…Then, the leaf positions and weights are optimized with a gradient algorithm. The result is a set of MLC segments ready for delivery [22-24]. For the VMAT plans the option VMAT was used.…”

Application of volumetric modulated arc therapy (VMAT) in a dual-vendor environment

“…In the next step, the gradients of the objective function are calculated with respect to leaf positions and weights, allowing direct optimization of deliverable MLC segments, which leads to improved results as compared to IM [28-30]. …”

“…Several planning studies have been published comparing fluence modulation with subsequent leaf sequencing IM and the direct aperture optimization DSS in Oncentra MasterPlan ® , showing clear advantage for DSS [28-30]. Therefore, the reference IMRT plans were optimized with DSS in this study.…”