Quality of treatment plans and accuracy of in vivo portal dosimetry in hybrid intensity-modulated radiation therapy and volumetric modulated arc therapy for prostate cancer.

This study investigates the quality of treatment plans and the accuracy of in vivo portal dosimetry in such a hybrid approach for the case of prostate radiotherapy. MATERIAL AND METHODS: Conformal and limited-modulation VMAT plans were produced, together with five hybrid IMRT/VMAT plans, in which 0%, 25%, 50%, 75% or 100% of the segments were sequenced for IMRT, while the remainder were sequenced for VMAT. Integrated portal images were predicted for the plans. The plans were then delivered as a single hybrid beam using an Elekta Synergy accelerator with Agility head to a water-equivalent phantom and treatment time, isocentric dose and portal images were measured. RESULTS: Increasing the IMRT percentage improves dose uniformity to the planning target volume (p
Source: Radiotherapy and Oncology : journal of the European Society for Therapeutic Radiology and Oncology - Category: Radiology Authors: Tags: Radiother Oncol Source Type: research

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ConclusionDifferent medical physicists or dosimetrists, photon energies, treatment planning systems, and treatment machines have an impact on the resulting dose distribution. However, the differences only become apparent when comparing DVH, analysing dose values, comparing CI, HI, GI, as well as reviewing the dose distribution in every single plane. A  new score was introduced to identify treatment plans that simultaneously deliver a low dose to all OAR. Such inter- and intra-institutional comparison studies are needed to explore different treatment planning strategies; however, there is still no automatic soluti...
Source: Strahlentherapie und Onkologie - Category: Cancer & Oncology Source Type: research
Conclusions: A LASSO-based multivariable NTCP model comprising three important predictors (platelet count, risk group and V65) was established to predict the incidence of grade 2+ late rectal bleeding after IMRT.
Source: Journal of Cancer - Category: Cancer & Oncology Authors: Tags: Research Paper Source Type: research
Abstract The purpose of this study was the evaluation of the impact of a variable relative biological effectiveness (RBE) compared to a constant RBE value of 1.1 in proton therapy prostate trials due to uncertainties in α/β ratio.
 Twenty patients receiving passive scattered proton therapy (PSPT) and fifteen patients receiving intensity modulated proton therapy (IMPT) were compared to twenty patients treated with 7-field intensity modulated photon therapy (IMRT). For proton beam therapy (PBT), the RBE was estimated using two different RBE models. Tumor control probabilities (TCP) and n...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research
Modern radiation therapy aims to concentrate the dose to the tumor while sparing the surrounding normal tissues [1]. For instance, intensity-modulated radiation therapy (IMRT) and volumetric arc therapy achieve this purpose by generating high conformal dose distributions [2]. However, tumors can be located very close to normal organs, such as the rectum and the bladder in prostate cancer, the brain stem in brain cancer, the parotid grand and optic chiasm in nasopharynx cancer, and the spinal cord in spine cancer.
Source: Physica Medica: European Journal of Medical Physics - Category: General Medicine Authors: Tags: Original paper Source Type: research
Conclusion: In this study, we decoupled the influence of optimization parameters from the potential use of EUD-based cost functions on plan quality by generating both plans in the same TPS.
Source: Journal of Cancer Research and Therapeutics - Category: Cancer & Oncology Authors: Source Type: research
Abstract External beam radiation therapy for prostate cancer can result in urinary, sexual, and rectal side effects, often impairing quality of life. A polyethylene glycol-based product, SpaceOAR© hydrogel (SOH), implanted into the connective tissue between the prostate gland and rectum can significantly reduce the dose received by the rectum and hence risk of rectal toxicity. The optimal way to manage the hydrogel and rectal structures for plan optimization is therefore of interest. In 13 patients, computerized tomography (CT) scans were taken pre- and post-SpaceOAR© implant. A prescription of 60 G...
Source: Journal of Applied Clinical Medical Physics - Category: Physics Authors: Tags: J Appl Clin Med Phys Source Type: research
This study compared dosimetric indices of volumetric-modulated arc therapy (VMAT) with intensity-modulated radiation therapy (IMRT) accounting for cold spots in prostate cancer plans. IMRT plans were retrospectively generated from 30 prostate cancer patients with ten cases for each risk group, who received VMAT plans. The mean, maximum, and minimum doses, and conformity and homogeneity indexes were evaluated for planning target volume (PTV) and the mean dose andV20 –V70 for organs at risk (OAR) including the rectum, bladder, right and left femoral heads, and rectum overlapped with PTV (ROP) regions. The numbers and v...
Source: Radiological Physics and Technology - Category: Physics Source Type: research
Abstract To evaluate the planning target volume (PTV) margins for prostate cancer patients treated with initial intensity-modulated radiation therapy (IMRT) to pelvic lymph nodes and a proton boost to the prostate using cone-beam computed tomography (CBCT) and radiographs as image guidance, We analyzed data from prostate patients (n = 15) treated with initial pelvic IMRT and a proton boost to the prostate. CBCT and 2-dimensional (2D) radiographs were used for IMRT and proton pre-treatment alignments, respectively. Translations from bony-matching, implanted marker seed matching, and seed-bony differences were...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research
Abstract To evaluate the accuracy of commercially available hybrid deformable image registration (DIR) algorithms when using planning CT (pCT) and daily cone-beam computed tomography (CBCT) in radiation therapy for prostate cancer. The hybrid DIR algorithms in RayStation and MIM Maestro were evaluated. Contours of the prostate, bladder, rectum, and seminal vesicles (SVs) were used as region-of-interest (ROIs) to guide image deformation in the hybrid DIR and to compare the DIR accuracy. To evaluate robustness of the hybrid DIR for prostate cancer patients with organs with volume that vary on a daily basis, such as ...
Source: Journal of Applied Clinical Medical Physics - Category: Physics Authors: Tags: J Appl Clin Med Phys Source Type: research
Conclusions: Local-dose effects are predicted to be significantly reduced by an IRS. The spatial NTCP model predicts a significant decrease in Gr 2 late rectal bleeding and subjective sphincter control. Dose constraints can be improved for current clinical treatment planning. PMID: 30456317 [PubMed]
Source: Clinical Prostate Cancer - Category: Cancer & Oncology Authors: Tags: Clin Transl Radiat Oncol Source Type: research
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