Calculation of delivered composite dose from Calypso tracking data for prostate cancer: And subsequent evaluation of reasonable treatment interruption tolerance limits.

In this study we calculate composite dose delivered to the prostate by using the Calypso tracking -data- stream acquired during patient treatment in our clinic. We evaluate the composite distributions under multiple simulated Calypso tolerance level schemes and then recommend a tolerance level. MATERIALS AND METHODS: Seven Calypso-localized prostate cancer patients treated in our clinic were selected for retrospective analysis. Two different IMRT treatment plans, with prostate PTV margins of 5 and 3 mm respectively, were computed for each patient. A delivered composite dose distribution was computed from Calypso tracking data for each plan. Additionally, we explored the dosimetric implications for "worst case" scenarios by assuming that the prostate position was located at one of the eight extreme corners of a 3 or 5 mm "box." To characterize plan quality under each of the studied scenarios, we recorded the maximum, mean, and minimum doses and volumetric coverage for prostate, PTV, bladder, and rectum. RESULTS AND DISCUSSIONS: Calculated composite dose distributions were very similar to the original plan for all patients. The difference in maximum, mean, and minimum doses as well as volumetric coverage for the prostate, PTV, bladder, and rectum were all 
Source: Journal of Applied Clinical Medical Physics - Category: Physics Authors: Tags: J Appl Clin Med Phys 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
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
In this study we propose a method to incorporate the dosimetric features in the construction of a more reliable dose prediction model based on the deep convolutional neural network (CNN). In addition to the contour information, the dose distribution from a PTV-only plan (i.e., the plan with the best PTV coverage by sacrificing the OARs sparing) is also employed as the model input to build a deep learning based dose prediction model. A database of 60 volumetric modulated arc therapy (VMAT) plans for the prostate cancer patients was used for training. The trained prediction model was then tested on a cohort of 10 cases. Dose...
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
ConclusionsThe volume of the bladder wall decreased during IMRT. The range of subtraction of the volume of the bladder wall was extensive. Thus, the estimation of the bladder wall may be useful to reduce the inter-fraction variation.
Source: Reports of Practical Oncology and Radiotherapy - Category: Cancer & Oncology 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
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