The effect of on-line position correction on the dose distribution in focal radiotherapy for bladder cancer

<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to determine the dosimetric effect of on-line position correction for bladder tumor irradiation and to find methods to predict and handle this effect.</p> <p>Methods</p> <p>For 25 patients with unifocal bladder cancer intensity modulated radiotherapy (IMRT) with 5 beams was planned. The requirement for each plan was that 99% of the target volume received 95% of the prescribed dose. Tumor displacements from -2.0 cm to 2.0 cm in each dimension were simulated, using 0.5 cm increments, resulting in 729 simulations per patient. We assumed that on-line correction for the tumor was applied perfectly. We determined the correlation between the change in D_99%and the change in path length, which is defined here as the distance from the skin to the isocenter for each beam. In addition the margin needed to avoid underdosage was determined and the probability that an underdosage occurs in a real treatment was calculated.</p> <p>Results</p> <p>Adjustments for tumor displacement with perfect on-line position correction resulted in an altered dose distribution. The altered fraction dose to the target varied from 91.9% to 100.4% of the prescribed dose. The mean D_99%(± SD) was 95.8% ± 1.0%. There was a modest linear correlation between the difference in D_99%and the change in path length of the beams after correction (R²= 0.590). The median probability that a systematic underdosage occurs in a real treatment was 0.23% (range: 0 - 24.5%). A margin of 2 mm reduced that probability to < 0.001% in all patients.</p> <p>Conclusion</p> <p>On-line position correction does result in an altered target coverage, due to changes in average path length after position correction. An extra margin can be added to prevent underdosage.</p

New developments in osteoarthritis. Posttraumatic osteoarthritis: pathogenesis and pharmacological treatment options

Joint trauma can lead to a spectrum of acute lesions, including osteochondral fractures, ligament or meniscus tears and damage to the articular cartilage. This is often associated with intraarticular bleeding and causes posttraumatic joint inflammation. Although the acute symptoms resolve and some of the lesions can be surgically repaired, joint injury triggers a chronic remodeling process in cartilage and other joint tissues that ultimately manifests as osteoarthritis in a majority of cases. The objective of the present review is to summarize information on pathogenetic mechanisms involved in the acute and chronic consequences of joint trauma and discuss potential pharmacological interventions. The focus of the review is on the early events that follow joint trauma since therapies for posttraumatic joint inflammation are not available and this represents a unique window of opportunity to limit chronic consequences

Image-guided radiation therapy for muscle-invasive bladder cancer.

International audienceOrgan preservation protocols that incorporate chemoradiotherapy have shown good efficacy in bladder cancer. Owing to changes in rectal filling, urinary inflow and subsequent bladder volume with bladder wall deformations, irradiation must take into account interfractional and intrafractional internal target motion. Growing evidence suggests that image guidance during irradiation is essential in order to appropriately treat bladder cancer in this way. We performed a literature search on the imaging techniques and margins used for radiation therapy planning in the context of whole-bladder and partial-bladder irradiation. The most common image-guided radiation therapy (IGRT) method was based on cone-beam CT using anisotropic margins. The role of cine-MRI for the prediction of intraindividual bladder changes, in association with cone-beam CT or ultrasonography, is promising. Drinking protocols, diet and laxatives were used in most cases to minimize large variations in bladder size and shape. IGRT is crucial for avoiding tumor undercoverage and undue toxicity during radiation therapy for bladder cancer. IGRT-based adaptive radiation therapy can be performed using cone-beam CT or ultrasonography: modeling of bladder changes with cine-MRI or other imaging techniques might also be useful for facilitating adaptive radiation therapy with personalized margins

Stable methane hydrate above 2 GPa and the source of Titan's atmospheric methane

Methane hydrate is thought to have been the dominant methane-containing phase in the nebula from which Saturn, Uranus, Neptune and their major moons formed1. It accordingly plays an important role in formation models of Titan, Saturn's largest moon. Current understanding1, 2 assumes that methane hydrate dissociates into ice and free methane in the pressure range 1\ufffd2 GPa (10\ufffd20 kbar), consistent with some theoretical3 and experimental4, 5 studies. But such pressure-induced dissociation would have led to the early loss of methane from Titan's interior to its atmosphere, where it would rapidly have been destroyed by photochemical processes6, 7. This is difficult to reconcile with the observed presence of significant amounts of methane in Titan's present atmosphere. Here we report neutron and synchrotron X-ray diffraction studies that determine the thermodynamic behaviour of methane hydrate at pressures up to 10 GPa. We find structural transitions at about 1 and 2 GPa to new hydrate phases which remain stable to at least 10 GPa. This implies that the methane in the primordial core of Titan remained in stable hydrate phases throughout differentiation, eventually forming a layer of methane clathrate approximately 100 km thick within the ice mantle. This layer is a plausible source for the continuing replenishment of Titan's atmospheric methane.NRC publication: Ye

Impact of exercise therapy on molecular biomarkers related to cartilage and inflammation in people at risk of, or with established, knee osteoarthritis: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE: To investigate the impact of exercise therapy on molecular biomarkers related to cartilage and inflammation in people at risk of, or with established, knee osteoarthritis by conducting a systematic review of randomized controlled trials (RCTs).METHODS: Literature search up to September 2017 in five major databases with no restriction on publication year or language. Data were extracted from the first available follow-up time point and we performed a narrative synthesis for the effect of exercise therapy on molecular biomarkers related to cartilage and inflammation. A subset of studies reporting sufficient data was combined in a meta-analysis, using an adjusted random effects model.RESULTS: Twelve RCTs, involving 57 study comparisons at 4 to 24 weeks following an exercise therapy intervention were included. Exercise therapy decreased molecular biomarkers in 17 (30%) study comparisons, had no effect in 36 (63%), and increased molecular biomarkers in four (7%) study comparisons. Meta-analyses of nine biomarkers showed that exercise therapy was associated with non-significant reductions of C-reactive protein, C-terminal crosslinking telopeptide of type II collagen, tumor necrosis factor alpha (TNF-α), soluble TNF-α receptor-1 and -2, C2C neoepitope of type II collagen and cartilage oligomeric matrix protein compared to non-exercising control groups and had no effect on interleukin-6 and soluble interleukin 6 receptor.CONCLUSIONS: Exercise therapy is not harmful, as it does not increase the concentration of molecular biomarkers related to cartilage turnover and inflammation, implicated in osteoarthritis progression. The overall quality of evidence was downgraded to low because of the limited number of RCTs available. This article is protected by copyright. All rights reserved