Interfractional diaphragm changes during breath-holding in stereotactic body radiotherapy for liver cancer

Aim and background

IGRT based on bone matching may produce a large target positioning error in terms of the reproducibility of expiration breath-holding on SBRT for liver cancer. We evaluated the intrafractional and interfractional errors using the diaphragm position at the end of expiration by utilising Abches and analysed the factor of the interfractional error.

Impact of interfractional changes in head and neck cancer patients on the delivered dose in intensity modulated radiotherapy with protons and photons

PurposeTo investigate the influence of interfractional changes on the delivered dose of intensity modulated proton (IMPT) and photon plans (IMXT).Methods and materialsFive postoperative head and neck cancer patients, previously treated with tomotherapy at our institute, were analyzed. The planning study is based on megavoltage (MV) control images. For each patient one IMPT plan and one IMXT plan were generated on the first MV-CT and recalculated on weekly control MV-CTs in the actual treatment position. Dose criteria for evaluation were coverage and conformity of the planning target volume (PTV), as well as mean dose to parotids and maximum dose to spinal cord.ResultsConsiderable dosimetric changes were observed for IMPT and IMXT plans. Proton plans showed a more pronounced increase of maximum dose and decrease of minimum dose with local underdosage occurring even in the center of the PTV (worst IMPT vs. IMXT coverage: 66.7% vs. 85.0%). The doses to organs at risk (OARs) increased during the treatment period. However, the OAR doses of IMPT stayed below corresponding IMXT values at any time. For both modalities treatment plans did not necessarily worsen monotonically throughout the treatment.ConclusionsAlthough absolute differences between planned and reconstructed doses were larger in IMPT plans, doses to OARs were higher in IMXT plans. Tumor coverage was more stable in IMXT plans; IMPT dose distributions indicated a high risk for local underdosage during the treatment course.     

Minimizing the potential of cancer recurrence and metastasis by the use of graphene oxide nano-flakes released from smart fiducials during image-guided radiation therapy

An increasing number of studies show that cancer stem cells become more invasive and may escape into blood stream and lymph nodes before they have received a lethal dose during radiation therapy. Recently, it has been found that graphene oxide (GO) can selectively inhibit the proliferative expansion of cancer stem cells across multiple tumor types. In this study, we investigate the feasibility of using GO during radiotherapy to synergistically inhibit cancer stem cells, and lower the risk of cancer metastasis and recurrence. We hypothesize that graphene oxide nano-flakes (GONFs) released from newly-designed radiotherapy biomaterials (fiducial) can reach targeted tumor cells within 14–21 days. These are the typical time periods between the implantation of the fiducial and the start of image-guided radiation therapy. To test this hypothesis, the spatial-temporal diffusion of GONFs in soft tissue is investigated as a function of different particle sizes. Toxicity of GONFs to normal (HUVEC) and cancer (A549) cells has been assessed using the MTT assay. In addition, the survival fraction of A549 cells treated with GONFs is determined via clonogenic assay during radiotherapy. The diffusion study shows that only GONFs sizes of 50 and 200 nm could achieve the desired concentration of 50 μg/mL for 2 cm diameter tumor after 14 and 21 days respectively. The clonogenic and the MTT assay confirm the additional benefit of GONFs in killing lung cancer cells during radiotherapy. This work avails ongoing in vivo studies that use GONFs to enhance the treatment outcome for cancer patients during radiation therapy.     

MRI in medical practice and its future use in radiation oncology. Resume of XXV GOCO Congress (Montpellier) 2017

This publication is a resume of the GOCO Congress (Montpellier 2017). A part of this congress was about the use of MRI in clinical practice, focused on the oncology field. The role of this tool was described in diagnosis, staging of tumors, evaluation of treatment response and the future use in prognostic and investigation (radiomics). After that, in the context of the present and future uses of MRI in radiation oncology, MRI guided radiotherapy was explained, as a method that allows an increased precision in image guided treatments. This publication is a resume of the GOCO Congress (Montpellier 2017). A part of this congress was about the use of MRI in clinical practice, focused on the oncology field. The role of this tool was described in diagnosis, staging of tumors, evaluation of treatment response and the future use in prognostic and investigation (radiomics).     

Host plant choice and location by larvae of the wheat bulb fly (Delia coarctata)

Wheat bulb fly (Delia coarctata Fallen, Diptera: Anthomyiidae) is an important pest of winter wheat in the eastern half of the UK, and in northern and eastern Europe. The larvae must find a host plant and invade a tiller soon after hatching in late January. Chemical controls are costly and weather conditions may reduce their efficacy or prevent their application. Post‐emergence control relies on organophosphate insecticides, which may soon be withdrawn due to concerns about their negative health and environmental effects. Winter wheat (Triticum aestivum L.) is the preferred cereal host, but other winter cereals and related grasses may also be attacked, while oats (Avena spp.) are shunned. In choice test bioassays, neonate larvae chose couch grass (Elytrigia repens (L.) Nevski syn. Elymus repens (L.) Gould, Agropyearon repens (L.) Beauv.) seedlings and exudates over wheat seedlings and exudates, and exhibited geotaxis and negative phototaxis. Analysis of larval trails in choice test bioassays of seedling exudates showed that couch exudates are more attractive than wheat exudates, and that wheat exudates are more arrestant than couch exudates. This suggests that infochemicals isolated from couch, wheat, and oats could be used in wheat bulb fly control; possible delivery mechanisms are discussed. These findings, previous research, and a comparison of the phenologies and geographical distributions of D. coarctata and its hosts suggest that E. repens is the natural host of D. coarctata.     

Ecological studies to assess the efficacy of biological control on populations of alligator weed and lippia

Abstract  The risk of non-target effects from biological control agents can be reduced if we can better identify effective agents prior to release. Introducing only those agents with high potential for effective control will reduce the number of agents released and reduce the probability of both direct and indirect non-target impacts. Identifying effective agents requires understanding the roles that resources, disturbances and herbivory play in regulating plant populations under natural field conditions. Here we propose a series of experiments that will contrast the mechanisms of population regulation of two invasive wetland plants, alligator weed ( Alternanthera philoxeroides ) and lippia ( Phyla canescens ), with native congener species, Alternanthera denticulata and Phyla nodiflora . We hypothesise that the native plants will have greater growth rates when nutrients are low and herbivores are present, whereas the introduced plants will exhibit greater growth rates when nutrients are high and herbivores are absent.     

Using federated data sources and Varian Learning Portal framework to train a neural network model for automatic organ segmentation

PurposeIn this study we trained a deep neural network model for female pelvis organ segmentation using data from several sites without any personal data sharing. The goal was to assess its prediction power compared with the model trained in a centralized manner.MethodsVarian Learning Portal (VLP) is a distributed machine learning (ML) infrastructure enabling privacy-preserving research across hospitals from different regions or countries, within the framework of a trusted consortium. Such a framework is relevant in the case when there is a high level of trust among the participating sites, but there are legal restrictions which do not allow the actual data sharing between them. We trained an organ segmentation model for the female pelvic region using the synchronous data distributed framework provided by the VLP.ResultsThe prediction performance of the model trained using the federated framework offered by VLP was on the same level as the performance of the model trained in a centralized manner where all training data was pulled together in one centre.ConclusionsVLP infrastructure can be used for GPU-based training of a deep neural network for organ segmentation for the female pelvic region. This organ segmentation instance is particularly difficult due to the high variation in the organs’ shape and size. Being able to train the model using data from several clinics can help, for instance, by exposing the model to a larger range of data variations. VLP framework enables such a distributed training approach without sharing protected health information.     

Evidence of widespread hybridization among couch grasses (Elymus,Poaceae)

Hybridization, polyploidization, and crop‐to‐wild gene transfer within the agriculturally important tribe Triticeae are well explored experimentally, but the true consequences of both phenomena under natural conditions remain understudied. The present paper reports on an investigation of three species of couch grasses (Elymus hispidus, E. repens, and E. caninus) examining the ploidy levels and absolute genome sizes (1081 plants from 302 natural populations in Central Europe, verified by chromosome counts) and their morphological delimitation. In the present study, the hexaploid level prevailed in E. hispidus and E. repens whereas E. caninus was exclusively tetraploid. Introgressive hybridization between hexaploid species, unidirectionally shifted towards E. hispidus, was indicated by a continual pattern of genome size values. We did not find any evidence for heteroploid hybridization involving tetraploid E. caninus; however, we detected minority cytotypes among both E. caninus plants (hexaploid) and E. repens–E. hispidus hybrids (heptaploid and nonaploid) suggesting the formation of unreduced gametes. Morphometric results (367 plants, redundancy analysis, principal component analysis, and correlation analysis) mirrored the continual homoploid pattern of absolute genome size (including the unidirectional shift), and a significant correlation between absolute genome size and morphology was confirmed. Moreover, morphometric analyses detected additional characteristics for the delimitation of the Elymus taxa under study. Considering the crossability of E. hispidus with Triticum aestivum (bread wheat), the revealed extent of introgressive hybridization has implications for assessing the potential risk of gene flow between crops and troublesome weeds.     

Imaging practices and radiation doses from imaging in radiotherapy

Modern radiotherapy treatments require frequent imaging for accurate patient positioning relative to the therapeutic radiation beam. Imaging practices in five Finnish radiotherapy clinics were assessed and discussed from the patient dose optimization point of view. The results show that imaging strategies are not jointly established and variations exist. The organ absorbed doses depend on imaging technique and imaging frequency. In particular, organ doses from the cone beam computed tomography can have very large variations (a factor of 10–50 in breast imaging and factor of 5 in prostate imaging). The cumulative imaging organ dose from the treatment can vary by a factor of ten or more for the same treatment, depending on the chosen technique and imaging frequency. Awareness and optimization of the imaging dose in image-guided radiotherapy should be strengthened.     

Agro-ecology of onion couch (Arrhenathemm elatius var. bulbosum).

The agro-ecology of onion couch (Arrhenatherum elatius var. bulbosum), a well known weed of arable land is studied. Contribution of seeds from onion couch and a more widespread variety of Arrhenatherum elatius: tall oat-grass, towards future ingress of onion couch in arable fields has indicated that the tall oat-grass variety is not a potential weed of arable land. It appears that vegetative propagules rather than the seeds are the effective means of propagation of the onion couch variety in arable fields. An experiment performed to test any modifying effect of the soil texture indicated that onion couch is restricted to loamy soils and there is a complete absence from heavy clays and sandy soils. This could be due to the moist and protective micro-environment provided by the texture of the soils to partially buried vegetative propagules of onion couch, which are susceptible to drought.