64 research outputs found
Infodemiological data of West-Nile virus disease in Italy in the study period 2004–2015
No full textAbstractGoogle Trends (GT) was mined from 2004 to 2015, searching for West-Nile virus disease (WNVD) in Italy. GT-generated data were modeled as a time series and were analyzed using classical time series analyses. In particular, correlation between GT-based Relative Search Volumes (RSVs) related to WNVD and “real-world” epidemiological cases in the same study period resulted r=0.76 (p<0.0001) on a monthly basis and r=0.80 (p<0.0001) on a yearly basis. The partial autocorrelation analysis and the spectral analysis confirmed that a 1-year regular pattern could be detected. Correlation between GT-based RSVs related to WNVD yielded a r=0.54 (p<0.05) on a regional basis. Summarizing, GT-generated data concerning WNVD well correlated with epidemiology and could be exploited for complementing traditional surveillance
MRI-based radiomics: Quantifying the stability and reproducibility of tumour heterogeneity in vivo and in a 3D printed phantom
No full textMagnetic resonance imaging (MRI) is a key component in the oncology workflow. Radiomics analysis is a new approach that uses standard of care (SOC) magnetic resonance (MR) images to non-invasively characterise tumour heterogeneity. For radiomics to be reliable, the imaging features measured must be stable and reproducible. This thesis aims to quantify the stability and reproducibility of MRI-based radiomics in vivo and in a 3D printed phantom.
Chapter 4 explores the feasibility of constructing a 3D printed phantom using an MRI visible material (‘red resin’). The study shows that the material used to construct an anthropomorphic skull phantom mimicked human cortical bone with a T2* of 411 ± 19 µs. The phantom material provided sufficient signal for tissue segmentation however was only visible with an ultrashort echo time sequence, not commonly used in SOC imaging.
Chapter 5 investigates a high temperature resin (‘white resin’) where a texture object was developed for analysis. The ‘white resin’ was visible using SOC sequences. The interscanner repeatability measurements of the texture phantom demonstrated high reproducibility with 76% of texture features having an ICC > 0.9. In chapter 6, further texture and shape objects were developed and employed in a multi-centre study assessing inter and intrascanner variation of MRI-based radiomics. The phantom was stable over a period of 12 months, with a T1 and T2 of 150.7 ± 6.7 ms and 56.1 ± 3.9 ms, respectively. The study also found that histogram features were more stable (ICC > 0.8 for 67%) compared to texture (ICC > 0.8 for 58%) and shape texture (ICC > 0.8 for 0%) across the 8 scanners.
In chapter 7, phantom measurements found that radiomics features were more sensitive to changes of image resolution and noise. The in vivo test-retest component of chapter 7 detected many unstable features not suitable for use in a radiomics prognostic model. In chapter 8, of the 83 features computed only 19 features had significant changes between the baseline, mid and post radiation treatment and may be informative to assess rectal cancer treatment response.
When considering using radiomics analysis for SOC MRI scans, caution must be taken to ensure imaging protocols, imaging equipment including scanners and coils are consistent to improve intra and inter-institutional feature robustness. This can be achieved with regular quality assurance (QA) of imaging protocols using a suitable phantom and appropriate feature selection using phantom and in vivo datasets
Frobenius structure for rank one adic differential equations
No full textInternational audienceAccording to a criterion of B. Chiarellotto and G. Christol [Compositio Math. 100 (1996), no. 1, 77-99; MR1377409 (97b:14021)], a solvable rank one p-adic differential operator d/dx−g, with g=∑ni=1a−ixi, has a Frobenius structure if and only if a−1 is p-integral. Using natural estimates on tensor products, the author here generalizes this criterion to all g's in the Robba ring. As a corollary, he extends to the case p=2 the qualitative part of Matsuda's theorem [S. Matsuda, Duke Math. J. 77 (1995), no. 3, 607-625; MR1324636 (97a:14019)], according to which the Dwork-Robba twisted Artin-Hasse exponentials have Frobenius structures
Assessment of solid/liquid equilibria in the (U, Zr)O2+y system
No full textSolid/liquid equilibria in the system UO2eZrO2 are revisited in this work by laser heating coupled with
fast optical thermometry. Phase transition points newly measured under inert gas are in fair agreement
with the early measurements performed by Wisnyi et al., in 1957, the only study available in the literature
on the whole pseudo-binary system. In addition, a minimum melting point is identified here for
compositions near (U0.6Zr0.4)O2þy, around 2800 K. The solidus line is rather flat on a broad range of
compositions around the minimum. It increases for compositions closer to the pure end members, up to
the melting point of pure UO2 (3130 K) on one side and pure ZrO2 (2970 K) on the other. Solid state phase
transitions (cubic-tetragonal-monoclinic) have also been observed in the ZrO2-rich compositions X-ray
diffraction. Investigations under 0.3 MPa air (0.063 MPa O2) revealed a significant decrease in the melting
points down to 2500 Ke2600 K for increasing uranium content (x(UO2)> 0.2). This was found to be
related to further oxidation of uranium dioxide, confirmed by X-ray absorption spectroscopy. For
example, a typical oxidised corium composition U0.6Zr0.4O2.13 was observed to solidify at a temperature
as low as 2493 K.
The current results are important for assessing the thermal stability of the system fuel e cladding in an
oxide based nuclear reactor, and for simulating the system behaviour during a hypothetical severe
accident
X-ray spectroscopic study of the ADC source X1822-371
No full textWe analyse two Chandra HETGS (High Energy Transmission Grating Spectrometer) observations and one XMM-Newton observation. The HETGS and XMM/Epic-pn observed X 1822-371 for 140 and 50 ks, respectively. We extracted an averaged spectrum and five spectra from five selected orbital-phase intervals that are 0.04-0.25, 0.25-0.50, 0.50-0.75, 0.95-1.04; the orbital phase zero corresponds to the eclipse time. The spectra cover the energy band between 0.4 and 12 keV. We confirm the presence of local neutral matter that partially covers the X-ray emitting region; the equivalent hydrogen column is 3.5 × 1022 cm-2 and the covered fraction is around 60 %. We detected and identified several emission lines associated with He-like and H-like ions. The He-like transitions of O vu, Ne ix, Mg xi, Si xm show that the intercombination dominates over the forbidden and resonance lines. The fluxes of the lines are higher during the orbital-phase interval 0.04-0.75 while their intensities decrease during the dip and the eclipse. We discuss the presence of an optically thin corona with optical depth of 0.01 that scatters the luminosity from the inner region indetyfing it with the hot corona showed by [12] in the disc illuminated by a central sources. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence
Pteropoda (Gastropoda, Euthecosomata) from the Australian Cainozoic
No full textAll Tertiary euthecosomatous gastropods from the Australian continent known to the author are described. The species introduced by Ralph Tate (1887) are revised. Altogether 18 species are discussed. A new genus, Spoelia, and five new species, viz. Limacina curryi, L. lunata, L. tatei, Spoelia torquayensis and Vaginella victoriae, are introduced. Potential tools in the Australian pteropod fauna for a future biostratigraphical zonation and for long distance correlations are indicated. In an annex Vaginella sannicola sp. nov. is introduced for specimens from the Miocene of Gargano, Italy, which were incorrectly identified as V. eligmostoma Tate by d'Alessandro & Robba, 1980
Substitute CT generation from a single ultra short time echo MRI sequence: preliminary study
No full textIn MR guided radiation therapy planning both MR and CT images for a patient are acquired and co-registered to obtain a tissue specific HU map. Generation of the HU map directly from the MRI would eliminate the CT acquisition and may improve radiation therapy planning. In this preliminary study of substitute CT (sCT) generation, two porcine leg phantoms were scanned using a 3D ultrashort echo time (PETRA) sequence and co-registered to corresponding CT images to build tissue specific regression models. The model was created from one co-registered CT-PETRA pair to generate the sCT for the other PETRA image. An expectation maximization based clustering was performed on the co-registered PETRA image to identify the soft tissues, dense bone and air class membership probabilities. A tissue specific non linear regression model was built from one registered CT-PETRA pair dataset to predict the sCT of the second PETRA image in a two-fold cross validation schema. A complete substitute CT is generated in 3 min. The mean absolute HU error for air was 0.3 HU, bone was 95 HU, fat was 30 HU and for muscle it was 10 HU. The mean surface reconstruction error for the bone was 1.3 mm. The PETRA sequence enabled a low mean absolute surface distance for the bone and a low HU error for other classes. The sCT generated from a single PETRA sequence shows promise for the generation of fast sCT for MRI based radiation therapy planning.</p
The current and future role of the MRI radiographer in radiation oncology: A collaborative, experiential reflection on the Australian rollout of dedicated MRI simulators
No full textAbstract Magnetic Resonance Imaging (MRI) has proven value in radiotherapy treatment planning (RTP). MRI provides excellent soft tissue contrast, and improves lesion detection, definition and extent, allowing for increased conformal treatment. Recent installation of dedicated MRI simulators and MRI‐guided linear accelerators (MR Linacs) within radiation oncology departments has led to a sudden and rapid expansion in the scope of practice for many radiation therapists and MRI radiographers. The lack of current recommendations, guidelines and credentialing for both MRI radiographers and radiation therapists working within these atypical MRI environments poses a significant challenge for the education and training of staff, and the safe operation of these units. This commentary discusses current pathways for radiographers and radiation therapists entering the emerging field of MRI‐guided radiation oncology, and the future role of the MRI radiographer in addressing the unique issues found in non‐standard MRI environments. The authors draw on their collective experience as MRI radiographers assisting the rollout of dedicated MRI simulators in radiation oncology departments across Australia and reflect on the need for close collaboration between radiographers, radiation therapists and their respective departments. There is also a critical role for professional bodies to play in supporting existing and future roles in MRI and recognising advanced practitioner scope of practice
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