Purpose
Dose deposition around unplanned air cavities during magnetic resonance‐guided radiotherapy (MRgRT) is influenced by the electron return effect (ERE). This is clinically relevant for gas ...forming close to or inside organs at risk (OARs) that lie in the path of a single beam, for example, intestinal track during pelvic treatment. This work aims to verify Monte Carlo calculations that predict the dosimetric effects of ERE around air cavities. For this, we use GafChromic EBT3 film inside poly‐methyl methacrylate (PMMA) –air phantoms.
Method
Four PMMA phantoms were produced. Three of the phantoms contained centrally located spherical air cavities (0.5, 3.5, 7.5 cm diameter), and one phantom contained no air. The phantoms were split to sandwich GafChromic EBT3 film in the center. The phantoms were irradiated on an Elekta Unity system using a single 10 × 10 cm2 7‐MV photon beam under the influence of a 1.5‐T transverse magnetic field. The measurements were replicated using the Elekta Monaco treatment planning system (TPS). Gamma analysis with pass criteria 3%/3 mm was used to compare the measured and calculated dose distributions. We also consider 3%/2 mm, 2%/3 mm, and 2%/2 mm pass criteria for interest.
Results
The gamma analysis showed that >95% of the points agreed between the TPS‐calculated and measured dose distributions, using 3%/3 mm criteria. The phantom containing the largest air cavity had the lowest agreement, with most of the disagreeing points lying inside the air cavity (dose to air region).
Conclusions
The dose effects due to ERE around spherical air cavities are being calculated in the TPS with sufficient accuracy for clinical use.
The Challenges of Using MRI During Radiotherapy McWilliam, A.; Rowland, B.; van Herk, M.
Clinical oncology (Royal College of Radiologists (Great Britain)),
November 2018, 2018-11-00, 20181101, Letnik:
30, Številka:
11
Journal Article
Recenzirano
Odprti dostop
In this article we aim to introduce the main considerations in integrating magnetic resonance imaging (MRI) into the radiotherapy workflow. We will cover the use of MRI for improved delineation, ...considerations regarding MRI-only workflows, and the potential of functional imaging techniques. The challenges of implementing each of these will be discussed to ensure safe usage in radiotherapy.
Despite an emphasis on family-centered practices in early intervention, the translation of this philosophy into practice is unclear. We, therefore, measured practices of 250 early intervention ...service providers in Spain, with the Families in Natural Environments Scale of Service Evaluation. We analyzed the “difficulty” of practices, through Rasch analysis, and reasons for the discrepancy between typical and ideal practices, through qualitative analysis. Results showed that the typical high-quality practices were working with families and demonstrating strategies, whereas the typical low-quality practices were identifying family supports and letting the family set the agenda for the home visit. Lack of training was the most frequently reported reason for the discrepancy. Rasch analyses showed that the items participants were most likely to score low were identifying family supports, addressing families’ satisfaction with routines, and letting families set the agenda for the visit.
We investigated the reliability and construct validity of the Professionals' Perceptions about Collaborative Consultation in Early Childhood Intervention Scale (ProPerCECIS), a rating scale developed ...to measure collaborative consultation in early childhood intervention (ECI). ProPerCECIS was completed by 427 professionals from 78 ECI teams. The full sample was randomised into sample A, 170 participants, for conducting an exploratory factor analysis (EFA) - and sample B, 257 participants, for performing confirmatory factor analysis (CFA). Multiple-group analysis, with the overall sample, was conducted. The EFA final solution comprised three correlated factors, with acceptable to very good internal consistency: Intervention, Context, and Planning. The CFA supported the three-factor structure. Results supported configural invariance and partial metric invariance, but partial scalar invariance did not hold. Results supported the conceptual framework of collaborative consultation in ECI and suggest that ProPerCECIS can be a useful measure of professionals' perceptions about collaborative consultation practices in ECI. ProPerCECIS seems to be particularly suited to assess collaborative practices within services providing routines-based family-centred interventions. Importantly, because the factor structure for ProPerCECIS holds up for different professional groups, it might be used by transdisciplinary ECI teams. Keywords: collaborative consultation, early childhood intervention, rating scale, reliability, construct validity.
► Sophisticated engagement was consistent across settings owing to the effects of age. ► Absolute levels of children's engagement outcomes varied as a function of context. ► Sophisticated engagement ...emerged as a likely generalized tendency to behave. ► Nonengagement emerged as a primarily context-dependent behavior. ► Child care quality in Porto, Portugal, needs improvement.
This study documented the consistency of child engagement across two settings, toddler child care classrooms and mother–child dyadic play. One hundred twelve children, aged 14–36 months (M=25.17, SD=6.06), randomly selected from 30 toddler child care classrooms from the district of Porto, Portugal, participated. Levels of engagement were coded, and sophisticated engagement, but not nonengagement, was consistent across settings. Consistency in children's sophisticated engagement was primarily accounted for by chronological age. Children spent more time in sophisticated behaviors and less time nonengaged during mother–child dyadic play than in center-based child care. For sophisticated engagement, effects of child predictors were stronger than effects of environmental features; whereas for nonengagement, effects of environmental features were stronger than effects of child predictors. Findings suggest children's sophisticated engagement may be generalizable across settings, as a function of age, whereas their nonengagement is most likely context dependent.
ABSTRACT
We use photometric and spectroscopic observations of the eclipsing binary E32 in the globular cluster 47 Tuc to derive the masses, radii, and luminosities of the component stars. The system ...has an orbital period of 40.9 d, a markedly eccentric orbit with e = 0.24, and is shown to be a member of or a recent escaper from the cluster. We obtain $M_{\rm p} = 0.862\pm 0.005 \, \mathrm{M}_\odot$, $R_{\rm p} = 1.183\pm 0.003 \, \mathrm{R}_\odot$, $L_{\rm p} = 1.65\pm 0.05 \, \mathrm{L}_\odot$ for the primary and $M_{\rm s} = 0.827\pm 0.005 \, \mathrm{M}_\odot$, $R_{\rm s} = 1.004\pm 0.004 \, \mathrm{R}_\odot$, $L_{\rm s} = 1.14\pm 0.04\, \mathrm{L}_\odot$ for the secondary. Based on these data and on an earlier analysis of the binary V69 in 47 Tuc, we measure the distance to the cluster from the distance moduli of the component stars, and, independently, from a colour – surface brightness calibration. We obtain 4.55 ± 0.03 and 4.50 ± 0.07 kpc, respectively – values compatible within 1$\, \sigma$ with recent estimates based on Gaia DR2 parallaxes. By comparing the M–R diagram of the two binaries and the colour–magnitude diagram of 47 Tuc to Dartmouth model isochrones we estimate the age of the cluster to be 12.0 ± 0.5 Gyr, and the helium abundance of the cluster to be Y ≈ 0.25.
To identify imaged regions in which dose is associated with radiation-induced trismus after head and neck cancer radiation therapy (HNRT) using a novel image-based data mining (IBDM) framework.
A ...cohort of 86 HNRT patients were analyzed for region identification. Trismus was characterized as a continuous variable by the maximum incisor-to-incisor opening distance (MID) at 6 months after radiation therapy. Patient anatomies and dose distributions were spatially normalized to a common frame of reference using deformable image registration. IBDM was used to identify clusters of voxels associated with MID (P ≤ .05 based on permutation testing). The result was externally tested on a cohort of 35 patients with head and neck cancer. Internally, we also performed a dose-volume histogram-based analysis by comparing the magnitude of the correlation between MID and the mean dose for the IBDM-identified cluster in comparison with 5 delineated masticatory structures.
A single cluster was identified with the IBDM approach (P < .01), partially overlapping with the ipsilateral masseter. The dose-volume histogram-based analysis confirmed that the IBDM cluster had the strongest association with MID, followed by the ipsilateral masseter and the ipsilateral medial pterygoid (Spearman's rank correlation coefficients: R
= -0.36, -0.35, -0.32; P = .001, .001, .002, respectively). External validation confirmed an association between mean dose to the IBDM cluster and MID (R
= -0.45; P = .007).
IBDM bypasses the common assumption that dose patterns within structures are unimportant. Our novel IBDM approach for continuous outcome variables successfully identified a cluster of voxels that are highly associated with trismus, overlapping partially with the ipsilateral masseter. Tests on an external validation cohort showed an even stronger correlation with trismus. These results support use of the region in HNRT treatment planning to potentially reduce trismus.
The reference standard treatment for cervical cancer is concurrent chemoradiotherapy followed by magnetic resonance imaging (MRI)-guided brachytherapy. Improvements in brachytherapy have increased ...local control rates, but late toxicity remains high with rates of 11% grade ≥3. The primary clinical target volume (CTV) for external-beam radiotherapy includes the cervix and uterus, which can show significant inter-fraction motion. This means that generous margins are required to cover the primary CTV, increasing the radiation dose to organs at risk and, therefore, toxicity. A number of image-guided radiotherapy techniques (IGRT) have been developed, but motion can be random and difficult to predict prior to treatment. In light of the development of integrated MRI linear accelerators, this review discusses the potential value of MRI in external-beam radiotherapy. Current solutions for managing pelvic organ motion are reviewed, including the potential for online adaptive radiotherapy. The impacts of the use of MRI in tumour delineation and in the delivery of stereotactic ablative body radiotherapy (SABR) are highlighted. The potential role and challenges of using multi parametric MRI to guide radiotherapy are also discussed.
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