Background The diagnosis of B-cell lymphoma, one of the commonest cancers seen in childhood and adolescence, is challenging. There is a crucial need to identify and delineate the prevalence of ...associated symptoms in order to improve early diagnosis. Aims To identify clinical presentations associated with childhood and adolescent B-cell lymphomas and estimate symptom prevalence. Methods A systematic review of observational studies and meta-analysis of proportions was carried out. Medline and EMBASE were systematically searched, with no language restrictions, from inception to 1st August 2022. Observational studies with at least 10 participants, exploring clinical presentations of any childhood and adolescent lymphoma, were selected. Proportions from each study were inputted to determine the weighted average (pooled) proportion, through random-effects meta-analysis. Results Studies reported on symptoms, signs and presentation sites at diagnosis of 12,207 children and adolescents up to the age of 20. Hodgkin's lymphoma most frequently presented with adenopathy in the head-and-neck region (79% 95% CI 58%-91%), whilst non-Hodgkin's lymphoma presented abdominally (55% 95% CI 43%-68%). Symptoms associated with lymphoma included cervical lymphadenopathy (48% 95% CI 20%-77%), peripheral lymphadenopathy (51% 95% CI 37%-66%), B-symptoms (40% 95% CI 34%-44%), fever (43% 95% CI 34%-54%), abdominal mass (46% 95% CI 29%-64%), weight loss (53% 95% CI 39%-66%), head-and-neck mass (21% 95% CI 6%-47%), organomegaly (29% 95% CI 23%-37%), night sweats (19% 95% CI 10%-32%), abdominal pain (28% 95% CI 15%-47%), bone pain (17% 95% CI 10%-28%) and abnormal neurology (11% 95% CI 3%-28%). Conclusion This systematic review and meta-analysis of proportions provides insight into the heterogeneous clinical presentations of B-cell lymphoma in childhood and adolescence and provides estimates of symptom prevalence. This information is likely to increase public and clinical awareness of lymphoma presentations and aid earlier diagnosis. This review further highlights the lack of studies exploring childhood and adolescent lymphoma presentations in primary care, where patients are likely to present at the earliest stages of their disease. Keywords: "childhood lymphoma", "adolescent lymphoma", "clinical presentation", "symptom prevalence", "meta-analysis of proportions"
In response to the increasing needs for control and optimization of hybrid systems, this work is concerned with such asymptotic properties as recurrence (also known as weak stochastic stability in ...the literature) and ergodicity of regime-switching diffusions. Using Liapunov functions, necessary and sufficient conditions for positive recurrence are developed. Then, ergodicity of positive recurrent regime-switching diffusions is obtained by constructing cycles using the associated discrete-time Markov chains.
In monolayer MoS2, optical transitions across the direct band gap are governed by chiral selection rules, allowing optical valley initialization. In time-resolved photoluminescence (PL) experiments, ...we find that both the polarization and emission dynamics do not change from 4 to 300 K within our time resolution. We measure a high polarization and show that under pulsed excitation the emission polarization significantly decreases with increasing laser power. We find a fast exciton emission decay time on the order of 4 ps. The absence of a clear PL polarization decay within our time resolution suggests that the initially injected polarization dominates the steady-state PL polarization. The observed decrease of the initial polarization with increasing pump photon energy hints at a possible ultrafast intervalley relaxation beyond the experimental ps time resolution. By compensating the temperature-induced change in band gap energy with the excitation laser energy, an emission polarization of 40% is recovered at 300 K, close to the maximum emission polarization for this sample at 4 K.
Magnetization reversals through the formation of a vortex state and the rotation of an onion state are two processes with comparable probabilities for symmetric magnetic nanorings with a radius of ...about 50 nanometers. This magnetic bistability is the manifestation of the competition between the exchange energy and the magnetostatic energy in nanomagnets. The relative probability of the two processes in symmetric nanorings is dictated by the ring geometry and cannot be altered after fabrication. In this work, we report a novel type of nanorings--asymmetric nanorings. By tuning the asymmetry, we can control the fraction of the vortex formation process from about 40% to nearly 100% by utilizing the direction of the external magnetic field. The observed results have been accounted for by the dependence of the domain-wall energy on the local cross-section area for which we have provided theoretical calculations.
Background
With radiotherapy having entered the era of image guidance, or image‐guided radiation therapy (IGRT), imaging procedures are routinely performed for patient positioning and target ...localization. The imaging dose delivered may result in excessive dose to sensitive organs and potentially increase the chance of secondary cancers and, therefore, needs to be managed.
Aims
This task group was charged with: a) providing an overview on imaging dose, including megavoltage electronic portal imaging (MV EPI), kilovoltage digital radiography (kV DR), Tomotherapy MV‐CT, megavoltage cone‐beam CT (MV‐CBCT) and kilovoltage cone‐beam CT (kV‐CBCT), and b) providing general guidelines for commissioning dose calculation methods and managing imaging dose to patients.
Materials & Methods
We briefly review the dose to radiotherapy (RT) patients resulting from different image guidance procedures and list typical organ doses resulting from MV and kV image acquisition procedures.
Results
We provide recommendations for managing the imaging dose, including different methods for its calculation, and techniques for reducing it. The recommended threshold beyond which imaging dose should be considered in the treatment planning process is 5% of the therapeutic target dose.
Discussion
Although the imaging dose resulting from current kV acquisition procedures is generally below this threshold, the ALARA principle should always be applied in practice. Medical physicists should make radiation oncologists aware of the imaging doses delivered to patients under their care.
Conclusion
Balancing ALARA with the requirement for effective target localization requires that imaging dose be managed based on the consideration of weighing risks and benefits to the patient.
In monolayer MoS2, optical transitions across the direct band gap are governed by chiral selection rules, allowing optical valley initialization. In time-resolved photoluminescence (PL) experiments, ...we find that both the polarization and emission dynamics do not change from 4 to 300 K within our time resolution. We measure a high polarization and show that under pulsed excitation the emission polarization significantly decreases with increasing laser power. We find a fast exciton emission decay time on the order of 4 ps. The absence of a clear PL polarization decay within our time resolution suggests that the initially injected polarization dominates the steady-state PL polarization. The observed decrease of the initial polarization with increasing pump photon energy hints at a possible ultrafast intervalley relaxation beyond the experimental ps time resolution. By compensating the temperature-induced change in band gap energy with the excitation laser energy, an emission polarization of 40% is recovered at 300 K, close to the maximum emission polarization for this sample at 4 K.
•The macro-meso failure mechanism of pre-flaw hollow-cylinder under cyclic loads was revealed.•Flaw angle influences the rock deformation, lifetime, AE activities and crack pattern.•A damage ...evolution model was proposed by AE b value to describe three-phase damage propagation.•Communication degree and crack network is relatively large for rock having a high flaw angle.
The structural deterioration and associated macro-meso fracture behaviors of granite containing crack-like and hole-like flaws subjected to multi-level cyclic loads are studied in this paper. The tested samples were prepared with a hollow hole of 15 mm and different flaw approach angles of 10°, 30°, 50° and 70°, respectively. The real-time AE monitoring combined with post-test CT scanning was employed to reveal the effects of flaw angle on the strength, deformation, AE activities and crack network pattern. Results show that the communication of the crack network and hole controls the rock volumetric deformation and the final failure modes. The output AE activities are influenced by the flaw arrangement. The progressive crack unstable propagation is much more severe for rock with low flaw angle and the recorded AE count/energy curves present multi-stage skips. The AE b value shows a first increase and then a decrease pattern. A damage evolution model was proposed by AE b value, the first fast and then steady increase and the final abrupt increase of accumulative damage can be well described. The complexity of crack network is larger for rock has high flaw angle, and the communication of crack and hole wall is severe accordingly. It is suggested that the failure of the pre-flawed hollow-cylinder granite is the interaction of crack coalescence and hole spalling.
Differentiating the types of pediatric posterior fossa tumors on routine imaging may help in preoperative evaluation and guide surgical resection planning. However, qualitative radiologic MR imaging ...review has limited performance. This study aimed to compare different machine learning approaches to classify pediatric posterior fossa tumors on routine MR imaging.
This retrospective study included preoperative MR imaging of 288 patients with pediatric posterior fossa tumors, including medulloblastoma (
= 111), ependymoma (
= 70), and pilocytic astrocytoma (
= 107). Radiomics features were extracted from T2-weighted images, contrast-enhanced T1-weighted images, and ADC maps. Models generated by standard manual optimization by a machine learning expert were compared with automatic machine learning via the Tree-Based Pipeline Optimization Tool for performance evaluation.
For 3-way classification, the radiomics model by automatic machine learning with the Tree-Based Pipeline Optimization Tool achieved a test micro-averaged area under the curve of 0.91 with an accuracy of 0.83, while the most optimized model based on the feature-selection method χ
score and the Generalized Linear Model classifier achieved a test micro-averaged area under the curve of 0.92 with an accuracy of 0.74. Tree-Based Pipeline Optimization Tool models achieved significantly higher accuracy than average qualitative expert MR imaging review (0.83 versus 0.54,
< .001). For binary classification, Tree-Based Pipeline Optimization Tool models achieved an area under the curve of 0.94 with an accuracy of 0.85 for medulloblastoma versus nonmedulloblastoma, an area under the curve of 0.84 with an accuracy of 0.80 for ependymoma versus nonependymoma, and an area under the curve of 0.94 with an accuracy of 0.88 for pilocytic astrocytoma versus non-pilocytic astrocytoma.
Automatic machine learning based on routine MR imaging classified pediatric posterior fossa tumors with high accuracy compared with manual expert pipeline optimization and qualitative expert MR imaging review.
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