Effects of Teacher-led Think-aloud Instruction on L2 Listening Comprehension

In this mixed-methods research study, 13 middle school students did activities to enhance their second language listening comprehension. The students were shown a video from This is Language and were given questions to answer that pertained to the video. Their ability to comprehend the video was measured based on how they answered the questions. They used two methods while doing the activities; partner work, and the Think-aloud method. After doing the activities, students were interviewed to see what they thought about the two methods and how metacognitive awareness came into play. According to Vandergrift & Tafaghodtari (2010), metacognitive awareness is necessary to successfully use the Think-aloud method. Looking at the listening comprehension questions and the interviews, there seems to be an improvement in listening comprehension when using the Think-aloud method, however the students did not seem to be aware that it helped. Further research on metacognitive awareness might be necessary to better explain these results

Dose Conformation in Tumor Therapy with External Ionizing Radiation: Physical Possibilities and Limitations

The central problem in tumor irradiation is to deposit a high and spatially uniform dose in the tumor target volume while sparing the surrounding normal tissue as much as possible. The present work investigates how such an adaptation ("conformation") of the spatial dose distribution to arbitrarily shaped target volumes can be achieved, and where the physical limits lie. In particular, the specific possibilities of irradiation with different types of radiation are determined under these aspects, whereby a rough distinction is made between irradiation with charged and uncharged particles. Due to the different mechanisms of radiation-tissue interaction, a conformal dose distribution can be achieved with only one radiation field in the case of heavy charged particles; in the case of uncharged particles, several radiation fields from different directions are required. First, the possibilities and limits of dose conformation are evaluated theoretically. Analytical approximations for modeling dose distributions with uncharged and charged particles are developed. Within the framework of these approximations, the theory of the exponential Radon transform is used to determine the optimal parameters for obtaining a desired dose distribution. It is shown that for an infinite number of radiation fields in the plane, it is possible to adapt the high-dose region to arbitrarily shaped target volumes for both uncharged and charged particles. The dose in a small radiation-sensitive organ at risk in the immediate vicinity of the target volume can be reduced to small scatter contributions. In the case of charged particles, this is also possible for multiple organs at risk. Furthermore, the non-conformal "dose background" is always smaller for charged particles than for uncharged particles. In a more application-oriented chapter, an algorithm is developed for the optimization of dose distributions under practical boundary conditions, i.e. in three dimensions, with finitely many radiation fields and for finite resolutions of the beam shaping devices. To achieve optimal dose distributions, the use of fluence- and (in the case of charged particles) energy-modulated radiation fields is necessary. Especially in the case of uncharged particles, the technical prerequisites for this are not yet available in clinical practice. Therefore, newly developed approaches to fluence modulation for uncharged particles using a dynamically or quasi-dynamically driven "multileaf collimator" are presented. Furthermore, the first phantom experiment is described in which these generalized methods for achieving the best possible conformal dose distribution were realized with high-energy photons (15-MV bremsstrahlung spectrum). The high degree of practically achievable dose conformation is thus verified. Finally, a comparison of the optimized dose distributions achievable with photons and protons is performed for challenging clinical cases where conventional radiotherapy reaches its limits. The most important result is that irradiation with uncharged particles, and in particular with high-energy X-rays, can be optimized in such a way that, in all clinically relevant cases, tumor-conformal dose distributions can be achieved with relatively few (less than ten) radiation fields. The exposure of healthy tissue is naturally higher than for heavy charged particles. However, the tolerance dose values are not exceeded. Exceptions are the rare cases in which the target volume is surrounded on almost all sides by particularly radiation-sensitive risk organs. Only in these cases can a much better result be achieved with the technically more demanding heavy charged particle therapy

New methods for solving the inverse problem of radiotherapy planning

New methods for the automatic determination and optimization of irradiation parameters for percutaneous radiotherapy with high energy photons are developed. The methods are based on an irradiation technique with intensity-modulated radiation fields. The essential problem is therefore to determine the shape of the modulation profiles for the individual fields, based on the specified target dose distribution. This problem is called the inverse problem of radiotherapy planning. It is shown that this is the mirrored version of the problem of reconstructing an image from its projections, such as occurs in computed tomography (CT). Based on this fact, the methods for image reconstruction known from CT are consistently transferred to the optimization of radiotherapy. By appropriate modifications of the methods, special features characteristic for this new field of application are taken into account. This includes in particular the fact that no negative radiation intensities can be realized and that one is limited to a few fields for practical reasons. It is shown that in most cases seven or nine radiation fields are sufficient and that the use of more fields does not lead to clinically significant improvements. The main methods of image reconstruction, namely filtered back projection and iterative reconstruction technique, are used alternatively in CT. In the present application, on the other hand, these methods are used quasi “symbiotically”. The filtered back projection, referred to here as filtered projection is used to quickly determine a starting value for the modulation profiles. These initial profiles are further optimized by an iterative procedure corresponding to the iterative reconstruction technique. The introduction of penalty functions makes it possible for the first time to adequately consider medically indicated constraints. The iterative optimization procedure is based on an algorithm for three-dimensional dose calculation. Therefore, another focus of this work is the development of such an algorithm for intensity modulated radiation fields. Conventional dose calculation algorithms cannot adequately account for modulations. To verify the newly developed method, a first comparison of the dose calculated with it with measured data is carried out. The methods presented here allow the direct determination of the irradiation parameters without the trial and error procedure that is common today. In addition, dose distributions can be generated that are hardly feasible even with the most complex conventional irradiation techniques. These are especially those with extended concave areas. Some examples of this type are presented

Joint Attention in Hearing Parent-Deaf Child and Hearing Parent-Hearing Child Dyads.

Here we characterize establishment of joint attention in hearing parent-deaf child dyads and hearing parent-hearing child dyads. Deaf children were candidates for cochlear implantation who had not yet been implanted and who had no exposure to formal manual communication (e.g., American Sign Language). Because many parents whose deaf children go through early cochlear implant surgery do not themselves know a visual language, these dyads do not share a formal communication system based in a common sensory modality prior to the child's implantation. Joint attention episodes were identified during free play between hearing parents and their hearing children (N = 4) and hearing parents and their deaf children (N = 4). Attentional episode types included successful parent-initiated joint attention, unsuccessful parent-initiated joint attention, passive attention, successful child-initiated joint attention, and unsuccessful child-initiated joint attention. Group differences emerged in both successful and unsuccessful parent-initiated attempts at joint attention, parent passive attention, and successful child-initiated attempts at joint attention based on proportion of time spent in each. These findings highlight joint attention as an indicator of early communicative efficacy in parent-child interaction for different child populations. We discuss the active role parents and children play in communication, regardless of their hearing status

Compact Method for Proton Range Verification Based on Coaxial Prompt Gamma-Ray Monitoring: a Theoretical Study

Range uncertainties in proton therapy hamper treatment precision. Prompt gamma-rays were suggested 16 years ago for real-time range verification, and have already shown promising results in clinical studies with collimated cameras. Simultaneously, alternative imaging concepts without collimation are investigated to reduce the footprint and price of current prototypes. In this paper, a compact range verification method is presented. It monitors prompt gamma-rays with a single scintillation detector positioned coaxially to the beam and behind the patient. Thanks to the solid angle effect, proton range deviations can be derived from changes in the number of gamma-rays detected per proton, provided that the number of incident protons is well known. A theoretical background is formulated and the requirements for a future proof-of-principle experiment are identified. The potential benefits and disadvantages of the method are discussed, and the prospects and potential obstacles for its use during patient treatments are assessed. The final milestone is to monitor proton range differences in clinical cases with a statistical precision of 1 mm, a material cost of 25000 USD and a weight below 10 kg. This technique could facilitate the widespread application of in vivo range verification in proton therapy and eventually the improvement of treatment quality

Near-Infrared Spectroscopy and Cortical Responses to Speech Production

This research demonstrates near-infrared spectroscopy (NIRS) as a flexible methodology for measuring cortical activity during overt speech production while avoiding some limitations of traditional imaging technologies. Specifically, language production research has been limited in the number of participants and the types of paradigms that can be reasonably investigated using functional magnetic resonance imaging (fMRI) – where a sensitivity to motion has encouraged covert (i.e., nonvocalized) production paradigms – and positron emission tomography (PET), which allows a greater range of motion but introduces practical and ethical limitations to the populations that can be studied. Moreover, for these traditional technologies, the equipment is expensive and not portable, effectively limiting most studies to small, local samples in a relatively few labs. In contrast, NIRS is a relatively inexpensive, portable, noninvasive alternative that is robust to motion artifacts associated with overt speech production. The current study shows that NIRS data is consistent with behavioral and traditional imaging data on cortical activation associated with overt speech production. Specifically, the NIRS data show robust activation in the left temporal region and no significant change in activation in the analogous right hemisphere region in a sample of native, English-speaking adults in a picture-naming task. These findings illustrate the utility of NIRS as a valid method for tracking cortical activity and advance it as a powerful alternative when traditional imaging techniques are not a viable option for researchers investigating the neural substrates supporting speech production