Teaching out-of-field : factors shaping identities of secondary science and mathematics

It is widely recognised that many teachers work 'out of field', taking subjects outside their specialities. Studies undertaken by the author and by other researchers shed light on how teachers themselves experience and understand out-of-field teaching. The article discusses the issue in relation to junior secondary science and mathematics. Evidence is drawn from the 2009 Teacher Identity In and Across Subjects (TIIAS) study. The article also includes a table summarising the findings of eight major research reports relevant to this issue. The author draws a range of conclusions. Teachers' experience and understanding of out-of-field teaching is determined not only by their subject content knowledge and their pedagogical content knowledge, but also by their context and by the personal resources available to them. Rural teachers often accept the need to teach across a number of subject areas, as part of their professional identity, despite the fact that they often lack easy access to subject specialists. Teachers tend to be more positive about out-of-field teaching when they themselves have had input into which subjects they will teach, and when they have an interest in or informal knowledge of the subject area. Teachers' interest in professional development to support their out-of-field teaching is influenced by whether they see themselves as simply filling in for someone, making the most of an opportunity, or pursuing an interest. Professional learning should ideally be initiated by or negotiated with the teachers, and should be provided at the point of need. School leaderships should maximise teachers' input into subject allocation and provision of professional learning opportunities. Teacher education courses need to prepare pre-service teachers to cope with out-of-field teaching.

Factors influencing mathematics and science teachers' self-assessment as teaching 'out-of-field' in rural and regional schools

Teaching 'out-of-field' occurs when teachers teach a subject for which they have no disciplinary or methods qualification. The incidence of out-of-field mathematics, science and technology teaching are particularly high in rural and regional areas. Given that mathematics and science are key areas of policy concern, there is an urgent need to understand teachers‟ position in this increasingly common practice in order to provide appropriate system responses. This paper asks the question, how are mathematics and science teachers‟ professional identities influenced by having to teach out-of-field? Twenty teachers who had taught science or mathematics at some time in their career, two school leaders, and two support staff, took part in semi-structured interviews, which I then transcribed. This paper reports on a thematic analysis of a subset of the data that isolated factors influencing teachers‟ self-assessment of themselves as out-of-field or in-field. Excerpts from the interviews are used to introduce and contextualise these factors within rural and regional settings. These factors are used to generate a theoretical model, the Boundary Between Fields (BBF) Model, that enables analysis of the impact of these factors on identity construction during a boundary crossing event. The Model highlights the influence of support mechanisms, contextual factors and personal resources on the nature of teachers‟ negotiation of subject boundaries and its impact on professional identity. This innovative model provides a platform for re-conceptualising these experiences as opportunities for professional learning occurring within schools as communities of practice, where teachers are supported and enabled to expand their professional identity. These findings provide insight for policy-makers, school leaders and teacher educators, into the complexity of the issue for teachers, as well as the conditions required for such teaching to be considered learning opportunities.

Pre-service teachers’ perceptions of the support, challenges and opportunities associated with teaching out-of-field

While pre-service teacher (PST) education programs prepare teachers for certain specialisations, the reality is that many secondary teachers will be expected to teach out-of-field, especially in Australia. Do universities have a role to play in preparing teachers for out-of-field teaching? At the very least, they should aim to produce adaptable, well-informed, capable teachers. This project uses case study methodology to examine teacher educator and PST perceptions relating to the role that universities play in preparing teachers for a reality that is likely to include out-of-field teaching. This paper focuses on PST perceptions of the associated expected support, challenges and opportunities. A small PST survey sample and PST interviews have shown that there is general positivity towards this practice, around the opportunities that can emerge, and an expectation of support accessibility; but diversity surrounds the challenges, suggesting a variation in respondents’ capacity to cope with the challenges that might emerge. Implications for teacher education are discussed.

Origins of the observed asymmetry in out-of-field dose from a linac fitted with an external micro-MLC

Objective Recently, Taylor et al. reported that use of the BrainLAB m3 microMLC, for stereotactic radiosurgery, results in a decreased out-of-field dose in the direction of leaf-motion compared to the outof- field dose measured in the direction orthogonal to leaf-motion [1]. It was recommended that, where possible, patients should be treated with their superior–inferior axes aligned with the microMLCs leafmotion direction, to minimise out-of-field doses [1]. This study aimed, therefore, to examine the causes of this asymmetry in outof- field dose and, in particular, to establish that a similar recommendation need not be made for radiotherapy treatments delivered by linear accelerators without external micro-collimation systems. Methods Monte Carlo simulations were used to study out-of-field dose from different linear accelerators (the Varian Clinacs 21iX and 600C and the Elekta Precise) with and without internal MLCs and external microMLCs [2]. Results Simulation results for the Varian Clinac 600C linear accelerator with BrainLAB m3 microMLC confirm Taylor et als [1] published experimental data. The out-of-field dose in the leaf motion direction is deposited by lower energy (more obliquely scattered) photons than the out-of-field dose in the orthogonal direction. Linear accelerators without microMLCs produce no asymmetry in out-offield dose. Conclusions The asymmetry in out-of-field dose previously measured by Taylor et al. [1] results from the shielding characteristics of the BrainLAB m3 microMLC device and is not produced by the linear accelerator to which it is attached.

Out-of-field cell survival following exposure to intensity-modulated radiation fields

PURPOSE:
To determine the in-field and out-of-field cell survival of cells irradiated with either primary field or scattered radiation in the presence and absence of intercellular communication.
METHODS AND MATERIALS:
Cell survival was determined by clonogenic assay in human prostate cancer (DU145) and primary fibroblast (AGO1552) cells following exposure to different field configurations delivered using a 6-MV photon beam produced with a Varian linear accelerator.
RESULTS:
Nonuniform dose distributions were delivered using a multileaf collimator (MLC) in which half of the cell population was shielded. Clonogenic survival in the shielded region was significantly lower than that predicted from the linear quadratic model. In both cell lines, the out-of-field responses appeared to saturate at 40%-50% survival at a scattered dose of 0.70 Gy in DU-145 cells and 0.24 Gy in AGO1522 cells. There was an approximately eightfold difference in the initial slopes of the out-of-field response compared with the a-component of the uniform field response. In contrast, cells in the exposed part of the field showed increased survival. These observations were abrogated by direct physical inhibition of cellular communication and by the addition of the inducible nitric oxide synthase inhibitor aminoguanidine known to inhibit intercellular bystander effects. Additional studies showed the proportion of cells irradiated and dose delivered to the shielded and exposed regions of the field to impact on response.
CONCLUSIONS:
These data demonstrate out-of-field effects as important determinants of cell survival following exposure to modulated irradiation fields with cellular communication between differentially irradiated cell populations playing an important role. Validation of these observations in additional cell models may facilitate the refinement of existing radiobiological models and the observations considered important determinants of cell survival.

Relative biological effectiveness (RBE) and out-of-field cell survival responses to passive scattering and pencil beam scanning proton beam deliveries

The relative biological effectiveness (RBE) of passive scattered (PS) and pencil beam scanned (PBS) proton beam delivery techniques for uniform beam configurations was determined by clonogenic survival. The radiobiological impact of modulated beam configurations on cell survival occurring in- or out-of-field for both delivery techniques was determined with intercellular communication intact or physically inhibited. Cell survival responses were compared to those observed using a 6 MV photon beam produced with a linear accelerator. DU-145 cells showed no significant difference in survival response to proton beams delivered by PS and PBS or 6 MV photons taking into account a RBE of 1.1 for protons at the centre of the spread out Bragg peak. Significant out-of-field effects similar to those observed for 6 MV photons were observed for both PS and PBS proton deliveries with cell survival decreasing to 50-60% survival for scattered doses of 0.05 and 0.03 Gy for passive scattered and pencil beam scanned beams respectively. The observed out-of-field responses were shown to be dependent on intercellular communication between the in-and out-of-field cell populations. These data demonstrate, for the first time, a similar RBE between passive and actively scanned proton beams and confirm that out-of-field effects may be important determinants of cell survival following exposure to modulated photon and proton fields

In-vitro investigation of out-of-field cell survival following the delivery of conformal, intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans

The aim of this work is to determine the out-of-field survival of cells irradiated with either the primary field or scattered radiation in the presence and absence of intercellular communication following delivery of conformal, IMRT and VMAT treatment plans. Single beam, conformal, IMRT and VMAT plans were created to deliver 3 Gy to half the area of a T80 flask containing either DU-145 or AGO-1522 cells allowing intercellular communication between the in-and out-of-field cell populations. The same plans were delivered to a similar custom made phantom used to hold two T25 culture flasks, one flask in-field and one out-of-field to allow comparison of cell survival responses when intercellular communication is physically inhibited. Plans were created for the delivery of 8 Gy to the more radio-resistant DU-145 cells only in the presence and absence of intercellular communication. Cell survival was determined by clonogenic assay. In both cell lines, the out-of-field survival was not statistically different between delivery techniques for either cell line or dose. There was however, a statistically significant difference between survival out-of-field when intercellular communication was intact (single T80 culture flask) or inhibited (multiple T25 culture flasks) to in-field for all plans. No statistically significant difference was observed in-field with or without cellular communication to out-of-field for all plans. These data demonstrate out-of-field effects as important determinants of cell survival following exposure to modulated irradiation fields when cellular communication between differentially irradiated cell populations is present. This data is further evidence that refinement of existing radiobiological models to include indirect cell killing effects is required.

Immune modulation in advanced radiotherapies: Targeting out-of-field effects

By virtue of being a localized treatment modality, radiotherapy is unable to deliver a tumoricidal radiation dose to tissues outside of the irradiated field. Nevertheless, ionizing radiation may result in radiation damage mediated by a bystander like effect away from the irradiated field, but this response is likely to be modest when radiotherapy is the sole treatment modality. Over the last decade there has been a re-emergence of immune modulating therapies as anti-cancer treatment modalities. Clinical trials on vaccines have on the whole been largely disappointing, but greater response rates have been observed from the immune checkpoint modulators. A clinical benefit of using such agents has been shown in disease sites such as melanoma and non-small cell lung cancer. There is growing pre-clinical data and a number of case reports which suggest the presence of abscopal effects when radiotherapy is co-administered with immune checkpoint inhibitors, suggesting that this combination may lead to an enhanced tumour response outside of the primary treatment field. In this review, the mechanisms of such an enhanced out-of-field tumour response, the potential clinical utilities, the optimal radiotherapy delivery and considerations for clinical follow-up following treatment are discussed.

Impact of fractionation on out-of-field survival and DNA damage responses following exposure to intensity modulated radiation fields

To limit toxicity to normal tissues adjacent to the target tumour volume, radiotherapy is delivered using fractionated regimes whereby the total prescribed dose is given as a series of sequential smaller doses separated by specific time intervals. The impact of fractionation on out-of-field survival and DNA damage responses was determined in AGO-1522 primary human fibroblasts and MCF-7 breast tumour cells using uniform and modulated exposures delivered using a 225 kVp x-ray source. Responses to fractionated schedules (two equal fractions delivered with time intervals from 4 h to 48 h) were compared to those following acute exposures. Cell survival and DNA damage repair measurements indicate that cellular responses to fractionated non-uniform exposures differ from those seen in uniform exposures for the investigated cell lines. Specifically, there is a consistent lack of repair observed in the out-of-field populations during intervals between fractions, confirming the importance of cell signalling to out-of-field responses in a fractionated radiation schedule, and this needs to be confirmed for a wider range of cell lines and conditions.