A simple and fast physics-based analytical method to calculate therapeutic and stray doses from external beam, megavoltage x-ray therapy

State-of-the-art radiotherapy treatment planning systems provide reliable estimates of the therapeutic radiation but are known to underestimate or neglect the stray radiation exposures. Most commonly, stray radiation exposures are reconstructed using empirical formulas or lookup tables. The purpose of this study was to develop the basic physics of a model capable of calculating the total absorbed dose both inside and outside of the therapeutic radiation beam for external beam photon therapy. The model was developed using measurements of total absorbed dose in a water-box phantom from a 6 MV medical linear accelerator to calculate dose profiles in both the in-plane and cross-plane direction for a variety of square field sizes and depths in water. The water-box phantom facilitated development of the basic physical aspects of the model. RMS discrepancies between measured and calculated total absorbed dose values in water were less than 9.3% for all fields studied. Computation times for 10 million dose points within a homogeneous phantom were approximately 4 min. These results suggest that the basic physics of the model are sufficiently simple, fast, and accurate to serve as a foundation for a variety of clinical and research applications, some of which may require that the model be extended or simplified based on the needs of the user. A potentially important advantage of a physics-based approach is that the model is more readily adaptable to a wide variety of treatment units and treatment techniques than with empirical models

Grænsearbejde blandt grænsependlere

Inspireret af Chris Rumfords teori om grænsearbejde fokuserer artiklen på måden, hvorpå den dansk-tyske grænse praktiseres og derigennem udleves af grænsependlere, der bor og arbejder på forskellige sider af den. I vores etnografiske studier har det vist sig, at måden, grænsependlere praktiserer og lever med grænser i deres hverdag på, udtrykker en mangfoldighed af grænser, der er i konstant dialog i pendlernes hverdagsliv. Særligt betydningen af mobilitet og det at være mobil, og af bevægelse mere generelt, er et væsentligt fundament for at udleve grænsen, men også nationale forskelle og identitetsdannelse og ikke mindst sproglig praksis danner grundlag for særlige måder at udleve grænser på. Det er vores indtryk at grænser og deres konsekvenser først forstås i lyset af den praksis, i hvilken de virkeliggøres, og at denne praksis aldrig er entydigt geopolitisk determineret, men nærmere åbner op for en konstant forhandling af, hvad grænser er

A descriptive and broadly applicable model of therapeutic and stray absorbed dose from 6 MV to 25 MV photon beams

Purpose was to develop a simple model of therapeutic and stray absorbed dose for a variety of treatment machines and techniques without relying on proprietary machine-specific parameters. Dosimetry measurements conducted in this study and from the literature were used to develop an analytical model of absorbed dose from a variety of treatment machines and techniques in the 6 MV to 25 MV interval. A modified one-dimensional gamma-index analysis was performed to evaluate dosimetric accuracy of the model on an independent dataset consisting of measured dose profiles from seven treatment units spanning four manufacturers. The average difference between the calculated and measured absorbed dose values was 9.9% for those datasets on which the model was trained. Additionally, These results indicate that the model can provide accurate calculations of both therapeutic and stray radiation dose from a wide variety of radiotherapy units and techniques. We have developed a simple analytical model of absorbed dose from external beam radiotherapy treatments in the 6 MV to 25 MV beam energy range. The model has been tested on measured data from multiple treatment machines and techniques and is broadly applicable to contemporary external beam radiation therapy

Gensyn med Ballybogoin – linjer, spor og tidevandsmarkeringerne i det nordirske grænseland

Artiklen tager udgangspunkt i bogen, The Troubles in Ballybogoin fra 2003, hvor William F. Kelleher undersøger, hvordan det nordirske grænselands beboeres hverdagspraksisser – fra hvem de interagerer med til deres fysiske bevægelser i landskabet – er styret af en ”social hukommelse” omkring adskillelse og politisk identitet, der har rødder i den nordirske konflikt og den britiske imperiale fortid. Ved hjælp af Michel de Certeaus begreb om rumlige, kulturelle praksisser viser Kelleher, at hverdagspraksisser stabiliseres af, at udformningen af byrummene i grænselandet er forankret i en allestedsnærværende fysisk adskillelse af befolkningsgrupper, som hele tiden bliver italesat af befolkningen. I yderligere dialog med Sarah Greens begreb om linjer som ”spor” og ”tidevandsmarkeringer” og igennem sine feltstudier i grænselandet, særligt i og omkring den nordirske by Derry, genbesøger forfatteren disse hverdagspraksisser for at illustrere, hvordan grænselandet gennemsyres af linjer, der deler ”de to sider af huset”.&nbsp

Revisiting Ballybogoin: Lines, traces and tidemarks in the Northern Irish borderlands

The article departs from William F. Kelleher book (2003), The Troubles in Ballybogoin, investigating how everyday practice in the Northern Irish borderland – ranging from whom people interact with to where they move – is influenced by the social memory of division and political identity, with origins in the Troubles and the British imperial legacy. In dialogue with Sarah Green’s concepts of lines as traces and tidemarks (2018) and by way of field studies in the borderlands, particularly the border town (London)Derry, the author revisits the everyday practices to illustrate how the borderland is infested with lines parting ”the two sides of the house.” Michel de Certeau’s concept of spatial practice, also applied by Kelleher, makes the divisions physically present in the town scape – as the case is in Belfast – and the local tradition of “telling” keeps the divisions alive in stories and other mental images. The borderlandscapes are thus haunted by the ever-present mapping of the populations in us/them, either/or, here/not there, a mapping of people, which is also constantly brought into being by local talk

Sensing, imagining, doing Europe: Europeanisation in the boundary work of welcome cultures

In the article, we shed light on and problematize the everyday sensing, imagining, and doing of Europe in the boundary work of welcome cul-tures. By relating the practices and performances of the welcome cultures to a long tradition of thought problematizing European identity around the notion of cosmopolitanism, we read welcoming activities as openings for imagining and doing an inclusive Europe in a space apart from and beyond the institutional violence of exclusive borders. It is our argument that through the everyday activities of welcoming, ‘other Europes’ emerge, heterotopia, materialized as ‘elsewheres’ articulated in resistance to and as well as mirroring and mimicking the EU and state bordering. We thereby illuminate how European welcome cultures open for renegotiat-ing and reimagining the boundaries and contours of what it means to be European, and this is sensed, imagined and performed in the everyday practices