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2 results

  • 6 - “How Much from the Point”: Saving Appearances at the Edge of the Universe

  • Alison Cornish, New York University
  • Book:
    Believing in Dante
    Published online:
    10 June 2022
    Print publication:
    30 June 2022, pp 208-243

  • Summary

    The primum mobile is the largest body of the universe, giving impetus to the whole complex system of natural causes. Limit of the physical world, it serves as a vantage point on the metaphysical structure that undergirds it. The planets are moved by angels that appear to whirl at different speeds in nine concentric fiery wheels variously distant from the common focus of their orbits. The angels are uninterruptedly intent on what they know and love, to the degree that they know and love it. The opening astronomical simile serves to describe a single moment of perfect balance in an ambiguous twilight before the universe took sides and split into light and dark, good and evil. It is a moment of expectation, in which what comes next depends on whether one settles for what appears in the here and now or believes that it promises something more yet to come.

  • Does inadequate Point-A dose warrant treatment plan modifications in CT-image-based cervix high dose-rate brachytherapy planning? A dosimetric perspective

  • R. Yaparpalvi, K. J. Mehta, S. Mutyala, H. C. Kuo, L. Hong, S. Kalnicki
  • Journal:
    Journal of Radiotherapy in Practice / Volume 12 / Issue 4 / December 2013
    Published online by Cambridge University Press:
    07 June 2013, pp. 318-325
  • Background and purpose

    To investigate whether inadequate dose to Point-A necessitates treatment plan changes in a time of computed tomography (CT)-image-guided brachytherapy treatment planning for cervix cancer.

    Materials and methods

    A total of 125 tandem and ovoid insertions from 25 cervix patients treated were reviewed. CT-image-based treatment planning was carried out for each insertion. Point-A is identified and the dose documented; however, dose optimisation in each plan was based on covering target while limiting critical organ doses (PlanTarget). No attempts were made to equate prescription and Point-A dose. For each insertion, a second hypothetical treatment plan was generated by prescribing dose to Point-A (PlanPoint-A). Plans were inter-compared using dose–volume histogram analyses.

    Results

    A total of 250 treatment plans were analysed. For the study population, the median cumulative dose at Point-A was 80 Gy (range 70–95) for PlanTarget compared with 84·25 Gy for PlanPoint-A. Bladder and rectal doses were higher for PlanPoint-A compared with PlanTarget (p < 0·0001). Target D90 did not correlate with Point-A dose (p = 0·60).

    Conclusions

    Depending on applicator geometry, tumour size and patient anatomy, Point-A dose may vary in magnitude compared with prescription dose. Treatment plan modifications purely based on inadequate Point-A dose are unnecessary, as these may result in higher organ-at-risk doses and not necessarily improve target coverage.